Topics of projects in chemistry 10. Research work in chemistry "study of foodstuffs". The results of the chemical analysis of the chips
The project can be completed by any student!
If you decide to participate in project work, then set yourself really significant problem taken from life., apply certain knowledge and skills to solve it, including new ones that have yet to be acquired, and as a result get a real, tangible result.
The American philosopher, psychologist and educator John Dewey is considered the founder of the project activity. It was this scientist who proposed a hundred years ago to conduct education through the expedient activity of the student, taking into account his personal interests and goals.
Literally translated from Latin, the word "project" means
"thrown forward"
PROJECT is "SIX P":
1. Problem.
2. Design (planning).
3. Search for information.
4. Product of work.
5. Presentation.
The sixth "P" of the project is the portfolio of your project, i.e. project folder, which contains all the working materials, including plans, reports, photos and other necessary materials.
Useful tips for the student (designer)
and their advisors (parents, etc.):
1. For all questions, please contact the teacher coordinating the project.
2. Use more active reference literature (encyclopedias, historical documents, printed publications, material from the Internet, etc.).
3. Keep in mind the traditions of our school, don't forget that your native school turns 52 this year!
4. Think about what your work may be useful to you in the future.
5. Be creative, but rely only on scientific knowledge.
6. Try to use modern technology in your work (computer, photo and video equipment, copy machine, etc.).
7. When carrying out a project, always remember the ecology of your native land and your health.
8. The project cannot be an abstract, and even "downloaded" from the Internet.
Possible types of project presentation:
1. Scientific report at the conference.
2. Business or role-playing game.
3. Report of the research expedition, travel.
4. Games with the audience.
5. Sports games.
6. Generalization of the poll data at the scientific conference.
7. Create a video.
8. Theatrical production.
9. Dramatization of a real or fictional historical event.
10. Illustrated comparison of facts, documents, events, eras, civilizations.
11. Works of fine or decorative art.
12. Excursion, as a summing up of research activities.
Project classification:
1. A practice-oriented project is aimed at solving social problems. These projects are distinguished by the result of the activity of the participants that is clearly marked from the very beginning, which can be used in the life of a class, school, city, state. At the same time, the form of the final product is diverse - from a textbook for a school office to a package of recommendations for restoring the Russian economy.
2. A research project is similar in structure to a scientific study. It includes the substantiation of the relevance of the chosen topic, the formulation of the research problem, the obligatory advancement of a hypothesis with its subsequent verification, discussion and analysis of the results obtained. Methods to be used in the execution of the project modern science: laboratory experiment, modeling, sociological survey, etc.
3. The information project is aimed at collecting information about any object or phenomenon in order to analyze, summarize and present information to a wide audience. Such projects require a well-thought-out structure and the possibility of its correction in the course of work. The output of the project may be a publication in the media, including the Internet.
4. creative project involves the most free and unconventional approach to its implementation and presentation of results. These can be almanacs, theatricals, sports games, videos, etc.
5. Role project. The development and implementation of such a project is the most difficult. By participating in it, the designers take on the roles of literary or historical characters, fictional characters in order to create various social or business relationships through game situations.
The result of the project can be open until its completion.
For example, how will the historic court session end? Will the conflict be completed or an agreement concluded?
preparation note,
design and presentation of the project.
1. Basic requirements for participants
Design competition:
- clarity, conciseness and accessibility of the presentation of the material;
- compliance of the topic of the work with its content (and are the goals, objectives, conclusions formulated in the project?).
- relevance and practical significance of the work, connection with life;
- erudition of the author, skillful use of different points of view on the topic of the work; fluency in the material;
- competent use of visibility during the speech;
- a reasoned justification for what was done in the project with your own hands;
- the presence of their own views and conclusions on the problem;
- the presence in the content and design of the project of a certain exclusivity - "zest", which will make the presentation of your project more advantageous;
- the ability of students to use special popular science terminology and literature on the topic;
- registration of project work;
- the presence of a catalog of used literature, passports and business cards;
- uniform in accordance with the theme of the project;
- the ability not to get lost in the answers to the questions of the jury members;
- correctness of behavior in the process of defending the project work;
- the culture of the student's performance at the conference
(performance time - 7 minutes;
time for answering questions - 3 minutes).
2. Design and content of the project (in the project folder):
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Whoever has the opportunity can submit a project for the Competition using multimedia technologies, without forgetting all the other requirements for the design of the project.
Additional information for teachers - leaders of project work.
The project activity program should include:
The name of the program.
Basis for program development.
The main developers of the program.
Purpose of the program.
Program objectives.
Program participants.
Terms and stages of the program implementation.
List of sections of the program.
program executors.
Expected final results of the program implementation.
Organization of control over the execution of the program.
Basic moments scheduling work on projects.
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Preparation for public defense of projects: Issuance of a decree on the procedure for protection and the composition of the audience (including an independent expert commission). |
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When working with students on a project, it is necessary to constantly keep in touch not only with the students doing this project, but also with the parents, consultants of this project.
At the same time, it is necessary that the teacher himself clearly understand the essence of the project, the methodology for its preparation, design and presentation (presentation).
When organizing this cooperation with students, it is necessary to take into account their child's age psychology.
Project work in the classroom is organized in accordance with the goals and objectives of the school Project Competition.
In the work on the project, it is necessary to take into account the achievements of advanced science and practice in the field of research and design work.
When preparing your students for the presentation of projects at the Competitions, it is necessary to proceed from the general requirements for the presentation of projects
(i.e. it is necessary to draw up projects in a single style, the requirements for which are developed by the CMC)
When working with students on a project, it is necessary to pay attention to the psychological preparation of the children so that students defend their project convincingly, express their thoughts competently and are not afraid to answer questions from the jury members.
Protocol for jury members _______________ round of the competition
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Name of jury member (and school number): __________________
Dear Colleagues!
Taking into account the recommendations of the methodologists on the design and research activities of the UMC SOUO, with a 10-point evaluation of the answers of the contestants, the following points should be adhered to:
The presence of a properly designed project work folder, including a work passport and a list of references.
Having a business card.
On a separate sheet of paper, the project is summarized with illustrations and valuable excerpts from the project. Business cards are distributed to members of the jury and guests to present in a short form the goals and objectives of their project.
The project presentation time should not exceed 10 minutes:
7 minutes of which are allocated to the defense of the project,
3 minutes - to prepare the presentation of the project and answer the questions of the jury.
The contestant, presenting the project, must:
- competently and eruditely state the project,
- use visuals correctly during the presentation,
- show the connection of your project with life,
- demonstrate the product of the project made by one's own hands and substantiate the need for its creation,
- to draw conclusions from the previously outlined goals and objectives.
The maximum number of points that a contestant can score is 100 points when presenting and defending their project.
Chemistry project topics for grade 7
1. Nitric acid HNO3 - "explosive royal lady".
2. Protein in the human body.
3. Influence of motor transport on the content of ions heavy metals in the soil.
4. Is lipstick harmful?
5. Harmful chemicals.
6. Growing crystals in the home laboratory.
7. Hygienic aspects of food contamination.
8. Combustion.
9. Graphite and diamond: similarities and differences.
10. Chewing gum: good or bad?
11. Life and work of A.M. Butlerov.
12. Fats, proteins and carbohydrates.
13. Pollution of natural waters.
14. Signs of chemical elements. Relative atomic mass of chemical elements.
15. The value of chemistry in the creation of new materials, dyes and fibers.
16. Interesting and useful chemical phenomena in nature.
17. Ionizing radiation.
18. Food research.
19. Research of soils.
20. Research chemical composition school chalk.
21. Sources and types of air pollution.
22. How to isolate essential oils from plants?
23. How do smells affect a person?
24. How to investigate the quality of tea.
25. How to determine the quality of honey.
26. How to choose the right scales for work in the laboratory.
27. Complex compounds and their use in medicine.
28. Beauty through chemistry. Household chemicals.
29. Crystals around us.
30. Laboratory equipment, utensils and protective equipment.
31. Metals in the human body.
32. Models of molecules of simple and complex substances.
33. Is it possible to get rubber from potatoes? Plastics yesterday, today, tomorrow.
34. Scientific chemical laboratory of Lomonosov.
35. The formation of ammonia in the body.
36. Redox reactions.
37. Determination of vitamin C in food products.
38. Determination of the content of nitrates in the roots of vegetables.
39. Determination of the content of acidity regulators in pickled products by acid-base titration.
40. Basic properties of water.
41. Assessment of soil contamination in the city of Grodno using watercress as a bioindicator.
42. The paradox of the influence of chemicals on a living organism.
43. Plant pigments.
44. Sweeteners as food additives (natural and
45. Search for plant corrosion inhibitors for iron and its alloys.
46. Obtaining and using ethylene.
47. Obtaining and properties of essential oils.
48. Obtaining indicators from natural sources.
49. Why was tooth powder replaced with toothpaste?
50. Food as chemical compounds.
51. Various properties of water and the importance of water in animate and inanimate nature.
52. Composition and medicinal properties natural mineral water.
53. The structure of the atomic nucleus.
54. The structure of gaseous, liquid and solid bodies.
55. Unique honey.
56. Scientists - chemists during the Great Patriotic War.
57. Physical and chemical phenomena
58. Chemical nature of oxygen, carbon dioxide and hemoglobin.
59. Chemical phenomena in Everyday life.
60. Chemistry is the science of miracles and transformations.
61. Chemistry and medicinal substances.
62. Chemistry and food.
63. Tea is a familiar stranger.
64. What can replace natural rubber?
65. What is included in the perfume?
66. What can be found in a jar of cream?
67. What do we know about acids.
68. What do we know about mobile phones?
69. Foreign substances and preventive measures.
Chemistry project topics for grade 8
1. Alchemy and the search for the philosopher's stone
2. Analysis of food quality.
3. Analysis of drugs.
4. Aromatherapy.
5. Safe food. Evaluation of food quality.
6. Dietary supplements: profanation or benefit?
7. Household filters for purification of tap water and a method for their regeneration.
8. Tasty - tasteless. ABOUT food additives.
9. Does the pH of the water affect the growth of legumes.
10. Influence of heavy metals on pea plants.
11. Water: unusual properties.
12. Hydrogen is the fuel of the future.
13. Harm of energy drinks.
14. Growing salt crystals.
15. Identification of the quality of leaf tea from different companies.
16. Chewing gum: history bad habit(myths and realities).
17. Iron and human health.
18. Yellow, red, green - which is more useful? (About apples).
19. Hardness of water and ways to eliminate it.
20. Mysteries of malachite.
21. Do you know what the body of your fountain pen is made of?
22. Study of the influence of green spaces on the content of heavy metals in the soil.
23. The art of photography and chemistry.
24. Study of the features of the formation of insoluble silicates. Silicate garden and silicate jellyfish.
25. Study of the effect of iodine on the human body and determination of its content in food by iodometric titration.
26. Research chemical properties zinc and its effect on the human body.
27. History of receipt and production of aluminum.
28. How is phenol and formaldehyde converted into resin?
29. How to recognize the authenticity of milk?
30. What are polymers?
31. What molecules can be called giants?
32. What plastics are called semi-synthetic?
33. What polymers can bacteria synthesize?
34. What glass is called organic?
35. Which polymer is considered the most resistant?
36. Colloidal solutions and their role in human life.
37. Medical polymers.
38. Metals in human life.
39. Methane in our life.
40. World of metals through the eyes of a chemist, physicist and biologist.
41. Garbage crisis.
42. Oil - past, present, future.
43. Determination of the quality of honey.
44. Determination of the quality of bee honey.
45. Determination of the amount of vitamin C in lemon.
46. Determination of vitamin C content in juices and fruits.
47. Organic acids - food preservatives.
48. Organic acids as antioxidants.
49. Environmental protection. Water quality control.
50. Cleaning the surface of copper alloy.
51. Periodic system of chemical elements of DIMendeleev.
52. Food additives: harm or benefit?
53. Is film a polymer?
54. Why is Styrofoam so light?
55. Drugs household chemicals in our house.
56. Rare elements and their geography.
57. The role of inorganic substances in the life of living organisms.
58. Salt on the roads.
59. Means for washing dishes.
60. Means of protection against insects (insecticides and repellents).
61. Physical and chemical phenomena in nature.
62. Chemical laboratory in our house.
63. Chemical reactions in the service of man.
64. Chemistry in forensic examination.
65. Chemistry and art: what keeps painting?
66. Chemistry and cooking: what do they have in common?
67. Chemistry and transformations of alcohol.
68. Chemistry and transformations of sugar.
69. Chemistry and color. Natural and artificial dyes.
70. Chemistry of smoking.
71. Chemistry of drugs and drugs.
72. Dry cleaning at home.
73. What can be isolated electrical wire?
74. Lipstick examination.
75. Examination of the organoleptic properties of wheat bread.
76. Examination of shampoo.
Chemistry project topics for grade 9
1. Safety of essential oils.
2. Biological and food additives.
3. Pest control.
4. Effect of heavy metals on the activity of the catalase enzyme.
5. Effect of fluoride ion on tooth enamel.
6. The water we drink
7. Hydrogen as an alternative fuel.
8. Hydrogen.
9. The air we breathe
10. Everything about food from the point of view of a chemist
11. Does water have a memory?
12. Snow pollution.
13. Smells that heal (phytotherapy).
14. Manufacture of a thermocouple battery and temperature measurement.
15. Manufacturing homemade appliances to demonstrate the effect of a magnetic field on a current-carrying conductor.
16. Study of the impact of acid rain on the environment (plants, monuments).
17. Study of the composition and properties of anti-icing agents used on city roads.
18. Study of the enzymatic activity of biological fluids.
19. Study of the chemical basis of food additives.
20. Artificial cultivation of crystals, including pearls, diamonds.
21. Usage mineral fertilizers.
22. Use of petroleum products.
23. Study of the influence of the concentration of reactants, temperature and catalyst on the rate of a chemical reaction.
24. Examination of almond nuts for the content of cyanide ions.
25. Study of the physicochemical properties of starch.
26. Study of the chemical properties of aspirin and the study of its effect on the human body.
27. Study of the chemical composition of marmalade.
28. Study of the chemical composition of tea.
29. How to get electricity from chemical interactions of substances (lithium-nickel batteries and other types).
30. What chemical reactions convert a liquid into a fourth state of aggregation(plasma).
31. Carboxylic acids in human life.
32. Corrosion of iron in various environments.
33. Dyes - natural or artificial?
34. Is linden honey?
35. Methods of freezing water.
36. "People's" use of non-utilized chemical drums.
37. Science on guard of health. The influence of ultrasound on the human body and ultrasound diagnostics.
38. Adverse environmental consequences of heat engines.
39. Determining the quality of water in our reservoir.
40. Determination of the surface tension of water in the presence of various impurities.
41. Determination of the chemical composition of butter from different manufacturers.
42. Tea brewing optimization.
43. The discovery of PSCE by D. I. Mendeleev is an accident or regularity.
44. Cleaning and use Wastewater
45. Transmission mechanisms and their types.
46. Nutrition and health.
47. Truths and lies about tap water.
48. Natural and synthetic fibers.
49. Natural and synthetic dyes.
50. Natural and synthetic medicines.
51. Natural and synthetic detergents.
52. Production of soda.
53. Production of mirrors.
54. Development of the food industry.
55. Development of gunpowder, explosives and weapons.
56. Calculation of the current output of copper.
57. Rational nutrition (vitamins and trace elements).
58. Combustion reactions at work and in everyday life.
59. The role of metals in creating the historical face of the city.
60. Sugar in food
61. Composition and medicinal properties of natural mineral water.
62. Edible from inedible (about synthetic food).
63. Carbohydrates and their role and importance in human life.
64. Fertilizers - good or evil?
65. Is a pharmacist a physician or a chemist?
66. Enzymes - what is it?
67. The chemical essence of photography.
68. Chemical analysis of gasoline.
69. Chemistry and food
70. Chemistry and economics: the main nomenclature.
71. Chemistry of a spacecraft (air reserves in solid form, water purification).
72. Chemistry of pulp and paper production.
73. Electronic cigarettes, no.
74. Energy-saving lamps and the ecological crisis.
Mokrousovskaya average comprehensive school №1.
Scientific - research work in chemistry:
Shanaurova Tatiana,
10th grade students
Scientific adviser: Kokorina
Tatyana Sergeevna
chemistry teacher MSOSh №1.
With. Mokrousovo, 2010
Content
1.Introduction………………………………………………………3p.
2.Goals and objectives……………………………………………….….4p.
3.Classification……………………………………………….4-6p.
4.Properties and structure……………………………………………7-10p.
5.Receipt……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….
6.Our research………………………………………………………………………………………….
7.Application………………………………………………….19-26p.
8.Plastics…………………………………………………….27-33p.
9. Conclusion……………………………………………………34-35pp.
10.Appendix №1………………………………………………36-
11. Appendix №2………………………………………………
12. Appendix №3…………………………………………………
13. References…………………………………………..
Introduction
We chose chemical substances such as polymers as the topic of research work. The relevance of this topic is due to the fact that polymers are widely used in science, technology and other areas, modern life is unthinkable without them. Not a single industry can do without plastics (app. No. 1, fig. 1), chemical fibers (app. No. 1, fig. 2), rubbers and rubber based on them. It is difficult to imagine a modern car, from which all parts made of polymers are removed. Such a car is an unpainted metal frame, in which half of the equipment is missing, there are no tires, no battery, such a car, of course, will not go. Everyday life is unthinkable without polymer products from plastic wrap to dishes, as well as chewing gum, milk proteins, fish, meat and carbohydrates such as starch. And if we take the production of medicines, medical equipment, then we certainly cannot do without polymers. Having decided to become medical workers, we realized that the topic of polymeric materials is very relevant and necessary for us.
The term “polymeria” was introduced into science by I. Ya. Berzelius (Appendix No. 1, Fig. 3) in 1833 to denote a special type of isomerism, in which substances (polymers) having the same composition have different molecular weights, for example, ethylene and butylene, oxygen and ozone. This content of the term did not correspond to modern ideas about polymers. “True” synthetic polymers were not yet known at that time.
A number of polymers were apparently obtained as early as the first half of the 19th century. However, chemists then usually tried to suppress polymerization and polycondensation, which led to the “tarring” of the products of the main chemical reaction, i.e., in fact, to the formation of polymers (until now, polymers are often called “resins”). The first references to synthetic polymers date back to 1838 (polyvinylidene chloride) and 1839 (polystyrene).
The chemistry of polymers arose only in connection with the creation by A.M. Butlerov (Appendix No. 1, Fig. 4) of the theory of chemical structure. A.M. Butlerov studied the relationship between the structure and relative stability of molecules, which manifests itself in polymerization reactions. The science of polymers was further developed mainly due to the intensive search for ways to synthesize rubber, in which the largest scientists from many countries participated (G. Bushard, W. Tilden, the German scientist K. Garries, I.L. Kondakov, S.V. Lebedev and other). In the 1930s, the existence of free radical and ionic mechanisms of polymerization was proved. The work of W. Carothers played an important role in the development of ideas about polycondensation.
Purpose of the study:
To study the properties of chemical substances of polymers from various sources and find out the most important compounds used in nature, life, medicine and technology.
Tasks:
1. To study the use of polymers in medicine, various types technology, construction.
2. Conduct an experimental study of polymers widely used in everyday life, technology and medicine, as well as independently obtain some polymers.
3. Draw conclusions, prepare presentation materials and speak at the Science Day at school.
General characteristics and classification.
The polymer is called organic matter, whose long molecules are built from the same repeatedly repeating units of monomers.
The size of the polymer molecule is determined by the degree of polymerization n , those. the number of links in the chain. If n=10...20, the substances are light oils. With increasing P viscosity increases, the substance becomes waxy, and finally, at n=1000, a solid polymer is formed. The degree of polymerization is unlimited: it can be 10 4 , and then the length of the molecules reaches micrometers. The molecular weight of a polymer is equal to the product of the molecular weight of the monomer and the degree of polymerization. Usually it is within 10 3 ... 3*10 5 . Such a large length of molecules prevents their proper packing, and the structure of polymers varies from amorphous to partially crystalline. The proportion of crystallinity is largely determined by the geometry of the chains. The closer the chains fit, the more crystalline the polymer becomes. Of course, crystallinity, even at best, is imperfect.
Amorphous polymers melt in a temperature range that depends not only on their nature, but also on the length of the chains; crystalline have a melting point.
By origin, polymers are divided into three groups.
Natural are formed as a result of the vital activity of plants and animals and are found in wood, wool, and leather. These are protein, cellulose (appendix No. 1, fig. 5), starch, shellac, lignin, latex.
Typically, natural polymers are subjected to isolation, purification, modification, in which the structure of the main chains remains unchanged. The product of such processing are artificial polymers. Examples are natural rubber, made from latex, celluloid, which is nitrocellulose plasticized with camphor to increase elasticity.
natural and artificial polymers have played a large role in modern technology, and in some areas they remain indispensable to this day, for example, in the pulp and paper industry. However, a sharp increase in the production and consumption of organic materials occurred due to synthetic polymers - materials obtained by synthesis from low molecular weight substances and have no analogues in nature. The development of chemical technology of macromolecular substances is an integral and essential part of modern scientific and technological revolution. Not a single branch of technology, especially new ones, can do without polymers. According to the chemical structure, polymers are divided into linear, branched, network and spatial. The molecules of linear polymers are chemically inert with respect to each other and are interconnected only by van der Waals forces. When heated, the viscosity of such polymers decreases and they are able to reversibly transform first into a highly elastic and then into a viscous flow state (Fig. 1). Since the only effect of heating is a change in plasticity, linear polymers are called thermoplastic. It should not be thought that the term "linear" means straight, on the contrary, they are more characteristic of a serrated or helical configuration, which gives such polymers mechanical strength.
Thermoplastic polymers can not only be melted, but also dissolved, since van der Waals bonds are easily torn under the action of reagents.
Branched (grafted) polymers are stronger than linear ones. Controlled chain branching is one of the main industrial methods for modifying the properties of thermoplastic polymers.
The network structure is characterized by the fact that the chains are connected to each other, and this greatly limits the movement and leads to a change in both mechanical and chemical properties. Ordinary rubber is soft, but when vulcanized with sulfur, covalent bonds of the S-0 type are formed, and the strength increases. The polymer can acquire a network structure and spontaneously, for example, under the action of light and oxygen, aging occurs with a loss of elasticity and performance. Finally, if the polymer molecules contain reactive groups, then when heated, they are connected by many cross-linked strong bonds, the polymer turns out to be cross-linked, i.e., it acquires a spatial structure. Thus, heating causes reactions that dramatically and irreversibly change the properties of the material, which acquires strength and high viscosity, becomes insoluble and infusible. Due to the high reactivity of molecules, which manifests itself with increasing temperature, such polymers are called thermosetting. It is easy to imagine that their molecules are active not only in relation to each other, but also to the surfaces of foreign bodies. Therefore, thermosetting polymers, in contrast to thermoplastic ones, have a high adhesive ability even at low temperatures, which allows them to be used as protective coatings, adhesives, and binders in composite materials.
Thermoplastic polymers are obtained by the reaction polymerization, flowing according to the scheme pM-->M P(Fig. 2), where M - monomer molecule, M P- a macromolecule consisting of monomer units, P- degree of polymerization.
During chain polymerization, the molecular weight increases almost instantly, the intermediate products are unstable, the reaction is sensitive to the presence of impurities and, as a rule, requires high pressures. It is not surprising that such a process is impossible under natural conditions, and all natural polymers were formed in a different way. Modern chemistry created a new tool - the polymerization reaction, and thanks to him a large class of thermoplastic polymers. The polymerization reaction is realized only in complex equipment of specialized industries, and the consumer receives thermoplastic polymers in finished form.
Reactive molecules of thermosetting polymers can be formed in a simpler and more natural way - gradually from monomer to dimer, then to trimer, tetramer, etc. Such a combination of monomers, their "condensation", is called the reaction polycondensation; it does not require high purity or pressures, but is accompanied by a change in the chemical composition, and often by the release of by-products (usually water vapor) (Fig. 2). It is this reaction that occurs in nature; it can be easily carried out by only a slight heating in the most simple conditions up to home. Such high manufacturability of thermosetting polymers provides ample opportunities to manufacture various products at non-chemical enterprises, including radio plants.
Regardless of the type and composition of the starting materials and production methods, materials based on polymers can be classified as follows: plastics, fibers, laminates, films (Appendix No. 1, Fig. 6), coatings, adhesives (Appendix No. 1, Fig. 7 ).
Properties of polymers.
Mechanical properties.
One of the main features of polymers is that individual chain segments (segments) can move by turning around the bond and changing the angle (Fig. 3). Such a displacement, in contrast to the stretching of bonds during elastic deformation of true solids, does not require much energy and occurs at a low temperature. These types of internal movement - change of conformations, unusual for other solids, give polymers a similarity to liquids. At the same time, the large length of curved and helical molecules, their branching, and cross-linking make it difficult to shift, as a result of which the polymer acquires the properties of a solid body.
Some polymers in the form of concentrated solutions and melts are characterized by the formation under the influence of a field (gravitational, electrostatic, magnetic) of a crystalline structure with parallel ordering of macromolecules within a small volume-domain. These polymers are the so-called liquid crystals - are widely used in the manufacture of LEDs (Appendix No. 1, Fig. 8)..
Polymers, along with the usual elastic deformation, are characterized by its original look- highly elastic deformation, which becomes predominant with increasing temperature. The transition from a highly elastic state to a glassy state, characterized only by elastic deformation, is called vitrification. Below the glass transition temperature Tst the state of the polymer is solid, vitreous, highly elastic, superelastic. If the glass transition temperature is higher than the operating temperature, then the polymer is used in the glassy state, if Tst
For strong (structural) polymers, the stretching curve is similar to that for metals (Fig. 4). The most elastic polymer-elastomers (rubbers) have an elastic modulus E=10 MPa . As can be seen, even high-modulus polymers are inferior in rigidity to metals by tens and hundreds of times. This shortcoming can be largely overcome by introducing fibrous and sheet fillers into the polymer.
A feature of polymers is also that their strength properties depend on time, i.e., the ultimate strain is not established immediately after the application of the load. Such a slow reaction to mechanical stresses is explained by the inertia of the process of changing conformations, which can be represented using the model (Fig. 4). For polymers in a highly elastic state, Hooke's law in its simplest form does not apply, i.e., stress is not proportional to deformation. Therefore, conventional methods for testing mechanical properties in relation to polymers can give ambiguous results. For the same reason, engineering computational methods for designing parts from polymers do not yet exist and the empirical approach prevails.
Thermophysical properties.
The range of temperatures at which polymers can be operated without deteriorating their mechanical properties is limited. The heat resistance of most polymers, unfortunately, is very low - only 320 ... 400 K and is limited by the onset of softening (deformation resistance). In addition to the loss of strength, an increase in temperature can also cause chemical changes in the composition of the polymer, which manifest themselves as weight loss. The ability of polymers to maintain their composition when heated is quantitatively characterized by the relative weight loss when heated to operating temperature. The acceptable value of weight loss is 0.1 - 1%. Polymers that are stable at 500 K are considered heat-resistant, and at 600–700 K they are considered highly heat-resistant. Their development, expansion of production and use bring a great economic effect.
Chemical properties.
The chemical resistance of polymers is determined in different ways, but most often by the change in mass when a sample is kept in an appropriate medium or reagent. This criterion, however, is not universal and does not reflect the nature of chemical changes (destruction). Even the standards (GOST 12020-66) provide only its qualitative assessments according to the point system. Thus, polymers that change their mass by 3–5% in 42 days are considered stable, by 5–8% relatively stable, and more than 8–10% unstable. These limits depend on the type of product and its purpose.
Polymers are characterized by high resistance to inorganic reagents and less resistance to organic ones. In principle, all polymers are unstable in environments with pronounced oxidizing properties, but among them there are also those whose chemical resistance is higher than that of gold and platinum. Therefore, polymers are widely used as containers for ultra-pure reagents and water, protection and sealing of radio components, and especially semiconductor devices (Appendix No. 1, Fig. 9) and ICs.
Another feature of polymers is that they are not vacuum tight by nature. Molecules of gaseous and liquid substances, especially water, can penetrate into microvoids formed during the movement of individual polymer segments. even if its structure is defect-free.
Polymers play the role of protecting metal surfaces from corrosion in cases where:
thick layer
the polymer has a passivating effect on the active (defective) centers of the metal, thereby suppressing the corrosive effect of moisture penetrating to the metal surface.
For most polymers, aging- an irreversible change in the structure and properties, leading to a decrease in their strength. The set of chemical processes that lead under the action of aggressive media (oxygen, ozone, solutions of acids and alkalis) to change the structure and molecular weight is called chemical destruction. Its most common type - thermal-oxidative degradation - occurs under the action of oxidizing agents at elevated temperatures. During degradation, not all properties degrade equally: for example, during the oxidation of organosilicon polymers, their dielectric parameters deteriorate insignificantly, since Si is oxidized to an oxide, which is a good dielectric.
electrical properties.
As a rule, polymers are dielectrics, which are the best in modern technology in many respects. The value of specific volume resistance p v depends not only on the structure, but also on the content of ionized impurities - anions Cl-, F-, I-, cations H +, Na + and others, which are most often introduced into the resin along with hardeners, modifiers, etc. d. Their concentration may be high if the curing reactions have not been completed. The mobility of these ions increases sharply with increasing temperature, which leads to a drop in resistivity. The presence of even very small amounts of moisture can also significantly reduce the volume resistivity of polymers. This is because the impurities dissolved in water dissociate into ions, in addition, the presence of water contributes to the dissociation of the molecules of the polymer itself or the impurities present in it. At high humidity, the specific surface resistance of some polymers decreases significantly, which is due to the adsorption of moisture.
The structure of macromolecules, the nature of their thermal motion, the presence of impurities or special additives affect the type, concentration and mobility of carriers. Thus, the specific resistance of polyethylene increases by 10-1000 times after purification from low molecular weight impurities. Sorption of 0.01-0.1% water by polystyrene leads to a decrease in resistivity by a factor of 100-1000.
The permittivity more or less sharply depends on two main external factors: temperature and frequency of applied voltage. In nonpolar polymers, it only slightly decreases with increasing temperature due to thermal expansion and a decrease in the number of particles per unit volume. In polar polymers, the permittivity first rises and then falls, and the maximum usually occurs at the temperature at which the material softens, i.e., lies outside the operating conditions.
For polymers, as for some other dielectrics, the processes of accumulation of surface charges are characteristic - electrification . These charges arise as a result of friction, contact with another body, electrolytic processes on the surface. The mechanisms of electrification are not fully understood. One of them is the appearance of the so-called double layer upon contact of two bodies, which consists of layers of positive and negative charges located opposite each other. It is also possible to form a thin water film on the surface of contacting materials, in which there are conditions for the dissociation of impurity molecules. Upon contact or friction, the double-layer water film is destroyed and part of the charges remains on the separated surfaces. The electrolytic mechanism of charge accumulation during contact takes place in polymeric materials, on the surface of which there can be low-molecular ionic substances - catalyst residues, dust, moisture.
Technological properties.
The belonging of polymers to thermoplastic or thermoset species largely determines the ways of their processing into products. The ratio of their output is approximately 3:1 in favor of thermoplastic materials, but it should be borne in mind that thermosetting polymers are usually used in a mixture with fillers, the proportion of which can reach 80%. Therefore, in finished products, the ratio turns out to be the opposite: most of them are thermoplastics (Appendix No. 1, Fig. 10) .. This is due to the high manufacturability of phenol-formaldehyde, polyester, but especially epoxy resins. In the production of the latter, the production of a polymer can be stopped at the initial stage, when the molecular weight is only 500 - 1000. Such substances along the chain length are average between monomers and polymers, which have low viscosity, are called oligomers. It was their appearance that made a revolution in the 60s in the technology of processing polymers into products, which was previously based on the use of pressure.
The advantage of oligomers (Appendix No. 1, Fig. 11)- low viscosity - makes it possible to form products with minimal pressing force or without it at all, under the action of its own weight. Moreover, even when mixed with fillers, oligomers retain fluidity, which makes it possible to throw the material onto the surface of the layout without applying pressure, to obtain large-sized parts of complex shape. The low viscosity of the oligomers also makes it possible to impregnate fabric sheets, and their bonding under pressure and curing is the basis for the production of laminated bases for printed circuit boards. Oligomers are more suitable than any other polymer for impregnating and bonding components, especially when pressure is unacceptable. To reduce the viscosity, additives can be introduced into the oligomer, which increase plasticity, incombustibility, biological stability, etc. We have studied such oligomers as textolite and glass-textolite. Phenol-formaldehyde resin was obtained by ourselves and a piece of oligomer with fillers was made from it.
The resin used for these purposes is most often a mixture of various substances, which is not always convenient to prepare on site, at the consumer enterprise, due to the need for mixing and dosing equipment, fire hazard, toxicity, and other restrictions. Therefore, it has become widespread compounds (Appendix No. 1, Fig. 12)- mixtures of oligomers with hardeners and other additives, completely ready for use and having sufficient viability at normal temperature. Compounds - liquid or solid low-melting materials are formed into a product, after which curing and formation of a spatial structure is carried out at an elevated temperature.
If products based on thermosetting resins are produced by hot pressing, then a composition containing, in addition to resin, chopped glass fiber (Appendix No. 1, Fig. 13) or some powdered filler and other additives is prepared in advance, and it is supplied to the consumer in the form of granules or powder, called pressing material (sometimes press powder). The technological properties of both thermosetting and thermoplastic polymers are characterized by fluidity (the ability to viscous flow), shrinkage (reduction of the linear dimensions of products in relation to the dimensions of the forming tool), and tabletability (press powders).
Unusual properties of mixtures of liquid resins with finely dispersed fillers, the particles of which have an asymmetric shape (talc, mica flour, aerosil-colloidal SiO 2), are manifested in the fact that in a calm state they have a high viscosity characteristic of gels, and under mechanical action (mixing or shaking) become liquid. Mixtures with this property are called thixotropic . Thixotropic compounds are widely used to protect radio components by the simplest method - dipping. The viscosity of the compound is reduced by vibration (no heating required). When removing a part from a liquid mixture with simultaneous shaking, its excess drains, and the remaining part of it gels again after removal, forming a coating that is uniform in thickness and does not contain bubbles and swellings, since the product and the compound do not heat up. The thixotropic properties of some polymer compositions are also used in the manufacture of specialty paints and adhesives.
Receipt.
Polymerization and polycondensation
Synthetic polymers are obtained as a result of polymerization and polycondensation reactions.
Polymerization- this is the process of connecting with each other a large number of monomer molecules due to multiple bonds (C \u003d C, C \u003d O, etc.) or opening cycles containing heteroatoms (O, N, S). During polymerization, the formation of low molecular weight by-products usually does not occur, as a result of which the polymer and monomer have the same elemental composition:
n CH 2 \u003d CH 2 → (-CH 2 -CH 2 -) n
copolymerization
paste from my presentation)
polycondensation- this is the process of connecting with each other the molecules of one or more monomers containing two or more functional groups (OH, CO, COC, NHS, etc.) capable of chemical interaction, in which low molecular weight products are cleaved. The polymers obtained by the polycondensation method do not correspond in elemental composition to the initial monomers.
The polymerization of monomers with multiple bonds proceeds according to the laws of chain reactions as a result of the breaking of unsaturated bonds. A macromolecule during chain polymerization is formed very quickly and immediately acquires finite dimensions, that is, it does not increase with an increase in the duration of the process.
Polymerization of monomers of a cyclic structure occurs due to ring opening and in some cases bakes not according to a chain, but according to a stepwise mechanism. A macromolecule during stepwise polymerization is formed gradually, i.e., first a dimer is formed, then a trimer, etc., so the molecular weight of the polymer increases with time.
polycondensation, the process of obtaining polymers from bi- or polyfunctional compounds ( monomers), accompanied by the release of a side low molecular weight substance (water, alcohol, hydrogen halide, etc.). A typical example of polycondensation is polyester synthesis:
n+ n HOOCA'COOH Û [¾OAOOCA'CO¾] n + 2 n H2O
where A and A "- residues, respectively, of glycol (-O-CH 2 -CH 2 -O-) and dicarboxylic acid (-CO-C 6 H 4 -CO-). The process is called homopolycondensation if it involves the minimum possible for a given case, the number of types of monomers.Most often this number is 2, as in the above reaction, but it can also be one, for example:
n H 2 NACOOH Û [¾HNACO¾] n + n H2O.
If, in addition to the monomers necessary for this reaction, at least one more monomer is involved in the polycondensation, the process is called copolycondensation, polycondensation, which includes only bifunctional compounds, leads to the formation of linear macromolecules and is called linear. If molecules with three or more functional groups participate in polycondensation, three-dimensional structures are formed, and the process is called three-dimensional polycondensation. In cases where the degree of completion of polycondensation and the average length of macromolecules are limited by the equilibrium concentrations of reactants and reaction products, polycondensation is called equilibrium (reversible). If the limiting factors are not thermodynamic, but kinetic factors, polycondensation is called non-equilibrium (irreversible).
Polycondensation is often complicated by side reactions, which can involve both the initial monomers and their polycondensation products ( oligomers and polymers). Such reactions include, for example, the interaction of a monomer or oligomer with a monofunctional compound (which may be present as an impurity), intramolecular cyclization, and destruction of macromolecules of the resulting polymer. The competition (in terms of rates) of polycondensation and side reactions determines the molecular weight, yield, and molecular weight distribution of the polycondensation polymer.
Polycondensation is characterized by the disappearance of the monomer in the early stages of the process and a sharp increase in molecular weight with a slight change in the depth of the process in the region of more than 95% conversion.
A necessary condition for the formation of high-molecular polymers during linear polycondensation is the equivalence of the initial functional groups reacting with each other.
Polycondensation is carried out in three different ways: in the melt, when the mixture of starting compounds is heated for a long time at a temperature 10–20 °C higher than the melting (softening) temperature of the resulting polymer; in solution, when the monomers are in the same liquid phase in a dissolved state; at the interface between two immiscible liquids, in each of which one of the initial compounds is dissolved (interfacial polycondensation).
Polycondensation processes play an important role in nature and technology. Polycondensation or similar reactions underlie the biosynthesis of the most important biopolymers - proteins, nucleic acids, cellulose and others. Polycondensation is widely used in industry to obtain polyesters ( polyethylene terephthalate, polycarbonates, alkyd resins), polyamides, phenol-formaldehyde resins, urea-formaldehyde resins, some silicone polymers and others. In 1965-70, polycondensation acquired great importance in connection with the organization of industrial production of a number of new, including heat-resistant, polymers (polyarylates, aromatic polyimides, polyphenylene oxides, polysulfones, etc.).
Our research
1. Test for melting.
First, let's find out if the plastic under study melts at all. To do this, we heated the test samples on an asbestos support. Depending on what will happen to the plastic, we will be able to classify it as a thermo- or thermoset. We took 5 samples for research: polyvinyl chloride, polytetrafluoroethylene, polyethylene, polyethylene high pressure, textolite.
Of the test samples, it was found that 3 samples melt (polyvinyl chloride, high-density polyethylene, polyethylene), and therefore they belong to thermoplastics. Two other samples belong to thermoplastics, as they do not melt. (Appendix No. 2, Fig. 1)
2.softening temperature.
We inserted samples of plastic - strips 5-10 cm long and 1 cm wide - into an iron crucible filled with dry sand. The crucible was gradually heated with a small burner flame. A thermometer was inserted into the sand. When the strips were bent, according to the readings of the thermometer, the softening point was noticed. We determined the melting point of polyethylene - 117º, plastic - 93º, polystyrene - 83º, polyvinyl chloride - 77º. (Appendix No. 2, Fig. 2)
3.Fluidity temperature.
The pour point was determined similarly, i.e. the temperature range in which plastics become fluid. We have observed that phenol-formaldehyde resin and the plastic based on it decompose before the pour point is reached. From this we can conclude that products made of such plastics cannot be kept near stoves and heating appliances. As they decompose, they release toxic chemicals (phenol, formaldehyde) into the room (Appendix No. 2, Fig. 3)
4.combustion test.
We took a sample of plastic with crucible tongs and placed it briefly in the upper part of the high-temperature zone of the burner flame. When the plastic was taken out of the flame, we looked to see if it would continue to burn. At the same time, attention was paid to the color of the flame; noticed whether soot or smoke is formed, whether the fire crackles, whether the plastic melts with the formation of drops. Polyethylene, polypropylene, polymethamethylacrylate with characteristic crackling, polyvinyl chloride (soot) burn well, studied by us, polytetrafluoroethylene did not burn. According to the research, a table has been compiled (Appendix No. 2, Fig. 4)
5. Research of decomposition products.
In small test tubes, crushed samples of various plastics were heated and attention was drawn to the smell, color, and reaction to litmus paper of the resulting decomposition products. So polyvinyl chloride decomposes with the release of hydrogen chloride (Appendix No. 2, Fig. 5)
6.Chemical resistance.
Plastic samples were immersed in dilute and concentrated solutions of acids and alkalis. To study the swelling of plastic - polystyrene, placed in various liquids: - in water, acids, alkalis, methylbenzene (toluene). The tubes were left for 5 days. To reduce the evaporation of liquids, plugged the test tubes with stoppers. As a result, polystyrene was dissolved only in toluene, and remained unchanged in the other test tubes. We conclude that polystyrene products are resistant to inorganic reagents and unstable to organic solvents. The same experiment was carried out with polyethylene and polypropylene. Here they found out that they are stable in organic and inorganic substances. Therefore, they are widely used in the chemical industry. (Appendix No. 2, Fig. 6).
7. Obtaining cellulose nitrate.
Cotton wool was nitrated in a 1:2 mixture of nitric and sulfuric acid, washed and dried. We have thus received dinitrate and trinitrate cellulose. (Appendix No. 2, Fig. 7).
8. Further processing of cellulose dinitrate.
To get acquainted with the properties of the resulting dinitrate, small pieces of untreated and nitrated cellulose were introduced into the flame with crucible tongs. We have seen that cellulose dinitrate burns slightly faster than the original cellulose.
We heat a small sample of dinitrate in a test tube over low heat. The substance decomposes producing brown fumes of nitric oxide(IV) NO2.
Approximately one third of the obtained cellulose dinitrate was placed in a test tube and a mixture of 2 parts of ether and 1 part of alcohol (denatured alcohol) was added. The tube was loosely stoppered. Depending on the amount of solvents, we can get a solution from dilute to very viscous. This solution is called collodion.
Spread a small amount of collodion on a small part of the arm and let it evaporate. The place on which the solution was applied is strongly cooled (the heat of evaporation is taken away). What remains is a transparent film of collodion that can serve as a “liquid plaster” for sealing minor wounds and abrasions. Collodion is also included as a film-forming agent in some varnishes. Along with it, cellulose trinitrate is also used for this purpose. Fast-drying colored nitro-varnishes and colorless zapon-lakshiroko are widely produced and used to coat various products made of wood, metal, and plastic.
The remainder of the cellulose dinitrate in the beaker was wetted with alcohol. At the same time, a little camphor was dissolved in alcohol in another glass - so much that in the final product it was 20-25% by weight. We will add cellulose dinitrate moistened with alcohol in small portions to the camphor solution, mixing thoroughly. The resulting slurry was applied in a not too thick layer on a metal or glass plate and left in a moderately warm place so that the alcohol evaporated. A rough layer is formed on the surface, similar to the coating of a photographic plate. This celluloid.
You can level its surface - you just have to put a heated metal plate on top. Since the softening point of celluloid is 70-80°C, its shape can be easily changed in hot water.
A strip of the resulting celluloid was introduced into the flame with crucible tongs. It ignites at 240 ° C and burns very intensely, greatly increasing the temperature of the flame and coloring it in yellow. In addition, when burning, the smell of camphor appears. (Appendix No. 2, Fig. 8)
9. Experiments with cellulose trinitrate
While we were experimenting with cellulose dinitrate, the trinitrate was air-dried. In appearance, this “cotton wool” has not changed after nitration, but if it is set on fire, it will burn out instantly - unlike the original cotton wool.
When treated with a mixture of alcohol and ether (1: 1), ethyl ethanate (ethyl acetate), cellulose trinitrate swells or, in other words, gelatinized. When the resulting mass is applied to the plate, a film is formed, which, when ignited, quickly burns out without residue.
10. Let's make parchment paper.
A flat porcelain cup was filled halfway with a solution of sulfuric acid. To prepare it in a thin stream, add 30 ml of concentrated sulfuric acid to 20 ml of water. Then the solution must be cooled - if possible to 5 ° C.
With plastic tweezers - place six samples of filter paper numbered with a pencil (strips 1 cm wide) for 5, 10, 15, 20, 25 and 30 seconds in acid. After that, the samples were quickly transferred to a large glass of water, to which a little ammonia. Left them in this water for a long time, and then dried. The previously soft and porous paper becomes hard and smooth. If we measure the strips, we will find that they have decreased in size.
Let's test the strength of our parchment paper» to break. To do this, stepping back from the edge of the strip by 0.5 cm, bend its end and put it on the rest. We will bend the other end in the same way. We attach two clamps to the reinforced edges and fix the strip in a tripod. In the middle we will hang a load on it.
Untreated paper (a 1 cm wide strip from a round filter) will most likely tear at a load of 450 g, while a sample treated with sulfuric acid will withstand a load of 1750 g. Not too thick paper was taken for experiments. In industry, paper 0.1-0.2 mm thick is used for the same purpose.
Using guide rollers made of glass and rubber, it is pulled through a bath of 73% sulfuric acid for 5-20 seconds. Thanks to special device, which holds the paper in a stretched state, while preventing excessive shrinkage.
fiber material for the manufacture of suitcases is obtained by treating paper with a solution of zinc chloride. The "parchmented" strips of paper are wound onto a drum where the layers are pressed together. The resulting roll is cut into plates, once again treated with water and then pressed.
To prepare a solution of zinc chloride, slightly dilute concentrated hydrochloric acid. We will add zinc to it until the acid stops reacting with it.
In the solution, which we separated by decantation from excess zinc, we lower the filter paper for 5-10 minutes. After that, it was thoroughly washed with water.
During these processes, which are called parchment, the paper swells a lot. Long cellulose molecules, as a result of partial cleavage, turn into the so-called hydrocellulose, and with longer processing - into a product with even shorter chains - amyloid.
As a result, the initially fluffy fibrous structure of the paper changes to a large extent, and drying is accompanied by shrinkage.
Under the action of ethanoic (acetic) acid and its anhydride, cellulose is converted into a soluble form - ethanate ( acetate) cellulose (Another name is also used - cellulose acetate).
The latter is used to produce plastics, and its solutions in organic solvents are used to produce varnishes, adhesives, photographic and film films, and fibers. Cellon- the material from which a non-combustible film is made - consists of cellulose ethanate and camphor (Appendix No. 2, Fig. 9).
11.Phenol-formaldehyde varnishes and adhesives
In a small beaker, 10 g of phenol were carefully heated on a water bath with 15 ml of formalin and 0.5 ml of a 30% sodium hydroxide solution ( caustic soda). After prolonged heating, the mass became viscous. When the sample taken with a glass rod began to solidify upon cooling, heating was stopped and part of the resole resin obtained in the beaker was transferred to a test tube filled one-third with denatured alcohol or methanol.
This will dissolve the resin. With the resulting solution, we can varnish small metal objects.
To prevent the varnish from being sticky, it will still need to be cured. To do this, the lacquered object is carefully heated to no higher than 160 ° C - by a stream of air heated by a burner flame, or in an oven. A stovetop oven is also suitable.
After firing, the varnish adheres reliably to the metal, it is resistant to acids and alkalis, hard, bending and impact resistant. Such varnishes in many industries have replaced the old natural varnishes. For varnishing wooden products, self-curing varnishes are used.
Resole phenol-formaldehyde resins can also stick together wood with wood or with metal. The bond is very strong and this method of bonding is now being used more and more, especially in the aviation industry.
Made again viscous resole resin by heating a mixture of phenol, formalin and sodium hydroxide solution. This resin was used to glue two thin wooden planks together. To do this, we smear one of them with the resulting resin, and apply concentrated hydrochloric acid to the other.
Press the boards tightly against each other, hold for several minutes in a stream of hot air or in a drying cabinet and then let cool. Hydrochloric acid serves as a hardener in this experiment and turns the resin into resit. The boards stick together very firmly.
In industry, bonding with phenol-based resins is used in the manufacture of plywood and wood-fiber plastics. In addition, such resins are successfully used for the manufacture of brushes and brushes, and in electrical engineering they perfectly glue glass to metal in incandescent lamps, fluorescent lamps and radio lamps (Appendix No. 2, Fig. 10).
12. Production of foam.
In a large test tube, 3 g of urea was dissolved in the most concentrated (40%) formalin. In another test tube, mix 0.5 ml of shampoo with 2 drops of 20% hydrochloric acid, add the solution from the first test tube and shake the resulting mixture until a rich foam forms.
The test tube was then heated on a low flame. At the same time, the foam hardened. Wait 10 minutes, heat the test tube slightly again, let it cool and then break it.
We will get a solid white foam, though with larger pores than the one that the industry produces (Appendix No. 2, Fig. 11).
13. Production of urea-formaldehyde resin.
The production of urea-formaldehyde resin is basically the same as the experience just described. The test tube was filled one third with a saturated solution of urea in formalin, 2 drops of 20% hydrochloric acid were added, and the mixture was heated over low heat to a boil. Then it boils spontaneously, eventually becomes cloudy and quickly thickens, acquiring the consistency of rubber.
The tube was kept for at least 20 minutes in a boiling water bath. In this case, the urea-formaldehyde resin is cured. Having broken the test tube, we will extract a very solid mass from it - from transparent to almost white.
Urea-formaldehyde plastics are used for the manufacture of household goods - dishes, handles, buttons, cases, etc. If these resins are obtained in a neutral environment, then condensation stops at the resol stage. The resulting syrupy mass is soluble in water. This solution is known as synthetic carbamide glue (In our country, K-17 brand glue, etc.) (appendix No. 2, fig. 12).
14. Prepare urea glue
In a round-bottomed flask with a reflux condenser, a mixture of 15 g of urea, 25 g of 30% formalin and 3 drops of concentrated sodium hydroxide solution was heated to a boil over low heat. After 15 minutes, the heating was stopped and the mass was observed to see if it became viscous. This state was reached, and we diluted it with a very small amount of water. With the resulting mass, we thickly smear one side of the wooden plank, and soak the other plank with a hardener.
We will conduct three experiments: we will test hydrochloric and methane (formic) acids as a hardener, as well as a concentrated solution of ammonium chloride. When using ammonium chloride, the adhesive should not be applied too thickly. Ammonium chloride decomposes when heated, forming hydrogen chloride and ammonia. This leads to cracks and sticking.
The samples were pressed tightly together. Bonding lasts 15-20 hours. The process can be accelerated by heating the samples for at least 30 minutes at 80-100 °C. In the laboratory, it is best to use an oven for this. Carbamide glue is well suited for gluing laminated wood, plywood, fiber, making models, etc. The most important property of the resulting adhesive joints is their resistance to cold and hot water (Appendix No. 2, Fig. 13).
The use of polymers.
Polymers in agriculture
Today we can talk about at least four main areas of use of polymeric materials in agriculture. Both in domestic and in world practice, the first place belongs to films. Thanks to the use of perforated mulching film in the fields, the yield of some crops increases up to 30%, and the ripening time is accelerated by 10-14 days. The use of polyethylene film for waterproofing the created reservoirs provides a significant reduction in the loss of stored moisture. Covering haylage, silage, roughage with a film ensures their best preservation even in adverse weather conditions. But the main area of use of film polymer materials in agriculture - the construction and operation of film greenhouses (Appendix No. 1, Fig. 14). At present, it has become technically possible to produce film sheets up to 16 m wide, and this makes it possible to build film greenhouses up to 7.5 m wide at the base and up to 200 m long. In such greenhouses, all agricultural work can be carried out mechanized; moreover, these greenhouses allow you to grow products all year round. In cold weather, greenhouses are heated again with the help of polymer pipes laid in the soil to a depth of 60-70 cm.
From the point of view of the chemical structure of polymers used in greenhouses of this kind, one can note the predominant use of polyethylene, non-plasticized polyvinyl chloride and, to a lesser extent, polyamides. Polyethylene films are characterized by better light transmission, better strength properties, but worse weather resistance and relatively high heat loss. They can only serve properly for 1-2 seasons. Polyamide and other films are still used relatively rarely.
Another area of wide application of polymeric materials in agriculture is land reclamation. Here and various forms of pipes and hoses for irrigation, especially for the most progressive drip irrigation at present; here and perforated plastic pipes for drainage. It is interesting to note that the lifetime plastic pipes in drainage systems, for example, in the Baltic republics, 3-4 times longer than the corresponding ceramic pipes. In addition, the use of plastic pipes (Appendix No. 1, Fig. 15), especially from corrugated PVC, makes it possible to almost completely eliminate manual labor when laying drainage systems.
The other two main areas of use of polymeric materials in agriculture are construction, especially livestock buildings, and mechanical engineering.
In this section you can find interesting chemistry project topics. The leader should pay attention to the level of complexity of a particular topic and its comparison with the level of knowledge of the student. The research process involves the consultation of the teacher and the selection of literature by him.
We recommend carefully choosing interesting Topics research work in chemistry students in grades 7, 8, 9, 10 and 11 and determine the topic that suits them according to complexity, interest and their own hobbies.
Also, you can choose the current topic of the project in chemistry of a less complex level, expand or generalize it in the future.
The topics of research papers in chemistry presented to schoolchildren are relevant and imply research and study of new, more in-depth information on the subject. In the future, the knowledge gained can be applied in chemistry lessons, as well as taken as a basis in subsequent studies. Through the links you can find research topics on the subject of chemistry for high school students.
Topic data research projects in chemistry will be of interest to students of grades 7, 8, 9, 10 and 11 who are fond of chemistry, conducting various interesting experiments and experiments who want to learn and understand, find answers to their questions in the process of exciting research.
The topics below are sorted alphabetically, they are exemplary and basic for use in the research activities of students in the subject of chemistry.
Research Topics in Chemistry
Sample topics for research projects in chemistry:
Highway, snow, soil, plants.
Car as a source of chemical pollution of the atmosphere.
Automobile fuel and its application.
Agronomy. The effect of mineral fertilizers.
Nitrogen in food, water and the human body.
Nitrogen and its compounds
Nitrogen as a biogenic element.
Watercolor paints. Their composition and production.
Aquarium as a chemical and biological object of study.
Activated carbon. adsorption phenomenon.
Actinides: a look from the past into the future.
Diamond is an allotropic modification of carbon.
Diamonds. Artificial and natural growth.
Alchemy: myths and reality.
Aluminum is the metal of the 20th century.
Aluminum and its welding.
Aluminum in the kitchen: a dangerous enemy or a faithful assistant?
Aluminum. aluminum alloys.
Spring water quality analysis.
Analysis of drugs.
Analysis of soft drinks.
Analysis of the content of ascorbic acid in some currant varieties.
Chips analysis.
water anomalies.
Antibiotics.
Antiseptics.
Anthropogenic impact of wastewater on spring waters.
The aroma of health.
Aromatherapy as a way to prevent colds.
Aromatherapy.
Flavorings based on esters.
Aromatic oils are a priceless gift of nature.
Aromatic essential oils and their uses.
Fragrances, scents, vibes.
Ascorbic acid: properties, physiological action, content and dynamics of accumulation in plants.
Aspirin - friend or foe?
Aspirin - good or bad.
Aspirin as a preservative.
Aspirin: for and against.
Aerosols and their application in medical practice.
Proteins are the basis of life.
Proteins and their importance in human nutrition.
Proteins and their nutritional value.
Proteins as natural biopolymers.
Benzopyrene is a chemical and environmental problem of our time.
Biogenic classification of chemical elements.
Biologically active substances. Vitamins.
Dietary supplements: profanation or benefit?
Biorol vitamins.
noble gases.
Paper and its properties.
Sandwich with iodine, or the whole truth about salt.
Would there be life on Earth without the existence of iron?
Household filters for purification of tap water and a method for their regeneration.
In the world of acids.
In the world of metal corrosion.
in the world of polymers.
IN wonderful world crystals.
What is the taste of bread?
The most important indicator of the ecological state of the soil is pH.
The great secret of water.
The great scientist M.V. Lomonosov.
Great Britain in the life and work of D.I. Mendeleev.
Topics of projects in chemistry (continued)
Approximate topics of research papers in chemistry:
Types of chemical bond.
Vitamin C and its importance.
Vitamins in human life.
Vitamins and vitamin deficiency.
Vitamins and human health.
Vitamins as the basis of life of living organisms.
Contribution of D.I. Mendeleev in the development of agrochemistry, its significance for modern agriculture.
Contribution of D.I. Mendeleev in the development of the oil industry.
Contribution of M.V. Lomonosov in the development of chemistry as a science.
Influence road transport on the degree of air pollution.
The effect of metals on the female body.
Water is number one.
Water is a familiar and unusual substance.
Water is the basis of life.
The water is amazing and amazing.
Water: death or life? Study of water quality in reservoirs and water supply.
Hydrogen in industry, production and marketing.
Hydrogen indicator in our life.
Air is a natural mixture of gases.
The air we breathe.
Air is invisible.
All secrets of amber.
Isolation of tartaric acid from the studied grape variety.
Growing at home single crystals from a saturated solution of salts and alum.
Growing a crystal at home.
Growing crystals in the home laboratory.
Growing crystals at various external conditions.
Carbonated water - harm or benefit.
Carbonated drinks are poison in small doses.
Carbonated drinks in a teenager's life.
Carbonated drinks: good or bad?
Soda. Tasty! Healthy?
Monosodium glutamate is the cause of food addiction.
Rock crystal is a symbol of modesty and purity of thoughts.
Long live scented soap!
Decorative cosmetics and its effect on the skin.
Edges of bright nature. DI. Mendeleev.
Baby food.
The dietary sugar substitute aspartame is a toxic substance.
What is iodine for?
Additives, dyes and preservatives in foods.
Home first aid kit.
A dozen spices through the eyes of a chemist.
To eat or not to eat - that is the question!?
Chewing gum. Myth and reality.
Chewing gum: good or bad?
Iron is an element of civilization and life.
Iron and its compounds.
Iron and human health.
Iron and the environment.
Water hardness: current aspects.
Painting and chemistry.
Liquid dishwashing detergents.
The vital value of honey.
Life without gluten.
Fats: harm and benefit.
Protective properties of toothpastes.
Labels on food packaging.
Famous drinks. Pros and cons of Pepsi and Coca-Cola, Sprite and Fanta drinks.
Toothpastes
From the life of a plastic bag.
What is the clothes made of. fibers.
We study silicates.
The study of the properties of shampoos.
Learning the secrets of making glue.
Study of the composition and properties of mineral water.
The study of the composition of ice cream.
Study of the ability and dynamics of accumulation of heavy metals medicinal plants(on the example of one type of medicinal plants).
The study of the characteristics of ice cream as a food product.
Indices of food additives.
home indicators.
indicators around us.
Indicators. Application of indicators. natural indicators.
inert gases.
Artificial fats are a threat to health.
Using daphnia to determine threshold values for heavy metal ions.
The use of yeast in the food industry.
Investigation of pH-solutions of some types of soaps, shampoos and washing powders.
Study of the effect of chewing gum on the human body.
Study of water hardness and ways to reduce it.
Study of water quality in the city and suburbs.
The study of the properties of aspirin and the study of its effect on the human body.
Study of the properties of sulfuric acid.
Study of the level of corrosion of city monuments.
Study of the physico-chemical properties of milk from different manufacturers with an environmental certificate.
Study of physical and chemical properties of natural juices from different manufacturers.
Study of the chemical composition of water to determine the effectiveness of the filter "Barrier-4".
Study of the chemical composition of local clays.
The history of chocolate.
Iodine in food and its effect on the human body.
Iodine in food and its effect on the human body.
How to determine the quality of honey.
Which ice cream tastes best?
Calcium and its compounds in the human body.
Catalysis and catalysts.
Porridge is our health.
Quartz and its application.
Acidity of the pH environment and human health.
Acid rain.
Acid rain and its impact on the environment.
Acids and alkalis in everyday life.
Cranberry - northern lemon?
Sausage is tasty and healthy?!
Quantitative determination of mercury in energy-saving light bulbs.
Corrosion of metals and ways to prevent it.
Coffee in our life
Caffeine and its impact on human health.
Dyes and food.
Silicon and its properties.
Kumys is the national drink of the Kazakhs.
Kumis and its healing properties
Medicines and poisons in antiquity.
Medicinal plants.
Medicine or poison?
Mayonnaise is a familiar stranger!
Mendeleev and the Nobel Prize.
Metals are the elements of life.
Metals in human life.
Metals in art.
Metals in space.
Metals in the human body.
Metals of antiquity.
Metals and alloys, their properties and application in electronic equipment.
Metals on the human body.
Metals of the Periodic Table of Chemical Elements D.I. Mendeleev.
Biogenic metals.
Microelements in the body
Trace elements: evil or good?
Minerals.
The world of water. Secrets of the tap, secrets of the mineral.
The world of plastics.
The world of glass.
Milk: for and against.
Dairy products.
We live in a world of polymers.
Soap: yesterday, today, tomorrow.
Soap: friend or foe?
Soap: history and properties.
Soap story.
The presence of iodine in food and its biological role.
Drink "Coca-Cola": new questions of the old problem.
Oil and oil products.
Detection of water content in gasoline.
Determination of fats, carbohydrates and proteins in chocolate.
Determination of lead ions in grassy vegetation of city parks.
Determination of iodine in iodized table salt.
Determination of the amount of vitamin C in lemon.
Determination of impurities in tap water.
Determination of physico-chemical parameters of milk.
Organic poisons and antidotes.
Beware of beer!
Pectin and its effect on the human body.
Hydrogen peroxide.
Periodic system of D.I. Mendeleev as the basis of the scientific worldview.
Food additives keep bread fresh longer.
Is table salt just a seasoning?
Table salt - crystals of life or white death?
Table salt is a mineral of extraordinary importance.
Why are chestnut trees dying in the industrial area of the city.
Why are fruits and vegetables acidic?
Application of chlorophyll in the synthesis of acrylamide hydrogels.
The problem of iodine deficiency.
Recycling problem. Recycling.
Spices through the eyes of a chemist.
Psychoactive substances in everyday life.
Soluble mortal (poisons).
beauty recipes.
The role of saliva in the formation and maintenance of caries resistance of tooth enamel.
Sugar and sweeteners: pros and cons.
Collection of poems "Chemistry and Life".
Secrets of a white-toothed smile.
Sulfur and its compounds.
Synthetic macromolecular compounds (VMC).
Synthetic detergents for automatic washing machines.
Synthetic detergents and their properties.
Soda: familiar and unfamiliar.
The content of nitrates in drinking and table-mineral waters.
Juice as a source of ascorbic acid.
Air composition and pollution.
Composition and properties of toothpastes.
Composition and properties vegetable oils.
composition of detergents.
The composition of tea.
The state of atmospheric precipitation at the school site and outside the city.
Means for washing dishes.
Washing powders: review and comparative characteristics.
Is it worth eating a pood of salt?
Silent power of poisons.
Amazing "silver" reactions.
Phosphorus, its properties and allotropic changes.
Chemical analysis of tap water at my school to determine the organoleptic parameters, the content of chloride ions and iron ions.
Chemical analysis of water in the river.
Chemistry is an ally of medicine.
Chemistry of colors.
Chemistry of silicon and its compounds.
Chemistry of manganese and its compounds.
Chemistry of copper and its compounds.
Water chlorination: forecasts and facts.
What is protein afraid of?
Chernobyl. This shouldn't happen again.
Chips: harm or benefit?
Chips: treat or poison?
Chips: good or bad?
What do we know about shampoo?
What you need to know about nutritional supplements.
Which is better - tea or coffee?
What's behind the "E"?
What is in a cup of tea?
What is acid rain and how does it form?
What is oil and how did it appear on Earth?
What is sugar and where does it come from.
What do we have in the salt shaker and in the sugar bowl?
Cast iron and its welding.
Wonders of glass
Silk natural and artificial.
Chocolate is the food of the gods.
Chocolate: harm or benefit?
Chocolate: treat or medicine?
Environmental safety in everyday life.
Ecological problems of outer space.
Examination of the quality of honey and methods of its falsification.
Examination of the organoleptic properties of wheat bread.
Element number one.
Energy drinks are new generation drinks.
Energy-saving lamps and the ecological crisis.
Those tasty dangerous chips.
I am on a diet!
Amber - magic tears of a tree.
