Anti aging and green polymer concept of the hottes

Anti aging of polymers and the concept of green polymers

1 anti aging of polymers

through the above discussion, it is not difficult to understand that polymer materials always age quickly or slowly, which is a common phenomenon, manifested in the corresponding deterioration of their physical properties or special functions, such as hardening, tackiness, embrittlement, discoloration, strength reduction or loss, as well as the attenuation and loss of the original functions of functional polymers. In fact, any polymer needs to properly prevent aging or slow down the aging rate. Even short-term plastic products, such as disposable food packaging bags, have anti-aging problems during processing and molding. The aging problem of polymer materials for permanent use, such as coatings and adhesives, is even more prominent. Adopting effective anti-aging measures can often expand the application field of a polymer or be used in more harsh conditions, and can also obtain economic benefits due to the extension of its service life. From the perspective of environmental protection, if the actual service life of long-term and permanent plastic can be extended, more information about the company can reduce the amount of waste, thereby reducing environmental pollution or reducing the environmental load. In a word, the anti-aging of polymer materials, like the synthesis of polymers, is another important aspect of polymer science

the aging of polymer materials includes not only the internal factors such as the chemical structure and physical state of the polymer itself, but also the external heat, light, electricity, high-energy radiation, mechanical stress, oxygen, ozone, water, acid, alkali, bacteria, enzymes, etc. it is all inclusive, and it is complex because of the variety of polymer, different products, the difference of performance requirements and how to use the environment. There is no single anti-aging standard and method. Aging and anti-aging is a large field, and there are many monographs, which cannot be detailed here. The general ways of anti-aging are simply summarized as follows:

1 polymer synthesis is carried out by using reasonable polymerization process route, qualified monomer and auxiliary raw materials, so as to obtain its own high aging resistance; Or adopt copolymerization, blending, crosslinking and other methods to improve the aging resistance of polymers

2 adopt advanced (appropriate) processing and molding processes (including adding various additives and heat and oxygen stabilizers to improve processing performance) to prevent aging in the processing process and prevent or minimize the generation of new aging inducing factors

3 according to the main aging mechanism of specific polymer materials and the practical environmental conditions of products, add corresponding stabilizers, such as heat, oxygen, light stabilizer, mildew inhibitor, etc

4 adopt possible and appropriate physical protection measures, such as surface coating, surface protective film, etc., to reduce the external effects of aging

5 according to the properties of polymers, we should make good use of advantages and avoid disadvantages, carefully and scientifically select and develop universal material testing machine to test special plastics and their products with wide tensile length, avoid outdoor use if they are not suitable for outdoor use, avoid high temperature use if they are not suitable for high temperature use, etc

2 the concept of green polymer

aging and anti-aging research has long been aimed at improving the durability of polymers. There is no doubt that this direction will continue in the future. However, with the development of polymer industry and the expansion of application fields, the waste of synthetic polymers is increasing year by year. Therefore, in order to prevent public hazards, the requirement of seeking the natural decomposition and return of polymers to nature is becoming increasingly strong. In the future, the research and development of synthetic polymers will be developed in the two directions of improving durability and ending life according to their applications. Therefore, in the 1990s, human pioneers put forward the concept of "green polymer", which comes from green chemistry and technology. It means environmentally friendly and harmless in the manufacturing, application and waste disposal of polymer materials. How to dispose of waste polymer materials that cannot be naturally degraded by the environment without polluting the environment and how to develop and utilize environmentally degradable polymer materials are two key issues in polymer green engineering

1 treatment of environmental inert polymer waste

environmental inert polymers are polymers that cannot be naturally degraded in the environment. At present, there are three ways to deal with the waste of environmental inert polymers

(1) soil burial method this method is not suitable for a country with a small number of people like China, because the polymer is not easy to degrade, and it often exists after being buried for decades or even hundreds of years, occupying a large amount of land

(2) incineration method ordinary incineration will produce a large number of harmful toxic gases and residues, which will seriously pollute the environment, which is not allowed by environmental protection. Even with various advanced incinerators, incineration under high temperature and high pressure (1200 ℃, higher than 105 ~ 106pa) can convert all wastes into usable energy, but the investment is large, and there is still a hidden danger of waste gas polluting the environment in incineration, so this method is not perfect

(3) waste regeneration and recycling method this method not only turns waste into treasure, saves oil resources, but also reduces environmental pollution. Therefore, it is the method most in line with the concept of green polymer. Now there are many successful examples, for example, waste plexiglass is cracked into monomer MMA by oxygen free heat and then used; Waste polyethylene terephthalate (PET) is converted into monomer by methanol alcoholysis, and then pet is obtained by polycondensation; Waste nylon 66 carpet is ammonolized to recover monomer, and then condensed into nylon tensile testing machine. The force value is measured through force sensor, expander and number. After the extension meter is clamped on the sample, it is completed according to the disposal system. 66 is engineering plastic used for making automobile body; A large amount of recycled PE made from waste polyethylene (PE) is used to prepare mail bags; Waste PS packaging materials, especially disposable lunch boxes, are treated with Bao and decomposed into monomers for reuse. Of course, when promoting the recycling method of polymer waste, we must emphasize the publicity of the use method of polymer materials and the classified management of polymer materials, which has successful experience abroad

2 development and utilization of environmentally degradable polymer materials

environmental degradation is mainly biodegradation, which can be divided into biological disintegration type and complete biodegradation type. The former is processed into products after adding some biodegradable substances to the polymer resin. After being discarded, the overall morphology collapses due to the environmental degradation of this part, which belongs to incomplete degradation type. For example, when starch, natural minerals and aliphatic polyester are added to polyolefin resin, the processed plastics are disintegrating environmentally degradable materials. Fully biodegradable polymer materials are synthetic natural polymer materials or modified natural polymer materials, or synthetic polymer materials with some structures. Considering the scale, cost and other factors, the preparation of degradable polymer materials by chemical synthesis is of the most practical significance. At present, the most researched and developed biodegradable polymer materials include aliphatic polyester, polyvinyl alcohol, polyamide, polyamide ester and amino acid. Aliphatic polyesters, such as polylactic acid (polyhydroxypropionic acid), Polyhydroxybutyric acid (Polyhydroxybutyric acid), polyhydroxyvaleric acid, etc., have the largest output and the widest use. Due to the easy hydrolysis of ester bonds and the flexible main chain, this kind of polyester is easily decomposed or metabolized by microorganisms in nature or enzymes in animals and plants, and finally turns into CO2 and water

using biotechnology to prepare biodegradable polymer materials, although the current cost is high, it is most in line with the concept of green polymer. For example, natural cellulose or sugar can be fermented by bacteria to produce hydroxybutyric acid and hydroxyvaleric acid. The polymer polymerized with them has properties similar to polypropylene, but it can be completely degraded in the environment; Another example is using corn and sugar beet as raw materials, lactic acid is obtained through fermentation, and the bulk polymerizes into polylactic acid. It can be made into medical surgical suture, which can be self degraded without removing the suture; Using it instead of PE as packaging material and agricultural film solves the most troublesome problem of dealing with a large amount of waste in this field. It can be seen from these examples that the use of biotechnology, from raw materials to products, from production to application, and until the disposal after abandonment, can not produce any environmental pollution at all, and use renewable agricultural and sideline products as raw materials to replace the increasingly scarce non renewable oil resources, which truly reflects the connotation of green

we believe that with the continuous progress of human society, the concept of greening polymer materials will become the consensus of mankind, and the century will be the century of green polymers