PET can be processed into fibers, films and plastic products. Polyester fiber is an important variety of synthetic fiber, which is mainly used for wearing. Generally, the thickness of thin film is between 4 ~ 4 μ m, and it has high strength, good dimensional stability and good chemical and dielectric resistance. As a support, it is widely used to make various magnetic tapes and cards. 9% of the tape substrate is made of PET film, of which 8% is computer tape. This film is also used in the production of photosensitive materials, as the base of photographic film and X-ray film, as the insulating material of motors, transformers and other electronic appliances, and as various packaging materials.
because the crystallization speed of PET melt is very fast when it is cooled, and the molding process is difficult, the mold temperature must be kept above 14℃ to obtain a product with good performance, otherwise the product will be brittle. Therefore, people have not used PET as a thermoplastic engineering plastic for a long time. With the development of science and technology, the above difficulties in molding and processing have been overcome by adopting new polycondensation catalyst system or polycondensation process, reinforcing with glass fiber, or controlling crystal structure and preparing high molecular weight polyester. PET has been increasingly used to make beverage bottles and glass fiber reinforced plastics. The advantages of polyester bottles are light weight (only 1/9 ~ 1/15 of the weight of glass bottles), high mechanical strength, not easy to break, convenient to carry and use, good transparency, glossy surface, non-toxic, good air tightness, good freshness, low energy consumption for producing polyester bottles, and recyclable waste bottles. It is also used to make packaging bottles for food oils, condiments, sweet foods, medicines, cosmetics and alcoholic beverages. Not only transparent bottles, but also colored bottles are produced, and composite bottles of polyester and other resins are being developed. In 1984, Dupont Company developed a super-toughness glass fiber reinforced PET, which has excellent rigidity, impact toughness and heat resistance, good melt fluidity, easy processing into products with complex shapes, short molding cycle, good coloring, and good surface gloss when the mold temperature is above 8℃. Mainly used in automobile shells, bumpers, steering wheels, sports equipment requiring impact resistance, electrical products, bathtubs, bulletproof armor, hulls and excellent building materials.
PBT was mainly used to replace metal parts in automobile manufacturing at the initial stage of development, and then it was widely used to make electrical products, such as transformer parts for TV sets, due to the advent of flame-retardant glass fiber reinforced PBT and other varieties. Poly (aryl ester) is mainly used in electrical appliances and mechanical parts, and polyester is also widely used in plastic knitting industry.
The following is a comparative analysis of the performance of polyester woven bag and polypropylene woven bag:
1. Because the tensile strength of PET flat yarn is 2-3 times that of PP, it can save raw materials and reduce production costs.
2. Because the aging resistance of PET flat yarn is very strong, which is four times that of PP, it is unnecessary to add any anti-ultraviolet agent to produce container bags and woven bags, which saves the cost of adding anti-ultraviolet agent and will not age for several years.
3. Due to the high transparency and gloss of PET, the transparent bag or mesh bag produced has high transparency and smooth surface.
4. Due to the high softening temperature and melting point of PET, which are 248℃ and 276℃ respectively, the heat resistance is good. After being heated at 15℃ for 7 days, the strength loss of the uniaxially stretched PET film is 3%, and only 5% after being heated for 4 days. At 14℃ for 48 hours, its performance will not change, which will break through the difficulty of producing high-temperature resistant cement bags and so on, which will be the utilization place of low-grade PET recycled materials with a price of about 5, yuan in the future.
5. Because of the good low temperature resistance of PET, the use temperature is -1℃. Even in cold Siberia, Russia, there is no need to worry about cold brittle skin breaking in winter.
6. Because PET products have high strength and modulus, good elasticity, wear resistance and impact resistance, good creep resistance under load, and do not crack during weaving, the produced lawn yarn has good wear resistance, does not crack after repeated trampling, and is anti-aging and does not fade.
7. Due to the characteristics of PET, such as high tensile strength and anti-aging, it is expected that the strength retention rate of geotextile will reach 5% in the underground for 2 years, and the tarpaulin will not obviously age in the sun for several years.
the performance of polyester (PET) is superior to that of polypropylene (PP), which will inevitably lead to the emergence of new plastic woven products, expand the application fields of plastic woven products and increase the social demand of plastic woven products.