I. Styrene thermoplastic elastomer
Styrene TPE, also known as TPS, is a block copolymer of butadiene or isoprene and styrene, and its performance is closest to SBR rubber. At present, the world TPS production has reached more than 700,000 t, accounting for about half of all TPE. The representative variety is styrene-butadiene-styrene block copolymer (SBS), which is widely used in footwear industry and has largely replaced rubber. At the same time, its application in industrial rubber products such as adhesive tape and rubber sheet is also expanding. SBS is also widely used as an impact modifier for PS plastics, and it is also an excellent modifier for wear resistance, crack resistance, softness resistance and skid resistance of asphalt pavement. PS plastics modified by SBS can not only greatly improve the impact resistance like rubber, but also have very good transparency. Compared with SBR and WRP rubber powder, SBS modified asphalt pavement is easier to dissolve in asphalt. So although the price is more expensive, it is still widely used. Now the waterproofing membrane is further extended to the waterproofing and moistureproof of building roofs, subways, tunnels and ditches. Sponges made of SBS, S-SBR and NP rubber are richer in rubber touch than the original PVC and EVA plastic sponges, lighter than vulcanized rubber, with bright colors and clear patterns. Therefore, it is not only suitable for making sponges in rubber overshoes, but also an ideal material for disposable soles such as travel shoes, sports shoes and fashion shoes.
In recent years, isoprene-substituted butadiene block styrene polymer (SIS) has developed rapidly, accounting for about 1/3 of TPS, of which about 90% is used as adhesive. The hot melt adhesive made of SIS not only has superior viscosity, but also has good heat resistance. Now it has become the main material of hot melt adhesive in the United States, Europe and Japan. The biggest problem of SBS and SIS is that they are not heat-resistant, and the service temperature generally cannot exceed 80℃. At the same time, its tensile strength, weather resistance, oil resistance and wear resistance are incomparable to rubber. Therefore, in recent years, the United States and Europe and other countries have made a series of performance improvements, and SEBS and SEPS with saturated hydrogenation of SBS and SIS have appeared successively. SEBS (with BR hydrogenation as soft segment) and SEPS (with IR hydrogenation as soft segment) can greatly improve impact strength, weather resistance and thermal aging resistance. 1984 Mitsubishi chemical of Japan made a mixture with better performance on the basis of SEBS and SEPS, and named this saturated TPS "Rubberron" for listing. Therefore, SEBS and SEPS are not only common, but also blended materials of engineering plastics to improve weather resistance, wear resistance and thermal aging resistance, so they have rapidly developed into compatibilizers for engineering plastics such as nylon (PA) and polycarbonate (PC). In addition, many new varieties have been developed, such as highly transparent thermoplastics for epoxy resin and bio-nontoxic thermoplastics for medical care.
IPN TPS can also be formed when SBS or SEBS is melt blended with PP plastic. The so-called IPN is actually a polymer with two interpenetrating networks, so it is also called interpenetrating network compound. Although most of them belong to thermosetting resins, there are also many thermoplastic elastomers like TPE in the form of cross continuous phases. TPS formed by IPN——SBS or SES and other engineering plastics can be directly coated without pretreatment. The coating is not easy to scratch and has certain oil resistance, and the elastic coefficient does not change in a wide temperature range at low temperature; The cold resistance and heat resistance of engineering plastics are greatly improved. Styrene compounds can also become thermoplastic TPE by graft copolymerization with rubber. EPDM/ styrene, BR/ styrene, CI-IIR/ styrene, NP/ styrene and so on were developed.
2. olefin TPE
Olefin TPE is a blend with PP as the hard segment and EPDM as the soft segment, abbreviated as TPO. Because its specific gravity is lighter than other TPEs (only O.88), its heat resistance is as high as 100℃, and its weather resistance and ozone resistance are good, it has become another fast-growing variety of TPE. 1972 Since UniroyaI Company was first listed in the United States under the trade name of TPR, it has been growing by double digits for many years. In 2000, the output reached 350,000 tons, and it is expected to reach 400,000 tons in 2002. Now, TPO has become the main rubber and plastic material in the fields of automobiles and household appliances in the United States, Japan and Europe. Especially in cars, it has accounted for 3/4 of the total, and the car bumper made of it has basically replaced the original metal and PU. In 1973, a dynamic partially vulcanized TPO appeared. Especially, after Mansanto Company of the United States successfully developed a fully dynamic vulcanized TPO named Santoprere in 198 1, its performance was greatly improved, and the highest temperature could reach 120℃. This dynamic vulcanization TPO is called TPV for short. A cross-linking agent which can vulcanize the mixture of PP and EPDM in TPO is added in the melt blending process, and the fully vulcanized fine EPDM cross-linked rubber particles are fully dispersed in the PP matrix by using the high shear force of internal mixer, screw machine and other machinery. Through the "particle effect" of this cross-linked rubber, the compression deformation resistance, thermal aging resistance and oil resistance of TPO are obviously improved, even reaching the level of CR rubber, so people call it thermoplastic vulcanizate.
3. diene TPE
Diene TPE is mainly an isomer of natural rubber, so it is also called thermoplastic trans natural rubber (1-NR). As early as 400 years ago, people discovered that this material is natural rubber, but it is called Gupta rubber and balata rubber because it is produced in wild trees such as Gupta and balata, which is different from the three-leaf rubber tree. Although this T-NR has been used as the skin of submarine cables and golf balls for more than 65,438+000 years, its application has not been expanded for a long time due to its thermoplastic state, strong crystallinity and limited supply.
T-NR- trans polyisoprene rubber synthesized with organometallic catalyst is called TPI. Its microstructure is just opposite to that of isoprene rubber (IR), with 99% trans-bonding, 40% crystallinity and melting point of 67℃, which is very similar to natural Gutap and balata rubber. Therefore, natural products are gradually replaced and further developed into plastic surgery instruments, gypsum substitutes and sports protective equipment. In recent years, TPI has been successfully developed as a shape memory rubber material because of its excellent crystallinity and temperature sensitivity, which is favored by people.
Structurally, TPI is a thermoplastic rubber with high crystallinity, which is composed of trans structure as hard segment and then combined with other arbitrary soft segments in elastic phase. Compared with other TPE, it has the advantages of good mechanical strength, damage resistance and vulcanization, but the disadvantage is that the softening temperature is very low, generally only 40-70℃, and its use is limited. BR Isomer of rubber (cis-1, 4 polybutadiene)-syndiotactic 1, 2 polybutadiene, abbreviated as TPB. It is syndiotactic polybutadiene rubber with more than 90% 1, and its trade name is RB. The microstructure is a block polymer composed of crystalline parts with the same structure between any soft segment and hard segment. Although its heat resistance and mechanical strength are not as good as rubber, it is widely used in industrial rubber products such as shoes, sponges and optical films because of its good transparency, weather resistance, electrical insulation and photodegradation.
The biggest difference between TPB and TPI is that it can be vulcanized. It solves the problem that general TPE cannot be vulcanized by sulfur and peroxide, but must be vulcanized by special devices such as electric wave and radiation. It can improve the quality and modification, thus improving the shortcomings of TPE such as poor heat resistance, oil resistance and durability. TPB can be processed at will in the melting point range of 75- 1 10℃, and can be used to produce unvulcanized injection-molded slippers and casual shoes, as well as to vulcanize and foam the midsole of sports shoes and travel shoes. Compared with EVA sponge midsole, it is not easy to collapse and deform, and it is comfortable to wear, which is beneficial to improve the effect of sports competition. The film made of TPB has good air permeability, water resistance and transparency, is easily decomposed by light, is very safe, and is especially suitable for fresh-keeping packaging of families, vegetables and fruits.
4. Vinyl chloride thermoplastic elastomer
It can be divided into thermoplastic PVC and thermoplastic CPE. The former is called TPVC and the latter is called TCPE. TPVC is mainly the elastic modification of PVC, which is divided into two forms: chemical polymerization and mechanical blending. Mechanical blending is mainly the blending of partially crosslinked NBR and polyvinyl chloride (PVC/NBR). In fact, TPVC is just an extension of soft PVC resin, only because the compression deformation is greatly improved, thus forming a rubber-like PVC. This TPVC can be regarded as a modified product of PVC and a substitute of rubber, which is mainly used to manufacture rubber hoses, rubber sheets, adhesive tapes and some rubber parts. At present, more than 70% are consumed in the automotive field, such as steering wheel, wiper blade and so on. For other purposes, wires account for about 75%, and building waterproof membrane accounts for about 10%. In recent years, it has been extended to household appliances, gardening, industry and daily raincoats.
5. Polyurethane TPE
Polyurethane TPE is a kind of thermoplastic polyurethane rubber, which consists of polyurethane hard segment and polyester or polyether soft segment that react with isocyanate. TPU has excellent mechanical strength, wear resistance, oil resistance and flexibility, especially wear resistance. Disadvantages are poor heat resistance, hot water resistance and pressure resistance, easy yellowing of appearance and easy mold sticking during processing. At present, it is mainly used to manufacture sports goods such as ski boots and hiking shoes in Europe and America, and a large number of sports shoes and travel shoes are produced, which consumes a lot. TPU can also be used to produce automobile, machinery, clocks and other parts by injection molding and extrusion, and is widely used in high-pressure hoses (outer rubber), pure hoses, sheets, transmission belts, conveyor belts, wires and cables, adhesive tapes and other products. Injection molding accounts for more than 40%, and extrusion molding accounts for about 35%.
In recent years, in order to improve the processability of TPU, many new easy-to-process varieties have appeared. If it is suitable for two-color molding, it can increase transparency, high fluidity and high recovery, and improve processing and production efficiency. TPU with no plastic, low hardness and easy processing is used to manufacture transparent rubber hose. It can be used as a special TPU for large parts such as automobile bumper, reinforced with glass fiber, which can improve rigidity and impact resistance. Especially when reactive components are added to TPU, after thermoplastic molding, incomplete IPN (IPN formed by crosslinked polymer and non-crosslinked polymer) develops rapidly. This IPN TPU further improves the physical and mechanical properties of TPU. In addition, the blending of alloy TPU and TPU/PC improves the safety performance of automobile bumper. In addition, there are high moisture permeability TPU, conductive TPU, TPU and so on, which are specially used for living bodies, tapes, safety glasses and so on.
6. the difference between 6.TPE and PVC
Thermoplastic elastomer is a new material with high elasticity, high strength and high resilience of rubber. TPE material has soft hand feel, good weather resistance and no plasticizer. It is an environment-friendly and non-toxic material with a price of 25-50,000/ton, which is widely used in daily necessities in contact with human body.
PVC-PVC is a poisonous chlorine-containing resin. Plasticizer is added in the processing. The greater the plasticizer content, the softer the material. Widely used in building materials and artificial leather, the price is between 0.8-/kloc-0.2 million yuan/ton. PVC plastic products will slowly decompose hydrogen chloride gas at high temperature, such as about 50℃, which is harmful to human body.
Compared with PVC, TPE is more resistant to high and low temperatures and has better elasticity. In recent years, the voice of environmental protection is getting louder and louder, so TPE, an energy-saving and environmental-friendly thermoplastic elastomer, has begun to replace PVC in many fields.