Thermoplastic elastomer, or TPE, is a material with both rubber and plastic properties. It shows rubber elasticity at room temperature and is a polymer material
that can be plasticized and molded at high temperatures.
The basic structural feature of the thermoplastic elastomer polymer chain is that it simultaneously connects or grafts certain plastic segments (hard segments)
and rubber segments (soft segments) with different chemical compositions in series.
The force between hard segments is enough to condense into microdomains (such as vitrified microdomains or crystalline microdomains), forming physical
"cross-links" between molecules. The soft segment is a high-end chain segment with greater rotation ability.
Thermoplastic elastomers are an important part of elastomers. Common thermoplastic elastomers include the following categories: styrene thermoplastic
elastomers, polyurethane thermoplastic elastomers, polyolefin thermoplastic elastomers, and polyamide thermoplastic elastomers.
Styrenic block copolymer thermoplastic elastomer is the earliest thermoplastic elastomer studied. It is currently the largest and fastest growing thermoplastic
elastomer in the world. Mainly include SBS, hydrogenated SBS (SEBS), SIS and hydrogenated SIS, etc.
The properties of styrenic thermoplastic elastomers at room temperature are similar to those of vulcanized rubber, with an unusually high elastic modulus that
does not change with relative molecular mass.
With its high strength, softness, rubber elasticity and small permanent deformation, it is widely used in the shoemaking industry, plastic modification, asphalt
modification, waterproof coatings, liquid sealing materials, wires, cables, automobile parts, medical device parts, and household appliances. , office automation
and adhesives, etc. It has a wide range of applications.
Polyurethane thermoplastic elastomer (TPU) is generally the addition polymerization of long-chain polyol (polyether or polyester) with an average relative
molecular mass of 600 to 4000, a chain extender with a relative molecular mass of 61 to 400, and polyisocyanate. Linear polymer materials.
The long-chain polyol (polyether or polyester) in the main chain of TPU macromolecules constitutes the soft segment, which mainly controls its low-temperature performance, solvent resistance and weather resistance, while the chain extender and polyisocyanate constitute the hard segment. Since the ratio of hard and soft segments can
be adjusted within a wide range, the resulting thermoplastic polyurethane can be either a soft elastomer or a brittle high-modulus plastic.
It can also be made into films and fibers. It is a TPE. The only species in the world that can do this.
TPU has excellent wear resistance, oil resistance and cold resistance, and has sufficient resistance to oxygen, ozone and radiation. At the same time, as an elastomer,
it has high tensile strength and elongation at break, and it also has compression properties. Excellent properties such as small permanent deformation and large
load-bearing capacity. TPU has been widely used in many fields such as footwear industry, medical and health care, clothing fabrics and defense supplies.
Polyolefin thermoplastic elastomers (TPO) mainly include three types: block copolymers, graft copolymers and blends. Among them, polyolefin thermoplastic
elastomers ethylene-octene copolymer (POE) synthesized using metallocene catalysts and Thermoplastic dynamic vulcanizates prepared by dynamic vulcanization
are two main types of polyolefin thermoplastic elastomers.
Compared with the traditional Ziegler-Natta catalyst, the metallocene polyolefin elastomer ethylene-octene copolymer metallocene catalyst has an ideal single
active center, so it can precisely control the relative molecular mass distribution, comonomer content and its main content.
Distribution on the chain and crystallographic structure. The synthesized polymer is a highly stereoregular polymer with a very narrow relative molecular mass
distribution, which enables accurate control of the physical and mechanical properties and processing properties of the polymer.
The polyolefin thermoplastic elastomer ethylene-octene copolymer (POE) synthesized using a metallocene catalyst has a very narrow molecular weight and short
branch chain distribution, so it has excellent physical and mechanical properties (high elasticity, high strength, high elongation rate) and good low-temperature
properties, and because its molecular chain is saturated and contains relatively few tertiary carbon atoms, it has excellent heat resistance and UV resistance.
POE's thermal stability, optical properties and anti-drying performance are better than EVA, its weathering resistance is better than SBS, its embrittlement temperature is lower than -76°C, and it still has good
toughness and ductility at low temperatures. POE shear resistance Good, good for high-speed extrusion and molding, little or no plasticizer required, long service life.
POE can be cross-linked using peroxide, silane and radiation methods. The physical and mechanical properties, chemical reagent resistance and ozone resistance
of the cross-linked material are close to those of EPDM; the heat aging resistance and ultraviolet aging resistance are better than EPDM and EPM,
so POE It is more suitable for outdoor use, and the thermal compression permanent deformation of POE EPDM is small.
As a modifier, POE can modify both rubber and plastic. Due to the lower processing temperature of POE, it is easier to mix with non-polar rubber, especially EPR, EPDM, NR, SBR and BR.
The biggest application of POE is still in plastic products. Modifying PP with POE can greatly improve its notched impact strength;
using the elastomer grafted with maleic anhydride to POE to modify PA6 can reduce the hygroscopicity of the material and greatly increase the impact strength.
Thermoplastic dynamic vulcanizate rubber The thermoplastic elastomer produced by the dynamic vulcanization method is called thermoplastic vulcanizate (TPV).
TPV is a special type of thermoplastic elastomer (TPE). Unlike elastic block copolymers, it is generated by the synergistic effect of elastomer-thermoplastic polymer blends and has better performance than simple blends. nature.
The key technology for preparing thermoplastic vulcanized rubber is dynamic vulcanization technology. One of the advancements in this technology is to use low-
cost existing processing methods to prepare new products by blending existing polymers. The process also meets environmental requirements for large polymerizati
on units compared to traditional, capital-intensive processes for producing new materials. Other advantages of TPV technology over block copolymers as a
source of thermoplastic elastomers are: high upper operating temperature, resistance to hydrocarbon media and small compression set.
Polyamide thermoplastic elastomer (TPEA) is composed of high melting point crystalline polyamide hardness and amorphous polyester or polyether soft satin.
According to the raw materials required for the synthesis of polyamide thermoplastic elastomer, the synthesis method can be divided into dibasic acid method and isocyanate method.
Using the dibasic acid method, TPAE is prepared through an esterification reaction between a carboxyl-terminated aliphatic polyamide block and a hydroxyl-terminated polyether diol. The isocyanate method uses semiaromatic amide as the hard segment and aliphatic polyester, polyether or polycarbonate as the soft segment.
Using the isocyanate method, the semiaromatic amide hard segment is obtained by the reaction of aromatic diisocyanate and dicarboxylic acid, rather than the
traditional polymerization of diamine and dibasic acid, ring-opening polymerization of cyclic lactam, or diamine. It can be prepared by reacting with dibasic acid chloride. In contrast, the former avoids the problems of
low activity of aromatic diamines, difficulty in obtaining aromatic ring lactam monomers, and the release of corrosive hydrogen chloride by reaction.
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