Thermoplastic rubber, referred to as TR, is a material between rubber and plastic. A plasticized material, a part (or all) of the polymer chain of this material is a component that can show rubber elasticity, and there are constrained components that can form equivalent to intermolecular crosslinks at room temperature in the molecule, while At high temperatures, the aggregates of these constrained components will melt or melt to become plastic.
The advantages of this material are as follows:
①The molding machine used for thermoplastic resin can be quickly molded without vulcanization;
②Changing the chemical structure of raw materials can produce various elastomers with properties similar to soft vulcanized rubber to plastic;
③The prepared elastomer is thermoplastic because it is not cross-linked, and the waste can be recycled. This product can be divided into the following categories according to the type of polymer.
(1) Polystyrene is mainly a thermoplastic polymer of the SBS (styrene-butadiene-styrene) type. Since the performance of this type of polymer is closest to that of rubber, it is the main variety of thermoplastic rubber. Its molecule is composed of a hard segment (polystyrene) that acts as a cross-link and a soft segment (polybutadiene) that is rubbery. This type of rubber is characterized by high strength, good elasticity, good low temperature properties, and good acid and alkali resistance. In addition, there is a SIS (styrene-isoprene-styrene) type, which has good weather resistance and heat resistance in addition to the above characteristics. This type of rubber is mainly used for shoe soles, adhesives, plastic modified materials, asphalt modified materials, coatings and toys.
⑵Polyurethane is a general term for rubber-like elastic polymers with carbamic acid groups (—NHCOO—) in the molecular structure. It is composed of soft segment (polyol-diisocyanate) and hard segment (diol or diamine-diisocyanate) obtained from difunctional polyol, diol (or diamine) and diisocyanate of copolymers. Changing the ratio of soft and hard chain segments can adjust the hardness of the tool, and its performance will also change. This kind of rubber has excellent mechanical strength, quality, and wear resistance, and its ozone resistance and shock resistance are also quite good. It is mainly used for pipes, hoses, fillers, gaskets, conveyor belts, etc. that require heat resistance, cold resistance, oil resistance, and sanitation. Most notably, it is used to make parts such as bumpers on cars.
(3) Polyolefins are made from ethylene and α-olefins through coordination anionic polymerization and grafting reaction, or in olefinic thermoplastic resins Mixed with certain olefinic rubbers. The biggest feature of this type of rubber is its low relative density, wide operating temperature range of 120-50°C, good weather resistance, aging resistance, chemical resistance and electrical energy, and can be colored arbitrarily, but its adhesion and oil resistance are poor. Mainly used in auto parts, industrial supplies, wires and cables, etc.
(4) Polyesters In this type of polymer, the hard segment is polyester with high melting point and high crystallinity, while the soft segment is vitrified Polyethers with temperatures below -70°C. Vary the ratio of polyester and polyether. Its physical and chemical properties also change. It is characterized by wide temperature range, high load resistance, small creep, good bending fatigue resistance, good oil resistance and chemical resistance, and good formability. It has the characteristics of engineering plastics. Features, can be used as auto parts, hoses, bearings, gears, wires and resin modified materials.
(5) Others mainly include ethylene-vinyl acetate copolymer, ethylene-acrylate polymer, polyethylene-butyl rubber graft copolymer, etc. These polymers can be used directly, but are usually crosslinked with organic peroxides. Polyethylene-butyl rubber graft copolymer is obtained by grafting high-density polyethylene, low-density polyethylene and butyl rubber with an unsaturation of 1.4%. It has appropriate elasticity. Due to its excellent electrical properties, it is usually used as an electrical Insulation Materials.
Thermoplastic rubber is the third generation of rubber after natural rubber and synthetic rubber. This type of rubber has obvious advantages in saving energy and manpower, so it has developed in recent years. Faster, and it is also under development in China. But from a technical point of view, there are still shortcomings. First of all, there is a problem of poor thermal deformation resistance. The oil resistance and solvent resistance of polystyrene need to be improved, and the thermal decomposition resistance, chemical resistance and hydrolysis resistance of polyurethane need to be improved, while polyolefins generally have poor characteristics.
Although the performance of polyester is relatively comprehensive, due to the incomplete separation of the constrained phase and the rubber phase, the result is high stress at low elongation.
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