On the hottest polyolefin thermoplastic elastomer

2022-07-30
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Polyolefin thermoplastic elastomers (Part 1)

polyolefin thermoplastic elastomers mainly refer to thermoplastic elastomer materials that can be molded without vulcanization by blending ethylene propylene diene rubber (EPM) or ethylene propylene diene rubber (EPDM) with polyolefin resin. Butyl rubber grafted modified polyethylene also belongs to this category

synthesis of thermoplastic ethylene propylene rubber

(I) partially crystalline thermoplastic ethylene propylene rubber

partially crystalline thermoplastic ethylene propylene rubber is a blend of special ethylene propylene rubber and polyolefin. Its main feature is that there are partially crystalline segments in the molecular chain of ethylene propylene rubber. Due to the great cohesion between molecules, this partially crystalline segment shows the nature of hard segments and plays a physical "cross-linking" role. This physical "cross-linking" point shows plastic behavior when heated and has fluidity, so it can be formed by thermoplastic processing technology; The elastic rubber segment in the polymer shows similar properties to vulcanized rubber by means of physical "cross-linking"

1. synthesis of partially crystalline thermoplastic ethylene propylene rubber

partial crystalline special ethylene propylene rubber can be synthesized by using titanium tetrachloride ethyl benzoate triethyl aluminum catalyst system or modified aluminum titanium carrier catalyst. Monomer raw materials and their ratio, temperature, pressure, solution concentration, catalyst concentration and other factors are important parameters affecting ethylene propylene rubber. The characteristic of partially crystalline thermoplastic special ethylene propylene rubber is that the structure of copolymer elastomer endows the copolymer with partially crystalline properties. Its crystallinity is generally 10 ~ 20% (accounting for the weight of the copolymer)

2. blending of partially crystalline ethylene propylene rubber and polyolefin polyolefin resin blended with partially crystalline thermoplastic special ethylene propylene rubber, usually polyethylene or polypropylene. In high density, medium density and low density polyethylene, the effect of low density (940kg/m3) is better. In homo or syndiotactic poly (propylene)

ene, Homo structure is preferred. The ideal polyolefin resin is polypropylene, and the blending ratio varies with the application. The ideal ratio is 100 parts of ethylene propylene rubber mixed with 25 ~ 100 parts of polypropylene

mixing can be realized on open mill, benbury mixer, extruder and other equipment. According to the processing requirements and the performance and application requirements of rubber products, various additives such as antioxidant, plasticizer, tackifier and filler can be added in the mixing process. Benbury mixer is the most effective mixing equipment. There are several basic factors to achieve the best mixing of ethylene propylene rubber and polypropylene (or polyethylene). ① In 2005, the company founded compositeadvan to allow intelligent machines to operate the materials of tage company to produce high shear stress; ② Avoid local overheating; ③ What is the effect of ensuring sufficient mixing time so that the dispersion group can be implemented? The perihelion particles can reach the theoretical equilibrium size. In fact, benbury mixer can at least adjust the shear stress and the required discharge temperature of each batch of mixed rubber by controlling the upper top bolt pressure and the residence time of the rubber. In order to achieve good sorting. Although local overheating will not degrade the processed material itself or change the crosslinking density, it greatly increases the fluidity of polypropylene phase, resulting in the decline of the tensile strength and tear resistance of the interface between molten polypropylene and softened rubber phase

(II) partially vulcanized thermoplastic ethylene propylene rubber

partially vulcanized thermoplastic ethylene propylene rubber is a blend of amorphous ethylene propylene rubber and polyolefins such as polypropylene and polyethylene. Its main feature is to control the vulcanization degree of amorphous propylene rubber only to the extent of partial vulcanization (rather than most or complete vulcanization). The vulcanizing agent used for partial vulcanization is mainly peroxide or other crosslinking agents that produce free radicals. The above crosslinking system and sulfur vulcanization system can also be used together. The vulcanization degree of ethylene propylene rubber can be tested by measuring the gel content, crosslinking density and the amount of bound sulfur. It is proved that the vulcanizing agent for partial vulcanization is 1/4 ~ 2/3 of that for complete vulcanization. Partial vulcanization is carried out simultaneously with the mixing process, so this vulcanization is called dynamic vulcanization. The vulcanization temperature is 70 ~ 200 ℃, and the time is 5 ~ 10 minutes

blending of partially vulcanized ethylene propylene rubber and polyolefin resin is carried out by open mixer or benbury mixer. The blending temperature shall be higher than the softening point of thermoplastic polyolefin. The polyolefin resin involved in blending can be polyethylene of various densities or polypropylene of identical or syndiotactic structure with high crystallinity, just like the partially crystalline thermoplastic special ethylene propylene rubber. Polypropylene resin is more ideal than polyethylene

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