I. Polyethylene
Polyethylene is a thermoplastic resin, which is formed by addition polymerization of ethylene. According to different polymerization conditions, polyethylene with relative molecular weight ranging from tens of millions can be obtained. Polyethylene is a slightly white particle or powder, translucent, non-toxic, tasteless, good chemical stability, acid and alkali corrosion resistance. Commercially, polyethylene is divided into low density, medium density and high density. Generally, low density packaging (0.92g/cm3-0.93g/cm3) without plasticizer is adopted.
Second, polypropylene.
The relative molecular weight is between 90000 and 200000. The main chain of polypropylene has a methyl side chain. If all methyl groups are distributed on one side, it is called isotactic polypropylene; If methyl groups are regularly distributed on both sides of the main chain, it is called syndiotactic polypropylene; If methyl groups are randomly distributed in the main chain, it is called random polypropylene. Polypropylene is usually a translucent solid, odorless and nontoxic, with a density of (0.90g/cm3-0.9 1g/cm3), which has higher mechanical strength and better heat resistance than polyethylene. Among the three kinds of polypropylene, isotactic polypropylene has the largest output. Isotactic polypropylene was obtained by polymerization of propylene in hydrogenated gasoline with titanium trichloride-diethyl aluminum chloride as catalyst.
Third, PVC.
Polyvinyl chloride (PVC) is a thermoplastic resin with a relative molecular weight of 50,000-65,438+200,000. Amorphous white powder with no fixed melting point, density of (1.35g/cm3-1.45g/cm3) and good chemical stability. Soluble in cyclic ethyl ketone, chlorobenzene, dimethylformamide, toluene-acetone mixed solvent, etc.
Fourth, polystyrene.
The average relative molecular mass is about 200,000. Colorless and odorless transparent resin with good light transmittance. The surface is glossy and flammable, and the density is (1.05g/cm3-1.07g/cm3), which has excellent waterproof, corrosion resistance and electrical insulation.
Production methods: bulk polymerization, suspension polymerization and emulsion polymerization. Ontology aggregation is introduced here. Adding initiator and a small amount of additives into styrene monomer, polymerizing at low temperature in a prepolymerization kettle to prepare prepolymer, and then transferring the prepolymer to a polymerization tower for high-temperature heating, and keeping a certain temperature in stages; After the reaction, the molten polystyrene is extruded into strips, cooled and hardened in water, cut into pieces and packaged. Plasticizer, foaming agent, heat stabilizer, antioxidant, etc. Also added to these pollutants.