Analyze raw materials of PVC board and PE board

PVC board is made of polyvinyl chloride, and PE board is made of polyethylene. Now we come to understand the difference between PVC and polyethylene.　

Polyvinyl chloride is abbreviated as PVC, its natural color is light yellow translucent and shiny. Transparency is better than polyethylene and polystyrene, but worse than polystyrene. Depending on the amount of additives, it can be divided into soft and hard polyvinyl chloride. Soft products are flexible and tough, and feel sticky. The hardness of hard products is higher than that of low-density polyethylene. , And lower than polypropylene, whitening will occur at the inflection.

Material properties　　

Density 1380 kg/m3 　　

Young's modulus of elasticity (E) 2900-3400 MPa 　　

Tensile strength (σt) 50-80 MPa 　　

Elongation @ break 20-40% 　　

Notch test 2-5 kJ/m2 　　

Glass transition temperature 87 °C 　　

Melting point 212 °C 　　

Vicat B1 85 °C 　　

Thermal conductivity (λ) 0.16 W/m.K 　　

Coefficient of thermal expansion (α) 8 10-5 /K 　　

Heat capacity (c) 0.9 kJ/(kg・K) 　　

The biggest feature of PVC is flame retardant, so it is widely used in fire protection applications. But polyvinyl chloride will release hydrogen chloride and other toxic gases such as dioxins during the combustion process.　　

The combustion of PVC is divided into two steps. First, the hydrogen chloride gas and the diolefin containing double bonds are decomposed by burning at 240℃-340℃, and then carbon combustion occurs at 400-470℃.　　

Stable physical and chemical properties; not easy to be corroded by acids and alkalis; relatively resistant to heat; polyvinyl chloride has flame retardant (flame retardant value above 40), high chemical resistance (resistant to concentrated hydrochloric acid, 90% sulfuric acid , 60% nitric acid and 20% sodium hydroxide), good mechanical strength and electrical insulation. But its heat resistance is poor, with a softening point of 80°C, it starts to decompose and change color at 130°C, and precipitate HCI.　　

Industrial polyvinyl chloride resin is mainly amorphous structure, but also contains some crystalline regions (about 5%), so polyvinyl chloride has no obvious melting point, and it starts to soften at about 80°C. The thermal distortion temperature (under 1.82MPa load) ) Is 70-71 ℃, it starts to flow under pressure at 150 ℃, and slowly releases hydrogen chloride, which causes discoloration of polyvinyl chloride (from yellow to red, brown, or even black). The weight-average relative molecular mass of industrial polyvinyl chloride is in the range of 4.8-48,000, and the corresponding number-average relative molecular mass is 2-19.5 million. The weight average molecular weight of most industrial resins is between 100,000 and 200,000, and the number average molecular weight is between 45 and 64,000. Rigid polyvinyl chloride (without plasticizer) has good mechanical strength, weather resistance and Flame resistance, can be used alone as a structural material, used in the chemical industry to make pipes, plates and injection molded products. Rigid polyvinyl chloride can use reinforcing materials.

Polyethylene, abbreviated as PE, is a thermoplastic resin made by polymerization of ethylene.

Polyethylene is odorless, non-toxic, feels like wax, has excellent low temperature resistance (the lowest use temperature can reach -70～-100℃), has good chemical stability, and can withstand most acids and alkalis (not resistant to oxidation) It is insoluble in general solvents at room temperature, has low water absorption, and has excellent electrical insulation properties; but polyethylene is very sensitive to environmental stress (chemical and mechanical effects) and has poor heat aging resistance.　　

The properties of polyethylene vary from species to species, mainly depending on the molecular structure and density.

Specific gravity: 0.94-0.96 g/cm3

Molding shrinkage: 1.5-3.6%

Molding temperature: 140-220℃

Types of polyethylene:

　(1) LDPE: low density polyethylene (also known as high pressure polyethylene)

　 (2) LLDPE: linear low density polyethylene 　　

(3) MDPE: Medium density polyethylene 　　

(4) Modified polyethylene: chlorinated polyethylene (CPE), cross-linked polyethylene (PEX)