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Physical and chemical properties of Polyvinyl chloride

Aug 25, 2017

Natural color is yellowish translucent, shiny. Transparency is better than polyethylene, worse than polystyrene, with the amount of different additives, divided into soft, hard polyvinyl chloride, soft soft and tough, feel sticky, hard hardness is higher than low-density polyethylene.And lower than the polypropylene, in the inflection will appear whitening phenomenon. It has many characteristics ,for example:stable; easy to be acid, alkali corrosion; more tolerant to heat.

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Polyvinyl chloride has a flame retardant (flame retardant value of 40 or more), high chemical resistance (resistant to hydrochloric acid, 90% concentration of sulfuric acid, the concentration of 60% nitric acid and 20% concentration of sodium hydroxide), mechanical strength and the advantages of good electrical insulation.

PVChas poor stability to light and heat. The softening point was 80 ° C, and the decomposition was started at 130 ° C. In the case of non-heating stabilizer, PVC 100 ° C began to break down, more than 130 ° C decomposition faster. Heat decomposition of the release of hydrogen chloride gas, (hydrogen chloride gas is toxic gas) to discoloration, from white → light yellow → red → brown → black. Sunshine in the ultraviolet and oxygen will cause the photo-oxidation of PVC, so that the flexibility of PVC decreased, and finally brittle. From here is not difficult to understand why some PVC plastic for a long time will turn yellow, brittle reasons.

With a stable physical and chemical properties, insoluble in water, alcohol, gasoline, gas, water vapor permeability is low; at room temperature can be resistant to any concentration of hydrochloric acid, 90% of sulfuric acid, 50-60% nitric acid and 20% Caustic soda solution, that has a certain resistance to chemical corrosion; salt is quite stable, but can be dissolved in ether, ketone, chlorinated aliphatic hydrocarbons and aromatic hydrocarbons and other organic solvents.

Industrial polyvinyl chloride resin is mainly amorphous structure, but also contains some crystallization area (about 5%), so PVC has no obvious melting point, about 80 ℃ or so began to soften, heat distortion temperature (1.82MPa load) 70-71 ° C, began to flow at 150 ° C under pressure and began to slowly release hydrogen chloride, causing the discoloration of the polyvinyl chloride (red, brown, and even black).

The average molecular weight of industrial PVC is in the range of 4.8 to 48,000, and the corresponding number is relative to the molecular mass of 2-195 million. And the vast majority of industrial resin is the relative molecular weight of 10-20 million, the number of relative molecular mass in 4.55-6.4 million. Rigid polyvinyl chloride (without plasticizer) has good mechanical strength, weatherability and flame resistance, can be used alone as a structural material, used in chemical manufacturing pipes, plates and injection products. Rigid polyvinyl chloride can be reinforced with a reinforcing material.


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