Introduction To Polyvinyl Chloride (PVC) Resin

Polyvinyl chloride, abbreviated as PVC in English, is a polymer formed by the polymerization of vinyl chloride monomer (VCM) using initiators such as peroxides and azo compounds, or through free radical polymerization under the action of light and heat. Vinyl chloride homopolymers and vinyl chloride copolymers are collectively referred to as vinyl chloride resins. PVC materials can be manufactured into different products using twin-screw extrusion production line.

1.      Basic physical characteristics

PVC is an amorphous white powder with a low degree of branching and a glass transition temperature of 77-90 ℃. It begins to decompose at around 170 ℃ and has poor stability to light and heat. When exposed to sunlight for a long time or above 100 ℃, it will decompose and produce hydrogen chloride, which will further catalyze decomposition and cause discoloration. Its physical and mechanical properties also rapidly decrease. In practical applications, stabilizers must be added to improve its stability to heat and light.

The molecular weight of PVC produced in industrial production is generally in the range of 50000 to 110000, with a high degree of polydispersity. The molecular weight increases with the decrease of polymerization temperature, without a fixed melting point. It begins to soften at 80-85 ℃, becomes viscoelastic at 130 ℃, and transitions to a viscous flow state at 160-180 ℃; Has good mechanical properties, with a tensile strength of about 60MPa and an impact strength of 5-10kJ/m2; Has excellent dielectric properties.

Industrial polyvinyl chloride resin is mainly amorphous in structure, but also contains some crystalline regions (about 5%), so polyvinyl chloride does not have a clear melting point and begins to soften at around 80 ℃. The heat deformation temperature (under a load of 1.82MPa) is 70-71 ℃. Under pressure, it begins to flow at 150 ℃ and slowly releases hydrogen chloride, causing polyvinyl chloride to change color (from yellow to red, brown, or even black).

2.      Transparency and hardness:

The natural color is slightly yellow and translucent, with a glossy finish. Transparency is better than polyethylene and polypropylene, but worse than polystyrene. Depending on the amount of additives used, it can be divided into soft and hard polyvinyl chloride. Soft products are soft and tough, with a sticky touch, while hard products have a higher hardness than low-density polyethylene and a lower hardness than polypropylene. Whitening may occur at the bending point. stable; Not easily corroded by acid and alkali; Relatively tolerant to heat.

3.      Flame retardant

Polyvinyl chloride has flame retardancy (oxygen index value above 40), good mechanical strength, and electrical insulation properties.

4.      Photothermal stability

PVC has poor stability to light and heat. The softening point is 80 ℃, and decomposition begins at 130 ℃. Without heating the stabilizer, polyvinyl chloride begins to decompose at 100 ℃ and decomposes faster above 130 ℃. Heating decomposes and releases hydrogen chloride gas (which is a toxic gas), causing it to change color from white to light yellow to red, brown to black. The ultraviolet rays and oxygen in sunlight can cause photooxidative decomposition of polyvinyl chloride, resulting in a decrease in its flexibility and eventual brittleness. This is why some PVC plastics tend to turn yellow and brittle over time.

5.      Corrosion resistance

Has stable physical and chemical properties, is insoluble in water, alcohol, gasoline, and has low gas and water vapor leakage; It can withstand any concentration of hydrochloric acid, less than 90% sulfuric acid, 50-60% nitric acid, and less than 20% caustic soda solution at room temperature, and has a certain degree of chemical corrosion resistance; It is quite stable to salts, but can dissolve in organic solvents such as ethers, ketones, chlorinated fatty hydrocarbons, and aromatic hydrocarbons.

6.      Main applications

Hard polyvinyl chloride (without plasticizers) has good mechanical strength, weather resistance, and flame resistance, and can be used as a structural material alone. It is applied in the manufacturing of pipelines, plates, and injection molded products in the chemical industry. Rigid polyvinyl chloride can be reinforced with materials.

PVC is the world's largest general-purpose plastic in terms of production and has a wide range of applications.

Our PVC pipe extrusion machine, PVC profile making machine, and PVC wall panel production line can produce PVC pipes, PVC door and window profiles, PVC wall panels, and other products using PVC raw materials. These materials are widely used in construction, decoration, and daily life.