The Thermostabilization Mechanism Of PVC

In the process of processing, the thermal decomposition of PVC does not change other properties, which mainly affects the color of the finished product. The addition of thermal stabilizer can inhibit the initial colorability of the product. When the stripped HCl mass fraction reaches 0.1%, the PVC color begins to change.Depending on the number of conjugated double bonds formed, the PVC will appear in different colors (yellow, orange, red, brown, and black). If there is oxygen in the thermal decomposition process of PVC, there will be the generation of colloidal carbon, peroxide, group, and ester-based compounds. However, in the long time of the product, the thermal degradation of PVC has a great impact on the performance of the material. The addition of a thermal stabilizer can delay the time of PVC degradation or reduce the degree of PVC degradation.
Adding a thermal stabilizer in the process of PVC processing can inhibit the degradation of PVC, so the main functions of the thermal stabilizer are: inhibiting the degradation of PVC molecules by replacing unstable chlorine atoms, absorbing hydrogen chloride, and undergoing addition reaction with unsaturated sites.
An ideal thermal stabilizer should have multiple functions:
(1) Replace active and unstable substituents, such as chlorine atoms or allyl chloride attached to tertiary carbon atoms, to form stable structures;
(2) Absorb and neutralize the HCl released during PVC processing to eliminate the automatic catalytic degradation of HCl
(3) Metal ions whose neutralization or passivation and other harmful impurities that play a catalytic role for degradation;
(4) Various forms of chemical reactions can block the continuous growth of unsaturated bonds and inhibit degradation and coloring;
(5) It is best to have a protective and shielding effect on ultraviolet light.