Pure PVC resin is extremely sensitive to heat, when the heating temperature reached more than 90 ℃, there will be a slight thermal decomposition reaction, when the temperature rose to 120 ℃ after the decomposition reaction intensified, in 150 ℃, 10 minutes, PVC resin from the original white gradually into yellow-red-brown-black. The decomposition process of PVC resin is a series of chain reaction caused by HCL reaction, which leads to the fracture of macromolecular chain. The thermal stability mechanism to prevent PVC thermal decomposition is achieved by following several aspects.
By capturing the HCL produced by thermal decomposition of PVC, the catalytic degradation of HCL is prevented.
Lead salts mainly according to this mechanism, in addition to metal soaps, organic tin, phosphite lipids and epoxy class.
Replacement of active allyl chloride atoms. Metal soaps, phosphite lipids and organic tin can be used in this mechanism.
Reacts with free radicals, terminating free radicals. Organic tin and Phosphite are acting on this mechanism.
and conjugated double bond add action, inhibit the growth of conjugate chain.
The organic tin and the epoxy are acting on this mechanism.
Decompose peroxide and reduce the number of free radicals. Organic tin and Phosphite are acting on this mechanism.
Passivation of metal ions with catalytic removal of HCL.
The same stabilizer can be used in several different mechanisms to achieve thermal stability.
In food additive, stabilizer is a kind of additive which makes food structure stable and enhances food viscous solid.