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Do you know the principle of PVC processing?
The product has processing principles when it is processed. There are certain principles in the processing of PVC products. Do you know these principles?
PVC belongs to a kind of strong polar polymer, and its intermolecular force is large, resulting in higher softening temperature and melting temperature of PVC. Pure PVC generally needs to be plasticized and processed at 160-2100°C. In addition, the substitution of chlorine groups contained in the PVC molecule can easily lead to PVC dehydrochlorination, which can cause PVC degradation reaction. Therefore, PVC is extremely unstable to the heat, and the temperature is increased, which will greatly promote the removal of HCl from PVC. When the temperature reaches 1200C when pure PVC is used. At that time, the dehydrochlorination reaction starts, which leads to the thermal degradation of PVC.
In view of the above two characteristics of PVC, pure PVC begins to undergo thermal degradation before it reaches the softening temperature, resulting in that pure PVC cannot be processed by the plastic melting method. Therefore, pure PVC must be processed and modified so that it can be plasticized. Method processing.
The principle of PVC processing is adding plasticizer and heat stabilizer to pure PVC.
Adding plasticizers to PVC can weaken the interaction between PVC molecules and increase the mobility of the molecules, thereby lowering its processing melting temperature, which is lower than the thermal decomposition temperature of PVC.
Adding heat stabilizers to PVC can inhibit PVC from dehydrochlorination and increase the thermal decomposition temperature of PVC, making it higher than the melting processing temperature of PVC.
The melt processing temperature of the modified PVC is much lower than its thermal decomposition temperature.
In addition, PVC melts also have deficiencies such as low melt elasticity and poor ductility, and the addition of processing aids can improve the defects such as melt fracture and matt products during PVC processing.