PVC is the first ideal structure - tail structure -CH2-CHCl-CH2-CHCl-, is quite stable . But so far the PVC synthesis method can not be like synthetic butadiene rubber , as the role of catalyst in stearate aluminum Jigger so there are rules for orientation cis butadiene polymerization .
Radical polymerization of vinyl chloride is a random polymerization , in addition to its first stable - tail structure , there are first - the first structure - CH2-CHCl-CHCl-CH-, tail - tail structure -CHCl-CH2-CH2-CHCl - ; generating a coupling disproportionation vinyl Results CH2 = CH-CHCl-CH2- structure and allyl chloride -CH2-CH = CH-CHCl-CH2 and so on .
Generated in the PVC synthetic allyl chloride, chlorine and tertiary carbon double bond in its molecular chain structure magnesium stearate instability , unstable order : PVC within the molecular chain allyl chloride > tertiary carbon Chlorine > allyl end groups chloride > Chung chlorine. PVC is susceptible to degradation during processing because of the structure of PVC molecular chain instability exists , if not modified for stabilization , the decomposition temperature is about 130 ℃ , but that the PVC resin processed into useful articles , molding temperature to at above 190 ℃ . Therefore , you must add heat stabilizers stabilize its structure improvements.
Pvc in the synthesis process so you need to add PVC heat stabilizers.
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