Flame-retardant additive for PVC and preparation method of flame-retardant additive

The invention relates to a flame-retardant additive for PVC. The flame-retardant additive is mainly prepared from the following components in parts by mass: 1-3 parts of octabromo ether, 4-5 parts ofclosed-cell perlite, 6.5-8 parts of a flame-retardant polyether polyol, 4-6 parts of graphene, 1-2 parts of magnesium hydroxide, 1-2 parts of an ethoxylated aliphatic alkylamine and 5-10 parts of a linear polysiloxane. According to the flame-retardant additive, through mutual cooperation of octabromo ether, closed-cell perlite, the flame-retardant polyether polyol and magnesium hydroxide, a good combined flame-retardant effect is achieved, the smoke generation amount in the PVC combustion process is obviously improved, and harm to escape personnel is reduced. Besides, graphene and linear polysiloxane are added into the formula of the flame-retardant additive, so that the heat resistance of the PVC material is obviously improved, the flame resistance of the PVC material is enhanced by virtue of a silicon-carbon bar