Improvements of natural rubber for flame resistance

The present invention provides a process for treating natural rubber to increase its flame retardant capability. Theprocess comprises a mixture of a natural rubber with, (a) halogenated free flame retardant agent (zinc hydroxystannate;STORFLAM ZHS) and (b) halogenated flame retardant agent (decabromodiphenyl; Great Lake DE-83R and chlorinatedparaffins; Plastoil 152) and another material like antimony trioxide and aluminium hydroxide in appropriate amount, with ratio of halogenated flame retardant agent: antimony trioxide 3:1. In the resulting product with halogen flame retardant showed a more efficient flame retardant property than halogen free flame retardant, i.e. brominated flame retardant provide higher efficiency than chlorinated and ZHS, respectively. The minimum requirement ratio for being flame retardant of antimonytrioxide: brominated or chlorinated agent is 7:21 or 10:30 phr while aluminium hydroxide: ZHS is 10: 150 phr. It was found thatburning rate was zero for brominated and chlorinated agent used but not for zinc hydroxyl stannate system. Average time of burning (ATB) was 135, 118 and 41 second for brominated, chlorinated and ZHS flame retardant, respectively. Average extent of burning (AEB) was 24, 19 and 14 millimeters, respectively. An advantage of this invention is that chemicals (antimony trioxide and either brominated or chlorinated agent) added to natural rubber have the effect of rendering the natural rubber flame-resistant like synthetic rubbers, chloroprene.