Preparation of boric acid supported natural rubber as a reactive flame retardant and its properties

Boric acid supported natural rubber (BSNR) was prepared from the reaction between hydroxyl group in diol functionalized natural rubber and boric acid. The optimum condition was assessed by the influences of different boric acid concentrations used in a term of [boric acid]/[diol unit] molar ratio and reaction time. The increase of them led to increasing the participation of boric acid into the rubber molecules, which was structural as boronic acid unit in BSNR. The determination of boron element quantity of BSNRs was found to increase with increasing mole% of boron containing rubber. Furthermore, the increase of mole% of boron content caused the increase of Mooney viscosity, glass transition temperature (Tg), thermal stability and improving flammability behaviors by the reduction of HRRmax, THR, EHC, MRL, CO2 and burning rate as well as the increase of LOI values over original epoxidized natural rubber (ENR).