The thermal properties of porous polydivinylbenzene beads

The thermal properties of some porous polydivinylbenzene beads, prepared fr om commercial divinylbenzene, pure m-divinylbenzene, pure p-divinylbenzene or their mixture, were evaluated by thermogravimetry (TG) and differential scanning calorimetry (DSC). The results showed that two kinds of exothermal reactions were newly found, respectively, in the range of 150-160 and 220- 280 degreesC during heating in DSC measurement of the samples while thermal decomposition temperature in TG curves was increased with the content of d ivinylbenzene monomers. The further study indicated that all these exotherm al reactions were related to pendant double bonds in the porous polydivinyl benzene beads. The first kind of exothermal reaction should be the thermal coupling reactions of the double bonds close to each other in space. The se cond one might be the oxidation of double bonds or the sites activated by e thenylphenyl group. The mechanisms of two kinds of exothermal reactions wer e proposed and the factors to affect the thermal reactions or thermal stabi lity were discussed. As a conclusion, only those highly crosslinked polysty renes with little or without pendant double bond, other than polymers of pu re divinylbenzenes, would have better thermal stability chemically and/or p hysically. (C) 2001 Elsevier Science BY. All rights reserved.