UV curing behavior of hyperbranched polyphosphate acrylate/di(hydroxylpropyl methacrylate) piperazine and properties of the cured film

The hyperbranched polyphosphate acrylate (HPPA) was blended with di(hydroxylpropyl methacrylate) piperazine (DHMP) to form a photopolymerizable flame retardant resin. The photopolymerization kinetics was investigated and showed that as DHMP added, the polymerization rate increased greatly while the final unsaturation conversion in the cured film decreased moderately. The thermal degradation and flame retardant behaviors of the cured HPPA/DHMP film showed that although the initial decomposition temperature raised, both the char residue and the limiting oxygen index largely decreased due to the reduction of phosphorus in the film with increasing the DHMP content. From the results by the dynamic mechanical thermal analysis DHMP has good miscibility with HPPA. The crosslink density and glass transition temperature of the cured film increased along with the content of DHMP in the blend. The mechanical property measurements indicated that the addition of DHMP led to a decrease in elongation-at-break and an increase in tensile strength.