Expandable graphite systems for phosphorus-containing unsaturated polyesters. I. Enhanced thermal properties and flame retardancy

A series of flame retardant-containing unsaturated polyesters have been developed. The flame retardants include expandable graphite and phosphorous-containing materials (ammonium polyphosphate (APP) and triphenyl phosphate (TPP)). The effects of incorporating different flame retardants into the unsaturated polyesters were investigated by UL-94, DSC, TGA, LOI, MTGA, Py/GC/MS and adiabatic bomb calorimeter. The results indicate that the flame-retarding effect of APP type flame retardant was better than that of the TPP type as the phosphorous-containing flame retardant was the sole additive in this system. Moreover, the flame-retarded effect was further improved as the phosphorous-containing flame retardant and expandable graphite were both added to the polyester. This indicates that a pronounced additive effect was present as the expandable graphite was added to the phosphorous-containing unsaturated polyesters, especially the APP-containing type. (C) 2004 Elsevier Ltd. All rights reserved.