Pyrolysis of unsaturated polyester resin. Quantitative aspects

The thermal decomposition of this resin was examined by quantitative pyrolysis—gas chromatography. The decomposition does not follow the Hurd–Blunck mechanism generally obeyed by beta-hydrogen containing esters. Instead, phthalic anhydride is extruded almost quantitatively. It is proposed that the mechanism involves the rearrangement of the phthalate C O bonds to extrude the anhydride, leaving a maleic acid—dipropylene glycol polyester chain.