Thermo-chemical transition in cellulose esters and other polymers

Abstract A peculiar thermochemical phenomenon of coexistence of chemical decomposition and material softening, observed in cellulose acetate butyrate (CAB) and named glass chemical transition is further scrutinized. It is demonstrated that cellulose acetate (CA), also, exhibits a thermo-chemical transition and that mixed esters like CAB, may exhibit more than one thermo-chemical transitions. The DSC intense endotherm below 100 °C, common in cellulose esters, is shown to arise, mainly, from esterification. The variation of the stability of the acetyl bond in CAB and CA is also analyzed. A critical discussion of these findings along with corroborating experimental data for poly(vinyl alcohol) (PVA) and literature data for vinyl polymers is presented, suggesting that the thermo-chemical transition is not a phenomenon exhibited, exclusively, by cellulose esters. Instead, it is an often-encountered phenomenon encompassing physicochemical changes and material softening at temperatures erroneously attributed to glass transitions or melting points.