Thermo-chemical transition in cellulose esters and other polymers

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 degrees 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.

Automated summary

The peculiar thermochemical phenomenon called glass chemical transition is observed in cellulose acetate butyrate (CAB), as well as in cellulose acetate (CA) and other mixed esters. The intense endotherm below 100 degrees C in cellulose esters is mainly attributed to esterification. The stability of the acetyl bond in CAB and CA is analyzed, showing that thermo-chemical transitions are not exclusive to cellulose esters, but are instead a common phenomenon encompassing physicochemical changes and material softening.