DIAGNOSING MECHANISMS OF OLIGOMER FORMATION IN THE THERMAL-DEGRADATION OF POLYMERS

When attempting to find the mechanisms involved in the thermal degrada tion of polymers, a problem arises when oligomers are observed as the principal products of thermal decomposition. In this case, one or more of at least three different general mechanisms may be responsible: (i ) a high degree of random scission, (ii) intramolecular transfer durin g unzip, and/or (iii) secondary reactions of the primary products. Thi s paper illustrates how these mechanisms can be differentiated by: (i) appropriate statistical plots of the yields of the products, (ii) qua ntitative measurements of rate constants for the evolution of the vola tiles, and (iii) measurements of product yields and ratios as a functi on of sample size. Examples of the deduction of oligomer formation mec hanisms are chosen from results for the following polymers: BIOPOL, po lyisobutylene, polymethylacrylate, natural rubber, and polystyrene. (C ) 1996 Elsevier Science Limited.