As shown in Fig. 1 the molecular weight decreased as the num- ber of reprocessing cycles increased, although this decrease was not too drastic. Moreover, in the injection reprocessing, as a conse- quence of a higher temperature, the thermal degradation processes increased and the shear degradation effects were also favoured. As a result, the molecular weight decreased in a greater extent than for the extrusion reprocessing. Taking into account that the degrada- tion reactions do not change the chemical structure of the polymer, as tested by FTIR measurements, molecular scission seems to be the degradation process.
This result suggests that the properties that depend on the molecular weight are affected significantly due to reprocessing. The decrease of the molecular weight with the number of reprocessing cycles has been already reported by Abbas (1980) and Eguiazabal and Nazabal (1989), However, they only evaluated the injection process and a lower number of reprocessing cycles.