Consecutive steps of PET recycling by injection: Evaluation of the procedure and of the mechanical properties

The procedure of five consecutive recycling steps by injection moulding of postconsumer PET was evaluated on the basis of processing and drying parameters. The equations that govern the increase in sample mass of the polymer while in contact with the atmosphere were obtained on the basis of weight variation measurements before and after drying. Two series of consecutive recycling steps were also carried out, starting from virgin material (with and without sieving), which showed that, for the sieved material, the decrease in productivity was always in the same order of magnitude as the decrease in viscosity. Thus, the remaining differences, which exceeded 400%, can be attributed to the presence of powder. The crystallinity, transition temperatures, concentration of carboxyl end-groups, tensile properties, and impact resistance of the samples obtained in each step were determined. The number of carboxyl end groups increased by about three times after the five recycling steps and the crystallinity was enhanced, going from 23% to 37%, which explains the alterations in the modulus of elasticity, elongation at break, and impact resistance.