Efecto del reprocesado y envejecimiento en polímeros técnicos

Abstract

ABSTRACT In this doctoral thesis the viability of reprocessing has been assessed as a possible alternative for recycling two of the most used technical polymers , the polycarbonate of bisphenol A (PC) and the térpolymer acrylonitrile-butadiene-styrene (ABS). The techniques used for the reprocessing have been injection and extrusion because they are the most commonly used in the processing of thermoplastics. Up to ten cycles of reprocessing have been performed with each of them. The mechanical recycling of plastics does not only involve the problem of degradation during the reprocessing but, obviously, the material has already suffered a detriment of their properties during its life cycle. One factor that produces more a degradative effect on plastics is sunlight and, especially, ultraviolet light (UV). Therefore, in order to study this effect, the thermoplastics have been submitted to an accelerated ageing through exposure in chambers that simulate the UV light. The study has tried to determinate how the mechanical and thermal properties change when the material is reprocessed, aged and when both degradative effects are combined. As regards the thermal properties (glass transition temperature and thermal stability) it has been observed that in the case of polycarbonate, they decrease with the reprocessing cycles, however for the aged polymer the glass transition temperature remains constant, whereas the thermal stability decreases. In the case of ABS both properties remain unchanged for the two degradative effects. In the case of mechanical properties analyzed, tensile strength and impact, it has checked that in the polycarbonate both of them decrease with the cycles of reprocessing while in the ABS only slightly the impact resistance does . The accelerated ageing causes a decrease in the mechanical properties of polycarbonate when it has been previously reprocessed, while in the ABS this decrease occurs in all the cases. The most significant conclusion of the work is that the reprocessing may be an alternative for the recycling of polycarbonate and ABS terpolymer.