Recycled poly(ethylene terephthalate)/recycled polypropylene blend: Effect of hygrothermal treatment

The amount of waste that arise from post-consumer poly(ethylene terephthalate) (PET) and polypropylene (PP) especially in the packaging industry have stimulated an in depth investigation to produce innovative new products from recycled PET and recycled PP for application in the composite and synthetic fiber industries. Although PP absorbs very little moisture due to the absence of polar groups in its chemical structure, the main concern is the stability of hygroscopic PET in the presence of water. In this work, recycled poly(ethylene terephthalate)/ recycled polypropylene (RPET/RPP) blends with addition of compatibilizer was injection molded into dumbbell specimens and then subjected to hygrothermal aging in a water bath set at 60°C to determine the amount of moisture absorption. Evaluation of mechanical performance during the increment of water uptake provides information on the durability of the material after exposure to both water and temperature. Water absorption rate was found to be higher when higher compatibilizer content was present resulting into a significant decline in tensile strength. This suggests that the compatibilizers are mostly present at the interface between RPET and RPP phases to form an interphase region that is sensitive to both moisture and heat.