Compatibilization of polymer mixtures during processing of waste products from thermoplastics

Introduction. The recycling of thermoplastic waste into building materials with a long-life cycle is a promising and technologically feasible disposal direction. It is advisable to develop the processing of mixed polymer waste. Thermoplastics are thermodynamically incompatible, and technological compatibility can be controlled at the melt stage by the introduction of compatibilizers and nanofillers, the formation of free radicals in the melt, and reaction compatibilization. Materials and methods. The work aimed to study the effect of a compatibilizer – an ethylene-vinyl acetate copolymer with grafted acrylate and epoxy groups on the properties of composites obtained from mixtures of polyethylene terephthalate and polypropylene waste. The polymer mixture was melted, filled with limestone flour (50–85 wt.%), the samples were pressed, and their physical and mechanical properties were investigated. Results and discussion, conclusions. Differential thermal analysis established the melt preparation temperature of 240оC, which is below the onset of thermal oxidative destruction of the compatibilizer. It was established that the optimal ratio of polyethylene terephthalate: polypropylene: compatibilizer as 70:25:5 wt.% provided the greatest improvement in the bending strength without compromising the compressive strength of filled composites; the optimal degree of filling was found to be 60–70%. The volume fractions of polymers in the mixture are comparable. Therefore, one can expect the formation of both the matrix structure of the composite and the interpenetrating networks type structures. In both cases, the compatibilizer is distributed along the interphase boundaries. Its effect on properties can be attributed to its plastic deformation in the interfacial layer and morphological changes in the structure of the polymer mixture. There is evidence of increased structure-sensitive properties, tensile and tensile strength, of polymer mixtures containing this compatibilizer. This fact indicates an increase in adhesion between polymer phases, which is difficult to explain only for physical reasons. Possible reactions between the functional groups of the compatibilizer and polyethylene terephthalate in the melt with epoxy ring opening were analyzed. An increased effect of compatibility was revealed; however, the actual effectiveness of the compatibilizer is difficult to assess. Additional mechanical tests are required as well as optimization of the melt temperature. It is also necessary to find a balance between activating the reaction compatibilization and minimizing destructive processes in polymers.