Radio-frequency compression molding of recycled commingled polymers

The increasing consumption and resistance to natural decomposition of plastic materials has caused an ecological problem that is waiting for solutions, including economical recycling technologies. In this work, the properties of compression molded plastic boards made of commingled pellets of Polyethylene (PE) and Polyvinyl chloride (PVC), two incompatible widely used polymers, are investigated. The commingled pellets were mechanically mixed and flat boards with different ratios of PE and PVC were produced by compression molding, one set using radio frequency (RF) electromagnetic heating and the second using conventional conductive heating (CH). The main advantage of the RF system over the CH system is the much shorter heating time required to reach processing temperatures, making it an economically attractive alternative. However, the speed and intensity of the heat acting on the PVC in the RF process caused a reduction of the mechanical properties of the boards as a consequence of the degradation of the PVC. This problem was solved by the addition of process-specific additives, organic and inorganic, placed at the pellet's interface. The results of this work demonstrate that commingled plastics can be efficiently compression molded using radio frequency, providing an alternative to conventional compression molding using conductive heating.