Flexible thermoplastic composite of Polyvinyl Butyral (PVB) and waste of rigid Polyurethane foam

This study reports the preparation and characterization of composites with recycled poly(vinyl butyral) (PVB) and residue of rigid polyurethane foam (PUr), with PUr contents of 20, 35 and 50 wt %, using an extruder equipped with a Maillefer single screw and injection molding. The components of the composites were thermally characterized using differential scanning calorimetry (DSC) and thermogravimetry. The composites were evaluated by melt flow index (MFI), tensile and hardness mechanical tests and scanning electron microscopy (SEM). Tg determined by DSC of PVB sample (53 °C) indicated the presence of plasticizer (Tg of pure PVB is 70 °C). MFI of the composites indicated a viscosity increase with the PUr content and, as the shear rate was held constant during injection molding, higher viscosities promoted higher shear stresses in the composites, thereby causing breaking or tearing of the PUr particles. The SEM micrographs showed low adhesion between PVB and PUr and the presence of voids, both inherent in the rigid foam and in the interphase PVB-PUr. The SEM micrographs also showed that PVB/PUr (50/50) composite exhibited the smallest particle size and a more homogeneous and compact structure with fewer voids in the interface. The stiffness of the composites increases with addition of the PUr particles, as evidenced in the mechanical tests.