Polymer toughening using residue of recycled windshields: PVB film as impact modifier

In this work, poly(vinyl butyral) (PVB) film originated from the mechanical separation of windshields was tested as an impact modifier of Polyamide-6 (PA-6). The changes undergone by PVB film during the recycling process and the blend manufacturing were evaluated by thermal analyses, infrared spectroscopy and loss on ignition. Blends of PA-6/original PVB film and PA-6/recovered PVB film were obtained in concentrations ranging from 90/10 to 60/40. The mechanical properties of the blends were investigated and explained in light of the blends morphologies, which in turns were correlated to the changes undergone by the PVB film during the recycling process. The original film presented a plasticizer content of 33 wt.%, which decreased to as low as 20 wt.% after the recycling and blend preparation processes. The PA-6/PVB film blends presented lower values of tensile strength and Young’s modulus than Polyamide-6, but all blends presented a dramatic increase in their toughness, with a special feature for the 40 wt.% blend, which resulted in a super toughened material (impact strength exceeding 500 J/m). Similar results were obtained with recovered PVB film and super tough blends were also obtained. The use of recovered PVB resulted in a smaller improvement of the impact strength due to the loss of plasticizer undergone during the recycling process. The morphological observations showed that if the interparticle distance is smaller than around 0.2 μm (critical value), the notched Izod impact strength values increase considerably and the fracture surface of blends exhibit characteristics of tough failure.