The use of shredded car windscreen waste as reinforcement of thermoplastic composites for 3D (FDM) printing

The work presents preliminary attempts to create a filament for 3D printing (FDM technique) based on a low density polyethylene (LDPE) composite reinforced with shredded windscreen glass. The glass powder was obtained by grinding windscreen glass wastes. PVB (polyvinyl butyral), which is an integral part of safety glass car windscreens, was not removed from the obtained powder. The obtained powder had a range of grain diameters 90÷160 µm. The powder was then mixed mechanically and in an ultrasonic chamber with LDPE granulate. The composites were made by extrusion with one regranulation cycle. The filament for FDM printing was produced by extrusion winding with cooling in open air. A filament with a diameter of 1.45±0.05 mm was obtained. The produced filaments were subjected to a static tension test and SHORE hardness tests. In order to compare the material, the maximum stress recorded at 50% elongation was determined for each tested material. It was observed that along with the increase in the glass content, the strength of the filament decreased slightly. The basic stage in evaluation of the produced materials was to carry out trial prints on an FDM printer. The printing temperature was selected experimentally during a series of trials. The best results were obtained at the print temperature of 250°C and table temperature of 90°C. During printing, an unfavorable effect of filament bending was observed in the printer, below the supplying roller. This effect occurred during printing at a supply speed of more than 1 mm/s. Special additional printing tests with supply rates below 1 mm/s were carried out. This made the printing possible, and it showed the evident superiority of the composites over the neat LDPE. The problem with the stability of filament supply during printing was partially solved by mechanical stiffening of the line between the rollers, using specially printed inserts. The trial prints made from the tested composites occurred to be of better quality than those from the neat LDPE. They show less deformation caused by shrinkage. These effects result from stiffening of the material caused by the addition of hard glass particles. It was found that an addition of a minimum of 30% of the glass particles is required to have a significant effect on the LDPE stiffness.