Influence of radiation-crosslinking on the elongation behaviour of glass-fibre-filled sheets in the thermoforming process

Thermoforming is one of the most important processes in polymer processing. In the packaging industry, thermoformed parts such as blister packs are manufactured from amorphous plastics such as polystyrene (PS) or polyvinyl chloride (PVC). In the field of semi-crystalline thermoplastics, mainly standard thermoplastics, such as, for example, polypropylene (PP), polyethylene (PE), or polyethylene terephthalate (PET), are used. There is limited literature dealing with the thermoforming of thin filled systems. Filler bonding, in particular, represents a major challenge in strain rheology. Electron irradiation is a way to generate improved filler-matrix bonding. In this study, the influence of fillers and radiation-crosslinking on the elongation behaviour and on the wall thickness distribution was investigated. At higher areal draw ratios, an enormous benefit of radiation-crosslinking of thin filled sheets is shown. While non-crosslinked specimens could not be formed, it was possible to thermoform radiation-crosslinked sheets filled with 10 vol.% glass fibres. Furthermore, with the higher areal draw ratio, the influence of the filler orientation on the stretching behaviour became more apparent.