Influence of an Increased Fiber Filler Content on the Elongation Behavior of Filled Films in the Thermoforming Process

Abstract

Thermoforming belongs to one of the most important processes in polymer processing, especially in the packaging industry. It enables the forming of thermoplastic components into shaped parts at high temperatures. Since the thermoforming of films takes place in the rubbery state, amorphous thermoplastics are mainly processed, which have a wide rubbery state. Radiation crosslinking can be used to widen the thermoforming window of semi-crystalline thermoplastics. A benefit of the crosslinking is the increased short-term temperature resistance. In general, there are only a few investigations concerning the thermoforming of filled thin films. Within this investigation, the influence of an increasing glass fiber content up to 15 vol.-% as well as the effect of radiation crosslinking on the elongation behavior and the wall thickness distribution was examined. It can be summarized that especially thermoforming with an increased filler content at high areal draw ratios represents a challenge. Whereas non-crosslinked glass fiber filled films are thermoformable only at low areal draw ratios, radiation crosslinked films can be also formed at higher areal draw ratios without difficulties. For high filler contents and high areal draw ratios, no forming is possible at high areal draw ratios, although the films have been crosslinked. The use of radiation crosslinking enables the process limit in thermoforming of thin filled films to be increased and thus the range of applications to be extended greatly.