Papers # 2012 Barcelona
Bioriented pipes or plates show strongly improved mechanical properties compared with standard u-PVC. It is known that biorientation process is less efficient on PVC composition with lower molecular weight. The target of this study is to quantify the relationship between the molecular weight (Kw) of the composition and the mechanical properties obtained after biorientation. The study is realised mainly with bioriented sheets. PVC sheets were prepared with identical formulation from different molecular weights (from K 50 to K 69). These plates were stretched (above Tg) and cooled down in order to realise the biorientation process. The examination of mechanical properties of the plates shows that these properties are at a high level for all K-values except for very low K values ( 57). For the higher K-values, the level of gelation also shows a significant influence on the final properties of the item. These results were confirmed with an industrial scale pipe extrusion.