Properties of starch based blends. Part 2. Influence of poly vinyl alcohol addition and photocrosslinking on starch based materials mechanical properties

Mechanical properties of starch/PVA blends (maximum 5% wt PVA), with or without crosslinking, have been analyzed in order to study how the increase in the linear to branched chain can improve the materialʹs performances. As a result, elongation is enhanced without significant strength decrease for both casting and extrusion processes. Water sorption and photocrosslinking ability have also been measured showing a fairly good compatibility between the two macromolecular components: PVA and starch. For example, a decrease in water sorption on PVA addition was observed which could not simply be related to additivity between the two polymers. Finally, systems composed of pure glycerol plasticized starch blends were photocrosslinked at very low rates in order to ‘lengthen’ the macromolecules. The results of the mechanical tests on these materials showed an enhancement of the elongation at break. results highlighted the fact that a modification of the molecular weight distribution (or linear long chains ratio, i.e. PVA) led to the development of entanglements or long distance interactions (strain at break increase).