Effects of storage on thermomechanical properties of poly(epsilon-caprolactone) blends containing poly(vinyl pyrrolidone/iodine)

This study reports the effects of: the molecular weight ratio of poly(epsil on -caprolactone) (PCL) in blends containing polymer of high (50 000 g mol( -1)) and low (4000 g mol(-1)) molecular weight; the concentration (0, 1, an d 5 wt-%) of poly(vinyl pyrrolidone/iodine) (PVP/I); and storage at 30 degr eesC and 75% relative humidity; on the thermomechanical properties of films prepared by solvent evaporation from solutions containing both PCL and PVP /I. The tensile properties were found to be statistically dependent on the molecular weight ratio of PCL but not on the concentration of PVP/I. The re ductions in tensile strength and elongation at break associated with increa sing amounts of low molecular weight PCL were attributed to a reduction in the concentration of chain entanglements. No changes were observed in visco elastic properties or the glass transition temperature. Following storage t here were no changes in the tensile strength, glass transition temperature, or viscoelastic properties of the films; however, significant reductions i n elongation at break were observed. It is suggested that this is due to hy drolytic chain scission of amorphous PCL. Inclusion of 5 wt-% PVP/I increas ed this process in films containing 100:0 and 80:20 high/low molecular weig ht PCL (but not 60.40), but the extent of this was small. This study highli ghted significant aging properties of PCL in a moist atmosphere. Consequent ly, it is recommended that suitable packaging materials should be employed to control the exposure of PCL films to water during storage.