WATER-VAPOR PERMEABILITY OF BIODEGRADABLE POLYMERS

The water vapor transmission rates (WVTR) of several biodegradable pol ymers were evaluated to determine their suitability as water-resistant coatings and to understand WVTR better in terms of polymer structure. Values of WVTR at 25 degrees C ranged from 13 to 2900 g/m(2)/day and increased in the order PHBV < PLA (cryst.) < PLA (amorph.) < PCL < Bio nolle < BAK 1095 < CAP < CA. Values of WVTR were positively correlated with higher polymer solubility parameters, lower crystallinities, and higher free volumes. Although the WVTR of biodegradable polymers are much higher than those of good barrier materials such as low-density p olyethylene, they are sufficient for short-term (hours to days) protec tion of polysaccharide-based materials against water.