Hydrophilicity/hydrophobicity properties biodegradation mechanisms

Among others, chain flexibility/rigidity, crystallinity, hydrophilicity/hydrophobicity, molecular weight, chemical property, biodegradability, thermal property, mechanical property, and electrochemical property of polymers are considered to affect the performance of membranes most strongly. Moreover, these properties are often mutually interrelated. 

The naturally biodegradable polymers such as starch, chitosan and cellulose derived from natural sources have produced a number of interesting NR blends and IPNs. These blended systems have an advantage in that they create fewer waste disposal problems compared to the petroleum based polymeric materials. The use of stareh blends to enhance the biodegradability of conventional plastics has been reported by many researchers in order to reduce the environmental impaet of petroleum based plastic products and waste. The NR/maize stareh blends exhibited a decrease in their mechanical strength due to the speeifie properties of starch. However, the blended polymers showed a low interfaeial interaetion between the two phases due to the different polarity behaviour of the hydrophobic NR and the hydrophilic starch. 

Chitosan is a water-insoluble, nontoxic, edible, biodegradable polymer (polysaccharide) that is obtained commercially from chitin by alkaline deacetylation [103]. Chitosan is the second most abundant biopolymer in nature after cellulose. Since chitosan is a polycationic polymer, its high sensitivity to moisture limits its applications. One way to overcome this drawback is to blend the material with humidity resistant polymers such has PLA. Suyatma et al. [104] combined hydrophilic chitosan with hydrophobic PLA (92% L-lactide and 8% mesolactide, Mw = 49,000 Da) by solution and film mixing, resulting in improved water barrier properties and decreased water sensitivity of the chitosan films. However, testing of mechanical and thermal properties revealed that chitosan and PLA blends are incompatible. 

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