Modification of polymers by protein hydrolysate - A way to biodegradable materials

Abstract

The increasing use of plastics and their non-biodegradability have raised environmental awareness and hence the need for the development of environmently friendly degradable materials. One of the ways to reach this goal is via the modification of polymer with starch, cellulose, protein and other water-soluble materials. This can also be achieved by protein hydrolysate (HP) which is a biopolymer isolated from the chrome-tanned solid leather waste of the tanning industry by enzymatic hydrolysis. An investigation on the modification of metallocene-based linear-low-density polyethylene (mLLDPE) with HP is reported. It is interesting to note that HP easily blends with mLLDPE but like other biopolymers it also reduces the original mechanical properties of the mLLDPE. Modification of the latter with 10% HP does not have much effect on the physical, mechanical and rheological behaviour. About 35% biodegradation is observed when the polymer is modified with 20% HP and about 50% biodegradation is found in the case of polymer modified with 40% HP by Aspergillus oryzae (F-172) under controlled laboratory conditions, at a temperature of 25degreesC and after a period of 21 days incubation in malt extract media. Although polymer films with 40% HP have shown better performance in biodegradation, the mechanical strength properties, however, are rather poor in this case. The optimum polymer film composition for modification of mLLDPE is 20% HP, which retains both an acceptable range of mechanical strength properties and biodegradability behaviour. Copyright (C) 2003 John Wiley Sons, Ltd.