BIODEGRADABLE AND HIGHLY RESILIENT POLYURETHANE FOAMS FROM BARK AND STARCH

Abstract

Liquefaction of the Acacia mearnsii bark (BK) and cornstarch (CS) has been conducted by using a solvent mixture consisting of polypropylene glycol (PPG), glycerol and sulfuric acid with a weight fraction of (94/5/1) at 150 C. Solubilities of BK and CS were about 80% for 60 min and 100% for 20 min in the same solvent, respectively. Highly elastic or highly resilient polyurethane foams (PUFs) for car-seat cushions have been prepared from the liquefied BK and CS without removing insoluble residue from the liquefaction mixture. About 20% insoluble residue from BK contributed remarkably to the improvement of flame resistance of the resulting PUFs. PUFs having better resilience properties were prepared using PPG of molecular weight around 4000, as compared with polyethylene glycol having the same hydroxyl value. PUFs were synthesized from three BKs with different tannin contents to evaluate the effect of tannin content on their performances of resilience. Both the resilience value and density of the PUFs increased with increasing BK content for all BK systems. A BK with the largest tannin content, 48.5%, provided PUFs possessing the best resilient property. Density and flame resistance are the important properties for commercialization, from cost and burning safety points of view, respectively. When CS replaced partly BK, the density and compressive strength of the PUFs decreased with increasing CS proportion whereas resilience value had its maximum value when the weight ratio of CS:BK was 1:1. The PUFs were to some extent biodegradable, the average weight loss of samples buried in soil for 6 months was 15.6 wt %.