PROPERTIES OF FATTY-ACID ESTERS OF STARCH AND THEIR BLENDS WITH LDPE

In the present study, starch octanoates OCST1.8 and OCST2.7 with degre es of substitution (d.s.) of 1.8 and 2.7, respectively, and dodecanoat e DODST2.7 (d.s. = 2.7), were prepared by esterification of native sta rch with fatty acid chlorides. Our analyses, including elemental analy sis, FTIR, contact angle, DSC, and TGA measurements confirmed the este rification reaction of starch and the degree of substitution. The este r group was found to act like an internal plasticizer, with an increas e in the number and the size of fatty acyl chains grafted onto starch. These starch esters were mixed with low density polyethylene (LDPE) a t various proportions in a Haake Rheomixer. Water and moisture absorpt ion, thermal and mechanical properties, and biodegradation were invest igated as a function of blend composition. The DODST2.7/LDPE blends sh owed, in general, better thermal stability and higher elongation, but lower tensile strength and water absorption, than did corresponding OC ST/LDPE blends. The addition of starch esters to LDPE led to a very sl ow rate of biodegradation of these blends. (C) 1997 John Wiley & Sons, Inc.