Free-radical-initiated grafting of
maleic anhydride (MA) onto
poly(butylene adipate-co-
terephthalate) (PBAT), a biodegradable aliphatic-aromatic copolyester, was performed by reactive extrusion. 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane was used as the
free-radical initiator. The
peroxide concentration was varied between 0.0 and 0.5 wt % at 3.0 wt % MA concentration; the MA concentration was varied between 1.0 and 5.0 wt % at 0.5 wt %
peroxide concentration. The reaction temperature was maintained at 185 degrees C for all experiments. Under these conditions, between 0.194% and 0.691% MA was grafted onto the
polyester backbone. Size-exclusion chromatography, melt flow index, intrinsic viscosity measurements, thermal gravimetric analysis, and differential scanning calorimetry were used to characterize the maleated copolyester. Increasing the initiator concentration at a constant MA concentration of 3% resulted in an increase in the grafting of MA while decreasing the molecular weight of the resulting
polymer. Increasing the feed MA concentration also increased the grafting percentage. The maleation of the
polyester proved to be very efficient in promoting strong interfacial adhesion with high
amylose cornstarch in
starch foams as prepared by melt blending. Thus, the use of maleated copolyester as a compatibilizer between
starch and PBAT allowed the reduction of the density of resulting
starch foams to approximately 21 kg/m3 and improved the resilience from 84% to as high as 95%. Also, the resulting
starch foams exhibited improved hydrophobic properties in terms of lower
weight gain and higher dimensional stability on moisture sorption.