Effect of maleic anhydride concentration and reaction time on chemical modification of starch by reactive processing for compatibilization of starch/PBAT blends

Abstract

The increasing request for the use of sustainable packaging has driven developments in the area of biodegradable polymers. Such requests are due to the fact that these materials are usually used just once, which generates a large amount of waste. Among the biodegradable polymers, thermoplastic starch is the most important, mainly because it comes from natural and abundant sources. However, their intrinsic characteristics make it unsuitable for packaging applications because this polymer presents low moisture resistance, high stiffness, and difficulty in processing. To overcome such drawbacks, a viable alternative is to blend thermoplastic starch with low hydrophilicity, flexible and adequate processability polymers, such as poly (butylene adipate-co-terephthalate) (PBAT). However, because these polymers are incompatible, chemical modifications of starch become necessary. In previous works, developed with financial support from FAPESP (process 2012/08380-4), the chemical modification of starch with maleic anhydride and sebacid acid by reactive processing for the formation of esters in the starch chain was studied and, in a subsequent step, blends of thermoplastic starch (modified or not)/PBAT were produced and their compatibility studied by means of mechanical properties and morphological analyses. In this study, it was observed that the modification of thermoplastic starch with maleic anhydride has led to greater compatibility between the phases starch/PBAT, but the morphological analysis indicated the presence of crystals of unreacted maleic anhydride in the compatibilized blends. Thus, continuing with this study, we intend to evaluate the influences of the maleic anhydride content and reaction time on the chemical modification of thermoplastic starch by reactive processing and assess the influence of the concentration of reacted maleic anhydride, which may depend on the initial concentration and on the reaction time, in the mechanical properties, morphology and biodegradability of blends thermoplastic starch/PBAT. (AU)