Thermoreversible crosslinked thermoplastic starch

A novel furan-modified thermoreversible crosslinked thermoplastic starch was synthesized. The crosslinking mechanism was based on a thermoreversible furan/maleimide adduct formed by the Diels - Alder reaction. Thermoplastic starch (TPS) was first modified by forming a urethane linkage between the product of the reaction of furfuryl alcohol with 4,4-methylene diphenyldiisocyanate and a starch hydroxyl group. Crosslinking was then achieved by the addition of 1,1-(methylene-di-4,1-phenylene) bismaleimide to the furan-grafted starch in solution (dimethylsulfoxide) and in the molten state during conventional extrusion. The materials were characterized by Fourier transform infrared and H-1 NMR spectroscopy. The thermoreversible reaction was assessed by viscosity measurement and H-1 NMR, for the system in dimethylsulfoxide, and by solubility tests, hot-pressing experiments and dynamic mechanical analysis measurements for the extruded product. The crosslinked product showed a higher storage modulus and water resistance than its non-crosslinked counterpart, opening novel opportunities to widen the range of TPS applications. (c) 2015 Society of Chemical Industry (AU)