Study on the preparation of maleated thermoplastic starch by reactive extrusion

Maleated thermoplastic starches (MTPS) were prepared by reactive extrusion, with corn starch as raw material, glycerol as the plasticizer, and maleic anhydride (MAH) as esterification agent. The influence of the amount of MAH on MTPS properties was studied. With thermoplastic starch (TPS) as contrasting sample, Fourier transform infrared spectroscopy results displayed that esterification reaction successfully occurs between corn starch and MAH. The degree of substitution (DS) results showed that the DS of MTPS increased along with the increasing amount of MAH. X-Ray diffractometry results showed that esterification reaction resulted in the decrease of crystallinity of TPS, indicating that the thermoplastic property of starch was improved. The greater the proportion of MAH, the more decreased is the degree of crystallinity of MTPS. Differential scanning calorimetric results showed that the melting temperature and enthalpy of melting decreased with increasing the amount of MAH. The thermal weight loss initial temperature of MTPS was below TPS, and thermal weight loss rate was greater than TPS. The contact angle of MTPS was greater than TPS, while the water absorption of MTPS was less than TPS. Further, with increasing of MAH content, the contact angle increased, while water absorption decreased, which indicated that the hydrophobic was gradually improved.