甲酰胺塑化热塑性淀粉的性能研究

STUDIES ON THE PROPERTIES OF FORMAMIDE PLASTICIZED-THERMOPLASTIC STARCH

用甲酰胺作为塑化剂制备了热塑性淀粉 (TPS) ,扫描电镜显示甲酰胺可以使淀粉塑化 ,形成均一的连续相 ;流变性能说明在加工温度范围内 ,甲酰胺塑化淀粉 (FPTPS)的剪切应力对温度变化敏感性要小于甘油塑化淀粉 (GPTPS) ;用热重和DSC研究了热稳定性和玻璃化转变 ;FPTPS在 13%～ 2 3%的水含量时有较好的力学性能 ,水含量为 13%时 ,FPTPS有最大的断裂强度 3 9MPa ;水含量为 17%时 ,FPTPS最大的伸长率为 95 % ;与GPTPS相比 ,在RH(Relativehumidity) =0 5 0 %and 10 0 %环境下 ,FPTPS有良好的耐回生性能 。

The main disadvantages of thermoplastic starch ( TPS) are their retrogradation and unsatisfactory mechanical properties particularly under wet or dry environments. Formamide was used as an individual plasticizer to prepare thermoplastic starch ( TPS) to overcome the facile retrogradation of polyols-plasticized TPS with good mechanical properties or the poor mechanical properties of urea-plasticized TPS with good retrogradation resistance. By using scanning electron microscope (SEM) the native cornstarch granules were proved to transfer to a continuous phase with out crystallinity after plasticization with formamide. By rheology tests, it was shown that formamide made TPS less temperature sensitive than glycerol did in the processing temperature range of formamide-plasticized TPS (FPTPS) from 110degreesC to 150degreesC. Thermal analysis reveals that glycerol-plasticized TPS (GPTPS) exhibits better thermal stability and FPTPS has a slightly lower glass transition temperature. The effect of water contents on the mechanical properties of FPTPS and GPTPS was also studied, and FPTPS showed good ductility at water contents of 13% similar to 35%. The maximal failure stress and strain were 3.9 MPa and 95%, respectively. At three typical environment conditions of RH = 0,50 % and 100 % the influence of formamide and glycerol on the retrogradation of TPS was studied using X-ray diffractometry. It was found that compared to glycerol, formamide could effectively restrain the retrogradation at various humidities. The property improvement of TPS by using formamide was ascribed to the formation of more stable hydrogen bonds between plasticizer molecules and the hydroxy groups of the starch.