| Due to the high-reactivity between the isocyanate groups of polyurethane prepolymer(PUP)and hydroxyl group of starch,PUP was widely used to modify pure starch.In recent years,many studies about modify starch with PUP.Nevertheless,in the reaction many not being environmentally friendly organic solvent were used,furthermore,the reaction efficiency was low.For this reason,it is necessary to adopt a novel method to modify starch.In our previous work,we successfully used PUP and water to modify starch for preparing novel hydrophobic starch.In the process of modification,we did not use any organic solvents and the hydrophobicity and mechanical behavior of modified TPS were significantly enhanced being compared with pure starch.In this paper,firstly,we studied the effects of starch category on the structure/properties of modified starch.PUP was synthesized from castor oil polyol,and used to modify various starches from potato,tapioca,pea,lotus root and sweet potato in an intensive mixer for preparing modified TPS.Modified Potato starch showed the highest flexibility and modified sweet potato showed the lowest flexibility.Secondly,aging property is an inherent feature of starch material,which severely limited the application of starch.Compared with the glycerin-modified starch and pure starch,PUP-modified starch has better aging resistance.Finally,study the influence of the kinds of isocyanates in on the modified starches.In the experiment,we used a variety of isocyanate to synthesize PUP and used the product to prepare hydrophobic starch.It turned out that the hydrophilicity of isocyanates in PU can improve the performance of the modified TPS.In this paper,researches showed that the types of starch have some impacts on the modified starch,and the increased of the hydrophilicity of isocyanates in PUP could decrease the tensile properties of modified starch,in addition,the aging resistance of modified TPS was improved,which was beneficial to the promotion of the starch material. |
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