Studies On A Process To Use Novel Polyurethane Micro-particles For Modifying Starch

The solid phase melting method was adopted in this paper.Polyurethane prepolymers(PUPs)were first synthesized from various hydrophobic soft segments,and then mixed with native corn starch/potato starch to prepare modified TPS in a solid state mixer.The process of the modified starches was studied.First of all,the process of modified corn starch by polyethylene adipic acid 1,4-butane diol(PBA)polyurethane prepolymers(PBAPU)was explored.The results showed that with the increase of time,the reaction between starch and polyurethane also increased;the hydrophobicity and elongation at break of corn starch were relatively increased.There was an obvious change within the first ten minutes.From ten minutes-twenty minutes,the various observed parameters changed only a little;After twenty minutes,there was no significant change.Therefore,twenty minutes can be used as the optimum time for mixing.In addition,compared with unmodified starch,modified starch improved the brittleness of natural starch,as well as the hydrophilicity and other weaknesses.Following this,the process of modified potato starch by the castor oil(CO)polyurethane prepolymers(COPU)was explored.The preparation time was adjusted.The results showed that the viscosity value of potato starch was greater than that of corn starch,which indicates that the amylose content in potato starch was lower.Using the optimum mixing time of twenty minutes from the previous experiment,with the increase of time,the compatibility between potato starch and polyurethane increased;the hydrophobicity and elongation at break also relatively improved.This indicated that potato starch had been successfully modified by COPU.Finally,the process of modified corn starch by the poly caprolactone diol(PCL)polyurethane pre polymers(PCLPU)was explored.The results showed that compared with the previous studies,when the different kinds of polyurethanes were used to modify the different kinds of starch,modified starch showed the overall trend was consistent,but the performances were different.Because the PCL was glycol,in synthetic PCLPU,the content of isocyanate base(NCO)was only about 3.0%.Compared with the original starch,various performances were improved but not obviously.This suggested that the NCO content of modified starch in polyurethane was a very important factor.Anyhow,NCO content and the processing time has a certain influence of the structure/performance of the modified thermoplastic starch.Due to the hydrophobic polyurethane,the hydrophobicity of the modified starch increased,thereby enlarging the application value of starch.This shows that the modified method is feasible,efficient and environmentally friendly.