Novel Sodium Alginate And Modified Starch Prepared By Melt Processing

In this thesis,modified sodium alginate(SA)and starch respectively with polyurethane polymers(PUP),and starch/polycaprolactone(PCL)blends compatibilized with PCL-based PUP(PCLPU),were prepared by melt processing.Firstly,the structure and properties of hydrophobically modified SA were investigated,as well as its application to heavy metal pollution control.Secondly,a solution to eliminate residual isocyanate(NCO)groups of modified starch was found.Finally,the novel interface structure of starch/PCL blends was characterized,thereby to understand the compatibiliz-ing mechanism of PCLPU.Meanwhile,the compatibilizing effect of PUP was evaluated by various tests.(1)Structure and properties of modified SA with PUP microparticles:The melt processing method proved to be practicable to prepare modified SA.The results from the study indicated the film-forming property and hydrophobicity of the modified SA were significantly improved,compared with pure sodium alginate material.(2)Elimination of residual NCO groups in the modified starch with PUP microparticles:A series of modified starches with PUP microparticles were processed by melting method.By changing the processing conditions and the manner of after-treatment,charging the catalyst or not,using polyurethane prepolymers with different NCO content,the most excellent programme was obtained to remove residual NCO groups of modified starch.In the presence of external heat and catalyst,starch mixed for 20 min,with the NCO/OH of 1.5 polyurethane prepolymer mixtures,able to achieve the material of no NCO groups.(3)Structure and properties of starch/PCL blends compatibilized with PCLPU:The structure of each component separated from the blend material was characterized,which showed the compatibilizing mechanism of PCLPU,namely,PCLPU microparticles were linked to starch granules through urethane linkages and PCL soft segments of PCLPU were encased in PCL matrix due to good compatibility.The results revealed that,owing to the good compatibilizer PCLPU,various performances of starch/PCL blends with PCLPU were better than that without PCLPU.The material combined the advantages of PCL and starch.Its elastic modulus and tensile strength increased compared to pure PCL,and simultaneously it was hydrophobic in contrast with starch.