Effect Of Cyclodextrin And Dendrimer On The Crystallization Behavior Of Poly(3-hydroxybutyrate)(PHB)

Polyhydroxyalkanoates,PHA for short,is a family of intracellularPolyesters synthesized by different kinds of bacteria.It has a broadapplication prospect due to its advantages such as biodegradable andbiocompatible.Poly(3-hydroxybutyrate)(PHB) is a kind of PHA whichwas firstly discovered and have attracted many attentions. However,PHBhas some shortcomings which limited its applications,on one hand,thecryatallization rate of PHB is quite slow,making the spherulite size ofPHB are too large,and at the same time,PHB is tend to form secondcrystallization in the cryatallization process.All these elements haveresulted the brittleness of PHB.And on the other hand,as the meltingtemperature and the decomposing temperature of PHB are too close toeach other,PHB is unstable in the molten state.The two shortcomingslimited the broad application of PHB and increased the cost of industrymanufacture.As a result,the improvement of crystallization behavior forPHB has become a hot spot in research field,which is of great scientificsignificance and application value． In this study,two kinds of nucleating agents were used to form blendswith PHB to improve its crystallization behavior.Following are mainresearch contents and results:1. Solution casting method was used to prepare the pure PHB,PHB/α-CDblend,PHB/β-CD blend and PHB/γ-CD blend films,andDSC,POM,WAXR analysis were used to characterize the films toresearch the effect of these nucleating agents on the crystallizationbehavior of PHB.Research demonstrated that both three kinds of CDsaccelerated the crystallization rate and shortened the half-crystallizationtime of PHB,and moreover,the nucleating density and spherulite sizewere reduced and crystallinity was improved.And the nucleating effectorder of the three CDs is γ-CD>β-CD>α-CD.Furthermore,1wt%is theproper appropriation for CDs being nucleating agents.2. PHB/PAMAM blend was prepared by solution casting method andcharacterized by DSC,POM and WAXD analysis.Results showed that theadding of PAMAM restrained the isothermal crystallization ofPHB.However,it accelerated the non-isothermal crystallization ofPHB,due to that wt1%PAMAM decreased the melting temperature ofPHB and made the manufacture temperature range more narrow while theadding of wt2%PAMAM didn’t has the same effect on PHB,when theproportion of PAMAM is wt2%,it showed best effect of increasing thenon-isothermal crystallization rate.At the same time,PAMAM decreased the nucleating density and spherulite size of PHB and inproved itscrystallinity.