Study On Crystallization Kinetics Of Crosslinked PCL/SAN Blends Prepared Through Electron Beam Irradiation

Polycaprolactone(PCL)is an important semi-crystalline polymer.It has the advantages of biodegradability,low temperature adhesion and good compatibility with a variety of amorphous polymers.It is generally used as a biomedical material and biodegradable material.A large number of studies on the phase behavior and phase morphology of blends of polycaprolactone and amorphous polymers have been reported,but almost all previous studies have focused on the crystallization kinetics of linearly miscible polymer blends.No research has been reported on the crystallization kinetics in the cross-linked miscible polymer blend.In a cross-linking miscible blend system,the cross-linking network has an important effect on the mobility of the chain and the free energy of nucleation and chain folding,which may affect the compatibility between the components and the crystallization kinetics of the crystalline polymer.Whether the introduction of a cross-linked network in the blend of non-crystalline and crystalline polymers will inhibit the crystallization of crystallizable polymers,which is an important issue in the practical industrial application of cross-linked polymers.In this paper,cross-linked PCL and PCL/SAN(Styrene-acrylonitrile copolymer)samples are obtained by irradiation cross-linking.Based on this,the crystallization kinetics in the cross-linked miscible polymer blend is studied,which is very important for promoting the industrial application of cross-linked polymers.The work content and research results of this paper are mainly divided into the following two aspects:1.Three groups of cross-linked PCL and PCL/SAN samples with different gel contents are prepared by blending linear PCL,SAN and cross-linking agent TAIC(triallyl isocyanurate)with electron beam irradiation.First,we observe the cross-linked PCL/SAN samples through a polarized light microscope(POM)and find that no phase separation appeares in the cross-linked system,which shows that PCL and SAN are fully compatible.After that,we study the influence of SAN and cross-linking network on the rheological behavior of cross-linked polycaprolactone through rheological testing.In addition,we also explore the effect of SAN and cross-linking network on the tensile behavior of cross-linked PCL and PCL/SAN samples.We find that when the SAN content in each sample is the same,as the degree of crosslinking increases,the yield strain advances,the strain hardening is earlier,the yield stress decreases and the elastic modulus increases.2.We use differential scanning calorimetry(DSC),polarized light microscope(POM),etc.to study isothermal crystallization kinetics and non-isothermal crystallization kinetics of cross-linked PCL and PCL/SAN samples.We find that when the cross-linking degree of each sample is the same,the crystallization kinetics of cross-linked polycaprolactone slows down with the increase of SAN content.When the SAN content of each sample is the same,the crystallization rate of cross-linked polycaprolactone decreases with increasing crosslink density.Further,we separate the cross-linked network and the linear free chain from the cross-linked PCL/SAN samples to study the crystallization kinetics of the cross-linked part and the linear part,respectively.We find that when the gel contents of the samples are equal,the SAN content has little effect on the crystallization rate of the cross-linked portion.However,the crystallization rate of the linear part slows down as the SAN content increases.This phenomenon may be caused by the fact that SAN with radiation resistance does not substantially participate in the radiation crosslinking reaction and most of them remain in linear polycaprolactone,which suppresses the crystallization of polycaprolactone.