A Study Of The Crystallization Behavior Of Poly(?-caprolactone)/Poly(Vinyl Chloride) Blend Under Strain

In this work,the microstructural evolution of poly(?caprolactone)(PCL)/poly(vinyl chloride)(PVC)blend film that obtained by solution blending and casting has been investigated by means of in-situ fourier transform infrared spectroscopy(FTIR)and two-dimensional wide-angle Xray diffraction(WAXD).The influence of temperature and draw ratio on draw induced crystallization and formation mechanism of crystals with different orientation were discussed.The main results of the research are as following.It was found that stretching could accelerate the crystallization rate and reduce the growth dimension of crystals through the study of PCL/PVC blend film under strain at different temperature.Due to the smaller stretching stress under higher temperature,the crystallization kinetic parameters are gradually close to the unstretched sample with the increase of the temperature,which means that the effect of stretching on crystallization rate and growth dimension of crystals was weakened.After stretching,the molecular chains of PCL undergo conformational transformation and then go into the lattice.In addition,some of molecular chains of PCL that have undergone a conformational transformation but have not crystallized are return to the original state under the confinement of oriented PVC.The orientation of PCL crystals in cold-drawn and melt-drawn PCL/PVC blend film is obviously different.In the cold-drawn PCL/PVC blend film with high molecular weight PCL,the c-axis of PCL crystals is oriented along the stretching direction.However,the orientation of PCL crystals in melt-drawn PCL/PVC blend film is complicated.For the meltdrawn PCL/PVC blend samples,the crystallization of high molecular weight PCL in the blends under a draw ratio of ?=3 with a strain rate of 6 mm/min leads to a ring-fiber orientation.In the samples with draw ratios of ?=4 and 5,the uniaxial orientation of a-,b-,and c-axes along the strain direction coexist after crystallization of high molecular weight PCL.With a draw ratio of ?=6,mainly the b-axis orientation of high molecular weight PCL is identified.For the low molecular weight PCL,there is no change in the orientation of PCL crystals under the draw ratio of ?=3,compared to the high molecular weight PCL.Moreover,as the temperature increases,the degree of orientation decreases.By changing the draw ratio,molecular weight and temperature,PCL crystals with multiple orientations and single orientation were obtained,and the orientation of the crystals was significantly dissimilar to the results obtained at higher stretching rate.The results indicated that the draw ratio,draw rate and molecular weight play an important role in the crystallization behavior of PCL in its blend with PVC under strain.