Shear-induced Crystallization Morphology And Kinetics Of Isotactic Polybutene-1

Isotactic polybutene-1(iPB-1),as a typical polycrystalline semicrystalline polymer material,is often used in the preparation of plates and films.Shearing field is a kind of external field effect often encountered by polymers during polymer processing,and it can also be used as a way of orientation induction,which has a certain influence on the structure and performance of polymer materials.Therefore,it is necessary to study the crystalline morphology and crystalline behavior of iPB-1 under a shear field.This article mainly studies the effect of shearing on the crystallization behavior of iPB-1 through in-situ Fourier transform infrared spectroscopy(FTIR),polarized light microscope(POM),differential scanning calorimetry(DSC),etc.The characterization means detected the crystallization process of iPB-1 under the shear field in situ,and explored in detail the influence mechanism of the two key factors,the shear temperature and the crystallization temperature,on the crystal form and phase transition.It was found that when shear is applied to the sample,the crystallization temperature of isotactic polybutene-1 affected by shear is much higher than the crystallization temperature under static crystallization conditions,indicating that shear can greatly shorten the induction period of crystallization.In addition,shearing induces isotactic polybutene-1 to form a special crystalline morphology.Two structures are formed at and around the shearing traces:the core of the shear layer and the oriented transverse crystals.At the same time,the kinetic process of the phase transition from Form ? to Form I is tracked.We can figure out that shearing can speed up the growth rate of crystals in the sample,induce disordered polymers to grow at a high temperature such as 110?,,and generate a special transverse crystal morphology,promote the phase transition of Form ? to Form I.The phase transition completed in 400 h for the non-sheared sample was shortened to 120 h under the shear field,and the half crystallization time t1/2 of iPB-1 accelerated from 45.0 h to 4.77 h for the sheared sample.