| Due to the excellent mechanical performance of good mechanical properties,outstanding environmental stress-cracking resistance and heat resistance and so on,isotactic poly(1-butene)(iP-1-B)can be widely used in a variety of industrial fields.However,the low Ⅱ-Ⅰ crystal transition detracts the wide applications of iP-1-B.And it is known that the applied flow fields can affect the crystal structures and crystalline behaviors of iP-1-B.Further investigations on the slow Ⅱ-Ⅰ crystal transformation,crystal structures,and crystalline behaviors of isotactic poly(1-butene)are of social and economic significance.In this paper,the iP-1-B/graphene composites were prepared by melt-compounding method,the effect of graphene on composites’ crystal structure and crystallization behaviors were studied with a shear heating stage,polarizing microscope(POM),X-ray diffraction(XRD),DSC,and wide angle X-ray diffraction(WAXS)technology et al.,The results are shown as following:In the quiescent state,it has been found that the addition of graphene accelerates the nucleation of i P-1-B and decreases its spherulite size,and the half crystallization time of i P-1-B is significantly shortened.In conjuction with the effect of two-step crystallization,the time for the Ⅱ-Ⅰ crystal transformation of iP-1-B is shortened by graphene addition to be 3-4 days.When the graphene content is 0.01 wt%,the rate of phase Ⅱ-Ⅰ transformation reaches a maximum and the crystals in the composite are more densely stacked.Little crystal nucleus of crystal Ⅰ cannot induce i P-1-B molecular chains directly to enter crystal Ⅰ from melt,and phase Ⅱ still has the priority to grow,the melting melt of crystal nuleus has no memory of the structure of crystal Ⅰ.Under shear conditions,it has been found that low shear rate and low graphene content,higher shear rate and higher graphene content could promote the process of phase Ⅱ-Ⅰ transformation.However,over a certain range,the increase of shear rate and content of graphene slightly suppressed on the process of phase Ⅱ-Ⅰ transformation.From rheological measurements and impact and tensile tests,it has been found that within experimental paramaters,the higher the content of graphene,the greater the dynamic modulus,graphene barriers the mobility of iP-1-B molecular chains in the composites.When the graphene content is 0.03 wt%,the composite shows the highest tensile strength,and the elongation at break significantly decreases with the content of graphene.However,the nanocomposite with graphene content of 0.01 wt% has the best impact resistance property. |
