| Isotactic poly 1-butene(iP-1-B)has good applications in industrial production with good mechanical properties,outstanding environmental stress cracking resistance and heat resistance.However unstable metaphase crystal form II is kinetically favored which is commonly obtained by melt crystallization in quiescent conditions at atmospheric pressure and would slowly transform into stable modification form I.This brings serious problems to industrial productions during processing and in applications.In this paper,iP-1-B/LDPE blends was prepared by melt blending.Irradiated iP-1-B/LDPE blends were made with different doses of high-energy electron.The effects of LDPE and irradiation on iP-1-B crystal transitions and the related mechanism were focused on.Shear hot stage,polarizing microscope(POM),X-ray diffraction(XRD),DSC and wide angle X-ray scattering(WAXS)were used to study the crystallization behaviors of irradiated iP-1-B/LDPE with different doses and the melt memory effect.The results showed that:(1)Typical two-phase structure were formed by adding LDPE to iP-1-B.Addition of LDPE has influences on the crystallization behaviors of i P-1-B into crystal form II:increasing nucleation density,smaller spherulites,promoted or inhibited form II growth in different temperature ranges.And Addition of LDPE showed no promotion effect to crystal transition of form II to form I.(2)Irradiation significantly accelerates II-I transition of iP-1-B.Under irradiation,the compatibility between the two phases in the blends might be improved.(3)Heating iP-1-B in form II to 125 oC and then cooling to 30 oC,crystal I' would be generated directly from the melt.And the content of crystal I' could increase with increasing heating and cooling cycles and content of form II would decrease.This indicated that there is melt memory effect.Existence of form I in partially-melted iP-1-B promoted the formation of crystal I' and it would disappear by itself. |
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