Effects Of Imidazolium Ionic Liquids On The Crystallization Behavior And Mechanical Properties Of Polypropylene

This paper studied the effect of the addition of ionic liquids on the crystallizationbehavior and mechanical properties of iPP. Polypropylene, as a kind of non-polarthermoplastic resin, has a low relative density, low prices, good processability andbetter overall performance characteristics, such as better yield strength, tensilestrength, surface hardness and elastic modulus than excellent, and outstandingresistance to stress cracking resistance and abrasion resistance and other advantages.Ionic liquids, due to their superior design of the nature and structure, has received awide range of research and application in the areas of green chemistry processes,catalysis and functional materials preparation, etc. Using ionic liquids to plasticizeisotactic polypropylene, has a very important research value in reducing thedisadvantages and expanding the application of isotactic polypropylene. The maincontents of this paper include: the study of the effects of adding different amounts ofionic liquids on non-isothermal and isothermal crystallization behavior of iPP; thecrystals nucleation and growth of iPP upon isothermal crystallization processesinvestigated by polarized optical microscopy. Main conclusions are the following:(1) In iPP/ILs composite non-isothermal crystallization process, adding ionicliquids makes composite materials to reduce the degree of crystallinity, but it makesthe initial crystallization temperature of iPP matrix increases, and crystallization peakshift to higher temperature. In isothermal crystallization process, adding the ionicliquid also reduces the crystallinity of the composite material, while the Tc <132℃,the crystallization half time iPP/ILs composite materials has been significantlyreduced, and the iPP/ILs composites crystallization rate has been improved, however,varying the concentration of the crystallization is almost no effect on the iPP/ILscomposites at Tc≥132℃. Re-melting process studies on iPP/ILs compositecrystalline found, Tc≥132℃, it will appear the phenomenon of double meltingpeaks, adding ionic liquids have little effect on iPP/ILs composite radial lamellaegrowth, but not conducive to the growth of tangential lamellae in the crystals. (2)The spherulite growth of iPP/ILs composite isothermal crystallization processinvestigated by situ polarized optical microscopy found that the addition of ionicliquid increased the nucleation density of iPP gradually, the nucleation densityincreases with the increase of the amount of ionic liquid at lower temperature, andwhen the temperature is higher than132℃, the promotion of the addition of higherconcentration of ionic liquids to the nucleation density of iPP weakened. Adding ionicliquids have little effect on iPP crystal growth rate.(3) iPP/ILs specimen under a constant tensile rate, When a small amount of theionic liquid added, the yield strength of iPP increase, When the amount of the ionicliquid added is high, the yield strength of iPP reduce.