Effects of low molar mass liquid crystal addition on crystal structure of isotactic polypropylene

Abstract

To study the crystallization and the morphologies of polymer blends between isotactic polypropylene and low molar mass liquid crystal chemical (LCC) or glycerol monostearate (GMS). Propylene polymerization was carried out using the ansa-metallocene Et[Ind]2ZrCl2 as catalyst and methylaluminoxane (MAO) as cocatalyst and Ziegler-Natta - synthesized polypropylenes were purchased. The blends were investigated by Small Angle Light Scattering (SALS), X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscope (SEM). The correlative results of each analytically characteristic techniques were observed. Comparation between light scattering results obtained from SALS technique and crystallinity results from XRD technique are corresponded in the case of metallocene-synthesized polypropylene, namely better light scattering come from higher crystallinity. LCC and GMS can also slightly decrease melting temperature of the blendsbecause they reduce melt viscosity of the blends, therefore melting phenomena can occur at lower temperature. In the case of Ziegler-Natta - synthesized polypropylene, crystallization temperature of the GMS and LCC blends significantly increase because LCC and GMS are able to enhance molecular mobility, therefore crystallization is able to occur at higher temperature.