Effect of lanthanum-modified magnesium silicate on isotactic polypropylene crystallization in composite materials during shear flow

摘要

The activity of isotactic polypropylene (iPP) nucleating additives during shear flow of composite materials is still not entirely explained. In current work the sol-gel method was employed to synthesize MgO center dot SiO(2)filler, surface-modified with trivalent lanthanum. The crystallization of commercial iPP in the presence of 0.5% by weight La(3+)modified or unmodified silicates was analyzed. The wide angle X-ray scattering analysis proved that the presence of even small amount of filler influences significantly on supermolecular structure of iPP. The results of microscope observations confirmed that the lanthanum-modified filler shows the nucleating ability for iPP. In that case a significant reduction of crystallization induction time was noticed. The investigation of iPP crystallization in composites after shear treatment confirmed that the increase of shear rate reduces the nucleating ability of additives. Moreover, the flow of filler particles during shearing may impede the shear-induced crystallization phenomenon.