[Investigation of nascent polypropylene in-reactor alloy particles].

Heterogeneous nascent particles were observed in a pilot product of polypropylene in-reactor alloy, which was polymerized by Ziegler-Natta/Metallocene hybrid catalyst using Spheripol technology. Most of the particles in the product are translucent, and opaque particles were observed as well. The differences in morphology, composition, chain structure, thermal properties and mechanical properties between these two kinds of particles were investigated by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), polarized optical microscopy (POM), and differential scanning calorimetry (DSC) techniques. The results of FTIR, NMR and SEM indicate that different morphology of these two different particles is caused by different content of ethylene-propylene copolymers. The results of DSC and POM showed that the translucent particles has higher crystallization rate than opaque particles due to the presence of ethylene-propylene copolymers. The mechanical properties results showed that the impact resistance property of opaque particles is obviously lower than that of translucent particles, while its tensile strength and bending modulus are much higher than that of translucent particles. Based on the process of Spheripol technology, a preliminary explanation for the formation of different nascent PP in-reactor alloy particles is proposed.

[Investigation of the chain structure and thermal property of xylene solubles of impact polypropylene copolymers].

Impact polypropylene copolymers (IPC) are in-situ blends of polypropylene homopolymer and ethylene-alpha-olefin copolymers formed in the reactor, which is a multiphasic complex material with isotactic polypropylene (iPP) as a matrix in which poly(ethylene-alpha-olefin) elastomeric copolymer is finely dispersed, and ethylene-alpha-olefin random copolymer (EPR) acts as an elastomer to improve the impact resistance properties of iPP at room temperature and low temperature. In the present, the content of xylene soluble is used to evaluate the content of EPR rubber phase in IPC. The content, the chain structure, and glass transition temperature (T(g)) of EPR rubber are critical to the toughness of IPC. In the present report, Fourier transform infrared spectroscopy(FTIR), nuclear magnetic resonance (NMR) and differential scanning calorimetry(DSC) were utilized to study the comonomer content, chain structure and thermal property of xylene soluble of two IPC prepared by different catalysts. The results indicated that there are small amount of ethylene-propylene segmented copolymers containing short methylene sequence that is crystallizable in the xylene soluble in addition to the ethylene-propylene random copolymers. And the sequence length of crystallizable methylene group of ethylene-propylene segmented copolymers in these two kinds of xylene soluble is different. The random distribution degree of ethylene and propylene monomer in the ethylene-propylene copolymers in these two kinds of xylene soluble is similar. The xylene soluble with lower content of PPP sequence and higher content of ethylene monomer has lower T(g), which will benefit the improvement of impact resistance property of polypropylene.