SbstractThe influence of three nucleating agents from different generations on the crystallization behavior of propylene homopolymer was studied by differential scanning calorimetry (DSC) and atomic force microscopy (AFM). The amount of nucleating agent used varied between 1000 and 2200 ppm. The new generation nucleating agent, Hyperform HPN-68L, accelerates the crystallization more efficiently than the other nucleating agents tested. It was also possible to verify the effects of agglomeration and negative interaction between calcium stearate and sodium benzoate. Furthermore, AFM images allowed to differentiate the crystals generated by Millad 3988 through the observation of a fibrillar intertwining network structure, with characteristic spacing and length of crystals, justifying its excellent performance to improve polypropylene optical properties.
In this research, we describe the application of the complexes o-C 6 H 4 (NSiMe 3 ) 2 ZrCl 2 (1), o-C 6 H 4 (NSiMe 3 ) 2 TiBr 2 (2), o-C 6 H 4 (NSiMe 3 ) 2 TiCl 2 (3), C 2 H 4 (NSiMe 3 ) 2 ZrCl 2 (4), in the ethylene polymerization with different Al/M ratios and temperatures. These complexes presented significant catalytic activities in the presence of methyaluminoxane (MAO) as cocatalyst and toluene as solvent, producing high molecular weight linear polyethylenes. Zirconium complexes were more active at 608C and titanium complexes at 408C. Zirconium complex (1) showed the best values of activity (347 kg PE/mol Zr h atm) for Al/Zr ratio of 340 and 608C of temperature. In ethylene-1-hexene copolymerization, the best result was also reached with catalyst 1, at the same conditions.
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