Fernanda Oliveira Vieira da Cunha

Ethylene and 1-butene copolymerization catalyzed by a Ziegler–Natta/Metallocene hybrid catalyst through a 23 factorial experimental design

In this work, a 2 3 factorial experimental design for the evaluation of ethylene– 1-butene copolymerization was employed. The following reaction parameters were used as independent variables: catalyst type, Al/Ti molar ratio and 1-butene concentration. The copolymerization was carried out using hybrid Ziegler – Natta/Metallocene catalysts with different titanium molar ratios. The catalyst activity and polymer characteristics were statistically analyzed through response surface methods. It was found that the catalyst type has a significant effect on activity, melt flow index and 1-butene content. Copolymers presented crystallinity values ranging from 46 to 58% and melt temperature in the 128– 131 8C range. Copolymer comonomer content varied from 2 to 6% in weight. q 2002 Published by Elsevier Science Ltd.

Study of castor oil polyurethane - poly(methyl methacrylate) semi-interpenetrating polymer network (SIPN) reaction parameters using a 2³ factorial experimental design

3factorial experiment design to evaluate the castor oil polyurethane-poly(methyl methacrylate) semi-IPN synthesis. The reaction parameters used as independent variables were NCO/OH molar ratio, polyurethane polymerization time and methyl methacrylate (MMA) content. The semi-IPNs were cured over 28 h using two thermal treatments. The polymers were characterized by infrared and Raman spectroscopy, thermal analysis and swelling profiles in n-hexane. The glass transition temperature (Tg) and the swelling were more affect by the NCO/OH molar ratio variation. The semi-IPNs showed Tg from - 27 to - 6 °C and the swelling range was from 3 to 22%, according to the crosslink density. The IPN mechanical properties were dependent on the cure temperature and MMA content in it. Lower elastic modulus values were observed in IPNs cured at room temperature.

Characterization and evaluation of the nature of chemical species generated in hybrid Ziegler–Natta/metallocene catalyst

In the present work CpTiCl3 pretreated with tri-iso-butylaluminium was immobilized on MgCl2 supported Ziegler–Natta catalyst. The resulting catalysts were characterized by a series of techniques, namely thermal analysis (TGA/DTA), X-ray photoelectron spectroscopy (XPS), 27 Al magic angle spin nuclear magnetic resonance ( 27 Al MAS–NMR), UV–VIS spectroscopic analysis, inductively-coupled plasma–atomic emission spectroscopy (ICP–AES) and elemental analysis. The catalysts UV–VIS spectrum showed a broad absorption band at 390 nm indicating the presence of metallocene cyclopentadienyl ring. According to XPS analysis, only hybrid catalysts showed two peaks in the Ti (2p 3/2 ) region after the spectrum deconvolution, a lower binding energy peak at 455 eV and another one at 457 eV (Ti 4+ ). These appear to be due to difference of electronegativity in the coordination sphere of the Ti due to the TiCl4 and the Cp(i-Bu)TiCl2 fixed on the hybrid Ziegler–Natta catalyst. All catalyst systems were active in ethylene-1-butene copolymerization. The resulting polymers obtained with the hybrid catalyst showed a shoulder in the DSC thermogramme fusion peak. It might be caused by a polymer fraction produced by the additional Ti center in the catalyst due to the Cp(i-Bu)TiCl2. Microscopic analysis showed that the polymer replicated the spherical morphology of the catalyst grain.

Avaliação do desempenho de catalisadores híbridos Ziegler-Natta/Metaloceno na homo- e copolimerização de etileno

Foram preparados catalisadores hibridos a partir de um catalisador do tipo Ziegler-Natta heterogeneo (MgCl2.TiCl4) e de um metalocenico (CpTiCl3), afim de se obter catalisadores com diferentes tipos de centros ativos. Foi proposta a formacao de um novo centro ativo (CpTi(iBu)Cl2) na face 100 do suporte de MgCl2. Estes catalisadores foram avaliados na sintese de polietileno de alta densidade (PEAD) e de polietileno linear de baixa densidade (PELBD), utilizando-se somente trietilaluminio (TEA) como cocatalisador. Foi verificada a influencia da razao molar Al/Ti, temperatura e tempo de polimerizacao na produtividade dos catalisadores e nas propriedades dos polimeros obtidos. Os catalisadores mistos apresentaram atividade catalitica da ordem de 5,0 kgPol/gcat.h na polimerizacao de etileno e da ordem de 7,0 kgPol/gcat.h na copolimerizacao etileno-1-buteno.