Synthesis and characterization of butadiene-1,3 and octene-1 copolymer prepared by a Ziegler-Natta catalyst based on neodymium
The aim of this work is to evaluate the influence of octene-1 incorporation in the polybutadiene chain on the polymerization reaction and polymer characteristics. Thus, copolymerization of butadiene-1,3 with octene-1 using a Ziegler-Natta ternary catalyst based on neodymium was performed. The weight ratios of butadiene-1,3/α-olefin 100/0, 99/1, 97/3, 95/5, 90/10, 80/20 and 70/30 were evaluated. The copolymers were characterized by size exclusion chromatography (SEC), infrared spectroscopy (FTIR) and thermogravimetric analysis (TG). The results showed that the degradation temperature (Tmax) was not affected by the addition of alpha-olefin, while the thermal behavior has undergone significant changes. The polymer microstructure was not influenced by the increasing of octene-1 content. However, a tendency to molecular mass increase was observed with the increasing of octene-1 content. It was also observed a trend in reduction of the polymerization conversion as the octene-1 content increased.
Effect of comonomer type on the crystallization kinetics and crystalline structure of random isotactic propylene 1 -alkene copolymers
Isothermal crystallization kinetics and properties related to the crystalline structure of four series of random propylene 1-alkene copolymers have been comparatively studied in this work. Comonomers studied include ethylene, 1-butene, 1-hexene and 1-octene in a concentration range up to 21 mol%. All copolymers were synthesized with the same metallocene catalyst to provide an equivalent random distribution and a similar content of stereo and regio defects within the series. This has ensured that differences in crystallization kinetics and in crystalline properties of copolymers with matched compositions reflect the affinity of the comonomer type for co-crystallization with the propene units, and the effect of content and type of co-unit in the development of the crystalline structure. In the nucleation-driven crystallization range, that is for Tcs > Tc max, the values of the rate follow the sequence PB > PE > PH ¼ PO for comonomer contents PE > PH > PO for >13 mol% comonomer.
Tailoring the Physical Properties of Isotactic Polypropylene through Incorporation of Comonomers and the Precise Control of Stereo- and Regioregularity by Metallocene Catalysts
Random copolymers of propylene with ethylene, butene, and hexene comonomers have been prepared with different metallocene catalysts. The used catalysts have allowed a precise control of concentration of stereodefects and high degree of comonomer incorporation while maintaining high molecular mass and random distribution of comonomers. Incorporation of ethylene, butene, and hexene produces great enhancement of ductility, flexibility, and toughness, as compared to highly isotactic polypropylene, but with important differences in the values of elastic modulus and strength depending on the comonomer. In propylene−ethylene copolymers, the values of elastic modulus, ductility, toughness, and strength can be tuned by changing the concentrations of rr stereodefects and ethylene units, so that stiff and fragile plastics, highly flexible materials, and elastomers can be obtained. Propylene−butene copolymers behave as highly flexible materials with remarkable ductility and toughness and contemporary high strength an...