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.
The influence of the comonomer in the copolymerization of ethylene with α‐olefins using C2H4[ind]2ZrCl2/methylaluminoxane as catalyst system
Copolymers based on ethylene with different incorporations of 1-hexene, 1-octene and 1-decene were obtained. There is not any marked variation of activity when different metallocenes were tested. The type and the concentration of the comonomer in the feed do not have a strong influence on the catalytic activity of the system, but the presence of the comonomer increases the activity compared with that in the absence of it. From 13 C NMR it was found that below 8% of comonomer incorporated the comonomer units appear isolated between polyethylene blocks, sequences of the type ethylene-comonomer-ethylene-comonomer appear only above 8% of comonomer incorporated for all the systems studied. The reactivity of the comonomers for this particular system shows that the size of the lateral chain influences the percentage of comonomer incorporated, 1-hexene being the highest one incorporated. The crystallinity of the copolymers exerts a linear relation with the amount of comonomer incorporated, and it is independent of lateral chain lengths. The molecular weight of the copolymers obtained was found to be dependent on the comonomer concentration in the feed, showing that there is a transfer reaction with the comonomer. The polydispersity (M w /M n ) of the copolymers is rather narrow and dependent on the concentration of the comonomer incorporated.