A comparative study of ethylene and propylene polymerization over titanium–magnesium catalysts of different composition

Abstract

New data on the molecular weight characteristics of polypropylene (PP) and polyethylene (PE) were obtained from the polymerization over supported titanium–magnesium catalysts differing in their compositions (presence and absence of internal and external donors). Internal and external donors were found to affect the molecular weight of polymers in a different manner for ethylene and propylene polymerization. The introduction of the internal donor increases the molecular weight of PP and does not affect the molecular weight of PE. The effect of external donor introduced to catalytic system on the polymer molecular weight depends on catalyst composition: for a catalyst without internal donor, the introduction of the external donor increases the molecular weight of PP and does not affect that of PE. In the case of catalyst with the internal donor, the introduction of the external donor increases the molecular weight of PP and substantially decreases that of PE. The data on polymerization degree of the polymers produced under conditions when chain transfer with hydrogen was the dominant reaction were used to calculate the ktr normalH/kp values for ethylene polymerization over the catalysts of different composition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40658.

Effects of titanium dispersion state on distribution and reactivity of active centers in propylene polymerization with MgCl2‐supported Ziegler‐Natta catalysts: A kinetic study based on active center counting

“…The glass‐transition temperature appeared at around −9 °C (see Figure S1). Similar phenomena have been reported in previous literatures . It can be found that the melting temperature ( T m ) and melting enthalpy (Δ H m ) gradually increased with proceeding of the polymerization for both catalysts.…”

“…Similar phenomena have been reported in previous literatures. [34][35][36] It can be found that the melting temperature (T m ) and melting enthalpy (ΔH m ) gradually increased with proceeding of the polymerization for both catalysts. However, the T m and ΔH m of PP catalyzed by Cat-1 were lower than those of PP catalyzed by Cat-2 under the same conditions.…”

Effect of AlEt3and an External Donor on the Distribution of Active Sites According to Their Stereospecificity in Propylene Polymerization over TiCl4/MgCl2Catalysts with Different Titanium Content

“…It should be noted that T m2 for PP3 produced over TMC‐0.1 is lower compared to PP6 produced over TMC‐3.5. The presence of two peaks on the DSC curves for PP samples produced at polymerization over TMC in the absence of an external donor was previously reported in ref …”

Formation of Ziegler‐type catalytic systems on the surface of multi‐walled carbon nanotubes for the production of composite materials by in situ polymerization

“…2) lead to decreasing of the activity of the catalytic system and to decreasing of the polymer's molecular weight ( M w = 100 kg/mol). MWD is fairly narrow ( M w / M n = 5.0), which is ordinary for polyethylene that is produced on titanium–magnesium catalysts under similar conditions at 80 °C in the presence of hydrogen . Copolymerization in the presence of a comonomer (1‐hexene, exp.…”