Effects of supported (nBuCp)2ZrCl2 catalyst active center multiplicity on crystallization kinetics of ethylene homo- and copolymers
Hossain, Mohammad Mozahar
Al-Harthi, Mamdouh A.
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AbstractTwo different supported zirconocene, that is, bis(n-butylcyclopentadienyl) zirconium dichloride (nBuCp)2ZrCl2, catalysts were synthesized. Each catalyst was used to prepare one ethylene homopolymer and one ethylene-1-hexene copolymer. Catalyst active center multiplicity and polymer crystallization kinetics were modeled. Five separate active center types were predicted, which matched the successive self-nucleation and annealing (SSA) peak temperatures. The predicted crystallinity well matched the differential scanning calorimetric (DSC) values for a single Avrami-Erofeev index, which ranged between 2 and 3 for the polymers experimented. The estimated apparent crystallization activation energy Ea did not vary with cooling rates, relative crystallinity α, and crystallization time or temperature. Therefore, the concept of variable/instantaneous activation energy was not found to hold. Ea linearly increased with the weight average lamellar thickness Lwav DSC-GT; and for each homopolymer, it exceeded that of the corresponding copolymer. Higher Ea, hence slower crystallization, was identified as a pre-requisite to attain higher crystallinity. Crystallization parameters were correlated to polymer backbone parameters, which are influenced by catalyst active center multiplicity. © 2013 Taiwan Institute of Chemical Engineers.
CitationAtiqullah M, Adamu S, Hossain MM, Al-Harthi MA, Anantawaraskul S, et al. (2014) Effects of supported (nBuCp)2ZrCl2 catalyst active center multiplicity on crystallization kinetics of ethylene homo- and copolymers. Journal of the Taiwan Institute of Chemical Engineers 45: 1982–1991. Available: http://dx.doi.org/10.1016/j.jtice.2013.11.005.
SponsorsThe authors acknowledge the financial support provided by King Abdulaziz City for Science and Technology (KACST) via the Science & Technology Unit at King Fahd University of Petroleum & Minerals (KFUPM) through Project Number 08-PET90-4 as part of the National Science and Technology Innovation Plan. The technical assistance provided by the following KFUPM centers—Center of Refining & Petrochemicals (CRP) and Center for Engineering Research at Research Institute, and the Center of Research Excellence in Petroleum Refining & Petrochemicals (CoRE-PRP)—at Dhahran, Saudi Arabia; NMR Core Laboratory, Thuwal, King Abdullah University of Science & Technology (KAUST), Saudi Arabia; and the Department of Chemical Engineering at KFUPM and the Department of Chemical Engineering at Kasetsart University, Thailand is also gratefully acknowledged.