Two 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.
|Number of pages
|Journal of the Taiwan Institute of Chemical Engineers
|Published - Jul 2014
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The 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.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.