Iran Polymer and Petrochemical Institute Polyolefins Journal 2322-2212 1 2 2014 12 01 The role of 1-hexene comonomer content in thermal behavior of medium density polyethylene (MDPE) synthesized using Phillips catalyst 117 129 1099 10.22063/poj.2014.1099 EN Abbas Kebritchi Iran Polymer and Petrochemical Institute, 14965-115, Tehran, Iran Leibniz-Institut für Polymerforschung Dresden e.V., D-01069, Dresden, Germany 0000-0001-6129-9323 Mehdi Nekoomanesh Iran Polymer and Petrochemical Institute, 14965-115, Tehran, Iran Fereidoon Mohammadi Iran Polymer and Petrochemical Institute, 14965-115, Tehran, Iran Hossein Ali Khonakdar Iran Polymer and Petrochemical Institute, 14965-115, Tehran, Iran Leibniz-Institut für Polymerforschung Dresden e.V., D-01069, Dresden, Germany Journal Article 2014 07 09 In this work, the role of comonomer content of 1-hexene-medium density polyethylene (MDPE) copolymer, synthesized using Phillips catalyst, on thermal behavior parameters such as: crystallization, melting temperature and thermal degradation was investigated in detail. The copolymer was fractionated to homogenous short-chain branching (SCB) fractions by "preparative temperature rising elution fractionation" (P-TREF) method and then it was subjected to thermal analyses. A broad chemical composition distribution (CCD) in terms of SCB content and molecular weight (M<sub>w</sub>) was observed by P-TREF and gel permeation chromatography (GPC), respectively. Based on P-TREF results, a parabolic relationship between methylene sequence length (MSL) and elution temperature (ET) was presented. Differential scanning calorimetry (DSC) showed distinct, well-defined melting peaks over a 22 °C temperature range for SCB contents of about 3-12 (br/1000 C). The variations in physical characteristics such as melting temperature (T<sub>m</sub>), crystallinity (X<sub>c</sub>), crystallization temperature (T<sub>c</sub>) and lamellae thickness (L<sub>c</sub>) against SCB content were correlated. Thermogravimetric analysis (TGA) suggested linear relationships between the temperature at maximum degradation rate (T<sub>max</sub>) as well as the degradation initiation temperature (T5%) versus SCB content. Moreover, the TGA curves exhibited distinct differences at both initiation and propagation stages of thermal degradation at dissimilar comonomer contents. ethylene/1-hexene copolymer short-chain branching (SCB) thermal degradation phillips catalyst medium density polyethylene (MDPE) http://poj.ippi.ac.ir/article_1099_49570efc0704bbad3dcf60239275aa50.pdf