Thermal behavior of ethylene/1-octene copolymer fractions at high temperatures: Effect of hexyl branch content

• Main Authors: Abbas Kebritchi, Mehdi Nekoomanesh, Fereidoun Mohammadi, Hossein Khonakdar, Udo Wagenknecht
• Format: Article
• Language: English
• Published: Iran Polymer and Petrochemical Institute 2019-06-01
• Series: Polyolefins Journal
• Subjects: thermal behavior; ethylene/1-octene copolymer; hexyl branch content; thermal degradation
• Online Access: http://poj.ippi.ac.ir/article_1618_188b37926b434eeb4c5081c7233cf229.pdf

In this work, the effect of hexyl branch content on thermal behavior of a fractionated ethylene/1-octene copolymer with emphasis on high temperatures was investigated. The ethylene/1-octene copolymer was carefully fractionated to different fractions with homogenous hexyl branch (HB) content by preparative temperature rising elution fractionation (P-TREF) method. The P-TREF fractions were thermally analyzed via differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and evolved gas analysis (EGA). The P-TREF profile showed a short chain branch distribution (SCBD) of around 1.24. A linear relationship between P-TREF elution temperature (ET) and methylene sequence length (MSL) was presented. The DSC curves exhibited a monolithically increase in melting temperature (Tm) as well as crystallization temperature (Tc) by decreasing short chain branch (SCB) content. The calculated values of lamellae thickness suggested a linear function of SCB content and Tm. The TGA studies of P-TREF fractions depicted a two-stage thermal degradation behavior: pre-degradation and main degradation stages. Tmax for both pre-degradation and main degradation stages was increased for fractions with less hexyl branch content. As an interesting point the pre-degradation stage was found more intensified for more linear fractions. The concentration of main products was found to be affected by the content of hexyl branches using Py-GC-MS.