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

In this work, the effect of hexyl branch content on thermal behavior of a fractionated ethylene/1octene copolymer with emphasis on high temperatures was investigated. The ethylene/1octene copolymer was carefully fractionated to different fractions with homogenous hexyl branch (HB) content by preparative temperature rising elution fractionation (PTREF) method. The PTREF fractions were thermally analyzed via differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and evolved gas analysis (EGA). The PTREF profile showed a short chain branch distribution (SCBD) of around 1.24. A linear relationship between PTREF 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 PTREF fractions depicted a twostage thermal degradation behavior: predegradation and main degradation stages. Tmax for both predegradation and main degradation stages was increased for fractions with less hexyl branch content. As an interesting point the predegradation 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 PyGCMS.