Influence of Branching Density in Ethylene-Octene Copolymers on Electron Beam Crosslinkability

Polymers

Petr Svoboda¹ 

[1] Department of Polymer Engineering, Faculty of Technology, Tomas Bata University in Zlin, Vavreckova 275, 762 72 Zlin, Czech Republic

关键词: ethylene-octene copolymer;    electron beam irradiation;    crosslinking;    rheology;    creep;   

DOI  :  10.3390/polym7121530

来源: mdpi

【 摘 要 】

Two ethylene-octene copolymers (EOC) with the same melt flow index (MFI = 3 g/10 min) but different octene contents, being 20 and 35 wt % (EOC-20 and EOC-35), were compared with regard to sensitivity to electron beam crosslinking. Dynamic mechanical analysis (DMA) revealed a large influence of the octene content on the storage modulus and the glass transition temperature (T_g) but a smaller influence of irradiation on the properties below melting point (T_m). Rheology at 150 °C pointed out large differences in samples crosslinked in the 0–60 kGy range and at lower frequencies (0.1–1 Hz). The loss factor tanδ confirmed that before irradiation the two copolymers were very similar, while after irradiation to 120 kGy, the EOC-35 had considerably lower tanδ than EOC-20, which corresponds to a better elasticity (or a higher level of crosslinking). A high-temperature creep test showed a considerably lower creep for EOC with a higher octene content. An analysis of the insoluble gel content exhibited higher values for EOC-35 confirming a higher level of crosslinking. Analysis according to the Charlesby-Pinner equation revealed increased crosslinking-to-scission ratio, G(X)/G(S), for EOC-35. While the G(X) value changed only slightly, a significant decrease in the G(S) value was discovered.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.