کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5189903 | 1381193 | 2005 | 10 صفحه PDF | دانلود رایگان |
Polyethylenes and polyethylene/α-olefin-copolymers covering a range in crystallinity between 12 and 85% were investigated by means of dynamic-mechanical measurements between â145 °C and their melting point. From the temperature and frequency dependence of the complex modulus αâ²-, α-, β- and γ-relaxations were analyzed. The αâ²-relaxation was discovered in all HDPE-, LDPE- and LLDPE-samples but not in plastomer- and elastomer-samples. The activation energies (30-140 kJ/mol) of this relaxation were found to decrease with increasing crystallinity. The αâ²-transition temperature at a fixed frequency rises with increasing degree of crystallinity and tends to reach the melting point when approaching the fully crystalline state. Thus, it is concluded that the αâ²-relaxation originates from the interface between crystal lamellae and amorphous interlamellar regions. By extrapolation of the storage modulus to the amorphous state the entanglement molar mass was calculated as 2300 g/mol for a completely amorphous polyethylene/α-olefin-copolymer.
Journal: Polymer - Volume 46, Issue 23, 14 November 2005, Pages 10311-10320