کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5180866 | 1380945 | 2014 | 8 صفحه PDF | دانلود رایگان |
- The rigid amorphous fraction (RAF) is tailored by incorporation of random co-units.
- Exclusion of ethylene co-units from crystallization leads to an increase of the RAF.
- Increase of the RAF with ethylene content is due to lower perfection of fold-surfaces.
The effect of different amounts of ethylene co-units in the butene-1 chain, on the fold-surface structure of crystals of isotactic polybutene-1, has been probed by analysis of the rigid amorphous fraction (RAF). The exclusion of ethylene co-units from crystallization in random butene-1/ethylene copolymers and their accumulation at the crystal basal planes leads to a distinct increase of the RAF with increasing concentration of co-units. A specific RAF was determined by normalization of the RAF to the crystal fraction. While in the butene-1 homopolymer a specific RAF of 20-30% is detected, it increases to more than 100% in copolymers with 5-10Â mol% of ethylene co-units, being in accordance with the previously observed increase of the free energy of the crystal fold-surface due to copolymerization. It has also been shown that the specific RAF increases with decreasing temperature of crystallization, due to formation of a fold-surface of lower perfection, containing an increased number of chain segments traversing the crystalline-amorphous interface.
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Journal: Polymer - Volume 55, Issue 23, 5 November 2014, Pages 6132-6139