Amorphous linear polyethylene: Annealing effects |
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| Authors: | R Lam P H Geil |
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| Institution: | 1. Department of Macromolecular Science , Case Western Reserve University , Cleveland, Ohio, 44106, USA;2. Research Laboratories , Rohm and Haas Co. , P.O. Box 219, Bristol, Pennsylvania, 19007;3. Polymer Group, Department of Metallurgy and Mining Engineering , University of Illinois , Urbana, Illinois, 61801 |
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| Abstract: | The effect of annealing amorphous linear polyethylene films prepared by an improved ultraquenching technique at temperatures just below and above a dynamic mechanical relaxation peak (torsion braid) observed at ∽190K has been characterized by electron microscopy and torsion braid analysis. Based on the results described, this peak is believed related to the lower glass transition temperature Tg(L), the Tg of wholly amorphous linear polyethylene, whereas the β peak at 260K is Tg (upper). Annealing just below Tg (L) results in a growth in size of the nodules observed in the as-quenched samples, whereas annealing above Tg (L) can result in the growth of single crystal-like structures, spherulites, and shish-kebobs. Storage of the crystallized samples at room temperatures results in a decrease in size of the relaxation peak during subsequent torsion braid spectroscopy measurements. The results indicate significant amounts of molecular motion can occur during crystallization even at Tg. |
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| Keywords: | Crystal structure Differential scanning calorimetry Fiber Full-pattern x-ray diffraction Gel spinning Intermediate phase Phase transformation Polyethylene Powder x-ray diffraction Small-angle x-ray diffraction Solid-state 13C NMR Structure-property relationship Ultrahigh molecular mass polyethylene |
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