Structure of semi crystalline fibers from interpretation of anelastic effects
| Autor: | D. C. Prevorsek |
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| Rok vydání: | 2007 |
| Předmět: | |
| Zdroj: | Journal of Polymer Science Part C: Polymer Symposia. 32:343-375 |
| ISSN: | 1935-3065 0449-2994 |
| DOI: | 10.1002/polc.5070320119 |
| Popis: | A theory of fiber strength is reviewed which assumes that the rupture of fibers is a result of the formation and propagation of cracks across the fiber. The derived equations which include three parameters related to molecular structure, modulus, energy of the weakest bond and fracture surface energy are used to estimate the strength of flawless ensembles of perfectly oriented molecules. A method is discussed to estimate the fracture surface energy of such systems as function of molecular weight and degree of random chain folding. A comparison of theoretical data with the strength of a series of highly oriented poly-(ethylene terephthalate) fibers having approximately the same morphological characteristics but different molecular weight leads to the following conclusions. First, the strength determining phase of these fibers has a lower density than the fibers, and second, this low density phase consists of highly extended molecules whose average length between the folds exceeds 1500A. The characteristics of the two phase system of these fibers, the phase of the matrix and the aspect ratio of crystallites are determined by analyzing the intensity of viscoelastic transitions and by treating the data by means of Halpin-Tsai equations. A structural model is proposed which is consistent with the results of this analysis and with the small- and wideangle X-ray diffraction data. |
| Databáze: | OpenAIRE |
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