(1974).The crystalline conformation of polypivalolactone was determined by analysis of the chain conformational energies and it was found that the minimum energy corresponds to a planar tmrzs conformation for the ester group. The result was con~pared to published X-ray data based on fiber diffraction which show a significant deviation from trans planarity. This difference is discussed in terms of the relative energies involved and by comparison with literature crystallographic results of low molecular weight carboxylic esters. It is stressed that because of the paucity of information in fiber diffraction, internal energy considerations are important for assigning internal rotation angles. Crystallographic results for low molecular weight compounds show that deviations greater than 10" from trans planarity are rare for ester groups.J. COR~IBERT, N. V. MIEN, F. BRISSE et R. H. MARCHESSAULT. Can. J. Chem. 52,3742 (1974). On a determine la conformation cristalline de la polypivalolactone par analyse des energies conformationnelles de chaines; on a trouve que l'tnergie minimum correspond a une conformation trans coplanaire pour le groupe ester. Ce rCsultat est compare avec les donnees de rayons-)< publiees, basees sur la diffraction de fibre, qui montrent une deviation notable de la planarite trans. On discute de cette difference en termes d'knergies relatives impliquees et par comparaison avec les resultats cristallographiques rapportes dans la litterature pour des esters carboxyliques de faible poids moleci~laire. On fait remarquer que, dd ail peu d'information de la diffraction des fibres, la consideration d'energie internee est importante pour attribuer les angles de rotation interne. Les resultats cristallographiques pour des composes de bas poids moleculaires montrent que des deviations plus grandes que 10' par rapport a la planarite traits sont rares dans les groupes esters.[Traduit par le journal]
The morphology and mechanical properties of four different fibers-polyethylene, polypropylene, nylon 66, and polyethylene terephthalate-under the influence of twisting, were investigated. It was found that a model for affine deformation of the fibers can be applied only for very low-twist levels. At high-twist levels the s t r e s s distribution and the deformation made in the fiber were very complex. A preferred radial orientation occurred in polyethylene, nylon 66, and polyethylene terephthalate giving r i s e to an ideal situation for chain tilting and kinking. Polymorphic transition, twinning, and yielding were also observed in the c a s e of polyethylene. The fiber moduli decreased sharply with twist, and this was attributed to the effects of inhomogeneous s t r e s s distribution and fibril slippage.
SynopsisA method has been developed which permits the quantitative determination of fiber orientation in a cellulosic sample (paper, nonwoven or composite). From the measured fibril angle distribution function and the observed variation in intensity of the (002) plane of the x-ray pattern, a parameter governing the fiber distribution function is obtained analytically. The method is demonstrated for two different paper samples showing a narrow and a large fiber orientation distribution. The method is rapid for a series of samples involving the same fibers and does not involve any operator interpretation. It gives directly the average fiber orientation function from the bulk.of the sample, not just from its surface as microscopic methods do. It can be particularly useful in the analysis of paper-polymer laminates.
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