ISSN:
0887-6266
Keywords:
polyethylene, UHMW, crystal orientation in drawn films of
;
x-ray diffraction study of crystal orientation in drawn films of UHMW polyethylene
;
crystal orientation of UHMW polyethylene in drawn films
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
A wide-angle x-ray diffraction (WAXD) study of the development of molecular orientation in the crystalline phase of ultra-high-molecular weight polyethylene films prepared by the gelation-crystallization method is presented. WAXD scans of the undrawn films show that the lamellae are oriented in the plane of the films. Upon drawing at 130°C, the orientation of the molecular chains changes from the direction normal to the film surface (ND) to the elongation direction. The decrease of the 200/020 intensity ratio at low draw ration (λ 〈10) indicates that double orientation develops during the transformation from the lamellar to the fibrillar morphology, with the a-axis oriented parallel to ND. The orientation distributions of the 110, 200, 020, and 002 planes of the orthorhombic unit cell of polyethylene were studied and characterized by the coefficients of a Legendre polynomial series. At a draw ratio of 4.5, the second-order coefficient, 〈P2(cos χ〉, already gets close to its limiting value, but it is shown that higher order coefficients of the polynomial series can be used to describe the evolution of the orentation, even up to λ = 50. The coefficients relative to the molecular chain orientation, 〈Pn(cos χ)〉c, can be calculated from different crystalline reflections. Curve-fitting calculations were made in order to improve the correlation between the results obtained from the orientation distribution of the 110, 020, and 002 planes. A Person VII function was found to give a better fit of the experimental curves than Gaussian or Lorentzian equations. © 1993 John Wiley & Sons, Inc.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/polb.1993.090310303
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