Concerning the Negative Thermal Expansion for Extended Chain Polyethylene.
MASSACHUSETTS UNIV AMHERST MATERIALS RESEARCH LAB
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Thermal expansion coefficients have been measured on ultraoriented polyethylene fibers. Samples were prepared by a solid-state crystalline extrusion in an Instron Capillary Rheometer at 136C, 2100 atm. and at a draw ratio of 50. The expansion coefficients between -150 and 50C, perpendicular to the fiber axis, were positive and of the order of .0001deg C. Conversely, parallel to that direction, the observed values were both negative and small. Length changes were reversible and reproducible between -150 and50C. Negative coefficients were attributed to the presence of highly-extended and fully aligned chains along the fiber.
- Organic Chemistry
- Atomic and Molecular Physics and Spectroscopy