ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
A torsional pendulum which operates throughout the temperature range - 180° ⇄ +650°C, and permits the examination of specimens which conform to ASTM standard D2236 is reported. The same apparatus is used for torsional braid analyses for which a composite specimen is prepared by impregnating a multifilament glass braid with a solution of polymer and thermally removing the solvent. A linear-with-angle no-drag optical transducer which employs the linear transmission region of a pair of polarizers is described. The apparatus has been used for examining thermo-hysteresis effects in polymers. Hysteresis can arise in polymers from physical time-dependent phenomena such as crystallization ⇄ fusion, dry atmosphere ⇄ water vapor, annealing ⇄ cracking, and from chemical reactions. Thermally-induced chemical reactions can be regulated so as to freeze out preferentially longer range relaxations, thereby extending the glassy state behavior to higher temperatures. A comparison of the thermomechanical behavior of a commercially available polyimide film and of a polyimideforming varnish is reported using torsional pendulum and torsional braid analyses.
Additional Material:
14 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760110406
