Advances in instrumentation and technique of torsional pendulum and torsional braid analyses

Abstract

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.

Thermomechanical and thermogravimetric analyses of systematic series of polyimides

“…9) correspond closely u-ith those in the group of polyimides (Fig. 5) synthesized from pyromellitic dianhydride and one of the three diamines: p,p'-diaminodiphenyl ether, 1; p,p'-methylenedianiline, 2; and p,p'-diaminobenzophenone, 3.…”

Thermoset characterization for moldability analysis

“…The kinetics of thermosetting reactions ha\re been studied with the help of swelling measurements ( 18,19), spectroscopic analysis (20,21), rheological measurenieiits (22)(23)(24) , torsional and flexural braid analysis (25)(26)(27), electrical conductivity measurements (20,28), and a variety of other techniques.…”

Effect of Atmosphere and Temperature on Wear, Friction, and Transfer of Polyimide Films

“…Surface proffles of the polyimide film wear tracks were also taken at these same intervals and compared. basic polyimide structure (18)- (20). But, before polyimides can be synthesized with improved lubrication properties, a more basic understanding of the friction and wear processes of this polymer is necessary.…”