Accession Number:

ADA114555

Title:

Chemical Stress Cracking of Acrylic Fibers.

Descriptive Note:

Technical rept.,

Corporate Author:

MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MATERIALS SCIENCE AND ENGINEERING

Report Date:

1982-05-01

Pagination or Media Count:

57.0

Abstract:

The generation of periodic microscopic transverse cracks in oriented acrylic fibers immersed in hot alkaline hypochlorite solution is described in detail and shown to be a variety of chemical stress cracking. It is greatly accelerated by external tensile stress, high fiber permeability, moderate fiber orientation, and water-plasticization. The proposed mechanism for bond cleavage involves cyclization of nitrile groups similar to the prefatory reaction in pyrolysis of acrylic fibers, followed immediately by N-chlorination and chain scission. Mechanical retractile forces internal or external then cause chain retraction and crack growth. Despite the remarkable regularity of the crack pattern, which typically resembles a series of stacked lamellae, the process is independent of any such underlying fiber morphology. The cracking process does, however, appear to be a sensitive indicator of residual latent strain in the fiber, which may persist even after high-temperature annealing. Author

Subject Categories:

  • Polymer Chemistry
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE