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

Personal Author(s) : Herms,J ; Peebles,L H , Jr ; Uhlmann,D R

PDF Url : ADA114555

Report Date : May 1982

Pagination or Media Count : 57

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)

Descriptors :   *Fibers, *Acrylic resins, *Polymers, *Stresses, *Cracking(Fracturing), Tensile stress, Residual stress, Morphology, Pyrolysis, Permeability, Structural analysis, Microstructure, Crack propagation, Orientation(Direction), Solutions(Mixtures), Alkalinity, Hypochlorites

Subject Categories : Polymer Chemistry
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE