Crack Healing in Polymers (Fracture, Reptation, Tack)
O'Connor, Kevin Michael
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https://hdl.handle.net/2142/71812
Description
Title
Crack Healing in Polymers (Fracture, Reptation, Tack)
Author(s)
O'Connor, Kevin Michael
Issue Date
1984
Department of Study
Metallurgy and Mining Engineering
Discipline
Metallurgical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Abstract
The mechanical property development associated with the healing of polymer-polymer interfaces was studied using theoretical and experimental approaches. The healing of crazes in atactic polystyrene (PS) and microvoids in styrene-isoprene-styrene block copolymers was described phenomenologically, from dark-field optical microscopy and light transmission measurements. For the healing of bulk polymer surfaces, molecular-level models were coupled with experiments to investigate the effects of healing time t, temperature T, and molecular weight M. The reptation theory of self-diffusion in entangled polymers was used to describe chain motions and interpenetration at a polymer-polymer interface. Various dynamic quantities, including the average segment interpenetration depth (gamma), were related to the fracture strength (sigma) and fracture energy E through microscopic fracture criteria. For a polybutadiene elastomer, (sigma)(,o) is the surface wetting contribution, K is a constant, and t(,(INFIN)) is the time to achieve full healing. A reanalysis of literature data for natural rubber showed (sigma) (TURN) M('- 1/4) for a constant t 2.5 x 10('5). The M(' 1/2) behavior is consistent with chain pullout, and M('o) is consistent with chain fracture.
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