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Craze healing in polymer glasses
Author(s) -
Wool R. P.,
O'Connor K. M.
Publication year - 1981
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760211417
Subject(s) - materials science , polystyrene , self healing , amorphous solid , nucleation , composite material , polymer , optical microscope , bone healing , crystallography , scanning electron microscope , thermodynamics , chemistry , surgery , medicine , alternative medicine , physics , pathology
Abstract Craze healing was observed in many amorphous glassy polymers. A detailed study of the kinetics of craze healing in atactic polystyrene ( M w = 255,000) was conducted. The crazes were created in 0.08 mm films in air at room temperature, T o , and constant stress, σ o ⋍ 2,300 psi, healed at temperature T h for a time, T h , at σ = 0, and recrazed at T o and σ o . Nucleation times, τ 1 and τ 2 , and growth rates, L 1 , and L 2 , for the first and second loading, respectively, were measured as a function of t h and T h for individual crazes using dark field optical microscopy. Complete optical and mechanical healing was observed for T h ⩾ 70°C( T g ≅ 100°C). At constant T h , healing progressed in five stages with increasing th as follows; (i) no healing, τ 2 = 0, L 2 ≫ L 1 ; (ii) partial healing, τ 2 <τ 1 , L 2 > L 1 ; (iii) similar growth, τ 2 = τ 1 , L 2 = L 1 ; (iv) slower growth, τ 2 > τ 1 , L 2 < L 1 ; (v) disappearance, τ 2 → ∞, L 2 → 0. A craze healing envelope of T h vs T h was obtained for the above stages. Craze healing occurred by line mode in which uniform healing occurred along the entire length of the craze.