ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Craze healing was observed in many amorphous glassy polymers. A detailed study of the kinetics of craze healing in atactic polystyrene (Mw = 255,000) was conducted. The crazes were created in 0.08 mm films in air at room temperature, To, and constant stress, σo ⋍ 2,300 psi, healed at temperature Th for a time, Th, at σ = 0, and recrazed at To and σo. Nucleation times, τ1 and τ2, and growth rates, L1, and L2, for the first and second loading, respectively, were measured as a function of th and Th for individual crazes using dark field optical microscopy. Complete optical and mechanical healing was observed for Th ≥ 70°C(Tg ≅ 100°C). At constant Th, healing progressed in five stages with increasing th as follows; (i) no healing, τ2 = 0, L2 ≫ L1; (ii) partial healing, τ2 〈τ1, L2 〉 L1; (iii) similar growth, τ2 = τ1, L2 = L1; (iv) slower growth, τ2 〉 τ1, L2 〈 L1; (v) disappearance, τ2 → ∞, L2 → 0. A craze healing envelope of Th vs Th was obtained for the above stages. Craze healing occurred by line mode in which uniform healing occurred along the entire length of the craze.
Additional Material:
14 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760211417
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