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Natural weathering of polypropylene films. I. Exposure time and yield properties
Author(s) -
Uzomah T. C.,
Onuoha G. C.
Publication year - 1998
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19980725)69:4<667::aid-app5>3.0.co;2-h
Subject(s) - crystallinity , materials science , polypropylene , composite material , yield (engineering) , crystallite , elastic modulus , weathering , metallurgy , geomorphology , geology
The yield properties of about 500 h of outdoor weathering (in the rainy season) of polypropylene (PP) films have been studied. The yield strain, plastic strain, and initial modulus, work of yield attained local maxima at 48‐ and 240‐h exposure time; elastic strain attained near double maxima at these times. The yield stress reached a local minimum for the 144‐h exposed film before increasing with further exposure hours. The increase in yield strain, plastic strain, and initial modulus were explained in terms of crosslinking chemocrystallization; decreases were due to chain scission and leaching. Critical dissolution time data, interpreted in proportion to density, crystallite thickness, and percent crystallinity, increased with PP exposure time, reaching a maximum at 48 h before decreasing to values even lower than that of unexposed film from the 120‐h exposure. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 667–673, 1998