Abstract
This study explores the effect of hydrocarbon liquid
on creep behavior of Polylactic Acid (PLA)–based plastic. Evolution of the mechanical
properties of the material was investigated experimentally by measurement of
creep under tensile load. Tensile creep behavior was studied with a constant
load over a temperature range from 30 to 50ÂșC using specimens containing different
levels of liquid. It was shown that the hydocarbon liquid diffusion obeys the
Fickian law of diffusion. The viscoelastic properties vary with temperature and
these properties dramatically decrease above the glass transition temperature
(Tg). Significant decreases in modulus and in the peak of tan d
were observed with an increase in liquid concentration at low temperatures. In
contrast, at high temperatures, drier material recorded lower storage modulus. However,
only small changes of Tg were recorded. Dependence of compliance on temperature
was observed in the creep test at all levels of liquid content. With respect to drier samples, it was noted
that the high liquid content material had a lower rate of increasing creep
strain with temperature. Therefore, at elevated temperatures, higher creep
strain of dry specimens was observed compared to those with a higher liquid
content. The improvement of creep resistance and stiffening of material at high
temperatures can be attributed to the significant increase of crystallinity
fraction induced by liquid absorption. Understanding
the effect of liquid diffusion in conjunction with temperature provides useful
information for assessment of the potential use of this biodegradable plastic
in load-bearing applications exposed to an organic liquid.
The full text paper is available on:
Semoga bermanfaat......
No comments:
Post a Comment