30-11-2012, 05:38 PM
Effect of Uv Radiation on Dielectric Constant And Thermal Conductivity In Epoxy Phenol Blends
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Abstract
Epoxy-phenol system were prepared and studied before and after reinforcing with
glass fibers (woven roven 0ο-90ο direction) with volume fraction (vf = 48%). The
samples irradiated with uv radiation with wave length (λ= 320 nm), irradiation energy
(1.5 watt/ cm2) for 50 hours. The dielectric constant and thermal conductivity
measured for all samples before and after irradiation with uv radiation. The results
showed that the increasing percentage of phenolic resin in the blends decreasing the
dielectric constant and thermal conductivity of all samples before and after irradiation
with uv radiation. While the results before irradiation showed the effect of glass fibers
in increasing the dielectric constant and thermal conductivity. Finally the results
showed that the dielectric constant decreased, thermal conductivity increased for all
samples after irradiation with uv radiation.
Introduction
Polymer blends become very
important subject for scientific
investigation in recent years, because
of their growing commercial
acceptance blending polymers have
been successfully used in an increasing
number of applications, such success
encourage more attempts to apply this
technique to a wider range of problems
in polymer related industries [1].
A high dielectric constant is
associated with the polarization and
polarizability of the electrons that form
individual bonds in polymer matrix,
this in turn depends on the orientation
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Eng. & Tech. Journal, Vol.28, No.10, 2010 Effect of Uv Radiation on Dielectric Constant
And Thermal Conductivity In Epoxy Phenol
of polar groups in the matrix, hence
the ability of a polymer groups to
switch orientations in phase with an
alternating current may be limited [2].
Results and Discussion
From the results in table (1) before
weathering, addition phenolic resin to
epoxy resin to epoxy resin sample (2)
decreased the (εr) due to the holes or
voids which are collectively called
(free volume) in polymers, one of the
reasons for the reduced dielectric
constant in the blends may be
enhanced free volume, the morphology
of blends characterized them to be of
immiscible category, it seems that
more voids have been created at the
phase boundaries, enhancing free
volume, enhanced free volume lowers
polarization by decreasing the number
of polarization groups per unit volume
[5].