الفهرس 
1.1. ElastomersOnly 14 pages are availabe for public view
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Abstract
Polymeric fillers may open a door for the development of some
novel elastomer reinforcing agents which prepared by the free radical
polymerization method either in emulsion, dispersion or suspension state.
In the present work we have studied the effects of mixed emulsifiers
systems sodium dodecyl sulphate (SDS as anionic) and poly(oxy
ethylene) nonyl phenyl ether (NP-30 - as non-ionic emulsifier) on the
emulsion polymerization of styrene. The mixed emulsifier system (SDS:
NP-30) (20:80) and (80:20) give high monomer conversion and high
degree of emulsion stability in comparison with other series. So we
concerned on these ratios.
The crosslinked, monodispersed polystyrene (PS) particles was
successfully synthesized by radical emulsion polymerization under the
variation of DVB concentration as cross-linking agent which had
significant effect on the conversion of emulsion polystyrene with higher
conversion containing 20wt% DVB with smaller particle size. The
crosslinked PS took a spherical shape with an average diameter between
75nm and 160nm.
The noncrossliked and crosslinked polystyrene containing 20wt%
DVB were incorporated in acrylonitrile butadiene rubber (NBR) cured
with dicumyl peroxide. Crosslinked polystyrene shows a noticeable
increase in tensile strength more than in case of non crosslinked
polystyrene.
The permittivity ε’ and dielectric loss ε” were measured at fixed
frequency f = 100 Hz in case of PS content for crosslinked and non
crosslinked PS which show that there was slightly decrease in both values
for non crosslinked when compared with crosslinked PS. Also it is clear that 5 phr PS slightly increases the permittivity while 15 phr PS decreases
the permittivity.
HAF was chosen as conducting filler with NBR and NBR/
crosslinked PS (100/5phr) with various content to enhance electrical
conductivity of the polymeric matrix while Silica was chosen to be added
to NBR and NBR/ crosslinked PS (100/15phr) with various content to
reduce the dielectric loss of NBR in order to get an end product suitable
for insulation purposes.
The mechanical and electrical properties were determined using
carbon black as conductive filler and silica as non conductive filler. The
crosslinked PS was found to be effective in elastomer reinforcement. The
NBR filled with crosslinked PS composites exhibited dramatic
enhancement in mechanical performances and in electrical properties
compared with the neat elastomer matrices. NBR/PS vulcanizates have
higher mechanical properties when compared to those values obtained for
NBR vulcanizates after thermal aging.