Preparation and properties of poly (vinyl chloride) epoxidized natural rubber kenaf core powder composites
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Date
2016-03-01
Authors
Rohani Abdul Majid
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Abstract
An increase in the use of natural fibre-reinforced polymer composites has
attracted attention towards a greener environment, and at the same time has reduced
the production cost for synthetic fibres. On the other hand, researchers, in their
efforts to produce a flexible thermoplastic through the incorporation of elastomeric
materials, have also shown a positive trend towards improving certain properties of
the polymers. Efforts are currently underway to produce polyvinyl chloride (PVC),
epoxidized natural rubber (ENR) and kenaf core powder (KCP) composites. In this
study, the effects of KCP loading, compatibilizers, dynamic vulcanization and filler
chemical treatment on the tensile, morphological, water absorption and swelling,
thermo-oxidative ageing, and thermal properties of a composite were investigated.
Firstly, the PVC/ENR/KCP, containing 0 to 20 phr of KCP, was prepared using the
melt blending and compression moulding methods. The addition of KCP into the
PVC/ENR matrix resulted in a decrease in tensile strength and an elongation at
break. The Young’s modulus was observed to increase due to the addition of rigid
KCP into the PVC/ENR matrix. The reduction in tensile strength was due to low
interfacial adhesion between the filler and the matrix, leading to lower stress transfer.
Secondly, the effect of maleic anhydride as a compatibilizer on the properties of the
PVC/ENR/KCP composite was studied. Two types of MA compatibilizer were used.
It was found that PE-g-MA and PVC-g-MA compatibilizers elevated the tensile
strength and elongation at break. The PVC-g-MA compatibilized composites
exhibited higher tensile properties compared to the PE-g-MA compatibilized composites. The thermo-oxidative ageing of the PVC/ENR/KCP with PVC-g-MA
showed better resistance due to the enhancement in the interfacial adhesion as
compared to the PE-g-MA. Later, the incorporation of cross-linking or dynamic
vulcanization showed an outstanding improvement in tensile properties. Dynamic
vulcanization using a semi-efficient sulphur system improved the matrix-matrix
interaction with the sulphur cross-linking bond. It was also observed that thermooxidative
ageing improved with dynamic vulcanization. Next, filler treatments were
incorporated. The benzoyl chloride treatment improved the tensile strength, Young’s
modulus and elongation of the PVC/ENR/KCP composite. The benzoyl chloride
treatment was also observed to have improved the water absorption properties due to
the enhancement of interfacial adhesion. Unfortunately, there was a reduction in the
thermo-oxidative ageing properties as early as after 3 days of exposure. For the
sodium dodecyl sulphate-treated composite, there was a slight increase in the tensile
strength and an outstanding increase in the elongation at break. Unlike the benzoyl
chloride-treated composite, the Young’s modulus for the sodium dodecyl sulphatetreated
composite showed a lower value compared to the untreated composite. The
same observation as that of the benzoyl chloride-treated composite was recorded for
the thermo-oxidative ageing properties. The results indicated that there was a
reduction as early as after 3 days of exposure.