Munirah Mokhtar

Comparison of rice husk-filled polyethylene composite and natural wood under weathering effects

The weathering performance of rice husk-filled high-density polyethylene (RHPE) and natural wood was investigated in this study. The injection molded RHPE, in column end-cap (CECap) shapes, was exposed to both natural and accelerated weathering attacks. The durability of RHPE was compared to Kempas wood (Koompassia malaccensis) and neat polyethylene. Wood underwent the greatest losses in properties among the specimens. Four months of outdoor weathering turned the color of RHPE CECap into silvery grey. When the exposure time increased, the color of RHPE composite faded faster than neat polyethylene. The wood surface darkened and RHPE surface flaked off after being exposed to accelerated weathering conditions. Prolonged weathering exposure caused loss of impact strength of the RHPE composites. In general, RHPE is more resistible to weathering attacks as compared to Kempas wood.

Development of Scratch- and Abrasion-Resistant Coating Materials Based on Nanoparticles, Cured by Radiation

The aim of this study was to compare the effect of monomers, prepolymers, and nanosilica on the scratch and abrasion resistance of nanocomposite coatings. Ultraviolet (UV) and electron beam (EB) curing were used to cure the nanocomposite coatings. The effect of monomers, prepolymers and nanosilica particles on the viscosity, pendulum hardness, gel content, scratch and abrasion resistance were studied. It was found that the optimum formulation for scratch and abrasion resistance contained 15% Ebecryl 600 epoxy acrylate resin with 30% monomer PETIA and 30% of Aerosil OX-50 nanosilica.

Effect of SEBS on the mechanical properties and miscibility of polystyrene rich polystyrene/ polypropylene blends

Blends of polystyrene (PS) with polypropylene (PP) are usually developed to overcome the inherent brittleness of PS. However, PS with PP are immiscible and (in the absence of a compatibiliser) incompatible. The present study investigated the effects of styrene-b (ethylene-co-butylene)-b-styrene (SEBS) on the mechanical properties and compatibility of PS-rich PS/PP blends. Using a Brabender PL2000 twin-screw extruder, blends of PS/PP in various compositions ranging from 100-60 wt% PS with and without SEBS were prepared and injection moulded. The overall results clearly showed that the mechanical properties of PS/PP blends are dependent on blend composition (ratio of PS/PP) and SEBS content. The impact strength and elongation at break of the PS/PP blends increase with SEBS content, at the expense of tensile strength and flexural modulus. The improvements in impact strength and elongation at break with the addition of SEBS are due to the improved interfacial adhesion between the dispersed phase (PP) and matrix phase (PS). The improvement in miscibility of the PS/PP blend with the addition of SEBS is supported by DMA analysis. This showed that the 60/40 PS/PP blends possess two endothermic peaks whereas 60/40/25 PS/PP/SEBS blends have a single endothermic peak at 102 °C, indicating that they have an improved miscibility. The effectiveness of SEBS in enhancing the blends depends on the blend composition. A significant improvement was observed upon addition of more than 10 phr of SEBS into the 70/30 and 60/40 PS/PP blends, but not much improvement in the case of the 90/10 and 80/20 PS/PP blends. However, a higher SEBS content is more effective at higher PS contents, as illustrated by the 90/10/25 PS/PP/SEBS blends having higher impact strengths than 60/40/25 PS/PP/SEBS. The optimum blend, based on achieving a balance between toughness (impact strength) and stiffness (flexural modulus), is 90/10/25 PS/PP/SEBS, followed by 80/20/25 PS/PP/SEBS.

PLA/Kenaf/APP Biocomposites: Effect of Alkali Treatment and Ammonium Polyphosphate (APP) on Dynamic Mechanical and Morphological Properties

Kenaf-filled polylactic acid (PLA) biocomposites were prepared using dry blending, twin screw extrusion and compression molding. PLA was blended with raw and alkali treated kenaf, polyethylene glycol and ammonium polyphosphate (APP). Dynamic mechanical properties of biocomposites were investigated by dynamic mechanical analysis. Storage modulus of composites decreased, while magnitude of damping peaks increased with increase in APP content. The T g of composites shifted to lower values with APP addition. Alkali treatment improved interfacial adhesion between PLA and kenaf. SEM analysis indicates good dispersion of APP in PLA matrix, however interfacial adhesion between PLA and matrix decreased with increasing APP content.

Mechanical properties and morphology of polypropylene/poly(acrylonitrile-butadiene-styrene) nanocomposites: Effect of compatibilizer and montmorillonite content

Polypropylene (PP)/poly(acrylonitrile–butadiene–styrene) (ABS) blends containing montmorillonite (MMT) compatibilized with polypropylene-grafted maleic anhydride were prepared by melt extrusion using twin screw extruder followed by injection molding. Mechanical properties were evaluated through tensile, flexural, and impact testing. The microstructure and formation of nanocomposites were assessed by scanning and transmission electron microscopy and X-ray diffraction (XRD). Incorporation of polypropylene-grafted maleic anhydride and MMT into PP/ABS blend led to higher strength and stiffness but at the expense of toughness. Scanning electron micrographs revealed a fine and homogeneous dispersion of ABS phase in PP matrix. Both XRD and transmission electron microscopic analysis revealed the formation of intercalated clay silicate layer in PP/ABS nanocomposites.

Flow Characteristics and Dynamic Behavior of Polyamide 6/Acrylonitile Butadiene Styrene (PA6/ABS) Blends

The objective of this research was to investigate the effect of incorporation of maleic anhydride grafted acrylonitrile-butadiene-styrene (ABS-g-MAH) on rheological properties of PA6/ABS blends. Flow properties of the blends were examined by dynamic and capillary rheometers. The dynamic rheological analyses showed an increase in complex viscosity with the incorporation of a compatibilizer. The reduction of tan δ peaks showed enhanced interfacial interaction between PA6 and ABS phase, which resulted in the enhancement of melt strength. The power law index analysis showed that 1.5 wt.% resulted in minimum n and maximum K value for the blends while still retaining the pseudoplastics behavior necessary for plastics processing and prediction for the end use performance of the PA6/ABS blends.

The Effect of Radiation Dosages and UV/EB Radiation on the Properties of Nanocomposite Coatings

The aim of this study was to compare the effects of ultraviolet (UV) and electron beam (EB) radiation on the properties of cured nanocomposite coatings. Surface hardness increased with increasing radiation dosages (number of passes) for all samples. This was due to the increase in crosslinking with increasing radiation dosages. Pendulum hardness, gel content, and thumb twist results were analyzed to choose the appropriate curing dosage for both curing techniques. The selected dosages were then used to cure coatings for scratch and abrasion resistance tests. It was found that the UV curing produced coatings with better abrasion resistance, whereas EB curing was more suitable for producing scratch-resistant coatings.