Papers by Author: Allan J. Easteal

Abstract: Composite nanofibres of poly (lactic acid) (PLA) with polyaniline (PANI) or poly (aniline-co-m-aminobenzoic acid) (P (ANI-co-m-ABA)) were prepared by electrospinning. Thermal effects on the properties of the composite nanofibres were studied by means of DSC and TGA. TGA results show that the onset thermal degradation temperature of the composite fibres was slightly higher than that of pure PLA. The degree of the crystallinity of the nanofibres was determined from DSC data and compared to film with the same composition.

Abstract: Starve feed and semi-continuous seed emulsion polymerization were used to control the morphology of core shell latex particles with a vinyl acetate (VAc)/vinyl ester of versatic acid 10(VeoVa10) copolymer core surrounded by a poly(glycidyl methacrylate) (PGMA) shell. Pure core and core-shell structures were confirmed by TEM. The results suggest that core-shell morphology of the two stage emulsion was favoured by higher concentration of emulsifier in the seed latex: the particle size distribution of core-shell latex was broader than that of the core latex, and the average particle size of core-shell latex was larger than that of the core latex. The core-shell structure was not produced using seed emulsion with emulsifier concentration at or below the critical micelle concentration. The core shell emulsion containing epoxy functional group with added ethylene diamine showed an abrupt increase in dynamic shear moduli, G' and G'' and complex viscosity η* (several orders of magnitude) at about 35oC, during temperature ramps, over a wide range of angular frequencies. The time ramps showed that the crosslinking reaction did not occur at 15oC for the core-shell emulsion/amine system. The time for gel formation decreased with increase in temperature.

Abstract: Modified natural rubber latex can be used as paperboard barrier coating in order to replace unrecyclable wax coating material. Natural rubber latex (NRL) was prevucanized in different time interval and the efficiency of crosslinking were determined by swelling ratio test. Prevulcanized natural rubber latex (Pre-VNRL) was blended with modified lignin dispersion to decrease sticking tendency of the coatings. Particle size of lignin dispersion was reduced by Mannish reaction using octylamine which can increase hydrophobility in lignin. Compared with Pre-VNRL coating, a reduction of water vapour transition rate (WVTR) was observed in blendingcoated paper. Such moisture-barrier behaviour is attributable to a good compatibility of the nanosized modified lignin particles with rubber. The blocking (sticking) tendency decreased with the content increase of lignin due to stiffness of lignin.

Abstract: The usefulness of rotational moulding (rotomoulding) as a polymer processing technique is often limited by the selection of polymers, which in most cases happens to be polyethylene (PE). In the present study, PE polyethylene was blended with wollastonite microfibres and maleated polyethylene (as a coupling agent) with the purpose of developing an improved material for rotational moulding. The incorporation of wollastonite fibres without any coupling agent improved the tensile strength, but showed a reduction in impact strength. As expected, the most significant enhancement due to wollastonite was in the tensile modulus.. The addition of a coupling agent improved both the impact strength and the processability, especially when wollastonite was coated with aminosilane. Scanning electron microscopy revealed good adhesion between the coated fibre reinforcement and the polyethylene matrix at the fracture surface.

Abstract: Tensile properties and morphology of poly(ethylene naphthalate)/polyolefin blends and the relationship with the extrusion die size were investigated. Scanning electron micrographs of the blends reveal that the fibre morphology is developed during extrusion through the die. Skin-core morphology has been observed. As die diameter decreases, a droplet-to-fibre transition in morphology increases tensile strength and stiffness. After microfibrillization, up to 100% increase in the tensile stiffness was observed and the tensile strength could increase by one order of magnitude.