Robert Rhodes Mather

Evaluation of nonwoven polypropylene oil sorbents in marine oil-spill recovery.

Mechanical recovery of oil by oil sorbents is one of the most important countermeasures in marine oil-spill response. Polypropylene is the ideal material for marine oil-spill recovery due to its low density, low water uptake and excellent physical and chemical resistance. Different forms of polypropylene nonwoven sorbents were evaluated in this study in terms of initial oil-sorption capacities and oil-retention properties. The investigation revealed that the fibre diameter, sorbent porosity and oil property are the most important factors in the oil-sorption performance of polypropylene nonwoven sorbents.

Fibres from polypropylene and liquid crystal polymer (LCP) blends: 1. Effect of LCP concentration

Abstract Polypropylene (PP) resin and a thermotropic liquid crystal polymer (LCP) were mixed and coextruded on a screw extruder. The LCP was found to exist in fibril form above a PP/LCP (wt/wt) ratio of 100 5 and a PP/LCP ratio of 100 15 the LCP existed in a network structure. For the as-spun fibre, both the initial modulus and the yield stress increased with the increase in the LCP concentration. In the drawn fibres, however, the LCP fibrils were found to be split into short fragments. A two-stage drawing process was used in order to reduce the extent of fracture of the LCP fibrils. The drawn fibres were found to contain more long fibrils from the two-stage process and as a result, there were significant increases in both the tensile strength and initial modulus of the two-stage drawn fibres.

Fibres from polypropylene and liquid-crystal polymer blends using compatibilizing agents: 1. Assessment of functional and non-functional polypropylene—acrylic acid compatibilizers

Abstract A graft polymer based upon acrylic acid-functionalized polypropylene (PP-AA) and PP-AA itself were assessed as compatibilizers for polypropylene/liquid-crystal polymer (PP/LCP) polyblend fibres. It was found that the functional compatibilizer improved interfacial adhesion and thus fibre properties, depending on the type of hot-drawing process used, as well as significantly enhancing the thermal stability of the fibre. Incorporation of PP—AA increased fibre crystallinity and orientation, with a slight enhancement of fibre properties observed. This was attributed to the promotion of specific polar interactions between the blend components.

Fibres from polypropylene and liquid crystal polymer blends: 3. A comparison of polyblend fibres containing Vectra A900, Vectra B950 and Rodrun LC3000

Abstract Polyblend fibres were made of polypropylene (PP) and three thermotropic liquid crystal polymers (LCPs). The LCPs were found to exist in different morphological structures; the Vectra A900 and Vectra B950 LCPs existed mainly as fibrils, while the Rodrun LC3000 existed as short elongated ribbons. The tensile properties of the as-spun fibres were improved on addition of the LCPs, with the properties of the drawn polyblend fibres varying with the drawing procedure. In one-stage drawing, the polyblend fibres gave poorer tensile properties than the pure PP fibre. However in two-stage drawing, the Vectra A900 blend showed an increase in initial modulus over that of the pure PP fibre, while the Rodrun LC3000 blend produced an improvement in fibre tenacity.

Fibres from polypropylene and liquid crystal polymer blends using compatibilizing agents: 3. Assessment of graft side chain liquid crystalline compatibilizers based upon acrylic acid-functionalized polypropylene

Graft side-chain liquid crystalline functional copolymers based upon acrylic acid-functionalized polypropylene (PP-AA) were assessed as compatibilizers for polypropylene/liquid crystalline polymer (LCP) polyblend fibres. The compatibilization effect observed was found to be dependent upon the liquid crystalline phase temperature range of the compatibilizer, with the most favourable being in a liquid crystalline state during fibre melt extrusion and hot drawing, thus contributing a lubricating effect to the blend and giving enhanced physical properties as a result.

Fibres from polypropylene and liquid crystal polymer blends: 2. Effect of extrusion and drawing conditions

Abstract The drawing conditions were studied for a polyblend fibre of polypropylene (PP) and a thermotropic liquid crystal polymer (LCP). It was found that, in one-stage drawing, the LCP fibrils were split into short fragments with aspect ratios of around 10. Although fibre properties were improved with the increase in drawing temperature, the best properties of the polyblend fibre from one-stage drawing were poorer than those of the pure polypropylene fibre. A two-stage drawing process was studied in terms of the ratios and temperatures of the first- and second-stage drawings. It was found that the fibre properties were strongly affected by these parameters. At best, the fibre tenacity and initial modulus in the two-stage drawing were 14% and 39% higher than the highest values from the one-stage drawing. The LCP fibrils were found to split to a much lower extent in the two-stage drawing. The optimum drawing proceedure was applied to a series of polyblend fibres extruded under various extrusion rates and with a number of draw-down ratios.

The application of factorial experimental design to the processing of polypropylene fibres

This paper outlines the application of factorial experimental design to the processing of polypropylene (PP) fibres. Two examples are given. The first covers the effect of melt-extrusion conditions on the overall orientation of the PP macromolecular chains in as-spun fibres. The second covers the effect of drawing conditions on crystallographic order and chain orientation in the first-stage drawing of as-spun PP fibres.

Probing the morphology of polypropylene fibres by scanning probe microscopy

This paper highlights the application of scanning probe microscopy, notably atomic force microscopy in contact mode supported by lateral force microscopy, to the investigation of changes in the morphology of polypropylene (PP) monofilaments during melt-extrusion and subsequent drawing. A gradual deformation at the fibre surface from a spherulitic structure to a shish-kebab type structure is observed for the gravity spun and as-spun variants. In the drawn PP filaments, the surface structure is predominantly fibrillar in character, though the nature of the fibrillar structure is influenced by the drawing conditions. Wide angle X-ray scattering analysis, in conjunction with SPM, indicates contrasting features of surface and bulk crystal structure both at the as-spun and drawn stages of production. In addition, an unusual WAXS diffraction pattern is observed for the cold drawn PP filament. Studies of the bulk structures of the fibres by investigating fibre cross-sections using SPM will be the subject of a companion paper.

The degree of crystal aggregation in organic pigments

Abstract Organic pigments are normally dispersed as fine crystals, which have a marked tendency to cluster into aggregates. Pigment crystal aggregation is technologically undesirable, for it hinders the attainment of high colour strength by reducing the effective level of subdivision of the crystals. Two methods of assessing the degree of crystal aggregation are presented, both of which compare the BET surface area, determined from nitrogen adsorption isotherms, with the mean specific surface areas of the crystals. In the first method, the specific surface areas of the crystals are determined from the principal crystal dimensions. In the second method, a refinement is proposed based on the fractal nature of the pigment crystal surfaces. ©

ESEM study of size removal from ceramic fibers by plasma treatment

Plasma treatment has been increasingly used for surface cleaning, activation and polymerisation in many industries. In this study, the oxygen plasma treatment was used to remove the organic size from the ceramic fiber surface. The size removal from the fiber surface was characterized using an environmental scanning electron microscope. The combination of electron microanalysis and energy-dispersive X-ray allowed the observation of the fibre surface and the determination of the change in elements on the fiber surface. The use of low energy plasmas has been shown to be effective in the removal of the organic size from the ceramic fiber surfaces. It has also been revealed that the ESEM is a useful tool for surface characterization.