Ruodan Yang

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.

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.

ESEM Study of Wetting of Untreated and Plasma Treated Polypropylene Fibers

Polypropylene (PP) fibers have been increasingly used in the technical textile industry for a variety of applications. Wetting behavior of PP fibers is of importance in these applications. The wetting behavior of the untreated and oxygen plasma treated polypropylene fibers was studied by the environmental scanning electron microscope (ESEM) in this work. Water droplets were formed on the cooled fibers by directly condensing water from the vapor phase. This was achieved by slowly increasing the vapor pressure inside the chamber towards the dew point for water at the appropriate specimen temperature. By this method small droplets in the micron range were condensed onto fiber surfaces. Contact angles of water on fiber surfaces were measured from the ESEM micrographs. The investigations have shown that the plasma treatment significantly altered the surface wettability of polypropylene fibers and that the ESEM provides a new approach to wetting and contact angle of fibers on the micron scale.

Relationship Between Structure and Spinning Processing of As-Spun PP Fibres

Abstract As-spun polypropylene (PP) fibres, obtained under a one-step statistical experimental design using orthogonal arrays and involving all the common spinning parameters were studied with wide angle X-ray scattering (WAXS). The WAXS results revealed that the micro-structure of PP fibres can be altered progressively from less-ordered para-crystalline states to highly-ordered crystalline states with an α-monoclinic lattice. The degree of structural order has been evaluated quantitatively in terms of (W½)−1, the reciprocal of the half-height width of the first WAXS reflection peak. On the basis of such quantitative evaluation, which is shown to be consistent with the conclusions derived from “traditional” qualitative assessment, comprehensive quantitative analysis of the effects of processing parameters and their interactions on the degree of structural order is accomplished, using systematic but simple statistical methods. Parameters significantly affecting structure, including types of raw materials, winding speed, spinning temperature, application speed of spin finish and metering pump speed are identified, and correlation between structure and parameter setting is established in a concise statistical model. The model indicates clearly the combination of parameter levels for increasing or reducing the degree of structural order over the whole range from essentially amorphous to highly crystalline forms. Comparisons with the “conventional” approach of “one factor at a time” demonstrated the validity of the new approach and its significant advantages. The latter includes the economy in experiment scale, efficiency in result analysis and a comprehensive overview of the process being studied, which covers effects arising from synergistic interactions as well as from individual parameters.

Neural modelling of polypropylene fibre processing: Predicting the structure and properties and identifying the control parameters for specified fibres

This paper describes the application of artificial intelligence to data derived from polypropylene drawing carried out at Galashiels using designed experiments. The topology of the data is visualised in two dimensions with respect to specific properties to be modelled, as a quality check on the process data. A series of neural network models are used successfully to predict the tenacity, elongation, modulus and heat shrinkage and also the crystallographic order and polymer chains orientation of the output fibres from the draw parameters values. A software harness is constructed for using the neural predictors to find the draw parameters which come closest to achieving any specified combination of fibre properties.

Drawability of As-spun PP Fibres

Abstract The drawability of as-spun polypropylene (PP) filaments was studied using a statistical approach including an experimental design and statistical analysis. The use of a statistical experimental design allows all possible interactions as well as main factors to be evaluated. As a result, one two-factor interaction (between winding speed and metering pump speed, WS*MPS) and two main factors (winding speed WS and metering pump speed MPS) were identified as factors having statistical significance on drawability of as-spun PP filaments with risk levels (P values) less than 0.005. The drawability can be improved by controlling the structure of the as-spun filaments, that is a paracrystalline structure combined with a very low overall orientation (birefringence <3.2 × 10–3). Application of two-stage drawing also increases the drawability compared with one-stage drawing.