John M. Hodgkinson

Engineering and characterisation of the interface in flax fibre/polypropylene composite materials. Part II. The effect of surface treatments on the interface

Abstract Natural fibres have attracted much attention recently for use as reinforcing agents in composite materials. However, even though natural fibres possess many advantages over glass fibres, such as lower density, lower cost and recycleability, they are not totally free of problems. Natural fibres are comprised mostly of cellulose, a highly hydrophilic macromolecule with strong polarity and, as a result, problems of compatibility with very apolar matrices (e.g. polyolefins) almost certainly arise. Surface treatments, although having a negative impact on economics, may improve the compatibility and strengthen the interface in natural fibre composite materials. In Part I of the present study two such surface treatments, acetylation and stearation, have been developed and applied to flax fibres. In this second part, the effect of these treatments upon the interface of flax fibre/polypropylene composites is assessed by means of fragmentation tests. It has been found that both treatments led to improvement of the stress transfer efficiency at the interface, and both applied treatments were optimised, accordingly.

Bio-based macroporous polymer nanocomposites made by mechanical frothing of acrylated epoxidised soybean oil

Mechanical frothing is one of the most commonly used methods to create gas-liquid foams. Until recently, the polymerisation of mechanically frothed gas-liquid foams was limited to the synthesis of quasi two-dimensional polymer structures, such as films. In this study we show that three-dimensional bio-based polymer foams can be created by microwave curing of gas-soybean oil foams created by mechanical frothing using lauryl peroxide as the radical initiator. It was found that the introduction of air during the mechanical frothing was necessary to create the three-dimensional polymer foams. Using bacterial cellulose nanofibrils (BC) simultaneously as a foam stabiliser has potential because it obstructs the flow of liquid from the lamella region in these gas-soybean oil foams while simultaneously acting as nano-filler in the polymer foam. It was found that the stability of the gas-soybean oil foam templates and the mechanical properties of the polymer nanocomposite foams are enhanced upon the addition of BC in to the foams.