EFFECTS OF PROCESS PARAMETERS ON THE PROPERTIES OF RADIATA PINE HTMP-POLYPROPYLENE FIBRE COMPOSITES

摘要

The effects of process variables on the tensile and bending strengths of radiata pine HTMP-polypropylene fibre composite sheets (prepregs) are described. Commercial radiata pine HTMP fibres (Asplund) made by high temperature (160-170°C) refining were used for composite formation. Prepregs were prepared by hot-pressing HTMP fibre sheets with polypropylene. The HTMP fibre sheets were made either by wet-forming with the Centre Technique Papier (CTP) dynamic "sheet former or by a proprietary dry-forming process (DMF), in which dry fibre mats were prepared on a wire screen. The effects of fibre pretreatments with water on the properties of the dry-formed sheets, and of other process variables on the tensile and bending properties of prepregs made by wet and dry forming were also examined. The levels of CTP spray pressure and drum speed influenced fibre alignment. Mats with high fibre alignment (longitudinal) gave prepregs with higher longitudinal and lower transverse tensile and bending strengths than unreinforced matrix material. Longitudinal tensile and bending strengths increased with fibre mass fraction (over the range 30 to 50 %) for fibre-aligned sheets; conversely, transverse strengths decreased. Small variations in process conditions did not greatly change prepreg strength.