Even though fibrous wood filler is known to be effective for improving mechanical and water-resistant properties of wood plastic composite (WPC), it has not been commercially adopted because of its high cost and less handling ability. In the present study, with an expectation of similar positive effect of fibrous wood filler, we carried out a fibrillation of a surface of practical wood flour in pre-mixed compound, containing wood flour, polypropylene, and compatibilizer, for producing WPC with high filler content by means of wet disk-milling. Scanning electron micrography revealed a micro-fibrillation on the surface of wood flour in the ground pre-mixed compound. The size of the surface micro-fiber could be controlled by disk-milling conditions. The formation of the micro-fibrous structure affected the melt viscosity of the compounds and improved mechanical properties of molded samples. The positive effect of the surface micro-fiber formation can be attributed to an interaction among the micro-fibers such as hydrogen bonding and entanglement. The observed reinforcement effect by the surface fibrillation was essentially identical to that of wood fiber although fibrillation was attained just in the surface of wood flour.
The poly(vinylidene fluoride) monofilaments having diameter of 0.2 - 0.7 mm were drawn with heating by laser irradiation. It is estimated that the filament which have a diameter of 0.2 mm can be heated almost uniformly by the laser irradiation whereas only outer layer of the filament of 0.7 mm can be heated. Therefore, the 0.7 mm filament cannot be drawn stably under low drawing stress. And for the higher draw ratio, the drawing stress concentrated to the central part of the filament. The cross-sectional stress deviation in the filament with diameter of 0.7mm causes the α-form crystal remaining up to higher drawing stress, and restraining tensile strength of drawn filaments. By redrawing of the drawn filament still remaining α-form crystal not only improves the attaining tensile strength but also reduces the thermal shrinkage of drawn filaments.
We dyed cotton fabric samples using colored clay pigments, which can be recovered from dyehouse effluent and be reused. The Lab color space (CIE L∗a∗b∗) values of both the clay pigments and the fabric samples after dying were measured. The compounds in the pigments, and the compounds adhering to the dyed fabrics, were analyzed using XRF, XRD, SEM and EDS. We then determined which minerals affected the color of the clay pigments and the dyed fabrics and discussed their interrelationships in our analyses.
A hardwood bleached kraft pulp was oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation, and two TEMPO-oxidized pulps with different carboxylate but similar aldehyde contents were prepared. Handsheets were prepared from the reference and TEMPO-oxidized pulps with di(oleamidoethyl)ammonium formic acid salt (DOFAS) used as a de-bonder in handsheet-making. Density, DOFAS content and tensile strength of the handsheets were measured, and these properties were compared between the reference and TEMPO-oxidized pulps. When the TEMPO-oxidized pulps were used, sheet density was effectively decreased, but degrees of tensile strength reduction of the handsheets were diminished to some extent, in comparison with the reference pulp. Sheet density can be decreased by partial prevention of interfiber hydrogen bonds with DOFAS molecules added, although interfiber bonds are still present when TEMPO-oxidized pulps are used. Scanning electron microscopic observations of cross sections of the handsheets also supported the above hypothesis. TEMPO-oxidized pulps had significant amounts of aldehyde groups so that hemiacetal linkages are probably formed with hydroxyl groups at the interfiber bonding areas, thus resulting in higher tensile strength of the handsheets prepared thereof. Hence, an effective decrease in sheet density can be achieved with less reduction of tensile strength by preparation of handsheets from TEMPO-oxidized pulps with DOFAS. Aldehyde groups formed by the TEMPO-mediated oxidation and present on the pulp fiber surfaces are likely to contribute to higher tensile strength of the handsheets.