Sustainable Manufacturing Process in the Context of Wood Processing by Sanding

The aim of this paper is the issue of a sustainable manufacturing process in the context of woodworking by sanding, as one of the most important technological operations before its final treatment, focusing on a selected pillar of sustainable manufacturing process, waste management. The first step of the experiment was to optimize the pressures of the sanding means on the surface. The optimal pressure of 1.04 N·cm−2 was chosen. The second level was to obtain the wear curves of the abrasive means with grain size 80 (evaluated by wood removal) and the optimal pressure in dependence on the sanding direction (along and perpendicular to the wood fibres and in the direction of 60° to the wood fibres) and different types of woods (beech, oak, alder, pine). The set parameters were suitable for beech and were not suitable for alder and pine. By extending the operating life of the sanding belts via appropriate choice of input factor settings it can be influenced metrics of pillar waste management-savings of material and waste minimization.

Colour Fastness to Various Agents and Dynamic Mechanical Characteristics of Biocomposite Filaments and 3D Printed Samples

The aim of the study was to analyse the colour fastness of 3D printed samples that could be used as decorative or household items. Such items are often fabricated with 3D printing. The colour of filaments affects not only the mechanical properties, but also the appearance and user satisfaction. Samples of biocomposite filaments (PLA and PLA with added wood and hemp fibres) were used. First, the morphological properties of the filaments and 3D printed samples were analysed and then, the colour fastness against different agents was tested (water, oil, detergent, light and elevated temperature). Finally, the dynamic mechanical properties of the filaments and 3D printed samples were determined. The differences in the morphology of the filaments and 3D printed samples were identified with SEM analysis. The most obvious differences were observed in the samples with wood fibres. All printed samples showed good resistance to water and detergents, but poorer resistance to oil. The sample printed with filaments with added wood fibres showed the lowest colour fastness against light and elevated temperatures. Compared to the filaments, the glass transition of the printed samples increased, while their stiffness decreased significantly. The lowest elasticity was observed in the samples with wood fibres. The filaments to which hemp fibres were added showed the reinforcement effect. Without the influence on their elasticity, the printed samples can be safely used between 60 and 65 °C.

Testing of the fatigue strength along wood fibres at different moisture contents

Testing of the fatigue strength along wood fibres at different moisture contents. The paper determines the effect of wood moisture content on the fatigue strength in compression along fibres. The method of determining the maximum stress at the proportional limit was used for the measurements. Fatigue strength was investigated for three wood species: pedunculate oak (Quercus robur L.), bearded birch (Betula pendula Roth.) and Norway spruce (Picea abies L.), with two moisture contents: close to the absolutely dry state and above the fibre saturation point. The ratio of fatigue strength to short term strength depends on moisture content and is similar for birch (70.3% in the dry state and 72.1% in the wet state), for oak (67.4% and 69.5% in both states) and for spruce (66.6% in the dry state and 68.1% in the wet state). The moisture content of the wood clearly influences the fatigue strength of the wood. On average, the fatigue strength of wood with moisture contents above the fibre saturation point constitutes about 0.20 of the fatigue strength of wood with moisture contents close to 0%. This tendency was found regardless of the tested species. The simplified method for testing fatigue strength at the limit of proportionality has shown its limited usefulness, requiring further analysis and comparison with other methods in order to be thoroughly tested and possibly improved.

Mechanical characterisation of the developing cell wall layers of tension wood fibres by Atomic Force Microscopy

Trees can generate large mechanical stresses at the stem periphery to control the orientation of their axes. This key factor in the biomechanical design of trees, named “maturation stress”, occurs in wood fibres during cellular maturation when their secondary cell wall thickens. In this study, the spatial and temporal stiffening kinetics of the different cell wall layers were recorded during fibre maturation on a sample of poplar tension wood using atomic force microscopy. The thickening of the different layers was also recorded. The stiffening of the CML, S1 and S2-layers was initially synchronous with the thickening of the S2 layer and continued a little after the S2-layer reached its final thickness as the G-layer begins to develop. In contrast, the global stiffness of the G-layer, which initially increased with its thickening, was almost stable long before it reached its final maximum thickness. A limited radial gradient of stiffness was observed in the G-layer, but it decreased sharply on the lumen side, where the new sub-layers are deposited during cell wall thickening. Although very similar at the ultrastructural and biochemical levels, the stiffening kinetics of the poplar G-layer appears to be very different from that described in maturing bast fibres.HighlightNew insights into the changes in mechanical properties within the cell wall of poplar tension wood fibres during maturation have been obtained using atomic force microscopy.

Evaluation of Flexural Strength of Polymethylmethacrylate Denture Base Resin Incorporated with Alkali and Heat-Treated Teak Wood Fibers and Ultra High Molecular Weight Polyethylene Fibers

BACKGROUND Polymethyl-methacrylate (PMMA) resin is the most commonly used denture base material which satisfies colour stability, aesthetic demands, accurate fit, affordable cost, and ease in manipulation. The common disadvantages are incomplete flow, impact strength, transverse strength and fatigue resistance. The fracture of denture base is mainly due to flexural fatigue failure which can be minimised by reinforcing with various artificial and natural fibres. There are very few studies which have incorporated natural fibres to enhance the strength of PMMA resin. So, in this study both natural and artificial fibres were used to enhance the property and find the best fibres to strengthen the denture base. METHODS A total of 80 samples were prepared using a standardized stainless steel metal die and these samples were grouped into Group A as control group, Group B PMMA samples reinforced with raw teak wood fibres, Group C reinforced with alkali treated teak wood fibres, Group D reinforced with heat treated teak wood fibres and Group E samples were reinforced with Ultra-High molecular weight (UHMW) polyethylene fibres and processing was carried out by conventional method. The flexural strength of each sample was calculated. RESULTS The mean flexural strength of Group A, Group B, Group C, Group D and Group E were 82.338, 58.680, 62.259, 105.878, 90.2263 respectively with a P value of 0.001. Group D samples showed a P value < 0.001 which was statistically significant when compared to other groups. The obtained values were statistically analysed by oneway ANOVA and Tukey’s HSD test using statistical software SPSS 17. CONCLUSIONS This in-vitro study infers that the samples of Group D incorporated with heat treated teak fibres had shown increased flexural strength, which could be a good replacement for various synthetic and natural fibres to enhance the strength of denture base resins. KEY WORDS Teakwood Fibres, Heat Treatment, Alkali Treatment, Sandwich Technique, Polyethylene Fibres

Agricultural Residues as an Alternative Source of Fibre for the Production of Paper in Kenya-A Review

The pulp and paper industry is primarily dependent on fibrous wood for pulp and paper production. However, this over-dependence on fibrous wood poses serious environmental challenges such as the diminishing of the fibrous wood stocks, deforestation, emission of greenhouse gases, and global warming. Therefore, to mitigate these environmental challenges associated with its utilization for paper and pulp production, other sustainable raw material sources can also be considered for the production of paper and pulp. There are enormous benefits associated with the utilization of non-wood fibres as an alternative and sustainable raw materials source for the production of paper and pulp. These benefits have in the recent past prompted millers in China, India, Brazil, and the USA to consider the utilization of non-wood fibres in paper and pulp production. In Kenya, the pulp and paper industry is very much dependent on fibrous wood for production and the industry is yet to fully embrace the utilization of nonwood fibres for paper and pulp production. Further, the dependence on fibrous wood has contributed significantly to the decline of paper pulp and paper production, deforestation, and rise in paper importations due to insufficient raw material supplies. The importation of paper and pulp products has further led to the collapse of the paper industry in Kenya. The sector stands a chance of revival and vibrancy through the utilization of the abundant agricultural residues and feedstocks lying in the agricultural fields across the country. Similar experiences elsewhere have proved that the abundance of agricultural waste can be utilized for the production of paper and pulp due to their excellent fibre content for specialty papers, and easy pulpability. The agricultural residues are therefore considered a quintessential alternative and sustainable source of raw materials for the pulp and paper industry. Moreover, their utilization will mitigate environmental impacts such as deforestation, climate change, and pollution .

Effects of moisture and cellulose fibril angle on the tensile properties of native single Norway spruce wood fibres

Isolated single wood fibres with cellulose fibril angles from 10 to 43° were tested in microtensile tests under controlled temperature and relative humidity of 5, 50, 75, 90% and in the wet state. This systematic study provides experimental stiffness and strength data, calculated on cell wall cross sections. It has been shown that stiffness reduction with increasing moisture content is more pronounced in fibres with large cellulose fibril angles. Interestingly, stiffness reduction in fibres with low cellulose fibril angles has been observed for the fully hydrated state only. The experimental dataset was fed into a model to determine moisture dependent stiffness of the hemicellulose-lignin-matrix and the stresses acting on the fibrils and the matrix.

CEMENT COMPOSITES REINFORCED WITH TEOS-TREATED WOOD FIBRES

In this study, wood fibres were extracted from eucalyptus and pine woods, treated by immersion in tetraethyl orthosilicate (TEOS) and incorporated into a cementitious matrix at three weight contents (2 wt%, 5 wt% and 10 wt%). The fibres were characterized using chemical and morphological analyses and the cement-based composites were evaluated using chemical, hygroscopic, mechanical and morphological tests. The morphological and spectroscopic results satisfactorily justified the physical-mechanical properties. The wood fibre-cement composites reached similar water uptake and apparent porosity to those of the neat mortar, but exhibited higher mechanical properties. Furthermore, all treated fibres yielded composites with improved mechanical and hygroscopic properties compared to those with pristine fibres. Overall, the best performance (based on hygroscopic and mechanical results) was obtained for the wood fibre-cement composite with 2 wt% pine fibres.