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Abstract: A comprehensive testing program has been developed to assess different physical and mechanical properties of 26 commercial and lesser-known Papua New Guinea species from secondary and plantation forests. The impact of log position in a tree on the mechanical properties has also been assessed to optimize the utilization of timbers along the value chain. The results showed that stiffness and bending strength tend to decrease or remain unchanged along the stem. Shear strength and Janka hardness displayed a similar trend to a lesser extent where the position in the tree had a limited impact on compression strength properties. Thus, segregating based on log position can be of interest where desired mechanical properties and costs associated with segregating justify optimum mechanical properties for the intended end use. The properties of selected species from plantations and regrowth forests were generally lower than those found in the literature for timbers from old-growth forests. The size of specimens tested, the amount and provenance of tested material, and some adaptive traits for tropical tree species are some factors potentially explaining observed differences. However, a comparison with recent studies tends to confirm the overall reduction of physical and mechanical properties when compared with old-growth forests timbers.

In this paper, an attempt was made to assess the effectiveness of finger jointing in utilising mango wood sections for various end uses like furniture. The study was based on the estimation of Modulus of elasticity and Modulus of rupture under static bending and Maximum Crushing Stress and Modulus of elasticity under compression parallel to grain of finger jointed sections and comparing them with the values measured for clear wood sections from the same lot. For joining the sections, the Poly Vinyl Acetate and Urea Formaldehyde adhesives were used. It was found that the Modulus of elasticity of the sections joined by either adhesive showed significantly better values than that of unjointed clear wood sections. The Modulus of rupture values of sections joined with Urea Formaldehyde were similar to those of unjointed clear wood sections. However, sections jointed with Poly Vinyl Acetate adhesive exhibited lower Modulus of rupture. Under compression, the parameters of the jointed sections joined with either adhesive were either similar or better than those of the unjointed clear wood sections. The study demonstrates the utility of finger jointing of mango wood sections for furniture parts especially with the Urea Formaldehyde adhesive.

Dynamic modulus of elasticity was determined in clearwood samples of eight tropical hardwood species using longitudinal vibrations, flexural vibration and ultrasonic transit-time methods. These samples were subsequently subjected to three point static bending test to determine static modulus of elasticity and modulus of rupture. Acoustic velocity and wood density were found to be independent parameters as the velocity was nearly the same in wood with distinctly different densities. Among the three dynamic measurements, modulus from the ultrasonic method was the highest followed by the longitudinal vibration and flexural vibration. Any of three vibration methods could be used to predict static modulus as they exhibited a near perfect correlation with static MoE. However, the dynamic modulus determined by different vibration methods were found to diverge with increasing static modulus. Wood density was the dominating factor influencing both modulus of elasticity and modulus of rupture.

 In this paper result of working quality of Melia dubia was reported after testing them under six major wood working operations namely – planning, sanding, turning, shaping, boring and mortising based on Indian Standard IS 8292. The wood performed extremely well under planning. In shaping, the performance was good enough. Though all the other operations yielded poor results, the composite rating factor which is an overall performance indicator was 35 % more than that of Tectona grandis. The ease of working is only 93 % compared to teak. The working quality index which was based on the composite rating factor and ease of working worked out to 107 taking Tectona grandis as 100 mainly because of the high performance under planning and shaping and good performance under sanding.

Abstract: The durability of imported timber is a matter of growing concern in the tropical Indian climate, with their refractory nature further adding to the woes with respect to further processing. In the present study, the effect of microwave pre-treatment, exposure time and initial wood moisture content on retention, treatability and cross-sectional anatomical properties of Tectona grandis and Southern yellow pine imported from Ghana and South America were evaluated. Water based preservative copper chrome borate (CCB) of 2 % concentration was used for the study. The experimental study in combination with dip-diffusion method returned with significant improvement in retention of about 5-6 folds more than the control sets in Southern yellow pine and Tectona grandis. Another set of Southern yellow pine and Tectona grandis samples were further treated using a full cell pressure method after microwave, without initial vacuum, which showed similar trends with a 3-4 folds increase in retention over controls. Both experiments returned with significant improvement in the treatability class of Tectona grandis and Southern yellow pine. The anatomical analysis was performed using a light microscope with 5 and 10x magnifications on treated and untreated samples of both Tectona grandis and Southern yellow pine. The outcome of the anatomical study exhibited improvement in vessel diameters in the treated samples of Tectona grandis with a reduction in the degree of occlusion by the presence of tyloses. For Southern yellow pine, checks on micro level and cracks on macro level appeared along with the ray cells and the diameter of the resin canals was substantially expanded which ascertains that microwave pre-treatment ameliorated the flow of fluids in the wood microstructure which improved permeability and resulted in better uptake and penetration.

Wood finishes protect the surface of wood from external agents, enhance its looks and improve its gloss (luster). On constant external exposure, UV rays gradually degrade the film coating resulting in loss of gloss. In this study, two commonly used finishes namely spirit shellac and polyurethane finish were used to investigate the pattern of loss of gloss due to UV interference. Two coatings of polyurethane (PU) and spirit shellac finish were applied on the surface of eucalyptus samples. The gloss levels of these and unfinished samples were monitored for different times of exposure of them to UV light. Gloss was measured at 600 gloss head using a Tri micro gloss meter regularly for 20 hours durations of UV exposure. Observations and analysis revealed that the natural gloss of uncoated samples of eucalyptus were least affected on UV exposure with only 8,3%-10% loss in gloss. The PU and shellac coated surfaces also showed very little reduction in gloss (6,9%-15,4%) most of which happened in the first 40 hours of exposure. Thus both the finishes in this study were found effective to a good extent in maintaining the gloss of the finished surface against exposure to UV light.

Low permeability of many wood species due to their anatomical properties causes problems during timber drying as well as impregnating with preservatives and resins. Microwave (MW) treatment influences heartwood permeability and improves preservative uptake and distribution. In the present study, microwave treatment of chir pine (Pinus roxburghii) wood was done at 2,45 GHz frequency at different level of intensity and radiation time. The gas permeability of chir pine wood was measured in an in-house built apparatus. Preservative uptake was tested using acid copper chromate (ACC) preservative by a dipping process. The effect of radiation intensity and time on preservative uptake and air permeability were studied. The results revealed remarkable increase in longitudinal wood air permeability and preservative uptake with the increase of intensity and time of treatment. The results indicate that this technology can be tested and applied on pilot scale for application in wood preservation industry.