Band 78, Heft 1

South Africa is a water scarce country with minimal natural forests. Plantation forest species such as the Mexican tropical hard pine, Pinus patula Schiede & Deppe ex Schltdl. & Cham. , was introduced into the country to satisfy local fibre demand. Today, the majority of pine plantations in South Africa are found in the Mpumalanga province. The province has diverse growing conditions in relation to climate and soil properties. Sample plots were established in even-aged P. patula plantations and stratified according to soil parent material and altitude. Growing conditions of each sample plot were characterised according to climate and soil properties. A total of 540 sample trees were measured for height, diameter, density, and latewood content. The sample trees were harvested to produce 2690 logs. The logs were milled, and the resultant lumber was graded according to density, dynamic modulus of elasticity, and modulus of rupture. Annual maximum temperature had the most significant impact on tree growth, while rainfall correlated with wood density and latewood content of standing trees. However, annual maximum temperature and tree height had a negative relationship with the recovered lumber properties and dimensional stability. Spring rainfall appeared to be the most important factor influencing lumber twist and this was possibly due to the associated larger juvenile core present in the trees.

The bark anatomy was analysed, as was the overall chemical composition (extractives, lignin, suberin, ash and polysaccharides), and a quantitative elemental analysis was performed of the bark and two tannin extracts (extracted with water only and with a mixture of water and Na 2 SO 3 ). The phenolic composition and antioxidant activity of the bark extracts were quantified. The results indicated that the bark is composed of conductive phloem, nonconductive phloem, rhytidome, crystals and secretory cells. The average chemical composition was 15.9 % extractives, 35.3 % total lignin, 1.9 % suberin, 15.4 % ash and 31.5 % polysaccharides. The condensed tannin yield in the extract obtained with water alone was 5.1 %, and that in the treatment with water and Na 2 SO 3 was 8.1 %. The ethanol-water extract had a high phenolic content (112.6 mg GAE g −1 extract). The bark extract showed strong antioxidant activity, reaching 83.5 % inhibition of DPPH free radicals, which was higher than the value of 75.0 % for the commercial antioxidant BHT at the same concentration. These results demonstrate that Protium tenuifolium is a potential natural Amazonian source of phenolic compounds and antioxidants and can be used for medicinal purposes and the production of various sustainable products, such as cosmetics.

Glucuronoxylans have been considered as an alternative polymer for petroleum polymers in coatings, films, emulsifiers, and other industries. In this study, different molecule weight glucuronoxylans were obtained through xylanase hydrolysis. Dodecenyl succinic anhydride (DDSA) was used as a modifying agent to functionalize glucuronoxylans. At the same degree of substitution (DS), higher molecule weight glucuronoxylans led to better emulsifying properties and emulsion stability. Higher molecule weight DDSA modified glucuronoxylans showed smaller droplets size, lower zeta potential, higher EA (emulsifying activity) and better emulsion stability. These results suggested that molecule weight has positive impact on the emulsifying properties of DDSA modified glucuronoxylans. Furthermore, DS had positive impact on the emulsifying properties of DDSA modified glucuronoxylans.

The dimensional stabilisation of wood using thermosetting resins relies on the resin uptake into the cell walls. This study tested if a conditioning step after the impregnation and before the final heat-curing enhances the cell wall uptake to improve dimensional stabilisation without increasing the chemical consumption. Small blocks of Scots pine sapwood were vacuum-impregnated with an aqueous melamine formaldehyde solution and conditioned at 33, 70, or 95 % RH for up to 1 week before drying and curing the blocks at 103 °C. However, the conditioning step decreased the cell wall bulking and the moisture exclusion effect compared to the immediate heat curing of the impregnated samples. Analyses of the resin-treated samples by scanning electron microscopy, IR spectroscopy and confocal Raman microspectroscopy provided evidence of wood hydrolysis and polycondensation of the resin within the cell lumen during the conditioning step. Hydrolysis and removal of wood constituents may have counterbalanced the cell wall bulking of the resin. Polycondensation of the resin in the lumen increased its molecule size, which could have hindered the cell wall diffusion of the resin.

To develop an eco-friendly artificial turf filling for replacing rubber elastomer particles, seven kinds of natural materials (cork, soft oak, champagne bark, oak bark, pine bark, willow bark, and vermiculite) were selected and processed into particles with a dimension of 1–2 mm. The water absorption performance, mold resistance, resilience, compression characteristics, and the repose angle were tested, and the surface microscopic morphology of granular materials was observed. The experimental results showed that the champagne bark had the largest plastic deformation range under pressure load, which was 0.21–7.82 KN. And the champagne bark particles had the best resilience, which was respectively 8.9 % and 7.1 % before and after compression, and its angle of repose was 36.8°, which was 9 % higher than that of the thermoplastic elastomer (TPE) particle. Additionally, champagne bark had better mold resistance compared with the other six natural materials, and its mold only occurred in the mold inoculation center. In conclusion, champagne bark could be considered as an artificial turf filling granule to replace TPE rubber.

This research focuses on increasing wood resistance against UV degradation using trimethoxyphenylsilane as modifying agent and supercritical CO 2 as a green solvent and reaction medium. Trimethoxyphenylsilane was successfully grafted on European spruce ( Picea abies , H. Karst) and was characterized by SEM-EDX and UV–vis reflectance. SEM-EDX showed the presence of silicium inside the wood cell wall. Increased wood moisture content showed positive effect on weight gain of trimethoxyphenylsilane after treatment. UV resistance of treated wood was evaluated by following the color change during artificial weathering. Modified samples showed improved weathering resistance compared to unmodified wood with a Δ E value around 5 after 260 h. Processing and modifying wood using supercritical CO 2 is a promising route to increase wood performances and increase its use as a building material.

Bamboo culm is a natural material characterized by a graded structure of vascular bundles in the radial direction and a regular distribution of bamboo nodes in the axial direction. To investigate the adaptation of bamboo culm structure to its natural environment, the bamboo culm structure was analyzed using a vascular bundle identification model, complemented by mechanical simulations. The results showed a certain pattern in the macroscopic dimensional characteristics of bamboo from the base to the top: the outer diameter decreased linearly; the internode length initially increased before decreasing; the length-to-diameter ratio gradually increased; and the wall-to-cavity ratio initially decreased before increasing. In response to external forces, bamboo exhibited strong stability, which was attributed to the thin and hollow wall as well as parabolic distribution of bamboo nodes. Along the axial direction, vascular bundle numbers linearly decreased, while the ratio of fiber sheath tissue and the distribution frequency of vascular bundles increased from the base to the top. In the radial direction, the length and area of vascular bundles tended to increase before decreasing, while the width tended to increase, leading to a decreasing length-to-width ratio. Overall, the radial variation pattern of vascular bundles showed nonsignificant variations at different heights.