Furfuryl Alcohol Treatment of Bamboo Betung (Dendrocalamus asper Backer ex K. Heyne) Strips

Based upon successful chemical modification of wood, bamboo strips were subjected to furfurylation treatment. Furfurylation in the mean of impregnating furfuryl alcohol to the bamboo and then heated at 100°C for 24 hours to produce solid polymeric resin. The success of furfurylation is assessed by uptake and the weight percentage gain of furfurylated bamboo strips. However, the treatability of dry bamboo strip is relatively poor. This paper studies the furfurylation process of bamboo betung (Dendrocalamus asper Backer ex K.Heyne) strips by soaking, vacuuming and the combinations thereof. Results showed that soaking bamboo strips for two days after vacuum treatment achieved optimum uptake of furfuryl alcohol solutions and gave rise to an 80% weight gain. Catalyst addition during furfurylation did not increase the weight percent gain. Water was an active solvent carrier for achieving higher weight gains

Treatment of European beech with a new wood fire retardant agent based on in situ deposition of calcium oxalate

European beech (Fagus sylvatica L.) was impregnated in a two-step process with aqueous solutions of potassium oxalate and calcium chloride successively. These compounds are intended to react in situ to the water-insoluble salt calcium oxalate and the reaction by-product potassium chloride. In order to assess the treatability, the solid uptake after the first impregnation and after the treatment was examined. The fixation of the precipitated salts was measured in leaching tests according to the European standard EN 84. The reaction to fire of mineralized beech was tested following the standard ISO 11925-2. A weight percentage gain of appr. 35% indicates a sucessful treatment of the beech with the mineralization agents. The weight percentage gain after leaching indicates a sufficient fixation of calcium oxalate in the wood. Furthermore, results from flammability tests indicate improved fire resistance due to the mineralization.

Acetylation of three Ghanaian hardwood species - Asanfena (Aningeria robusta), Dahoma (Piptadeniastrum africanum) and Kaku (Lophira alata)

The diffusion of chemicals and chemical reaction within the wood bulk are affected by many factors. One of these factors is the wood ultrastructure because the chemicals have to diffuse through the wood matrix to reach the sites where they will react. In this study three Ghanaian hardwood species with different densities were acetylated and the effect of the densities on thepercentage hydrogen substitution and weight percentage gain as well as the effect of the modification on dimensional stabilization of the species were analyzed. The densities of the three wood species affected the percentage hydroxyl substitution as well as the weight percentage gain due to the modification. The results showed that the higher the density of the wood species, the lower the percentage hydroxyl substitution at the same condition of temperature, concentration of the reagent and time of reaction.

Covalent fixation of boron in wood through transesterification with vinyl ester of carboxyphenylboronic acid

Vinyl ester of 4-carboxyphenylboronic acid has been synthesized and tested as reactive reagent for permanent fixation of boron in wood based on an improved approach described previously. The essence of the method is a covalent incorporation of the boron compound via transesterification between wood hydroxyl groups and vinyl ester containing boron. The synthesis of this vinyl ester was accomplished by exchange reaction of vinyl acetate with 4-carboxyphenylboronic acid. The obtained vinyl ester of carboxyphenylboronic acid was characterized by FTIR and 1H-, and 13C-NMR spectroscopy. The covalent fixation of boron to wood’s hydroxyl groups was achieved through potassium carbonate (K2CO3) catalyzed transesterification of the vinyl ester containing boron. The transesterification was confirmed by weight percentage gain (WPG) calculation, curcumin staining, FTIR, and 13C CP-MAS NMR spectroscopy. The efficiency of the reaction improved with increasing temperature and reaction time.

A novel simple route to wood acetylation by transesterification with vinyl acetate

A novel method for the acetylation of wood was investigated and compared with the classical method based on acetic anhydride. The transesterification reaction between vinyl acetate (VA) and hydroxyl groups of maritime pine sapwood (Pinus pinaster Soland) was performed in the presence of potassium carbonate as a catalyst and led to acetylated wood in high yield. The transesterification reaction was confirmed by FTIR and 13C CP-MAS NMR spectroscopy. The efficiency of the VA transesterification increased with increasing temperature, reaction time, and catalyst amount, but a significant weight percentage gain (WPG) was obtained after only 3 h at 90°C.

The use of organo alkoxysilane coupling agents for wood preservation

Corsican pine (Pinus nigra) sapwood was treated with methanolic solutions of two organo alkoxysilanes ([γ-(methacryloxy)propylx] trimethoxy silane (TMPS), or vinyl trimethoxy silane (VTMS)). Various treatment parameters were studied in order to determine the optimum method for obtaining a stable weight percentage gain. For TMPS, it was found that best results were obtained when a free-radical initiator was used in conjunction with the silane. This indicates that polymerisation of this species occurs via the pendant methacryloxy moeity, a result confirmed by solid-state nuclear magnetic resonance studies of the treated wood. For VTMS, wood moisture content had a profound influence upon the weight percentage gain due to treatment, with higher weight percentage gains obtained as wood moisture content was increased. This indicates that polymerisation in this case occurred via the formation of silanol groups to form siloxane linkages. Solid-state NMR confirmed that the double bond of the organo-functional group was intact after polymerisation had occurred. Modified wood samples were then prepared using optimised treatments for each silane. The wood was prepared to a variety of weight percentage gains and the effect of treatment on the dimensional stability and decay properties of the treated material studied. Treatment of Corsican pine sapwood with the two organo-alkoxy silanes, resulted in only moderate increases in dimensional stabilisation, with anti shrink efficiency values (after 5 water-soak/oven-dry cycles) no greater than 40%. Treatments were found to be relatively stable to hydrolysis. Some differences were observed in the effectiveness of the two silanes in providing protection. Full decay protection required high treatment levels with the silanes.