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Timber deterioration and its prevention in marine environment
2005 - IRG/WP 05-10559
Wood-borer activity is an established fact in Mumbai harbour that leads to severe deterioration of timber. In order to prevent the deterioration caused by wood borers three resin preservatives containing Zinc borate, Organo-copper polymer (4 wt% Cu) and Organo-Tin polymer Copoly(TBTM-MMA) were used for timber treatment. Test panels were treated using standard method and their efficacy was tested. It was observed that among three preservatives, panels treated with copoly (TBTM-MMA) with 10kg/m3 remained free from borer attack for 42 months, panels treated with Organo-copper polymer and Zinc borate, incorporated with chlorinated rubber (CR) have protected timber for 8 and 15 months respectively, as compared to control panels which were severely affected within three months. The study revealed that preservative containing TBTM as a toxic moiety can be used as an anti-borer preservative and protect the timber in marine environment over long period.
B S Swami, M Udhayakumar, P Kumar, A B Samui
A new process for in situ polymerization of vinyl monomers in wood to delay boron leaching
1998 - IRG/WP 98-40110
Efforts were accelerated on effective use of boron compounds in wood preservation owing to their environmentally safe characteristics and relatively low costs in addition to their well-known high bioactivity and fire resistant properties. Although having these unique favorable properties, they are readily leachable from treated wood at humid conditions. Therefore, they had limited market for exterior applications. A supplementary combination treatment with vinyl monomers; styrene (ST) and methylmetacrylate (MMA) was studied in order to extend the service life of boron treated wood. Sapwood specimens of Japanese cedar (Cryptomeria japonica D. Don) first treated with boric acid (BA) at 1.00% aqueous solution concentration. Vinyl monomers were impregnated after air-drying of BA-treated wood at ambient temperatures. Polymerization was performed during compression of monomer impregnated wood to a 50 to 70% dry set of radial dimension under a hot-press heated to the polymerization temperatures of 60 and 90°C required by the selected catalysts VAZO (a, a' - Azobis-isobutyronitrile) and benzoyl peroxide, respectively. Wood acquired a perfect dimensional stability and remarkably high moisture exclusion efficiency with the minimum water holding capacity with the compressed-wood polymer composite (CWPC) process that was approved by submerging of the test specimens in tap water, boiling water exposure to a 10 cycles accelerated severe weathering. As a result, boron leaching rate from CWPC pretreated with BA was considerably slower than that from ordinary WPC. Scanning electron microscope (SEM) observations were found explanatory for controlled-but-continuous boron leaching determined analytically. An effective bulking was found necessary to accompany to polymerization in cell wall with an even distribution of monomer in wood. Grafting to cell wall components can be tried further to achieve an envelop polymerization of boron deposited sites in WPC for better boron immobility.
M K Yalinkilic, W Dwianto, Y Imamura, M Takahashi