Kemijska svojstva i primjena premaznih materijala na bazi vode i organskih otapala na drvu

Wood finishes are used extensively to improve the aesthetic value and protect wood products from moisture. These organic coatings generally contain volatile organic compounds (VOC) as solvents that evaporate when the coatings cure over the surface. Due to strict legislations against these hazardous VOCs, the buyers across the globe are shifting towards products finished with water borne coats. Two of the most commonly used wood coatings in India are polyurethane and nitrocellulose (NC) lacquer. This paper aims at comparing these two wood coatings with their water borne counterparts. The study was conducted on the wood substrate of Melia dubia. Chemical characterization of the cured coats was attempted through FTIR spectroscopy. Physical appearances in terms of gloss and film thickness were also studied. Bands of urethane, urea and nitric groups were identified, which helped in understanding the changes in chemical structure of the finishes after curing. The thickness of the organic coatings was significantly higher than that of their water-borne counterparts. Gloss of water based coatings was observed to be lesser than that of their organic solvent based counterparts in either coating material. In case of lacquer, the reduction was up-to 33 %. whereas in case of PU, gloss dropped down by about 54 %.Premazni se materijali primjenjuju na drvu kako bi se očuvao njegov estetski izgled i drvni proizvodi zaštitili od vlage. Organski premazni materijali u osnovi sadržavaju hlapljive organske spojeve (HOS) kao otapala koja isparavaju dok premazni materijal otvrdnjava na površini drva. Zbog strogih propisa o tim opasnim hlapljivim organskim spojevima kupci diljem svijeta prelaze na vodene premazne materijale. Dva najčešće upotrebljavana premazna materijala za drvo u Indiji jesu poliuretanski i nitrocelulozni (NC) lak. Cilj rada bio je usporediti ta dva premazna materijala s istim premaznim materijalima na bazi vode. Istraživanje je provedeno na drvu Melia dubia. Kemijska karakterizacija otvrdnutih premaza provedena je primjenom FTIR spektroskopije. Također su proučavani sjaj i debljina filma. Identificirane su skupine uretana, ureje i nitratne skupine koje su pridonijele razumijevanju promjena u kemijskoj strukturi premaza nakon otvrdnjavanja. Debljina premaza na bazi organskih otapala bila je znatno veća od debljine premaza na bazi vode. Uočeno je da je sjaj premaza na bazi vode manji od sjaja premaza na bazi organskih otapala. Za NC lak to je smanjenje bilo do 33 %, a sjaj PU laka smanjio se za oko 54 %

Machining properties of Melia dubia wood

 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

Machining properties of "Melia dubia" wood

 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