Abstract
Dimensional stability proves to be an important factor affecting the quality of wooden products. As a sort of crude and thermoplastic resin, shellac excreted by lac insects demonstrates water-repellent and environmental-friendly features. The research impregnated shellac with wood at room temperature and with a vacuum-pressure procedure. Efforts were made to examine how shellac treatment affected the dimensional stability, moisture absorption, chemical structure, thermostability, as well as morphological characteristics of wood. Results indicated that shellac treatment was a type of efficient solution useful in the enhancement of the dimensional stability of wood. Shellac solution had good permeability in the wood, and the weight percentage gain reached 13.01% after impregnation. The swelling coefficients of treated wood in the tangential and radial directions decreased by 20.13% and 24.12%, respectively, indicating that impregnation could improve wood dimensional stability. The moisture absorption of shellac-treated wood was reduced by 38.15% under 20 °C and 65% relative humidity. Moreover, shellac treatment significantly modified wood structure, although there were no drastic changes in the spectra. Specimens for shellac treatment ran across two decomposition peaks at 350 and 390 °C, and specimens in the control group saw one more common derivative thermogravimetric curve when the sharp peak approached 355 °C. After impregnation of shellac into wood, the shellac blocked pits and hardened on the intrinsic layer of the wood for fear of hygroscopicity. The practice was applicable to a variety of wood products, such as buildings, furniture, and landscape architecture.
Highlights
IntroductionWhen the temperature and humidity of surroundings change, wood can absorb or release moisture [4]
Wood has a porous structure and is made up of natural, organic macromolecular materials [1,2,3].when the temperature and humidity of surroundings change, wood can absorb or release moisture [4]
Reductions in hygroscopicity may be realized through a variety of means, such as steam-heat treatment [13,14,15], acetylation and silylation treatment [16], methyltrimethoxysilane modification [17], styrene modification [18], boron and compatibilizer modification [19], siloxane modification [20], alkoxysilanes modification [21], silicone oil heat treatment [6,22], and tricine and bicine modification [23]
Summary
When the temperature and humidity of surroundings change, wood can absorb or release moisture [4]. This general ability of wood to adjust to the environment has made it an important material in the field of building engineering, furniture manufacturing, and renovation [5,6] among other recent applications. If wood has defects, such as cracks, as moisture is absorbed and Coatings 2020, 10, 881; doi:10.3390/coatings10090881 www.mdpi.com/journal/coatings. Reinforcing the dimensional stability, hydrophobicity, and durability of wood by reducing its hygroscopicity has become a major focus of research in recent years [8,9,10,11,12]. Besides that, existing methods of improvement are quite complicated and energy-intensive
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