Qian Chen

Woody raw materials of wood-based panels like fiberboard and particleboard are one of the primary sources of product odor and one of the indicators affecting the comprehensive health risk assessment of wood-based panel products. This study employed Gas Chromatography-Mass Spectrometry-Olfactometry (GC-MS-O) to investigate the odorant composition and odor characteristics, including Total Odor Concentration (TOC), odor intensity (OI), odor activity value (OAV), and risk value (RV), of 22 wood species commonly used in fiberboard and particleboard production in China. This research identified the major odor-active compounds in wood and provided recommendations for selecting wood raw materials suitable for low-odor fiberboards and particleboards produced by integrating RV and toxicity classification data. The results showed that the main compound types influencing wood odor in 22 wood species were predominantly terpenes, aldehydes, and alcohols. Woods of Cinnamomum, Machilus, and Pinus contained a higher number of dominant odor compounds (OAV > 1 and OI ≥ 3). Wood with stronger odor intensity included Cinnamomum, Pinus, Machilus, Bischofia, and Saurauia. The total RV of Cinnamomum, Pinus, Machilus, Cunninghamia, and Bombax wood exceeded one, necessitating special attention when used as raw materials for wood-based panels. Camphor in Cinnamomum and Machilus wood was the most concentrated odorant, followed by 3-Carene in Pinus wood. Odorants with high OAV included Longifolene, δ-Cadinene, Terpinen-4-ol, 2-Nonenal, γ-Terpinene, d-Limonene, 3-methyl-Butanal, Octanal, α-Pinene, Hexanal, D-Camphor, and trans-Calamenene. Odorants with high RV included terpenes, alcohols, aldehydes, and ketones, such as Camphor, 3-Carene, Eucalyptol, α-Terpineol, β-Pinene, α-Santalene, δ-Cadinene, Safrole, Longifolene, and d-Limonene. Focusing on the reduction and control of these odor-active compounds represents a primary approach to mitigating odors in fiberboard and particleboard products. However, addressing health risks associated with product odors requires additional attention to four specific substances: Safrole, Camphor, Eucalyptol, and α-Terpineol. Although the total RV for the five wood species exceeds one, this does not necessarily mean the final wood-based panel product’s RV exceeds one, as it also depends on the influence of the production process. Therefore, further research should be conducted to investigate the effects of various process parameters in wood-based panel production on the odor compounds present in the final panels. From a comprehensive perspective, considering the overall odor characteristics of wood volatiles, all 18 wood species (Salix, Populus, Rhaphiolepis, Ligustrum, Prunus, Fagus, Pterocarya, Firmiana, Celtis, Cunninghamia, Bombax, Bischofia, Ficus, Saurauia, Eucalyptus, Aleurites, Melia, Bridelia) are suitable for the production of low-odor fiberboards and particleboards.

Wood, as the oldest natural polymer composite material on Earth, holds significant importance in the era of carbon neutrality and serves as an irreplaceable core material in the furniture and construction industries. As a primary raw material for furniture, wood-based lignocellulosic boards have drawn increasing consumer attention due to their odor characteristics. In order to achieve the determination of odor compounds in lignocellulose-based panels, this study established a method combining dynamic headspace sampling (DHS), gas chromatography–mass spectrometry (GC–MS), and odor activity value (OAV) analysis. To address the wide concentration range of odor compounds in lignocellulose-based panels, a three-level standard curve was established to meet the detection of odor substances in common lignocellulose-based panels. The favorable conditions for each factor were as follows: sheet-shaped samples, TENAX-TA adsorbent, 20 mL headspace vials, and a split ratio of 25:1. The method demonstrated good linearity within the range of 0.002–15 mg/m³, with recovery rates ranging from 94.74% to 103.44%. The method was applied to analyze commercially available particleboard, fiberboard, and plywood. A total of 33 odor components were detected. The results indicated that aldehyde contributed significantly to the odor of particleboard, acids were the main contributors to the odor of fiberboard, and terpenes dominated the odor of plywood. The established method is suitable for the qualitative and quantitative analysis of odor compounds in lignocellulose-based panels and provides reliable technical support for tracing, identifying, and controlling odors in these materials.

Analysis of changes in TVOC and VOCs chemical composition or odor characteristics of particleboard before and after decoration treatment with resin-impregnated paper (RIP), polypropylene (PP) film and polyvinyl chloride (PVC) film were studied. The effects of these three decoration treatments on masking or suppressing the release of VOCs and odorants from particleboard were explored. The substances that were covered or suppressed and newly introduced before and after processing were identified to provide a basis for reducing the odor emissions of PVC-, PP- and RIP-decorated particleboard. Taking undecorated particleboard and particleboard treated by three types of decorative materials as research subjects, the air permeability of the three decorative materials was tested using the Gurley Permeability Tester. TVOC emissions from the boards were evaluated using the 1 m³ environmental chamber method. Qualitative and quantitative analyses of the samples were conducted via thermal desorption–gas chromatography–mass spectrometry (TD-GCMS). The contribution of odor substances was determined using odor activity value (OAV). The results indicated that the permeability from high to low was PVC film, PP film and RIP. Compared with undecorated particleboard, the TVOC emissions of RIP-decorated boards decreased by 93%, PP-decorated particleboard by 83% but the TVOC emissions of PVC-decorated particleboard increased by 67%. PP decoration treatment masked or suppressed the release of 20 odor substances but introduced xylene, which can increase potentially the health risks for PP-decorated particleboard. PVC decoration treatment masked or suppressed 19 odor substances, but it introduced 12 new compounds, resulting in an overall increase in TVOC emissions. RIP treatment did not introduce new odor substances. After PP film and RIP treatments, both the variety of VOCs released and the number of key odor-contributing compounds and modifying odorants decreased. In contrast, the number of modifying odorants and potential odorants increased after PVC treatment. VOC emissions were effectively masked or suppressed by three decoration treatments, same as the release of substances contributing to overall odor of particleboard was reduced. Among them, PP and RIP decorative materials demonstrate better effects.

Bamboo is a natural fibre reinforced composite with excellent performance which is, to a certain extent, an alternative to the shortage of wood resources. The heterogeneous distribution and molecular structure of lignin is one of the factors that determines its performance, and it is the key and most difficult component in the basic research into the chemistry of bamboo and in bamboo processing and utilization. In this study, the distribution of lignin components and lignin content in micro-morphological regions were measured in semi-quantitative level by age and radial location by means of visible-light microspectrophotometry (VLMS) coupled with the Wiesner and Maule reaction. There as guaiacyl lignin and syringyl lignin in the cell wall of the fibre. Lignin content of the secondary cell wall and cell corner increased at about 10 days, reached a maximum at 1 year, and then decreased gradually. From 17 days to 4 years, the lignin content of the secondary cell wall in the outer part of bamboo is higher than that in the middle part (which is, in turn, higher than that in the inner part of the bamboo). VLSM results of the micro-morphological regions showed that bamboo lignification developed by aging. Guaiacyl and syringl lignin units can be found in the cell wall of the fibre, parenchyma, and vessel. There was a difference in lignin content among different ages, different radial location, and different micro-morphological regions of the cell wall. The fibre walls were rich in guaiacyl lignin in the early stage of lignification and rich in syringyl units in the later stage of lignification. The guaiacyl and syringyl lignin deposition of bamboo green was earlier than that of the middle part of bamboo culm, and that of the middle part of bamboo culm was earlier than that of bamboo yellow. The single molecule lignin content of the thin layer is higher than that of thick layers, while the primary wall is higher than the secondary cell wall, showing that lignin deposition is consistent with the rules of cell wall formation. The obtained cytological information is helpful to understand the origin of the anisotropic, physical, mechanical, chemical, and machining properties of bamboo.