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36. Emissions of Semi-Volatile Organic Compounds from Architectural Coatings and Polyvinyl Chloride Floorings: Microchamber Method.

Author

Guan, Hongyan, Jia, Qi, Guo, Zhongbao, Han, Xu, Zhang, Huiyu, Hao, Liteng, Wu, Chuandong, and Liu, Jiemin

Subjects
SEMIVOLATILE organic compounds, PLASTIC flooring, CONSTRUCTION materials, INDOOR air quality, PROPIONIC acid
Abstract

Semi-volatile organic compounds (SVOCs) are modern chemical substances that are present in large quantities in indoor environments. Understanding the emission of SVOCs from building materials is essential to identify the main sources of indoor SVOCs and to improve indoor air quality. In this study, a reference method employing custom-designed microchambers (630 mL) was optimized by improving the structure of the gas path and adding polytetrafluoroethylene inner coating to the chamber. After optimization, the recoveries of the microchamber method were significantly improved (75.4–96.7%), and the background in the microchamber was greatly reduced (<0.02 μg/h). By using the microchamber method, 33 SVOCs (including two alkanes, one aromatic, one nitrogen compound, and twenty-nine oxygenated compounds) and 32 SVOCs (including seven alkanes, eight aromatics, and seventeen oxygenated compounds) were detected in the emissions of the architectural coating and the PVC flooring samples, respectively. The area-specific emission rates (SERa) of total SVOCs emitted from architectural coatings and PVC floorings were in the range of 4.09–1309 μg/m2/h) (median: 10.3 μg/m2/h) and 0.508–345 μg/m2/h (median: 11.9 μg/m2/h), respectively. Propanoic acid had the highest SERa (3143 μg/m2/h) in architectural coatings, while methylbenzene (345 μg/m2/h), 2-methylnaphthalene (65.2 μg/m2/h), and naphthalene (60.3 μg/m2/h) were main SVOCs emitted from PVC floorings. Meanwhile, the average second-stage (adsorbed phase) emission mass of the total SVOCs accounts for 66.3% and 47.3% in architectural coatings and PVC floorings, respectively, suggesting that the SVOCs emitted from building materials have a strong tendency to be absorbed on the surface of the room, e.g., the interior wall, the desk or even the skin. [ABSTRACT FROM AUTHOR]

Published
2024
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42. Precipitation phenomena in Al-Zn-Mg alloy matrix composites reinforced with B4C particles.

Author

Wu, Chuandong, Ma, Kaka, Zhang, Dalong, Wu, Jialu, Xiong, Shuya, Luo, Guoqiang, Zhang, Jian, Chen, Fei, Shen, Qiang, Zhang, Lianmeng, and Lavernia, Enrique J

Abstract

To provide insight into precipitation phenomena in age-hardening Al-Zn-Mg(-Cu) matrix composites, an Al 7075 alloy composite reinforced with B4C particles was selected as a model system. The bulk composites were fabricated via plasma activated sintering and followed by a peak aged (T6) heat treatment. Two types of Al matrix zones were identified in the composite: (1) the regions in the vicinity of the matrix/reinforcement interface, defined as "matrix plastic zone" (MPZ) hereafter, and (2) the regions away from the matrix/reinforcement interface, simply defined as matrix hereafter. The precipitation behavior in the MPZ was characterized and compared to that in the matrix. The MPZ contained a high density of dislocations. The number density of GP zones in the MPZ is lower than that in the matrix while the average size of the GP zones in MPZ is coarser. In addition, semi-coherent platelet η' precipitates were observed but only in the MPZ. The dislocations and the Al/B4C interfaces provide more heterogeneous nucleation sites for the η' precipitates in the MPZ. The growth and coarsening of the η' precipitates caused rapid depletion of Mg and Zn solute atoms in the MPZ.

Published
2017

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