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Abstract
Odorous emissions from rubber materials and processing can cause odour nuisance impacts in the surrounding community, resulting in industrial closure due to public complaints. This research aims to improve our understanding on odorants behaviour across different variabilities of rubber including clonal, seasonal and pre-treatment variations. This will enable the rubber processing operators to develop better management strategies to control emissions, more effectively. Sulfur flow analysis was incorporated in this study to understand how each rubber processing stage affect the emission of malodorous sulfur compounds. A significant amount of sulfurs were retained in the solids and carried through to the final dried products.
Gas chromatography-mass spectroscopy (GC-MS) and gas chromatography-sulfur chemiluminescence detector/nitrogen chemiluminescence detector (GC-SCD/NCD) incorporated with several pre-concentration methods were initially used to evaluated analytical techniques for the collection, separation and identification of odorants from rubber materials. The major Volatile Sulfur Compounds (VSCs) identified within rubber emissions were methyl mercaptan, dimethyl sulfide, dimethyl disulfide, and dimethyl trisulfide. Due to their low Odour Threshold Value (OTV), all identified VSCs potentially contribute to the overall sensorial profile of the rubber odour. While Volatile Organic Compounds (VOCs) revealed a range of volatiles such as terpenes, aromatics, aldehydes, ketones, acids, alkanes, alcohols, cyclo hydrocarbons, as well as nitrogenous associated compounds. The variations of VSCs and VOCs across 14 different types of rubber were clearly identified and evaluated. Distinguished emissions profiles were displayed from different rubber clones, particularly during seasonal variations. Climate variabilities were observed to drive changes in raw rubber properties, which influence the emissions of different odorants profiles.
Gas chromatography-mass spectroscopy coupled with an odour detection port (GC-MS/ODP) was applied to the analysis of rubber emissions. The ODP profiles revealed the significant different odour perception between panellists towards particular odorants. The odorants identified along with their respective descriptors were used to develop a rubber odour wheel. Relationships between the identified odorants were linked to the main rubber processing stages. The rubber odour wheel is firstly developed and could be a useful tool to support onsite management of emission sources and their impact on surrounding communities.