The problem of car odor is a problem that is widely concerned in the automotive industry at present. The odor in the car is not only a category of vehicle health attributes, but also a focus on consumer comfort. In recent years, domestic research on the problem of odor in cars has had multiple directions, such as improving the traceability and improvement of odor in cars, studying the traceability of odor in common materials used in cars and characteristic odor substances; there are also research on the development of odor odor identification automation instruments, such as the development of odor recognition array electronic nose ; and there are also optimization and improvement of odor evaluation methods. No matter which direction the research is inseparable from the subjective evaluation methods of personnel that are widely used.
Therefore, we selected car seat samples and analyzed the correlation and differences between the two at different temperatures by combining gastric combinator analysis and odor evaluation methods.
experimental plan is two types: normal temperature bag method benzene system sampling and odor evaluation, and high temperature bag method benzene system sampling and odor evaluation. The room temperature test conditions are 25℃ and 16 hours; the high temperature test conditions are 65℃ and 2 hours. After the benzene sampling is completed, the odor in the sampling bag is directly evaluated. Other relevant parameters are carried out with reference to HJ/T 400-2007 "Methods for Sampling and Determination of Volatile Organic and Aldehydes and Ketones in Vehicles" and ISO12219-2:2012. Odor rating is carried out in accordance with T/CMIF 12-2016 "Odor Evaluation Specifications for Automotive Parts and Materials".
After experiments, the odor level has been increased from level 3.0 to level 3.5, and the content of compounds is generally increased, but the content of different compounds is different. The contribution of the odor level comes from the comprehensive factors of different compounds. Changing the content of a few compounds may not be effective in improving the overall odor.
To further compare the content changes of other compounds and the influence of the temperature of the compound changes, the VOC analytical spectrum was superimposed at different temperatures. Taking the retention times of butyl acetate (boiling point 126℃) and n-hexane (boiling point 286℃) as reference, the full spectrum is segmented according to the retention time to compare the changes in the distribution of compounds in different temperature segments.
From the perspective of compound distribution, low-level low-boiling point compounds account for 25%, and the increase ratio increases more, indicating that temperature changes have a more obvious impact on low-boiling point compounds; intermediate-boiling point compounds account for 72%, and change 7%; high-boiling point compounds account for only 2.5%, but the increase is obvious, and there are compounds that surge due to temperature increases. The distribution of TOP20 compounds at low temperatures is relatively balanced, with the content of benzene and aldehydes as the main ones. Such substances have solvent smell, fragrance and irritating odor. The TOP20 compounds in high temperature states are mostly alkyl, and these substances have odor, burnt and so on. The content of alkane compounds with medium boiling points surged under high temperature experimental conditions, and the interaction of multiple compounds caused an increase in the odor intensity.
From the above analysis, it can be seen that when odor checking is carried out for automotive parts materials, temperature is a very important factor to examine. On the one hand, we should consider the types and magnitude differences in compound release at different temperatures. For the improvement of odor in room temperature vehicles, it is recommended to screen interior parts and materials to use room temperature odor substances that are consistent with the whole vehicle to collect; on the other hand, we should also pay attention to the release of a large number of alkyl substances caused by the increase in temperature, covering the presentation of other compounds with low concentration but high odor intensity on the spectrum. In addition, due to the differences in raw materials and process, there are also obvious differences in the odor substances and odor characteristics of similar parts. When looking for compounds, we also need to fully consider the contribution of different compound concentrations and odor intensity, as well as the odor type matching between the compounds and the material, to ensure that the target compounds can be effectively identified and targeted improvements, and ultimately achieve reasonable control and effective rectification of odors.
The authors of this article are Zheng Yi, Wei Chengquan, Liu Yalin, Wang Ke, Fu Jiayong, Ying Yuji
The author's unit is China Automobile Parts Inspection Center (Ningbo) Co., Ltd.
Source: Consumer Guide Magazine
