Silicone Rubber Testing Methods Summarized
The analysis and detection of toxic substances in silicone rubber can be broadly divided into two ways. One is to directly and qualitatively detect the presence of toxic substances in silicone rubber materials.Second, by analyzing the changes in molecular structure of silicone rubber before and after aging, the aging mechanism can be inferred to determine the toxic substances that may be produced.
Silicone rubber testing properties can be said to be between organic and inorganic substances. It contains a variety of small molecules and polymers, food contact silicone rubber environment is complex and diverse. Food itself can be divided into water, alcohol, acid and oil. Such as steamer mats, baking mats, etc., need to be used for a long time in a high temperature and high humidity environment, so it is difficult to analyze.
The analysis and detection of toxic substances in silicone rubber can be broadly divided into two ways. One is to directly and qualitatively detect the presence of toxic substances in silicone rubber materials. For example, meteorological chromatography-mass spectrometry (MC-MS) technology can be used to directly detect toxic substances migrating from silicone rubber products, such as cyclosiloxanes, by utilizing the high efficiency of gas chromatography and the strong qualitative ability of mass spectrometry. Second, by analyzing the changes in molecular structure of silicone rubber before and after aging, the aging mechanism can be inferred to determine the toxic substances that may be produced. At present, infrared spectroscopy, nuclear magnetic resonance and other analytical methods are usually used to deduce the aging mechanism of silicone rubber, simple and fast.
1. Silicone Rubber Detection Methods - Gas Chromatography (GC) and Gas Chromatography-Mass Spectrometry (GC-MS)
Currently, GC and GC-MS have become the most commonly used methods for the stereotypic and quantitative detection of volatile cyclosiloxanes in silicone rubber for food contact. This method mainly utilizes the strong chromatographic separation ability and high resolution of mass spectrometry, which is suitable for the separation and analysis of complex components with volatility.GC-MS technology has high separation efficiency and high sensitivity, and is widely used in the fields of food safety, environmental pollution, and food and pesticide residue detection.
Silicone rubber produces small molecule cyclic siloxanes during thermal degradation, and low molecular weight cyclic siloxanes migrating from silicone rubber products for food contact were detected by GC-MS, and methyl cyclic siloxane had the lowest single component. The detection amount is 50mg/kg. October 1, 2012 “Determination of residual volatile methyl cyclosiloxane in silicone rubber” (GB/T 28112-2011) implementation details the principle of gas chromatography to determine the residual volatile cyclosiloxane (D4 ~ D10) content of silicone rubber raw rubber.
2. the detection method of silicone rubber - Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR)
FTIR and NMR are important tools for analyzing the organic structure of silicone rubber materials. Among them, infrared spectroscopy is an important method to identify the composition of silicone rubber materials. NMR can obtain information about the structure of its molecular skeleton, and they are both widely used in the study of the microstructure of silicone rubber. Infrared spectroscopy does not require sample pretreatment, is low-cost, efficient, and non-polluting, so it is widely used in the food industry.
Currently, NMR detection of silicone rubber is mainly used in medical field, industrial field and biological field. Although there are few reports on the detection of migratory toxic substances in silicone rubber in contact with food, NMR has been used by foreign scholars. Spectroscopic detection of cyclosiloxane, the method has a low detection limit and provides very specific qualitative and quantitative information.
3. silicone rubber detection methods - thermal analysis (TGA)
Thermal analysis is a measure of the properties of a substance as a function of temperature or time at a set temperature. Thermogravimetric analysis (TGA) is a technique for measuring the mass-temperature relationship of a substance under programmed temperature control. According to the relevant literature, thermogravimetric analysis can be used to study the process of detecting thermal degradation of silicone rubber at elevated temperatures, to determine its thermal stability, and to analyze toxic substances that may migrate out.
The TGA method was used to detect thermal degradation products of polydimethylsiloxane and montmorillonite nanocomposites. The detection results are mainly harmful to human body with low content of oligocyclosiloxanes (D3-D7), methane, propylene, and propionaldehyde. Currently, thermal analysis methods are mainly used to analyze and detect the thermal degradation behavior of silicone rubber. On the direct detection of toxic substances migrating from the silicone rubber for food contact reports are rare, and therefore has a broad application prospects.
4. the detection of silicone rubber - inductively coupled plasma mass spectrometry and atomic absorption method
In addition to aging decomposition produces low molecular weight cyclohexane and other toxic substances, due to long-term contact with food, heavy metal ions in addition to silicone rubber products, but also gradually migrate to the food, rich in the human body, posing a threat to human health. For the detection of heavy metal ions in silicone rubber can be determined by inductively coupled plasma mass spectrometry (ICP-MS) analysis technology, atomic absorption and other analytical methods. The content of tin in silicone rubber was determined by microwave digestion-flame atomic absorption spectrometry, and the effects of different digestion conditions, determination wavelengths and inorganic acid concentrations on the determination of tin were investigated.
