In-product environmental protection: evaluation of chemical emissions from resin fortified resistance spot welding in the automobile industry Part Ⅰ. Thermal analysis/mass spectrometry and laboratory pyrolysis measurements with the German VCI oven

摘要

The protection of the working and living environment can be ameliorated by in-product environmental protection. Products and processing technologies can be developed with fewer chemical emissions and result in less direct or lifetime environmental and workplace hazards. Laboratory studies were made to evaluate the organic emissions of the new joining technique, the resin fortified resistance spot welding. Laboratory investigations were carried out by thermoanalytic methods, coupled thermal analysis/mass spectrometer (TA/MS) studies, and pyrolysis experiments in the so-called German VCI oven. Especially in the case of welding temperatures over 1200℃, the evaluation of toxic and hazardous substances by pyrolytic processes is of special interest. We studied pyrolysis products, formed from the used oil (anticorrosive and auxiliary additive) and epoxy resin material. These materials were tested in the TA/MS instrument at different atmospheres to obtain information about principal pyrolytic products. The VCI combustion device simulated thermal degradation processes at different preselected temperatures. Incineration was performed at temperatures of 400, 600, 800, 1000 and 1200℃ with an air or nitrogen flow rate of 100 ml/min. The volatile combustion products were collected. Polycyclic aromatic hydrocarbons (PAHs) were trapped by XAD-4-resin and analyzed by GC/MS and aldehydes respectively on a 2,4-dini-trophenylhydrazine (DNPH) coated silica cartridge and analyzed by HPLC-DAD method. While incineration at 400 and 600℃ yields mainly characteristic fragments of the matrix and aldehydes, burning at 800 and 1000℃ leads to more polycyclic aromatic compounds resulting from aromatization and carbonization reactions. At 1200℃, the amount of pyrolytic products, mainly PAH, decreased significantly.