Investigation on the effect of novel cutting fluids with modified ingredients regarding the long-term resistance of polycarbonate used as machine guards in cutting operations (KSS-PC)

Machine guard enclosures prevent the accessibility of hazard zones and safeguard against ejection of parts during operation, such as chips, tool and workpiece fragments as well as cutting fluids (DGUV 2008, DIN EN 12417). Vision panels as part of machine tool enclosures allow the observation of the machining process. Due to its high ductility, impact resistance Y and its optical properties, polycarbonate is the primarily used material for machine guard windows (Uhlmann and Duchstein 2008, Uhlmann and Duchstein 2010). By influence of cutting fluids, chip impact, ultraviolet radiation and heat, polycarbonate underlies a reduction of long-term resistance, which is called aging. In order to improve the protection of human health and environment, the European Union adopted the regulation ""Registration, Evaluation, Authorization and Restriction of Chemicals"" (REACH) in 2007. The implementation of REACH leads to modified cutting fluids, which need to be analyzed regarding their effect on long-term resistance of polycarbonate. This is important due to a not yet verified suspicion that cutting fluids with increased alkalinity, use of solvents, such as phenoxyethanol, or application of amines, such as dicylohexylamine, might increase aging of polycarbonate. Two approaches are presented in this paper. First, a qualitative approach is proposed to compare cutting fluids by determination of resistance of environmental stress cracking. Secondly, the effect of three cutting fluids on the long-term resistance in a quantitative way is presented. Aging of the polycarbonate is carried out by a time-controlled exposition with cutting fluid and under defined conditions over ten weeks. Impact resistance Y is determined by impact tests. Material properties are measured by tensile tests.