Analysis of microplastic particles in environmental samples needs sophisticated techniques and is time intensive due to sample preparation and detection. Alternatives to the most common (micro-) spectroscopic techniques, Fourier transform infrared and Raman spectroscopy, are thermoanalytical methods, in which specific decomposition products can be analyzed as marker compounds for different kinds of plastic types and mass contents. Thermal extraction desorption gas chromatography−mass spectrometry allows the fast identification and quantification of MP in environmental samples without sample preparation. Whereas to date only the analysis of thermoplastic polymers has been realized, this is the first time that even the analysis of tire wear (TW) content in environmental samples has been possible. Various marker compounds for TW were identified. They include characteristic decomposition products of elastomers, antioxidants, and vulcanization agents. Advantages and drawbacks of these marker substances were evaluated. Environmental samples from street runoff were exemplarily investigated, and the results are presented.
FeCrMnCN stainless austenitic high-interstitial steels (HIS) combine the properties of conventional FeCrNi austenites (superior ductility and surface corrosion resistance) with the potential of significant strengthening. This combination of properties makes them promising candidates for environments that require resistance to both wear and corrosion, e.g., processing of plastics. The aim herein is to make use of the high work-hardening ability of HIS. Thus, machined preforms with an application-related design are formed by profile cross rolling. The preform design enables a hardness increase in component regions that are most subjected to wear. Rolling of the specimens results in a very high surface quality with a roughness Rz in the range of 1 μm. Hardness measurements in rolled specimens confirm a significant hardness increase in the subsurface up to a depth of %2.5 mm. Hardness values of about 600 HV1 are yielded within a surface distance of %0.3 mm. Furthermore, tests on a modified pin-on-disc tribometer suggest that the wear behavior of the work-hardened HIS is comparable with nitriding steel. Thus, the results of this study support the development of a forming technology for screws in corrosive environments.
The joining of plastics is required because component geometries are severely restricted in conventional manufacturing processes such as injection molding or extrusion. In addition to established processes such as hot plate welding, infrared welding, or vibration welding, hot gas butt welding is becoming more and more important industrially due to its advantages. The main benefits are the contactless heating process, the suitability for glass fiber reinforced, and high-temperature plastics as well as complex component geometries. However, various degradation phenomena can occur during the heating process used for economic reasons, due to the presence of oxygen in the air and to the high gas temperatures. In addition, the current patent situation suggests that welding with an oxidizing gas is not permissible depending on the material. On the other hand, however, there is experience from extrusion welding, with which long-term resistant weld seams can be produced using air. Investigations have shown that the same weld seam properties can be achieved with polypropylene using either air or nitrogen as the process gas. Experimental investigations have now been carried out on the suitability of different gases with regard to the weld seam quality when welding polyamides, which are generally regarded as more prone to oxidation. The results show that weld strengths are higher when nitrogen is used as process gas. However, equal weld strengths can be achieved with air and nitrogen when the material contains heat stabilizers.
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