The aim of this article is to investigate the optical properties of a recycled polymer during numerous processes. The effects of different process parameters (number of grinding-injection cycles, material temperature, mold temperature, and injection rate) on gloss and color properties of a buff-colored polypropylene containing 2wt%/wt of pigment was considered. The variations of properties are in the same range that is observed by changing processing parameters. It is found that the roughness is not able to explicate the variation of the optical properties for these variations of conditions. In addition, the optical properties of the skin layer of the injected parts are associated with the observed gloss and color variations. Moreover, the change of spherulite dimensions is related with optical changes.
In hot-forming processes, the interface tool/product is important for the quality of the finished product surfaces. Consequently, it is important to better understand the phenomena, namely, oxidation, which occurs at the interface between tool and sheet in this kind of process. It is in this context that an experimental program was conducted to analyse friction, wear and oxidation behaviours on the tribological performance of the combination of tool and sheet. A high-temperature pin-on-disc tribometer, with an original open-sliding contact, was used. Pins, representing tools are X40CrMoV5 high-alloyed steel, and discs, representing drawing products, are Fe360B steel plates (EN 10025–S235JRG2). The friction and wear study of the combination was carried out at temperatures ranging from ambient (room temperature) to 800℃ and within a normal load range of 35–140 N. Regarding oxidation effect and wear mechanisms, they are examined and characterized by scanning electron microscope and energy-dispersive X-ray spectrometer. As for the experimental results, they showed that the increase in temperature involves the decrease in the friction coefficient due to the oxide scales for all the tests. Pre-oxidized discs are also tested. It was found that the wear process is characterized by an adhesive wear with a transfer of oxides on the pins.
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