Effect of recycling and injection parameters on gloss properties of smooth colored polypropylene parts: Contribution of surface and skin layer

Abstract : 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.