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Adding textures to surfaces is known to improve the external appearance of injection moulded components. However, when high surface quality is required, normally a paint coating is applied on top of the moulded textured surface. In this work, an alternative to painting for obtaining high quality surfaces is proposed, following an environmental-friendly process and having low production cost. Three different surface textures obtained by injection moulding have been characterized and compared with a painted one. Alternative topographical parameters such as the absolute functional height (AFH), the functional height distribution (FHD), texture slope (TS) or texture aperture angle (TAA) besides to the traditional roughness parameters such as the arithmetical mean height (Sa) and the root mean square height (Sq) have been utilized to characterize the random surface textures. The relationships between these parameters and the surface quality appearance represented by gloss and reflectivity contrast have been established using a new total appearance measurement (TAM) apparatus. It was found that by applying secondary operation on the textured mould cavity, such as adding micro roughness features or coatings, equal apparent quality to the ones obtained by painting can be reached., Postprint (author's final draft)

In this work, the relations between the replication quality of random, coarse textured, surfaces with the injection-moulding process has been analysed through 3D areal characterisation techniques. The multi-scale surface approach has been applied to effectively separate the main surface components, roughness, waviness and form. Amplitude, functional, hybrid and spatial parameters, as well as alternative surface characteristics such as the number of micro-cavities (NG), grain area () and grain volume (GV) were used as a way to determine the influence of the manufacturing process on the replication quality of the mould texture, either at the macro- or micro-scale. A model to quantify the effect of the injection-moulding parameters on surface texture replication has been obtained through a 24 factorial design of experiments. It was found that the holding pressure was the main parameter to enhance the mould texture replication, followed by the melt and mould temperatures. The injection volumetric flow rate did not have a significant effect on the texture replication ratio. The surface analysis, at the human eye resolution, only allows the detection of macro-defects such as form deviation. On the other hand, the surface characterisation at the micro-scale allows the detection of roughness differences, up to 30% on average, as a function of the injection conditions, Peer Reviewed, Postprint (author's final draft)

In this research, the influence of the macro- and micro-topography on randomly micro-textured polypropylene surfaces has been studied. An initial characterization of the underlying surface was carried out using three-dimensional (3D) technologies such as chromatic and white light confocal microscopy. A multi-scale analysis methodology was employed for analysing the surface at either macro- or micro-scales. Among others, topographic characteristics such as peak-to-valley symmetry and the amount of micro-asperities were analysed to quantitatively determine the scratch and mar visibility resistance. The results show that surfaces with higher symmetry in their functional height distributions yield lower lightness variation (¿L*) between the scratch pattern and its residual background height (RBH). This allows for a better suitability in hiding the scratch damage. On the other hand, topographies with less amount of micro-asperities on top of the texture provided a better mar resistance. In these cases, deformation mechanisms such as ironing are minimized, resulting in a lower gloss variation and lower contrast between the damaged area and its surroundings., Peer Reviewed, Postprint (author's final draft)