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Powder coatings have gained a lot of attention since the 1960s and the 1970s (implementation of polyurethanes into the market) because of the environmental and ecological concerns. Over the decades, there have been several publications relating the manufacturing and development of powder coatings as an alternative for liquid/solvent or water-based organic coatings. In general, powder coatings can be divided into two main groups based on the properties of the resin being used, thermoplastic and thermoset powder coating systems. Among thermoset powder coatings, polyurethane powder coatings have outstanding properties such as weather stability and are the best choice for exterior applications comparing overall properties. This paper reviews the most recent advances in the field of powder coating by focusing on polyurethane powder coating as a group of thermoset powder coatings. It also considers the industrial problems engaged in this field, such as emission of the blocking agents, the low reactivity of uretdione systems, and high curing temperature and their solutions. Finally, it also suggests the future potential investigation of polyurethane powder coating compositions and improvements.

The effect of a thermal treatment, i.e. annealing, on the adhesion of a thermoplastic polyurethane overmolded on a precoated steel substrate was evaluated. The hybrid part was subjected to three different annealing temperatures after the overmolding process. Adhesion of the thermoplastic elastomer was achieved by using an in-house-developed, two-step curable organic powder coating, which was selectively crosslinked to a polyallophanate state. The powder material was applied to the steel substrate by electrostatic charging followed by molecular crosslinking in an oven. The influence of the metal surface pretreatment was also evaluated regarding adhesion. The effects of the postthermal treatment were assessed through mechanical peel test, differential scanning calorimetry, atomic force microscopy, and scanning electron microscopy. Interesting results were obtained regarding strong adhesion between the precoated metal sheets and thermoplastic polyurethane after injection molding, especially in hybrids that were annealed at higher temperatures with the in-house adhesive coating.

Polytetrafluoroethylene (PTFE) exhibits excellent non-stick properties and a very low coefficient of friction under tribological stress, but it is incompatible with almost all other polymers. In the first part of this study we presented the generation of the novel tribological material based on unsaturated oil, radiation-modified PTFE (MP1100) and Polyamide 66 (PA66). To get a better understanding of the chemical properties and chemical composition of the compounds, the PA66-MP1100-oil-cb (chemical bonded) compounds were examined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). In this part, the mechanical properties of the compounds are compared with plain PA66 and PA66-MP1100-cb. The tribological investigation was carried out using the Block-on-Ring tribometer. It was found that the mechanical properties of PA66-MP1100-oil-cb with 20 wt.% MP1100-oil-cb only show slight differences compared to PA66, but the tribological properties of the compounds have been significantly improved through chemical coupling between the three components. Finally, the amount of the compound that was deposited on the surface of the steel disc counterpart was analyzed after the tribological testing.

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