NEW BIOSOURCED POLYAMIDE UV-POWDER COATING

Powder coatings have been developed since a few years because of their several advantages: easiness of implementation, no material loss, no emission of volatile organic compound (VOC). Moreover, UV powder coatings are of great interest for heat sensitive substrates. Until now, these ones are essentially constituted of (meth)acrylic or unsaturated polyester resins. Polyamide-based UV powder coatings are therefore original in this application field.

In a general way, polyamides are semi-crystalline polymers with high melting points (around 200°C). In order to allow their application on heat sensitive substrates, low melting point copolyamides were synthesized. Nonetheless, it is well known that mechanical properties of the ultimate products are strongly dependent on the polyamide cristallinity. Thus, the crystallinity loss induced by the decrease in Tf was compensated for an additional crosslinking step under UV radiation. In this aim, polyamide chain ends were functionalized by allylic double bonds.

To prevent the decrease of fossil raw materials while protecting the environment, copolyamides were synthesized from biosourced monomers which are derivatives of vegetable oils such as castor oil. Thus, a 6/11/12 ,-unsaturated copolyamide was synthesized according to a process in molten state. The properties of the obtained UV-cured coating were then characterized.