The project aims at developing new composites materials (bulk or thin films systems). The scientific program is divided in three axes:
- Development of greener organic coatings
- Electrodeposited biomimetic apatite coatings
- Polymer composites with reinforcing plant fibers
1. Development of greener organic coatings
Organic coatings are widely used to prevent corrosion of metallic structures because they are easy to apply and cost effective. Corrosion inhibitors are incorporated in organic coatings to provide active corrosion protection. In the past, chromates were the most commonly used inhibitive pigments. However, due to their high toxicity, many studies have been devoted to the development of more environmentally acceptable organic coatings. In this context, our project aims to incorporate non-toxic corrosion inhibitors in organic coatings via natural clays (montmorillonite – MMT or layered double hydroxides – LDH), acting as nano-reservoirs for green inhibitors. The complementary effects of MMT and LDH on the microstructure of the coatings are investigated to search for synergistic effects by using different inhibitors. The study of the inhibitor leaching from the clays and their healing action in the case of damaged coatings will be specifically considered.
2. Biomimetic apatite coatings
A proper design of a bone implant material is aimed to provide the necessary durability, functionality, and biological response for long-term use. In this context, metallic materials, among which stainless steels, are most commonly implemented for load bearing implants. Durability and functionality of the implant are governed not only by the mechanical properties of the bulk material but also by the biological response, i.e. osteointegration that depends mainly on the surface/chemical characteristics of the implantable device. The challenges for electrodeposited coatings are twofold: (i) to be able to co-dope the apatite coating and to control the release kinetics and (ii) to produce coatings in lattices structures made from additive manufacturing (3D approaches), that is becoming the most usual method to produce the implants.
3. Polymer composites with reinforcing plant fibers
The tailoring of polymer composites with long reinforcing plant fibers is a major issue of research in the domain of structural organic composite. The main advantage of such materials is weight saving. The other issue is to design recyclable materials. This explain that the choice must be restricted to linear polymers i.e. thermoplastics. Now, the difficult point is to be able to make the processing at a temperature that is sufficiently low for avoiding the degradation of the plant fiber. Finally, we focus on biosourced polymers. The reinforcing long fibers are bamboo fibers growing in North Vietnam: Dendrocalamus barbatus. The major interest of bamboo fiber is to possess the highest Young modulus among vegetal fibers. The first keys point is to define a treatment allowing the handling of the fiber during the processing of the composite. Moreover, it must allow a satisfactory interface with the polymeric matrix: the interfacial region is insuring the stress transfer from the matrix to the reinforcing fiber.