NANOTALC

This project aims to bring about a step change in the performance of polymer composites and high performance industrial coatings by developing novel synthetic nanometric talc-based fillers. These materials will differ from existing clay-based nano-fillers as they will be intrinsically more hydrophobic and will require significantly less organic additives and chemical treatments to obtain a good dispersion in polymers; a pre-requisite for obtaining the desired mechanical, barrier (against moisture, gases), thermal or optical performance enhancements from the filler. A two-step process for producing synthetic nano-talc in the laboratory was discovered recently by researchers at the University of Paul Sabatier - LMTG (Laboratoire des Mécanismes de Transferts en Géologie) and CARNOT-CIRIMAT (Centre Interuniversitaire de Recherche et d'Ingénierie des Matériaux) - and Rio Tinto Minerals, a leading global producer of engineered talcs. Using this patented process it is possible to obtain high purity talc crystals synthetically which possess a high aspect ratio and sub-micron particle size. It is this material that will be developed for use in polymer composites and coatings and that is the subject of this project. It is anticipated that the synthetic nano-talc will possess the combined benefits of natural talc fillers in polymers (hydrophobic character and polymer nucleating properties), along with the fine particle size and high aspect ratio associated with nano-clays that are currently being used in polymer nanocomposites (PNCs). By employing this discovery, it is possible to obtain talc particles that are significantly smaller in size than is possible by conventional milling / jetmilling of natural talc. The process for producing synthetic nano-talc involves firstly a precipitation reaction to produce an amorphous magnesium silicate compound with the same chemical composition as natural talc and then conversion of this pre-cursor material, washed to remove soluble salt by-product, to crystalline nano-talc by hydrothermal treatment. Both the amorphous and crystalline products have potential to be used as polymer nano-fillers and both will therefore be investigated in the project. Following the synthesis steps the products may require some further treatments (physical and chemical modification) before mixing with polymers. Preliminary work has suggested that these treatments will be necessary to reduce the extent of particle agglomeration and obtain the optimum dispersion in the polymer resin. Following treatment, mixing with polymers will be carried out in two ways: (1) melt blending polymers with the dried materials (in the case of engineering composites and styrene butadiene rubber - SBR) and (2) wet blending of polymer latex with the materials in aqueous suspension form (in the case of SBR and coatings formulations). Having successfully dispersed the materials in bulk polymers or films / fibers, their influence on the mechanical, thermal, barrier and optical properties of the polymers will be measured and compared with those obtained with the best currently available fillers. Both intrinsic properties and the performance in industry specified tests will be assessed. For this project to succeed it will, be necessary to optimise in-turn each of the various steps in the production of the synthetic nano-talc ? (1) preparation of the amorphous material, (2) conversion to the crystalline material, and (3) subsequent treatments and incorporation in polymers. A different academic partner with specific expertise has been chosen to lead each of these activities: (1) - The Research centre (School of Mines of Albi-Carmaux) RAPSODEE (FRE 3213-CNRS); (2) LMTG (UMR 5563 CNRS; UMR 154 IRD) and (3) Laboratoire des Matériaux Macromoléculaires (UMR CNRS 5223-LMM-INSA, Lyon). To carry out the industrial testing and development there will be three industrial partners: (1) Rio Tinto Minerals (Toulouse) - project coordinator and talc producer; (2) MAPAERO - specialist producer of aeronautical coatings and (3) Multibase (Lyon) - polymer compounder and producer of polymer masterbatches. The project duration is 4 years.