To be more sustainable, fillers need to be derived from natural, growing products. But while there is already considerable use of natural fibers such as wood, cellulose, hemp, silk, and rayon, there is virtually no commercial use of natural product- derived particulates at present, apart from wood flour. The main activities to date are summarized below, and more information can be found in ? Chaps. 16, “Fillers from Organic Sources” and ? 23, “Nanofillers”.
Polysaccharides can be sustainably sourced and are potentially available in large quantities. The main polysaccharides of interest have been and remain starch and cellulose. These are briefly discussed here and more information can be found in ? Chaps. 16, “Fillers from Organic Sources” and ? 23, “Nanofillers”.
In the past, there was considerable interest in starch-derived products for use in tire applications, with Goodyear leading the way starting as long ago as 1997, when they had a patent (US 5,672,639) to a starch reinforced rubber composition and tire. In this work, the filler was a plasticized form of starch, with the plasticizer being necessary to soften the starch granules and allow dispersion into the rubber. Shortly later, it was reported that Novamont, working in conjunction with Goodyear, had developed a nanoparticle-sized, corn-derived starch product that significantly reduced the rolling resistance of tires compared to the use of precipitated silica, and this was reported to be used in Goodyear’s GT3 tire. This tire is still marketed and is described as an ecological tire for city cars which uses some materials derived from corn-starch to replace petroleum oil derivatives; it does not now specifically mention that these corn-starch products are fillers. The development work for this tire application was the subject of a European Union research grant, and the details can be found in “Bio Tyre Project, Layman’s Report, LIFE06ENV/L/000118, http://ec.europe.com). More details on nano-starch fillers can be found in ? Chap. 23, “Nanofillers” and in Lin et al. (2011).