Vegetable resources tannins

This chapter gives a general introduction to the book and describes briefly the context for which the editors established its contents and explains why certain topics were excluded from it. It covers the main raw materials based on vegetable resources, namely (i) wood and its main components cellulose, lignin, hemicelluloses, tannins, rosins and terpenes, as well as species-speciflc constituents, like natural rubber and suberin and (ii) annual plants as sources of starch, vegetable oils, hemicelluloses, mono and disaccharides and algae. Then, the main animal biomass constituents are briefly described, with particular emphasis on chitin, chitosan, proteins and cellulose whiskers from molluscs. Finally, bacterial polymers such as poly(hydroxyalkanoates) and bacterial cellulose are evoked. For each relevant renewable source, this survey alerts the reader to the corresponding chapter in the book. 

Closer to the focus of this book, petroleum products began to replace the vegetable oils, tannin, wool, cotton, leather, silk, rubber, etc. in a host of applications. Surely, it was argued, the new materials did the job better and cheaper. What they didn t say is that soon we would run out of oil. In any case, research on growing natural products, now called renewable resources, slowed, and these industries sought only to maintain their status quo. 

The loose term renewable resources adhesives has been used to identify polymerie eom-pounds of natural, vegetable origin that have been modified and/or adapted to the same use as some classes of purely synthetic adhesives [1]. At present two classes of these adhesives exist one already extensively commercialized in the southern hemisphere and the other on the slow way to commercialization. These two types of resins are tannin-based adhesives [2] and lignin adhesives [3 ]. Both types are aimed primarily at substituting synthetic phenolic resins. In some aspects, such as performance, they closely mimic, or are even superior to, synthetic phenolic adhesives, while in others they behave in a vastly different manner from their synthetic counterparts. In this chapter we focus primarily on tannin-based adhesives because they have already been in extensive industrial use in the southern hemisphere, in certain fields of application, for the past 20 years. These adhesives are of some interest not only for their excellent performance in some applications but also for their mostly environmentally friendly composition. Lignin adhesives are treated briefly here and in detail in Chap. 28. 

Processes and products developed to produce industrial materials from renewable resources have been too numerous to record here. For competitive reasons — supply of raw materials and technical and economic considerations — some of the products have varied widely in industrial use. Major U.S. industrial consumption of renewable resources have recently included oils and fats (animal and vegetable) industrial alcohol (wheat, corn, grain sorghum) fibers (cotton lint, flax, hides and skins) paper (forest products) isolated proteins (milk casein, animal glues, soybean, corn) turpentine and rosin (naval stores) and other chemicals (monosodiiim glutamate--wheat starch and dextrin—corn lactose—milk molasses and pulp residues --sugarcane and beet tannin lecithin pectin furfural). 

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