Renewable sources of adhesives

Most adhesives are polymers, which, at present, are derived fi om petroleum feedstocks. Clearly, petroleum is a non-renewable resource. Controversy attends predictions of how long reserves will last, but there are some authorities, at least, that predict a permanent downturn in production within the first or second decade of the present century. How this will affect polymer production and use is, of course, impossible to say. Here, it is relevant to point out that there have long been adhesives in use that are obtained from animal and vegetable sources see Renewable sources of adhesives and Adhesives - historical perspective. 

Renewable sources of adhesives C A FINCH Non-fossil fuel sources, biotechnology... 

The replacement of petroleum-derived (nonrenewable) sources of adhesive raw materials with renewable sources will follow three basic strategies 1) renewable materials will be used to replace part of the required petroleum-derived adhesive systems, 2) new polymeric adhesives will be synthesized from renewable materials and totally replace petroleum-derived adhesive systems, or 3) the adhesives systems now based on petroleum-derived materials will continue to be used, but the adhesive raw materials will be derived from renewable sources instead of from nonrenewable ones. Carbohydrates are very versatile chemicals that can be utilized in all three strategies as demonstrated by the preceding discussion. 

The first demonstration of the industrial importance of heme peroxidases in grafting applications has been the development of hybrid resins from renewable sources to replace phenol-formaldehyde based resins. Phenolic resins are widely used in surface coatings, adhesives, laminates, molding, friction materials, abrasives, flame retardants, carbon membranes, glass fiber laminates, fiberboards, and protein-based wood adhesives, [5]. Table 7.1 and Fig. 7.2 summarize some of the... 

Byproducts of the forest products industry are potentially primary sources of natural resource-based adhesives. Because this industry is both a producer of huge tonnages of residues and a major consumer of adhesives, this book focuses on adhesives from renewable resources derived from trees. Composites made from wood will remain the primary materials used for the construction of homes and their furnishings for the foreseeable future. 

The second category of industry-favored adhesive research involves synthetic resins of recognizable performance based on partial or total replacement of a critical petrochemical constituent such as phenol with a functional organic compound or residue derived from renewable sources. Examples here include ... 

Carbohydrates, in the form of gums, polysaccharides, oligomers, and monomeric sugars, are readily available in large quanitities from renewable biomass resources. Each of these substances, either directly or in a chemically modified form, is a source of intermediates (derivatives) that have potential use in adhesive formulation. Carbohydrates have been utilized historically for and in adhesives and are likely to be used more and more in the future as petroleum-derived chemicals become scarce and prices increase. Appropriate research emphasis can effectively further their use as adhesive raw material. 

Since the oil shortages of the 1970s, there has been a sustained search for materials to replace the petroleum-based resins used as durable adhesives for exterior wood products. Such alternatives are considered important, because supplies of petrochemicals for use in the wood industry could again become undependable. Ideally, the source of material for an adhesive would be readily available, possibly from materials already found near or used by wood processing plants, for example, agricultural or wood-based renewable resources. The purpose of this investigation was to explore the use of carbohydrates as constituents in water-resistant adhesives. 

Adhesives and sealants based on renewable sources show a number of advantages, but also major disadvantages that effectively limit their broader use at present. On the positive side they usually show an excellent bio-compatibility given that their chemical modification did not completely alter this. Natural-based products in general show a positive Greenhouse Gas (GHG) balance, and thus do not directly contribute to climate change. They show a fairly good price/performance ratio, usually are available in sufficient quantity and show no or low toxicity. 

In low to medium modulus applieations of sealant caulks and adhesives, however, where curing takes place through physical solidification, i.e. due to cooling and/or drying, the use of raw materials based on renewable sources is quite common, and can certainly be expanded with focused research for overcoming inherit shorteomings. 

Table 11.2 gives a survey about major use areas for adhesives based on renewable sources. The share of renewable raw materials in the sealants market is well below 5%. Numbers in Table 11.2 do not include polyurethanes containing oleochemical-based polyols, vegetable oil-based polyesters and polyamides based on dimer fatty acids in total estimated at 35 mto in 2006, 42 mto in 2010. Projection into 2010 shows that without disruptive innovations the share of natural-based adhesives will further decline to a mere 15% in total. 

Contains part of a presentation titled Adhesives Based on Renewable Sources, held by the author at the World Adhesives Conference in Miami, April 2008. 

The development and use of materials from renewable sources is not a new concept. Besides providing food, feed, clothes, shelter, and energy, biomass has been employed since ancient times to extract valuable products such as medicinal drugs, flavors, and fragrances. With the development of civilization of human society, in the nineteenth century various biomass resources were employed for the large-scale industrial production of chemicals and durable materials, such as cellulose esters (nitrate and acetate), oxidized linseed oil (linoleum), vulcanized rubber, adhesives from starches, and so on. However, the widespread use of such renewable materials diminished in the twentieth century since the development of fossil fuel derivatives, leading to the polymer renaissance. Today commodity polymers such as polyolefins are ubiquitous in our societies because they represent the optimal choice based on several factors, including monomer cost and... 

Rosin exploitation, a part of the so-called Naval Stores Industry, is at least as old as the construction of wooden naval vessels. In recent years, rosin components have attracted a renewed attention, notably as sources of monomers for polymers synthesis. The purpose of the present chapter is to provide a general overview of the major sources and composition of rosin. It deals therefore with essential features such as the structure and chemical reactivity of its most important components, viz. the resin acids, and the synthesis of a variety of their derivatives. This chemical approach is then followed hy a detailed discussion of the relevant applications, the resin acids and their derivatives, namely in polymer synthesis and processing, paper sizing, emulsion polymerization, adhesive tack and printing inks, among others. 

Proteins are natural, renewable, and biodegradable polymers which have attracted considerable attention in recent years in terms of advances in genetic engineering, eco-friendly materials, and novel composite materials based on renewable sources. This chapter reviews the protein structures, their physicochemical properties, their modification and their application, with particular emphasis on soy protein, zein, wheat protein, and casein. Firstly, it presents an overview of the structure, classification, hydration-dehydration, solubility, denaturation, and new concepts on proteins. Secondly, it concentrates on the physical and chemical properties of the four important kinds of proteins. Thirdly, the potential applications of proteins, including films and sheets, adhesives, plastics, blends, and composites, etc. are discussed. 

Most types of Hot melt adhesives used in the mannfacture of laminates and in rapid Packaging industry applications are mineral oil-derived, hydrophobic and essentially non-dispersible, so they cannot be considered as renewable. However, some basic polymers have been prepared over the last decade from vegetable sources, which are renewable, and are adhesive, although these properties have limitations. These include poly(hydro-xybutyrate/hydroxyvalerate) (PHBV), poly(lactide) (which has poor thermal stability), and starch esters. Adhesives based on sulphonated polyesters with polar petroleum waxes have improved adhesion and adequate water dispersibility. In general, however, the perfect adhesive from renewable resources with satisfactory adhesion properties remains to be discovered. 

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