Adhesives Sizes and Binders

The adhesive cements, or simply adhesives, are viscous liquid preparations used mainly for joining together different objects or parts of objects into coherent units, for sizing (sealing) porous surfaces, and as binders in the preparation of paints (see Textbox 18). Until the end of the nineteenth century the only adhesives known to humans were of natural origin, derived either from vegetable secretions or from animal fluids and tissues. Few modern adhesives are now derived from natural substances most are artificial, human-made (synthetic) substances developed since the twentieth century. 

Most adhesive preparations consist of at ieast two main components an adhesive and a solvent. The adhesive is the binding substance that, when dry, attaches and joins together adjacent surfaces, or sizes (covers and seais) porous surfaces. Water was, for many miiiennia, practicaiiy the oniy soivent used in adhesive preparations. Adhesives soiubie in water form soiutions and, if insoiubie, become suspended in the water, usuaiiy in such concentration as to render the preparation viscous and tacky. As weii as the adhesive and the soivent, a variety of additives have often been added to adhesive preparations so as to improve their spreading properties or modify other quaiities. Additives, which increase the viscosity of the preparations, are known as fillers, while those that increase their volume are referred to as diluents (Eagland 1988 Masschelein-Kleiner 1985). 

The chemical composition of the natural resins is very diverse, and their molecular structure may be highly complex most resins of vegetable origin, however, are chemically related to the carbohydrates. Dry vegetable resins 

Amber Extinct Pinus sucdnifera trees Gemstone varnish 

Dragon s blood Fruits of Daemonorop draco palms Varnish 

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Gums are complex carbohydrates exuded from plants, or produced by the decomposition of vegetable matter, that have been used since remote times as adhesives, sizes, and binders (see Table 73). Most gums are tasteless and odorless solids that either dissolve or swell in water to form adhesive, viscous mucilages. When the water evaporates from a mucilage, the... 

Examples of the fatty acids are oleic (c -9-octadecenoic) and linoleic (c ,c -9,12-octadecadienoic) acid. The major constituent of rosin acids is abietic acid. Uses of tall oil are tall oil rosin (31%, for paper size, protective coatings, adhesives, inks, and rubber), tall oil fatty acids (30%, in protective coatings, soaps, and inks), tall oil pitch (30%, in fuel, binders, coatings, rubber modifiers, asphalt, sizing, inks, and hardboard impregnation), and distilled tall oil (9%, in soaps, coatings, flotation, and board impregnation). 

Industrial separation membranes and ion-exchange resins can be made from chitin, especially for water purification. Chitin is also used industrially as an additive to thicken and stabilize foods and pharmaceuticals. Since it can be shaped into fibres, the textile industry has used chitin, especially for socks, as it is claimed that chitin fabrics are naturally antibacterial and antiodour (www.solstitch.net). Chitin also acts as a binder in dyes, fabrics and adhesives. Some processes to size and strengthen paper employ chitin. 

As shown previously, drop wet-in time decreases with increasing pore radius decreasing binder viscosity and increasing adhesion tension. In addition, drop penetration time decreases with decreasing drop size and increasing bed porosity Seff. Effective pore radius R i is related to the surface-volume average particle size ds2, particle shape, and effective porosity of packing Seff by... 

A method for coating microchannel walls with layers as thick as 25 pm was developed by Stefanescu et al. [181]. The microreactor was built from FeCrAl (Aluchrom ). The metal surface was first chemically treated in several steps and afterward annealed at 1200 °C for 1 h to trigger the segregation of aluminum and the formation of an alumina layer on the metallic surface. An alumina washcoat was subsequently deposited from a slurry onto the microstructure and characterized by various physical methods. The authors varied the properties such as viscosity, particle size, and pH of the slurry. Acrylic acid, a component used as dispersant and binder, was found to be particularly important for the adhesion of the alumina layer. 

Even in the world of nanoparticles, in addition to the always present natural adhesion forces (e.g., van-der-Waals), additives, for example ligand or linker molecules, are sometimes required, which work on a completely different level from the previously discussed classic binders (Chapter 3) for macroscopic agglomeration processes. The possibility of generating ordered structures from nanoparticles by self-assembly is often governed by the size and local concentration ratios of the constituent particles. Furthermore, the interparticle spacing of nanoparticle ensembles can be controlled by the choice of the ligand or linker molecules [11.6]. 

Starch has been extensively used for several non-food applications, in native state or modified by physical and/or chemical processes. The main areas for starch applications are in adhesives [2], paper [2, 3], drilling fluids for petroleum extraction [30], textile sizing [3], binder in medicines, and hot melt adhesive compositions [31-33]. 

One cause for paper machine foam problems is residual carry-over from the pulp mill or bleach plant. As much as possible the raw materials used should be as uncontaminated as possible. Black liquor is just one example of a contaminant that can cause foam on a paper machine. Another potential foam contributor is recycled fibre, used as part of a furnish. The recycled fibre contains all the ingredients used in paper manufacture and converting coatings, sizing, inks, adhesives and binders, wood components, etc. that impact foam creation and stabilisation. 

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