Adhesives powdered polyurethanes

Nonwoven scrim Adhesive film/powder Chopped glass mat Adhesive film/powder Central core Adhesive film/powder Chopped glass mat Adhesive film/powder Polyurethane foam Decorative (face) fabric Typically polyester Hot melt Adds rigidity Hot melt Semi-rigid PU foam or resonated waste fibres Hot melt Adds rigidity Hot melt Present if the need for soft touch is required Typically polyester... 

Adhesives from Diisocyanates and Starch. Reactions between diisocyanates and carbohydrates are possible, resulting in polyurethane-like polymers. Starch as a most abundant natural polymeric carbohydrate is, without additives, an inefficient wood adhesive, giving weak and nonwater-resistant bonds. Another disadvantage of starch is that, even at low concentrations, the viscosity of the starch solution is too high for application. In our tests, maize starch was used as an extender for diisocyanates. The potlife of formulations of three parts starch powder and seven parts diisocyanate was more than 24 hours. 

The directives apply to all materials used in the make up of electrical and electronic components and include paint, plastics, adhesives and rubbers, plastic parts, protective coating materials, epoxy adhesives, cyanoacrylate adhesives, polyurethane adhesives as well as complete computer motherboards. Computer and peripheral equipment are made up of different materials consisting of plastic, ferrous and non-ferrous metals, trace heavy metals, glass, foams, rubber, carbon powder and additives. Other non-metal materials posing environmental and health problems present in electrical and electronic products are beyond the scope of this book and will not be discussed here. The supportive components used in these products fall within the following ten product categories in the directive which are ... 

Use Manufacture of nylon and of polyurethane foams preparation of esters for use as plasticizers and lubricants food additive (acidulant) baking powders adhesives. 

Polyurethanes are also used to make paints, available as water-thinnable paints and powder coatings. Items painted with PU paints benefit not only from a lacquer film, but also from an improved chemical resistance. Polyurethane paints are scratch, abrasion, and impact resistant, and they adhere well to a variety of surfaces. Polyurethane adhesives are similarly good choices as they resist heat, water, solvents, grease, and oils. ... 

Uses Mfg. of nylon and polyurethane foams intermediate for paints prep, of esters for use as plasticizers and lubricants alkyd resin comonomer starch crosslinking agent buffer in cosmetics adhesives textile treatments wet str. paper resins synthetic flavoring agent, leavening agent, acidulant, buffer, neutralizer in foods baking powders buffer, neutralizer in pharmaceuticals... 

The most significant marine use of resins is actually in the form of paint corrosion protection systems for hulls. These include polyurethane and epoxide systems, the latter giving good alkali and solvent resistance in addition to providing superior adhesion to most substrates. Such systems take the form of zinc-rich epoxy and epoxy coal-tar combination hull paints. Epoxy powder coatings are also commonly used for the protection of steel pipelines, both on land and offshore. 

Thermoplastic linear polyurethanes which are usually chain-terminated so that no unreacted free NCO groups remain available. Environmental considerations direct growing attention to these newer non-polluting urethane adhesive forms, e.g. powders, films, aqueous dispersions and 100% solids reactive systems. Some systems do possess blocked diisocyanates which are activated on heating to produce chemically reactive solid systems. 

The total elastomer consumption in the United States and Canada in 1998 accounted for 245 kt/a. Automotive RIM applications accoimted for 65.3 kt/a, TPU for 53.5 kt/a, and Spandex for 26.5 kt/a. Cast elastomers had the highest consumption (100 kt/a). Coatings consumption in the United States and Canada in 1998 was 237 kt/a, and powder coatings accounted for about 20% of the total. Adhesives (105 kt/a) and sealants (80 kt/a) were other important polyurethane applications. 

Yet, another approach is to disperse the superabsorbent polymer powder deep inside a polyurethane foam and fix it so that the powder will not leak. A superabsorbent polymer is thinly dispersed behind polyurethane foam with a connected pore strueture. An adhesive layer is used to eover the powder layer to form an absorption sheet. If this sheet is adhered to a food tray, in addition to water absorptivity, additional functions such as impact strength and thermal insulation can be expected [6]. 

Their multiple use-forms (e.g., in in situ-XQ-acting, neat, liquid systems solutions aqueous dispersions films webs powders) and other valuable attributes (e.g., adhesion to a variety of substrates vibration-damping bonds " gasoline, oil, and solvent resistance etc.) continue to make polyurethane- and isocyanate-based adhesives the materials of choice in many adhesive applications. 

The elimination of organic solvents in the application of coatings, saturants, sealants, and adhesives and its importance in environmental pollution abatement and worker health and safety has already been discussed in connection with aqueous polyurethane latex and polyurethane film adhesives. The absence of troublesome and expensive solvents in their application must rank near the top in the list of advantages associated with the use of powdered polymers, including adhesives. 

Of the available polyurethane types, the virtually crosslinked thermoplastic polyurethane elastomers would seem to be best and ideally suited for supply and use in powdered form. Their uses include adhesive applications which exploit the advantages of the powder form. 

Ex. 1. Ultramoll PU is a highly flexible polyurethane based polymeric plasticizer in the form of a colorless and odorless powder of < 1000 micrometer particle size. It contains 5 3% of PVC and was especially designed for combination with PVC. It has 72 + 3 degrees Shore A hardness. Ultramoll PU yields improved adhesion strength in comparison with plasticized PVC in its injection molding as sole stock against shoe upper material. 

Blocked NCO + Polyol (polyurethane) Powder stoving Can and coil coatings, maintenance coatings, adhesives for metals... 

A coated granule containing a solid (carbofuran) and a liquid (diazinon) insecticide is to be prepared. The solid inseeticide is ground to a fine powder the liquid inseeticide is sprayed onto an absorbent silica. A combination of two adhesives is used. Granular (0.4-0.8 mm) quartz is first sprayed with a liquid polyurethane while tumbling the quartz in a shell blender. Once the mass is wetted the inseetieide powders are added. After tumbling the mass to adhere the powders, an aqueous solution of polyvinyl alcohol is sprayed onto the surface. In order to set the adhesive the mass is transferred to a drier and heated to about 60°C. 

In a typical operation, PVC powder compound is metered into a form that has been machined to a high finish to represent the desired part surface, then heated to a temp-eramre at which the compound will sinter and partly fuse, while sufficient rotation is applied to obtain a uniform coating of the inside of the form. The latter may be, in fact, the same form previously used to rotomold PVC plastisol. The polyurethane (PUR) component may be foamed within the form or, more often, prepared previously, placed in the form, and fusion of the PVC, with resultant high PUR adhesion, then completed. ... 

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