Powdered Polyurethane

Powdered forms of plastics and rubbers allow the economical, low-energy mixing of polymers with additives such as colorants, plasticizers, stabilizers, curatives, etc. The gentleness of powder mixing preserves polymer integrity and properties, and thus subsequent performance characteristics. 

The fluidity of powders is another asset. It permits conveyance, distribution and application without the benefit of other media such as organic solvents or water which must finally be removed and disposed of. It obviates the need for melting the polymer to convey and distribute it. 

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 identified in connection with aqueous polyurethane latex and polyurethane 

Of the available polyurethane types, the crosslinked thermoplastic polyurethane elastomers seem to be best for use in powdered form. 

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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... 

Farbenfabriken Bayer (Ultramoll) and Dai-nippon Ink and Chemical Company (Pandel) supply powdered polyurethane. And duPont has explored these materials. 

The company is one of major unsaturated polyester producers in China with annual capacity of 30 000 tonnes. Set up in 1971, it is a small stock-joint company with 250 employees. It specializes in production of unsaturated polyester, pesticides, coatings, synthetic plastics, plastic powder, polyurethane paints. 

Oil absorbers powdered polyurethane foams possess excellent hydrophobic properties and can absorb various types of mineral oils (1 kg of powder can absorb even up to 3.43 dm of oil [58]). Therefore, such reprocessed foams are used for the treatment of scenes of road accidents, in plants involved in the production and trade of petroleum derivatives, and as barriers removing pollution of inland and sea waters. 

Superabsorbents. Water-sweUable polymers are used extensively in consumer articles and for industrial appUcations. Most of these polymers are cross-linked acryUc copolymers of metal salts of acryUc acid and acrylamide or other monomers such as 2-acrylamido-2-methylpropanesulfonic acid. These hydrogel forming systems can have high gel strength as measured by the shear modulus (134). Sometimes inorganic water-insoluble powder is blended with the polymer to increase gel strength (135). Patents describe processes for making cross-linked polyurethane foams which contain superabsorbent polymers (136,137). 

Only a few commercial uses for TDA per se have been found. In epoxy curing appHcations, 2,4- I DA has been used as a component of a eutectic mixture with short chain aUphatic glycidal ether resins (46) as well as by itself (46,47) TDA (46) and single isomers (47) are also used as amine curatives. TDA can be used as a chain extender in polyurethanes (48,49). TDA is cited as a monomer in making aromatic polymers with unique properties, eg, amorphous polyamides (50), powdered polyamides (51), and low melting, whoUy aromatic polyamides (52). 

This includes wire enamels on a base of polyvinyl formal, polyurethane or epoxy resins as well as moulding powder plastics on phenol-formaldehyde and similar binders, with cellulose fillers, laminated plastics on paper and cotton cloth base, triacetate cellulose films, films and fibres of polyethylene terephthalate. 

Thin coatings consist of paints and varnishes, which are applied as liquids or powdered resin with a thickness of about 0.5 mm [e.g., epoxy resin (EP) [2]]. Typical thick coatings are bituminous materials [3] and polyolefins [e.g., polyethylene (PE) [4]], thick coating resin combinations [e.g., EP tar and polyurethane (PUR) tar [2]] as well as heat-shrinkable sleeves and tape systems [5]. 

Chandalia, K. et al.. In Storey, R. and Thames, S. (Eds.), Proceedings of 28th International Waterborne, High-Solids and Powder Coating Symposium. New Orleans, LA, 2001, p. 77. Woods, G., The ICI Polyurethanes Book. Wiley, New York, NY, 1987. 

Siloxane containing polyester, poly(alkylene oxide) and polystyrene type copolymers have been used to improve the heat resistance, lubricity and flow properties of epoxy resin powder coatings 43). Thermally stable polyester-polysiloxane segmented copolymers have been shown to improve the flow, antifriction properties and scratch resistance of acrylic based auto repair lacquers 408). Organohydroxy-terminated siloxanes are also effective internal mold release agents in polyurethane reaction injection molding processes 409). 

The mono- and disubstituted organotins considered here are used as stabilizers in PVC or as catalysts for the production of electrodeposited coatings (mainly in motor vehicle primers), sihcone rubbers, esterification and powder coatings, and polyurethanes, as well as for coating glass. 

To obtain the polyurethanes, typically a prepolymer was first prepared by reacting the diisocyanate with various diols in dimethylformamide or dimethylacetamide in a two to one molar ratio at 100-110°C for two hours under nitrogen atmosphere. A solution of chain extenders, such as BEP, was then added to the prepolymer reaction mixture and further reacted another three hours. The polymer was isolated by quenching the reaction mixture in cold water. Fine white powder was obtained with a typical yield of around 90%. 

Preparation of model compounds and polyurethanes. A procedure for the preparation of the non-silicon containing monocarbamate and biscarbamate models has been reported previously (8). In order to obtain the silicon containing model compound, 5.0 g of bis(4-aminophenyl) dimethyl silane [synthesized according to Pratt, et.al (9)] was added to 7.0 g ethyl chloroformate at room temperature. A salt immediately formed. The mixture was refluxed for 15 min. The solution was then cooled, vacuum filtered, and recrystallized from ethanol to yield 1.0 g of a white powder MP 162-3 °C Anal. c20H26°4N2Si Calc. C, 62.17 H, 6.70 N, 7.23 Found C, 62.01 H, 6.79 N, 7.42. 

Several benzimidazolone pigments are suitable candidates for use in powder coatings based on polyester, acrylic, or polyurethane resin. These pigments satisfy the heat requirements of this application and do not plate out in these media (Sec. 1.6.4.1). Various benzimidazolone pigments even meet the particularly high thermal standards of coil coating. These pigments are also suitable for use in architectural and emulsion paints. 

In practical application, most types of P.B.15 1 are completely fast to overcoating in oven drying systems. The pigments are suitable candidates for powder coatings, for instance for acrylate or polyurethane-based systems, in which they do not exhibit plate-out (Sec. 1.6.4.1). 

Several polymer-related uses of brassylic acid (BA) have been investigated. For example, a BA/l,3-butanediol/lauric acid oligomer is an effective plasticizer for poljrvinyl chloride,[6] BA/ethylene glycol and BA/propylene glycol polymers function as polyester based polyurethane elastomers,[7] and BA has been patented as a cross-linker for glycidyl methacrylate copolymer powder coatings.[8] However, the most detailed studies have involved polyamides selected data from these studies are summarized in Table I. 

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