Adhesives polyurethane, preparation

Polyesters [2] find use in fibers [poly(ethylene terephthalate), poly(ethylene oxybenzoate), poly(ester ethers), poly(ester amides), etc.] [1], coatings (especially unsaturated polyesters) [4], plasticizers, adhesives, polyurethane base resins, films, etc. Cross-linked polyesters prepared from glycerol and phthalic anhydride (alkyd resins) have been reviewed [20], High-melting poly aryl esters have been investigated for high-temperature applications. 

Polyurethane adhesives were prepared by mixing polyol, diisocyanate (MDI, TDI or HDI), solvent (DMF, benzene or ethylace-tate), and catalyst (T-9) in the following fashion The diisocyanate dissolved in half of the total solvent volume was mixed with two-thirds of the polyol in one-fourth of the solvent in the presence of a trace of the catalyst. The mixture was heated to 50°C until an exothermic reaction starts then, heat was temporarily removed and reapplied for 10 min to maintain a temperature of 80°C. The rest of the polyol, catalyst, and solvent were then added and mixed completely. The resin was ready for application when the consistency of the mixture had reached a suitable level. The adhesive was spread on 11 3/4" x 4 1/2" x 3/4" wood (hard maple or southern pine) strips. The moist adhesive-coated surfaces were exposed to ambient air (vented hood) for 20-30 seconds if DMF was used as solvent, or for 3-5 minutes if either benzene or ethylacetate was used. After pressing (100 psi), the strips were cut into small shear blocks and tested according to ASTM Standard D905-49. Polyurethane coatings were prepared by mixing the polyol (80 parts) in ethylacetate (60 parts) and toluene (40 parts), with a solution of TDI (53 parts) in 80 parts ethylacetate and 30 parts toluene, and T-9 catalyst... 

Starch polyurethane foams could be converted into sorbents for water when starch-acrylonitrile or starch-methacrylonitrile graft copolymers were crosslinked with diisocyanates.2655 2656 Such polyurethanes have been proposed as occlusive wound dressings,2657 as well as sizes for cotton yams.2658 Starch polyurethanes for reinforced paper were produced in reaction of iV-chlorocarbamoylethyl starch with cresol or thiolignin.2659 The addition of mineral salts to polyurethanes prepared from starch and urea improved their performance as adhesives.570... 

The adhesive manufacturer prepared several adhesives with different polyurethane mixes (details see Section 3). The adhesives were used in different thicknesses to connect two small beech pieces together. Altogether over two hundred... 

Chan-Chan LH, Vargas-Coronado RF, Cervantes-Uc JM, Cauich-Rodriguez JV, Rath R, Phelps EA, et al. Platelet adhesion and human umbilical vein endothelial cell cytocom-patibility of biodegradable segmented polyurethanes prepared with 4,4 -methylene bis(-cyclohexyl isocyanate), poly(caprolactone) diol and butanediol or dithioerythritol as chain extenders. J Biomater Appl 2013 28(2) 270-7. 

Most of the upper and sole materials used in shoe industry cannot be directly joined by using the current adhesives (polyurethane and polychloroprene adhesives) due to their intrinsic low surface energy, the presence of contaminants, and antiadherend moieties on the surface. Therefore, the surface preparation of upper and sole must remove contaminants and weak boundary layers, and roughness and chemical functionalities able to produce adequate bond strength should be created. 

Turner, S. Richard, 1 Two-component (2-K), nonsagging, polyurea structural adhesive, preparation of, 255-256 Two-component (2-K) systems, 238-241 Two-component (2-K) waterborne polyurethane coatings, 206 preparation of, 254-255 Two-shot cast elastomer, preparation of, 249-250... 

FIGURE 27.6 T-peel strength values of chlorinated styrene-hutadiene mhher (SBR)/polyurethane adhesive joints as a function of the ester used to prepare the 2 wt% trichloroisocyanuric acid (TCI) solution. EA = ethyl acetate PA = propyl acetate BA = hutyl acetate. (From Ramero-Sanchez, M.D., Pastor-Bias, M.M., and Martin-Martinez, J.M., Int. J. Adhes. Adhes., 21, 325, 2001.)... 

One of the more advanced technical offerings from castor oil is a line of polyester diols, triols, and higher functional polyols derived from 100% castor oil as products for the preparation of polyurethane prepolymers and elastomers [68]. The Polycin line of polyols are prepared by transesterification of ricinoleic acid and derivatives. The producers (Vertellus) offer diol and triol products, as well as a recently developed series of diol and triol glyceryl ricinoleate esters that are stated to be prepared from 100% castor oil, making them fully renewable in content. The products are recommended for coatings, sealants, and adhesive applications. 

Recently a solvent-free dual-cure laminating adhesive based on the combination of polyurethane chemistry and EB cure was developed that exhibits improved properties compared to laminates prepared by either method alone. ... 

Toluene diisocyanate is commonly produced as a mixture of the 2,4- and 2,6-iso-niers, that is used as a monomer in the preparation of polyurethane foams, elastomers and coatings, as a cross-linking agent for nylon-6, and as a hardener in polyurethane adhesives and finishes. Polyurethane elastomers made from toluene diisocyanates are used in coated fabrics and clay-pipe seals. Polyurethane coatings made from toluene diisocyanates are used in floor finishes, wood finishes and sealers, and in coatings for aircraft, tank trucks, truck trailers and truck fleets (United States National Library of Medicine, 1997). 

PVB combinations with the thermoplastic resins nitrocellulose or shellac have been used as sealers for wood finishing. In these applications the PVB component adds flexibility and adhesion. Tough, optically clear blends have been made with aliphatic polyurethanes. Thermosets are prepared with cross-linkers that form covalent bonds with hydroxy] groups. 

For laboratory-size experimentation, the most suited vessel is a widenecked flask with a clamp-on lid. This style has several advantages, one being that fitting an anchor stirrer is much easier. The discharging of the final product is relatively quick with this type of vessel. When a batch has been prepared, all parts that have been in contact with the polyurethane must be thoroughly cleaned and dried. Polyurethanes are a very effective adhesive and can be formed by the reaction between the resin produced and the moisture in the air. 

The polyurethane (PU) can be considered an environment-friendly material because the urethane bond resembles the amide bond, which implies possible biodegradability. It can be used in various elastomer formulations, paints, adhesives for polymers and glass, and artificial leather as well as in biomedical and cosmetic fields. Polyurethane spheres were prepared from 20/40% of PU prepolymer solution in xylene [91]. PU droplets were formed in water with the SPG membrane of different pore size (1.5-9.5 pm) and then polymerized to form the final microspheres. Finally, spherical and solid PU particles of 5 pm were obtained after the removal of the solvent. In another study, Ma et al. reported the formation of uniform polyurethane-vinylpolymer (PUU-VP) hybrid microspheres of about 20 pm, prepared using SPG membranes and a subsequent radical suspension polymerization process [92], The prepolymers were solubilized in xylene and pressed through the SPG membrane into the continuous phase containing a stabilizer to form uniform droplets. The droplets were left for chain extension at room temperature for some hours with di- and triamines by suspension polymerization at 70 °C for 24h. Solid and spherical PU-VP hybrid particles with a smooth surface and a higher destructive strength were obtained. 

Several hybrid epoxy emulsions have been commercially prepared. An epoxy emulsion blended with waterborne aliphatic urethanes exhibited peel strength on aluminum of 10 lb/in—1.5 times greater than with the polyurethane itself. The optimum concentration of urethane in the final emulsion was about 50 percent by weight.13 Epoxy-phenolic dispersions have also been developed to provide waterborne adhesive systems with high glass transition temperature and chemical resistance. 

Various adhesives can be used to bond polyphenylene oxide to itself or to other substrates. Parts must be prepared by sanding or by chromic acid etching at elevated temperature. Methyl alcohol is a suitable solvent for surface cleaning. The prime adhesive candidates are epoxies, modified epoxies, nitrile phenolics, and polyurethanes. Epoxy adhesive will provide tensile shear strength on abraded polyphenylene oxide substrates of 600 to 1300 psi and 1300 to 2200 psi on etched (chromic acid) substrates.71... 

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