Epoxy-polyurethane blends

Epoxy resins when cured are very hard. Their toughness can be improved by adding some polyurethane to the epoxy resin during curing. The polyurethane imparts more impact and a higher level of toughness to the epoxy. The blends maintain most of the epoxy s electrical and chemical properties. 

In the reaction between diamines and epoxys, all four hydrogen atoms in the amine group react with the epoxide groups therefore the functionality is four. (With polyurethanes, each amine group reacts with an isocyanate 

Material Molecular Weight Equivalent Weight for Polyurethanes Amine Hydrogen Equivalent Weight (AHEW) 

As with polyurethanes, the amount of hardener is calculated on 100 parts by weight (pbw). Epoxies are supplied with the epoxide value (EEW) of each batch. The basic calculation is 

For an epoxy resin with epoxide value of 183 if hardened with Ethacure 100, one would need (44.6 x 100)/183 = 24.5 ppw of E100 for 100 pbw of resin. The required amounts of curative for the polyurethane and the epoxy are calculated separately. 

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Nonvinyl polymers cured by TAG include polyamides (120), polyamide—polyurethane blends (121), caprolactone polymers (122), terephthalate polymers (123), epoxy resins (124), and acryflc epoxies (125). 

Mold A manufactured cavity which preserves a negative impression of a specimen. The cavity can be filled with uncured polyurethane blends. Can be manufactured from a variety of materials depending on the production requirements, such as steel, aluminum, polyurethane, epoxy, FRP, silicone rubber, or latex. It can be manufactured in "one piece" or in multiple interlocking pieces. Multi-piece molds are used when the cast has a complex shape or undercuts which would make demolding from a one-piece mold difficult or impossible. 

This technology was first commercially applied to polyurethane blend [121] and patented as Rimplast (for Reactive Injection Molding), but many polymers have since been blended with polysiloxane thanks to this method polyethylene [122], polypropylene [122,123], polyamide [124-130], polyesters [128,131-133], poly(phenylene ether) [134], fluorocarbons [135] and many more. Many of them include reinforcing fillers such as fumed silica. The silicone base involved can moreover contain reactive groups such as the epoxy group [136,137]. A typical silicone base useful for these blends was de-... 

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. 

Formacast Epoxy/polyurethane casting blends Formulated Resins... 

Benzene, toluene, and xylene are made mosdy from catalytic reforming of naphthas with units similar to those already discussed. As a gross mixture, these aromatics are the backbone of gasoline blending for high octane numbers. However, there are many chemicals derived from these same aromatics thus many aromatic petrochemicals have their beginning by selective extraction from naphtha or gas—oil reformate. Benzene and cyclohexane are responsible for products such as nylon and polyester fibers, polystyrene, epoxy resins (qv), phenolic resins (qv), and polyurethanes (see Fibers Styrene plastics Urethane POLYiffiRs). 

Waterproof. Waterproofing barrier systems may be either hot- or cold-appHed. The hot-appHed generaUy involve a bituminous material such as asphalt used in conjunction with a reinforcing fabric such as roofing felt, cotton, or glass cloth. Cold-appHed can be bituminous or elastomeric materials either in Hquid or sheet form, with or without fabric reinforcement. Liquid elastomeric treatments include neoprene, polyurethanes, and blends of these or epoxies with bituminous materials. Among the commonly used precured elastomeric sheet materials are neoprene, polyisobutylene, EPDM mbber, and plasticized PVC. Polyethylene and PVC films and nonwoven plastic or glass fabric coated with bituminous materials also find use (78). Because these... 

Itoh et al. [141] patented a blend of polyurethane and silicone gum with vinyl groups. The crosslinking reaction of the silicone component was achieved using a radical generator. Chorvath et al. [142] also patented a system composed of polyamide or polyester as the thermoplastic and vinyl-containing polysiloxane cured by a peroxide or non-peroxidic initiator such as 3,4-dimethyl-3,4-diphenylhexane (HTV). Moreover, they added different compatibilizers such as amino-terminated or amino-grafted polysiloxane, epoxy- or isocyanato-functionalized polysiloxane. 

A variety of polymers, both thermosets as well as thermoplastics, can be blended and coreacted with epoxy resins to provide for a specific set of desired properties. The most common of these are nitrile, phenolic, nylon, poly sulfide, and polyurethane resins. At high levels of additions these additives result in hybrid or alloyed systems with epoxy resins rather than just modifiers. They differ from reactive diluents in that they are higher-molecular weight-materials, are used at higher concentrations, and generally have less deleterious effect on the cured properties of the epoxy resin. 

An acrylate-terminated polyurethane modified epoxy compound and a polyethylene polyamine homologue and fatty acid combination were formulated into a two-component adhesive system. The adhesive is useful for bonding various thermoplastic resins such as ABS, PC, PBT-PC blends, and PPO.22... 

Adhesives may include styrene, styrene/isoprene blends, vinyl alcohol, vinyl acetate, epoxy resins, acrylates, cyanoacrylates (superglue), ethylene/vinylacetate (hot-melt), polyurethanes, etc. [19]. 

Fig. 13.7 The TEM image of the nanophase-separated structural epoxy adhesive containing nitrile rubber/phenolic polyurethane liquid rubber blends (cure with dicyandiamide at 180°C).

Fig. 13.8 The T-peel resistance as a function of the crosshead speed for nitrile rubber/phenolic polyurethane liquid rubber blend toughened epoxy (upper curve) and conventional nitrile rubber-toughened epoxy structural adhesives (lower curve).

Fig. 2, Representative bend specimens after testing at 76°K (a) butyl formal, butyl ether, and polysulfide blend (b) fluorosilicone (c) polysulfide (d) silicone (e) polyurethane (f) epoxy (g) epoxy-silicone and (h) carboxyl terminated polybutadiene and epoxy blend. 

Polyurethane/epoxy-based polymer blends (so-called toughened epoxies)... 

Other industrial applications include the fabrication of two-part epoxy resins (similar to those commonly found in household maintenance stores) [95-97], These were synthesized using triglycerides and diamines. These resins are often used as adhesives these have also been studied using soybean oil, which provided beneficial properties in terms of fast curing, thermal stability and ease of removal (peel strength) [98], A blend of divinylbenzene/styrene/tung oil mix gave a polyurethane-based material which behaved like a smart polymer with shape memory behaviour [66]. 

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