Urethane-based resins

Urethane acrylates Urethane adhesives Urethane alkyds Urethane-based resins... 

Urea—formaldehyde (UF) resins commonly were used in the past. However, because of the lack of moisture resistance and the potential for the resins to hydrolyze in the presence of moisture and decompose into urea and formaldehyde, they are not used as much now. Governmental regulations are under development that eliminate the use of UF resin in wood products. This would limit the exposure of the public to formaldehyde, a listed carcinogen, formed by the decomposition of UF resin. Today most wood products use phenol—formaldehyde (phenolic) resins, but urethane-based resins are becoming more common. 

Another fluorescent pigment class (23) is based on a urethane-type resin the primary raw materials are isocyanates, amines, and hydroxy compounds. 

Isocyanate-based resins, in paper manufacture, 13 116 Isocyanate curing agents, 10 410 Isocyanate group, urethanes and, 22 36 Isocyanates... 

Monofunctional urethane acrylate in EHA 26.1 Base resin (elastomer)... 

Li J, Isaac DH, Arnold JC (1996) Environmental stress cracking in uniaxial tension of urethane methacrylate based resins. Mater Sci Eng A 214(1—2) 68—77... 

Li J, Arnold JC, Isaac DH (1994) Environmental stress cracking behavior of urethane methacrylate based resins - I. Environmental crazing and cracking under bending conditions. J Mater Sci 29(12) 3095—3101... 

The mechanism of curing urethane alkyd resins is based on the oxidation with molecular oxygen of the allylic position (reaction 17.13). 

Pampouchidis et al. (83A.B) also synthesized urethane-based cationic electrodeposition resins. 

Urethane-modified alkyds are similar to simple alkyds except that dibasic acid is replaced with a difunctional isocyanate such as toluene diisocyanate or hexamethylene diisocyanate. The process is also similar to simple alkyds. Coatings made with urethane-modified alkyds dry faster and harder than alkyds, yet retain flexibility. These systems have better water-, chemical- and abrasion-resistance than alkyd resins, and cost is also relatively low (Wicks et al., 1998). These are used in clear finishes for wood floors, cabinets, OEM, maintenance, and architectural coatings. The aliphatic-based systems are excellent for exterior use, or where UV exposure is possible, while aromatic-based systems usually have better abrasion-resistance. Chemo-enzymatic synthesis of urethane-based systems produces better control of stereochemistry and can impart unique properties (Athawale Bhabhe, 1998 Athawale Gaonkar, 1999 Athawale Joshi, 2000, 2004 Bhabhe Athawale, 1998). 

PHENOLIC URETHANE 1. Gas hardened e.g. Cold-box Particulate matter - soot from the incomplete eombustion of the carbon based resins Odom may be a problem... 

The vinyl esters have similar levels of moisture absorption. Differences do exist and the base resin tends to be more polar, with hydroxyl groups on the network, but polar contaminants are much less likely. The premium chemically resistant resins are also sometimes based on vinyl urethane terminated polyesters. 

Uses Urethane-acrylic, solv. resist, aid, abrasion resist, aid in coatings, screen inks, overprint varnishes, wood coatings, plastic film, laminating adhesives, floor tile, and metal coating finishes Features Resilient, nonyel. supplied as base resin or as resin/monomer blends which offer resilience, water-wh. clarity, and exc. heat and light stability to UV/EB-cured prods. 

Chem. Descrip. Trifunctional aliphatic urethane acrylate Uses Film-fomier for flexible plastic, paper, metal substrates primary oligomerfor sec. coatings in optical fibers, fiber-optic sensors, light pipes base resin for screen printing inks... 

Chem. Descrip. Hexafunctional aromatic urethane acrylate oligomer Uses Film-former, base resin for clear and pigmented formulations for rigid substrates (wood, metal), UV/EB-curablefomiulations Features Fast cure speed exc. abrasion resist. good chem. resist. high surface hardness high tensile str. 

Chem. Descrip. Aliphatic urethane diacrylate oligomer Uses Film-former for UV/EB-curable coatings and inks for paper/paper-board, plastic, and metal substrates base resin for screen printing inks Features Mod. cure response exc. solv. resist., surface hardness, flexibility, toughness... 

Mesua ferrea L. seed oil-based poly(urethane ester) and poly(urethane amide) resins with an NCO/OH ratio of 0.5 are modified by commercially available bisphenol-A based epoxy resin and partially butylated ME resin... 

Two types of environmentally friendly jute fibre reinforced green composites have been studied. These are based on Mesua ferrea L. seed oil-based poly(urethane ester) and poly(urethane amide) resin blends with commercially available partially butylated melamine-formaldehyde and epoxy resins by solution impregnation and hot-curing methods. The composites were cured at a temperature of about 130-140°C under a pressure of 35.5 kg cm for around 2 h.The physical, mechanical and chemical properties of the epoxy-modified polyurethane composites were better than those of the MF-modified composites. They also possessed excellent chemical resistance and hydrolytic stability in water, acid and salt solutions, making them useful for low load-bearing applications. 

Such multifunctional esters are used to promote the formation of a rigid cross-linked structure on polymerization. Quantitation of these esters is normally based on GC analysis using an internal standard. Either narrow or wide bore capillary columns may be used. In the case of ultraviolet cure-initiated formulations, the use of higher-molecular mass urethane-methacrylate resins such as Scheme 7 is involved. 

Modification of properties in acryUc adhesives is more often conducted at the chemical level, through changes in formulation or combination with other base resins. Wide ranging properties can include impact resistance, surface insensitivity, environmental resistance, etc. The emergence of urethane acrylate adhesives, as well as acrylated epoxies, begins to make simplistic adhesive classifications more challenging. 

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