Loctite anaerobic adhesives

Vernon Krieble, chairman of the Chemistry Department at Trinity College in Hartford, Connecticut, learned about the product through his son, Robert Krieble, who was employed at General Electric. Vernon Krieble found a chemical solution to the problem by using cumene hydroperoxide (I) (see Section XII for all structures) as the initiator and packaging in half-filled oxygen-permeable polyethylene bottles [8]. He licensed the GE patent and in 1954 founded the American Sealants Corporation, which later became Loctite Corporation [9]. At the present time anaerobic adhesives and sealants are manufactured or sold on every continent by more than a dozen companies. Applications in virtually every industry, and technological iimovation, as measured by patent activity, continue unabated. 

The use of monomethacrylates in anaerobic formulations was disclosed in a patent assigned to Loctite. Specifically mentioned were hydroxyethyl (XIX), hydroxypropyl (XX), cyclohexyl (XXI), tetrahydrofurfuryl (XXII), dimethylaminoethyl (XXIII), and glycidyl methacrylates (XXIV), and cyanoethyl acrylate [26]. Methacrylate esters containing residual carboxylic add groups were prepared by the reaction of hydroxyethyl methacrylate with phthalic anhydride (XXV), pyromellitic dianhydride (XXVI), and benzophenonetetracarboxylic add dianhydride (XXVII). The residual acid provided improved adhesion [27,28]. The reaction product of hydroxyalkylmethacrylates with maleic anhydride (XXVIII) also produced monomers with residual acid as well as additional curable unsaturation [29]. The dimethacrylates of the bisglycol esters of dicarboxylic adds were used to formulate anaerobic adhesives. Among the dicarboxylic acids mentioned were phthalic (XXIX), maleic (XXX), fumaric (XXXI), and malonic (XXXII) [30]. 

Humphreys, of the Loctite Corporation, reported on the chemistry of accelerators for curing anaerobic adhesives. He showed that the reaction between N,N-dimethylaniline derivatives and cumene hydroperoxide is relatively slow even at lOO C. He concluded that the accelerated polymerization of anaerobic adhesives of ambient temperatures caused by cure systems containing combinations of tertiary aromatic amines, hydroperoxides, and sulfonimides does not result from the hydroperoxide-amine reaction. 

Robert W, R. Humphreys received his B,Sc, andPh.D. in Photochemistry and ESR Spectroscopy with Professor Donald R. Arnold at the University of Western Ontario. After 1 1/2 years postdoctoral work with Professor Cheves Walling at the University of Utah, he worked as a Research Chemist at Loctite Corporation in anaerobic adhesives chemistry. He recently joined Lever Research, Inc. as a Research Scientist. His current research interests include free radical and peroxide chemistry and metal catalyzed redox reactions. 

Synonyms oxybis(2,i-ethanediyloxy-2,i-ethanediyl)ester 2-methyl-2-propenoic acid oxybis(2,i-ethanediyloxy-2,i-ethanediyl) ester Uses methacrylate present in adhesives in polyethyleneglycol dimethacrylate in Loctite anaerobic sealants A... 

In a compilation of adhesives commercially available in the U.S., eight companies are listed as suppliers of anaerobic adhesives Devcon, Pel Pro, Loctite, Master Bond, Permabond, SPS Technologies, Sumitomo Chem Co., and Three Bond. This section contains a description of anaerobic products and their cured properties. 

Anaerobic adhesive compositions are blends of dimethacrylates or diacrylates with hydroperoxides and other ingredients. They are stable in the presence of air but polymerize when oxygen is excluded. This characteristic has made them popular for the locking of nuts and bolts in automotive and other product assembly. Originally developed at General Electric Co. [180], they were commercialized by Loctite Corp. [181]. Products with trade names Anaterm, Unigerm, and VAK were commercialized in Russia. 

Silicone methacrylates have been formulated into anaerobic adhesives by Dow Coming [156], Toshiba Silicones [157], and Loctite [158], [159]. 

One indication of the relatively innocuous nature of anaerobic adhesives is the fact that products such as Loctite Pipe Sealants 567 and 592 have been recognized by the U.S. Department of Agriculture as being chemically acceptable for use on meat or poultry processing machinery. Primers normally contain volatile solvents and should be used only in well ventilated environments. 

Anaerobic adhesives are derived from methacrylates, a monomer related to acrylic, or more commonly known as Plexiglas. The word anaerobic really applies to microbes that become active or live in the absence of oxygen. Although anaerobic sealants do not contain microbes, they become active and cure or polymerize in the absence of oxygen. These adhesives were developed by Professor Vernon Krieble, the founder of American Sealants Company, now known as Loctite Corporation. 

Malofsky and Baccei, from the Loctite Corporation, report on the significant mechanical property improvements obtained with maleimide and nadic capped monomers and prepolymers as additives in anaerobic methacrylate/ acrylate adhesive systems. Significant improvement in thermal resistance was noted in a PEGMA (polyethyleneglycol diroethacrylate) system in which a polymerizable maleimide addition was incorporated. A "neat" polymerized urethane methacrylate failed catastrophically within 1000 hrs. at... 

Adhesives recommended by the manufacturer (Phillips Chemical Company) include anaerobics (Loctite 306), liquid two-part epoxies (Hughson s Chemlok 305), and a two-part paste epoxy (Emerson Cuming s Eccobond 104). Also recommended are USM s BOSTIK 7087 two-part epoxy and 3M Company s liquid two-part polyurethane EC-3532. ° ... 

SpeedBonder, Anaerobic structural adhesive, Loctite Corp., North American Group Speedryer, Thermodynamic hopper dryer, Webb... 

Epoxy adhesives such as Huntman s Araldite AW 134 with HY 994 hardener (cured for 15 min at 120°C) and Araldite AV 1566 GB (cured for 1 h at 230°C) give the best results with this engineering resin. Other adhesives that can be used are cyanoacrylate (Loctite 414 with AC primer), anaerobics (Loctite 638 with N primer), and silicone sealant (Loctite Superflex). The highest lap-shear strength was obtained with Araldite AW 134. This adhesive has balanced properties, good resistance to mechanical shock, thermal resistance to 100°C, and reasonable stability in the presence of aliphatic and aromatic solvents. Some solvents, particularly chlorinated hydrocarbons, will cause deterioration of the bond [30]. 

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