Anaerobic adhesives/sealants

Their work on adhesives was not a major effort. Some anaerobic adhesives were developed by the Institute, and later produced by the Oriental Scientific Instruments Import Export Corporation in Guangzhou. Two of the series are GY-340 anaerobic adhesive-sealant and GY-168 anaerobic flexible sealant. Both have a polyacrylate-base, with a shelf-life of one year. The curetime for GY-340 was 2 to 6 hours at room temperature the curetime for GY-168 was 12 to 24 hours. 

Perma-Lok, Anaerobic adhesives/sealants, Permabond, Div. National Starch Chem. Co. 

The most important application of anaerobic adhesives/sealants is as liquid lock washers for screws and bolts. Because of their strong penetrating ability, they can be applied either before or after assembly. The prevailing torque for the strongest grades is many... 

There are altogether at least thirteen different ways in which anaerobic adhesives, sealants and gasketing compounds may be used. The more important applications are discussed below. 

Polyester resins and anaerobic adhesives and sealants have also exhibited high radiation resistance. Anaerobic adhesives have several years of long-term exposure in radiation environments due to their use as thread locking sealants in nuclear reactors and accessory equipment. 

Cyiiniock. [Hemon Mfg.] Retaining and mounting anaerobic adhesives and sealants. 

Ageflex THFMA AI3-08497 EINECS 219-529-5 HSDB 5461 Methacrylic acid tetrahydrofurfuryl ester NSC 32634 2-Propenoic acid, 2-methyl-, (tetrahydro-2-furanyl)methyl ester Sartomer SR 203 SR 203 Tetrahydrofurfuryl methacrylate THFMA. Used to produce anaerobic adhesives and sealants, printed circuit boards, artificial finger nails, modifier for hard rubber rolls, wire and cable... 

Vernon Krieble, then a professor at Trinity College in Hartford, Connecticut. Their first use was as threadlocking sealants, to lock nuts on threaded fasteners as a replacement for metal lock washers, and to lock threaded fasteners in tapped holes in metal parts. They were the first products termed sealants to have a viscosity lower than that of water. Today, such anaerobic adhesives and sealants are used in almost all mechanical equipment that is subject to vibration. 

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. 

Anaerobic adhesives and sealants have been developed primarily in industrial laboratories, and most of the published literature are patents. A number of papers have been published within the last two decades which discuss the reaction mechanisms of anaerobic adhesive cure [10-20]. 

Methacrylate esters have been prepared by the reaction of methacrylic acid with epoxies such as the diglycidyl ethers of bisphenol A (XXXVII) [37]. Methacrylate esters suitable for anaerobic adhesives have also been prepared by the reaction of glycidyl methacrylate (XXXVIII) with a hydroxyl-terminated polyester [38]. The reaction of isocyanatoethyl methacrylate (XXXIX) with polyols resulted in monomers that could be formulated into anaerobic adhesives and sealants [39]. 

The monomers used in anaerobic adhesives and sealants generally contain at least one free-radical stabilizer, such as hydroquinone or />-methoxyphenol. It was found that ben-zoquinone, naphthoquinone, and similar compounds provided improved shelf stability without retarding the anaerobic cure [56]. It was also found that anaerobic formulations could be stabilized with a stable nitroxide free radical such as di-/-butyl nitroxide (LIV) [57]. The use of a soluble metal chelating agent such as tetrasodium EDTA (V) was found to be an effective method of stabilizing an anaerobic formulation against small amounts of metal contamination [58]. 

The wide variety of applications of anaerobic adhesives and sealants is made possible by the modifications that make the viscosity appropriate to the application. An application that requires penetration into close-fitting parts should have very low viscosity, while a produet used with large, loose-fitting parts should have a high viscosity. A styrene aerylate eopolymer could be used to increase the viscosity [59]. Polymethacrylates, eellulose esters, butadiene-styrene eopolymers, acrylonitrile-butadiene-styrene copolymers, poly(vinyl ehloride), copolymers of vinyl chloride and vinyl acetate, poly(vinyl aeetate), eellulose ethers, polyesters, polyurethanes, and other thermoplastic resins have also been used to eontrol the flow eharacteristics of anaerobic sealants [60]. The flow eharaeteristies of anaerobic formulations can also be controlled by the addition of fumed siliea and other solid additives whieh can impart thixotropic properties [61]. 

Many anaerobie adhesives and sealants may require a relatively low strength so that the eomponents can be disassembled for repair or replacement. Many liquid plasticizers have been used for this purpose [62], but the use of a low-molecular-weight polyester has been found to be advantageous [63]. The toughness properties of anaerobic adhesives can be enhanced by the addition of a reactive elastomer [64]. The heat resistance of anaerobic adhesives and sealants can be enhanced by the addition of a bismaleimide... 

The addition of dyes to anaerobic adhesives and sealants assists in identification and inspection of the products. Automated inspection procedures are made possible with dyes that fluoresce under ultraviolet light. Titanium dioxide pigments can make the sealants more visible. 

Solid fillers are added to some anaerobic adhesives and sealants for various purposes. Mica, talc, and other mineral fillers can help to provide an instant seal capability to anaerobic pipe sealants. The sensitivity of the anaerobic cure system to metal contamination requires that these fillers be chosen very carefully. 

In Germany, standards have been published describing the Compression Shear Test (DIN 54452), Dynamic Viscosity Determination of Anaerobic Adhesives by Rotational Viscometer (DIN 54453), Initial Breakaway Test at Bonded Threads (DIN 54454), and Torsion Shear Test (DIN 54455). DIN 54455 is particularly interesting since it is one of a very few tests in which a nut and bolt (MIO) are seated to a measured torque before the anaerobic sealant is allowed to cure. 

The International Organization for Standardization (ISO) has finalized an International Standard (ISO/DIS 10964 1993) Adhesives Anaerobic Adhesives— Determination of Torque Strength of Anaerobic Adhesives on Threaded Fasteners. This standard describes testing procedures for liquid and preapplied sealants using manual and graphical procedures. 

Acrylics (cyanoacrylates anaerobic, by heating or UV-irradiation cross-linking acrylates) for mounting adhesives, sealants, and for adhesive tapes [2,3]... 

Uses Monomer in anaerobic adhesives and sealants, concrete/dental polymers, photopolymers/resists, inks, glass, reinforced plastics, plasli-sols, and surf, coatings where low shrinkage contributes to adhesion Properties Pt-Co 150 max. clear color m.w. 456 vise. 1100-1800 mPa-s-sapon. no. 230-250 0.2% max. water Toxicology TSCA listed... 

CAS 109-16-0 EINECS/ELINCS 203-652-6 Uses Adduct monomer for preparation of anaerobic adhesives and sealants, castings, plastisols, coatings, fibers, cast acrylic sheets, elec, photoresists, rubber prods., dental resins, overprint varnishes, and flexographic printing plates crosslinks and copolymerizes with other vinyl monomers imparting solv. resist., heat resist., and hardness Properties Pt-Co 100 max. clear liq. m.w. 286 vise. 10 mPa-s flash pt. 

Uses Acrylic resin comonomer anaerobic adhesives and sealants printed circuit boards cosmetics artificial finger nails modifier for hard rubber rolls wire and cable coatings screen printing inks emulsion polymerization plastic modifier EB-curable coatings reactive diluent for hot-melt prepregs and adhesives... 

Properties M.w. 170.21 dens. 1.044 b.p. 52 C (0.4 mm) flash pt. 90 C ref. index 1.4580 Uses Acrylic resin comonomer anaerobic adhesives and sealants printed circuit boards cosmetics artificial finger nails modifier for hard rubber rolls wire and cable coatings screen printing inks emulsion polymerization plastic modifier EB-curable coatings reactive diluent for hot-melt prepregs and adhesives Manuf./Distrib. Aldrich http //www.sigma-aldrich.com, CPS Monomer-Polymer 8i Dajac Labs Polysciences... 

Toluene-2,4-diisocyanate adhesive/sealant, anaerobic Tetrahydrofurfuryl methacrylate adhesive/stiffener, surgical dressings Dextrin... 

Adhesives and sealants are manufactured from a variety of polymers. Their selection and their combinations used impact solvent selection. Most solvent systems are designed to optimize the solubility of the primary polymer. Adhesives can be divided into ones which bond by chemical reaction and ones which bond due to physical processes. Chemically reactive adhesives are further divided into three more categories for those that bond through polymerization, polyaddition, or polycondensation. Physically bonding adhesives include pressure sensitive and contact adhesives, melt, or solution adhesives, and plastisols. Polymerization adhesives are composed of cyanoacrylates (no solvents), anaerobic adhesives (do not contain solvents but require primers for plastics and some metals which are solutions of copper naphthenate), UV-curable adhesives (solvent-free compositions of polyurethanes and epoxy), rubber modified adhesives (variety solvents discussed below). 

In this Institute, there are approximately 200 research personnel and one fourth of them are working on adhesives in two laboratories, one pilot-plant, one testing group and one adhesive-film manufacturing and testing facility. Their research and development broadly covered structural adhesives, strain gauge adhesives, wood adhesives, second-generation acrylics, anaerobic adhesives and composite binders. Their products varied from J-01 to J-53. There were at least thirty different kinds of adhesive and sealant, for example, nitrile-phenolics, modified epoxies, acrylics and epoxy-phenolics. 

The use of adhesives/sealants in both the industrial and consumer spheres has increased dramatically in the past 20 years. In the industrial segment, both reactive and nonreactive systems are used in a wide variety of applications. The increasing use of reactive systems has, however, tended to overshadow that of the nonreactive systems. Most prominent amongst the reactive systems favored in industrial applications are anaerobic sealants (methacrylate ester based), instant adhesives (alkyl cyanoacrylate ester based), acrylic (toughened) adhesives, epoxy resin adhesives, polyurethane/isocyanate-based adhesives, silicone adhesives/sealants, and phenolic resin adhesives. 

Anaerobic adhesives and sealants are based on acrylic (usually meth cryXic) functional monomers and cure by a redox-initiated free radical polymerization (see Chain polymerization). They are so named because of the characteristic of requiring a relatively air-free condition to allow curing. Hence, anaerobic adhesives are very suitable for the bonding and sealing of close-fitting metal components. 

In the Automotive industry there is a trend towards complete automation of production lines. In the application of adhesives/sealants for gasketing, the principles of dispensing have normally been to use a pressure-time system, or alternatively a cartridge system with a robotic head. However, a faster system is to screen print an anaerobic on to the surface of a component. 

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