Low-temperatures adhesive

Rather, microcrystalline waxes are used to provide adhesives with longer open times and better low temperature adhesion, due to better wet out, and toughness. 

Specialty waxes include polar waxes for more polar adhesive systems. Examples would be castor wax (triglyceride of 12-hydroxy stearic acid) or Paracin wax N- 2 hydroxy ethyl)-12-hydroxy stearamide) which are used in polyester, polyamide, or with high VA EVA copolymer-based systems. Other common polar waxes are maleated polyethylenes, which are used to improve the specific adhesion of polyethylene-based adhesives, and low molecular weight ethylene copolymers with vinyl acetate or acrylic acid, which are used to improve low temperature adhesion. High melting point isotactic polypropylene wax (7 155°C) and highly refined paraffin wax (7,n 83°C) are used where maximum heat resistance is critical. Needless to say, these specialty waxes also command a premium price, ranging from 2 to 5 times that of conventional paraffin wax. 

Miska, K. H., Which Low Temperature Adhesive Is Best for You Materials Engineering, May 1975. 

Low acrylonitrile) Gaskets, grommets, and O-rings (flexible at a very low temperature), adhesives. Fuel binder in solid rocket propellants. 

For aerospace adhesives and sealants, we need to consider not only extremely high temperatures, but also extremely low temperatures. Adhesives for cryogenic engines should maintain their mechanical performances between -184° and -196°C (-300° to -320°P), but this seems to be beyond the limits of polymer capability. To meet this need, an experimental composite or a blend of adhesives in a multilayer form has been developed. Some work has been carried out at Hughes Aircraft, McDonnell Douglas, or NASA-Lewis, but is not very well known to the public. 

Future research on intermediate low-temperature adhesives can be pursued along the following lines ... 

They have made contributions on fluoropolymers especially on high-temperature and low-temperature adhesives and elastomers. One interesting copolymer is ethylene and tetrafluoroethylene (1 1), which is emulsion polymerized in the presence of a persulfate catalyst. This copolymer, unlike PTPE, is radiation-resistant. Another fluoropolymer project is the copolymerization between tetrafluoroethylene and hexafluoropropene. One high-... 

Kausen, R.C., High- and low-temperature adhesives— where do we stand ... 

Use and storage at high humidity where condensation occurs Use and storage at high humidity where condensation occurs Use and storage at low temperature, adhesion of plating and coatings, physical distortion... 

The low temperature adhesive properties, as well as the impact properties at -320°F for molded PBI in TABLE IV are noteworthy. GiIlham s Torsional Braid Analysis observed a low temperature dampening maximum which indicates that relaxation mechanisms are available to dissipate energy [17]. 

Plasticizers are generally liquid substances of low molecular mass (some 10 to a few 10 ) that lower the Tg of the adhesive. Thus, they often reduce peel adhesion at ambient temperature but increase low-temperature adhesion. They increase tack and creep of the adhesive. 

In summary, it would seem that the best low-temperature adhesive, among those tested here, would consist of epoxy or epoxy-phenolic resins supported on a glass cloth film and filled with metallic dust to a degree necessary to approach the thermal expansion of the adherend. 

Stone, M. H. (1980) Strengths of metal-carbon fibre composite adhesives joints at low temperatures, Adhesion and Adhesives Science, Technology and Applications, Plastics and Rubber Inst. Conf. Durham, Paper 10. 

In general, most labels are applied using pressure-sensitive adhesives formulated with water-borne acrylic adhesives, solvent-borne adhesives, or hot-melt adhesives. The adhesives used for these labels can also be formulated for variable adhesion performance, such as instant permanence, repositionability, peelability (removability), low temperature adhesion, high tack for rough surfaces, UV resistance, or plasticizer migration resistance. The adhesive s performance is linked to the base carrier material upon which it is applied. 

Kausen RC. High- and low-temperature adhesives—where do we stand Proceedings of the Seventh National SAMPE Symposium on Adhesives and Elastomers for Environmental Extremes, Section 1, Los Angeles, CA May 20—22, 1964. 

Its advantages include impermeability to air, excellent adhesion to metal, and good resistance to oils, weathering, and low temperature. 

The physical properties of polyurethane adhesives result from a special form of phase separation which occurs in the cross-linked polyurethane stmcture. The urethane portions of polyurethanes tend to separate from the polyol portion of the resin, providing good shear strength, good low temperature flexibiUty, and high peel strength. Catalysts such as dibutyltin dilaurate [77-58-7], stannous octoate [1912-83-0], l,4-diazabicyclo[2.2.2]octane... 

Polyimides of 6FDA and aUphatic diamines with good low temperature processkig and low moisture swelling are known to be useful as hot-melt adhesives (109). Aluminum strips bonded by this polymer (177°C/172 kPa (25 psi) for 15 min) exhibited a lap-shear strength of 53 MPa (7690 psi) at room temperature and 35 MPa (5090 psi) at 100°C. The heat- and moisture-resistant 6F-containing Pis useful ki electronic devices are prepared from... 

Butyl mbber, a copolymer of isobutjiene with 0.5—2.5% isoprene to make vulcanization possible, is the most important commercial polymer made by cationic polymerization (see Elastomers, synthetic-butyl rubber). The polymerization is initiated by water in conjunction with AlCl and carried out at low temperature (—90 to —100° C) to prevent chain transfer that limits the molecular weight (1). Another important commercial appHcation of cationic polymerization is the manufacture of polybutenes, low molecular weight copolymers of isobutylene and a smaller amount of other butenes (1) used in adhesives, sealants, lubricants, viscosity improvers, etc. 

In the case of low temperature tar, the aqueous Hquor that accompanies the cmde tar contains between 1 and 1.5% by weight of soluble tar acids, eg, phenol, cresols, and dihydroxybenzenes. Both for the sake of economics and effluent purification, it is necessary to recover these, usually by the Lurgi Phenosolvan process based on the selective extraction of the tar acids with butyl or isobutyl acetate. The recovered phenols are separated by fractional distillation into monohydroxybenzenes, mainly phenol and cresols, and dihydroxybenzenes, mainly (9-dihydroxybenzene (catechol), methyl (9-dihydtoxybenzene, (methyl catechol), and y -dihydroxybenzene (resorcinol). The monohydric phenol fraction is added to the cmde tar acids extracted from the tar for further refining, whereas the dihydric phenol fraction is incorporated in wood-preservation creosote or sold to adhesive manufacturers. Naphthalene Oils. Naphthalene is the principal component of coke-oven tats and the only component that can be concentrated to a reasonably high content on primary distillation. Naphthalene oils from coke-oven tars distilled in a modem pipe stiU generally contain 60—65% of naphthalene. They are further upgraded by a number of methods. 

Bond and Adhesion (ASTM D1191). This test, designed for use on crack and joint sealers, is used primarily to determine whether a jointing material possesses an arbitrary amount of bonding strength at low temperatures where pordand cement concrete is being used. 

Wear. Eor a fixed amount of braking the amount of wear of automotive friction materials tends to remain fairly constant or increase slightly with respect to brake temperature, but once the brake rotor temperature reaches >200° C, the wear of resin-bonded materials increases exponentially with increasing temperature (26—29). This exponential wear is because of thermal degradation of organic components and other chemical changes. At low temperatures the practically constant wear rate is primarily controlled by abrasion, adhesion, and fatigue (30,31). 

Plasticizers and Processing Aids. Petroleum-based oils are commonly used as plasticizers. Compound viscosity is reduced, and mixing, processing, and low temperature properties are improved. Air permeabihty is increased by adding extender oils. Plasticizers are selected for their compatibihty and low temperature properties. Butyl mbber has a solubihty parameter of ca 15.3 (f /cm ) [7.5 (cal/cm ) ], similar to paraffinic and naphthenic oils. Polybutenes, paraffin waxes, and low mol wt polyethylene can also be used as plasticizers (qv). Alkyl adipates and sebacates reduce the glass-transition temperature and improve low temperature properties. Process aids, eg, mineral mbber and Stmktol 40 ms, improve filler dispersion and cured adhesion to high unsaturated mbber substrates. 

This low viscosity resin permits cure at low (70°C) temperatures and rapidly develops excellent elevated temperature properties. Used to increase heat resistance and cure speed of bisphenol A epoxy resins, it has utihty in such diverse appHcations as adhesives, tooling compounds, and laminating systems. A moleculady distilled version is used as a binder for soHd propellants (see Explosives and propellants) and for military flares (see Pyrotechnics). Its chief uses depend on properties of low viscosity and low temperature reactivity, particularly with carboxy-terminated mbbers. 

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