High-temperature adhesive

Gelva [Solutia], TM for a family of acrylic multipolymer products designed for high-performance, pressure-sensitive adhesive applications where skin adhesion, high temperature and/or diffi-cult-to-adhere-to surface are involved. Provided for both solvent and water based grades. 

HFC. See hydrofluorocarbon, high temperature adhesive. See adhesive, high temperature. 

Adhesives and sealants have become inseparable parts in mechanical and technological devices. Automobiles, airplanes and other transportation media cannot be built without structural adhesives, high-temperature adhesives and various sealants. Many mechanical devices are held together with bolts, nuts, and adhesives. More adhesives are going to replace metallic fasteners. 

In the following sections/ we shall discuss adhesion chemistry/ adhesion physics / radiation-curable adhesiveS/ high-temperature adhesiveS/ anaerobic and structural adhesiveS/ hot-melt adhesives/ film adhesiyes/ waterborne adhesives/ aerospace structural adhesiveS/ conventional sealants/ advanced aerospace sealants/ and adhesives and sealants for solar collectors. 

Further details regarding the advantages and limitations of different adhesives are given in articles already cited and in the articles listed below. Other sources include Refs. [2-4] and works discussed in the Appendix. See also Adhesive classification, Anaerobic adhesives, Cyanoacrylate adhesives. High-temperature adhesives, Rubber-based adhesives. 

New plastics for cases and covers (e.g., modified PPO, polysulfone) New adhesives High-temperature operation better mechanical properties More efficient at high temperatures comply with EPA requirements Higher cost... 

MIL-A-5534 Adhesive high-temperature setting resin (phenol, melamine, and resorcinol base) MlL-C-5339 Cement natural rubber... 

Formed commercially by the polymerization of S, NajCOj and PhX in a sealed container at 275--370 C, substituted derivatives are known but not fully evaluated. Used as high-temperature adhesives, for laminates and in coatings. 

They are used as high-temperature structural adhesives since they become rubbery rather than melt at about 300°C. 

Miscellaneous Applications. Ben2otrifluoride derivatives have been incorporated into polymers for different appHcations. 2,4-Dichloroben2otrifluoride or 2,3,5,6-tetrafluoroben2otrifluoride [651-80-9] have been condensed with bisphenol A [80-05-7] to give ben2otrifluoride aryl ether semipermeable gas membranes (336,337). 3,5-Diaminoben2otrifluoride [368-53-6] and aromatic dianhydrides form polyimide resins for high temperature composites (qv) and adhesives (qv), as well as in the electronics industry (338,339). 

Polyimides (PI) were among the eadiest candidates in the field of thermally stable polymers. In addition to high temperature property retention, these materials also exhibit chemical resistance and relative ease of synthesis and use. This has led to numerous innovations in the chemistry of synthesis and cure mechanisms, stmcture variations, and ultimately products and appHcations. Polyimides (qv) are available as films, fibers, enamels or varnishes, adhesives, matrix resins for composites, and mol ding powders. They are used in numerous commercial and military aircraft as stmctural composites, eg, over a ton of polyimide film is presently used on the NASA shuttle orbiter. Work continues on these materials, including the more recent electronic apphcations. 

Polyphenylquinoxalines (PPQ) are easier to make than the polyquinoxalines and offer superior solubiHty, processibiHty, and thermooxidative stabiHty (65). The PPQs exhibit excellent high temperature adhesive, composite, and film properties. However, to increase the use temperature of PPQs, acetylene... 

PBI is being marketed as a replacement for asbestos and as a high temperature filtration fabric with exceUent textile apparel properties. The synthesis of whoUy aromatic polybenzimidazoles with improved thermal stabUities was reported in 1961 (12). The Non-MetaUic Materials and Manufacturing Technology Division of the U.S. Air Force Materials Laboratory, Wright-Patterson Air Force Base, awarded a contract to the Narmco Research and Development Division of the Whittaker Corp. for development of these materials into high temperature adhesives and laminates. 

A Methylolhydantoins. l,3-Bis(hydroxymethyl)-5,5-dimethyIhydantoia [6440-58-0] is used extensively as a preservative in cosmetic and industrial appHcations, and carries EPA registration for the industrial segment. It is available in soHd and in aqueous solution forms, including low free formaldehyde versions of the latter. A related derivative, l,3-bis(hydroxyethyl)-5,5-dimethyIhydantoia [26850-24-8] is used in the manufacture of high temperature polyesters, polyurethanes, and coatings, offering improved heat resistance, uv stabiUty, flexibiUty, and adhesion. 

Under severe conditions and at high temperatures, noble metal films may fail by oxidation of the substrate base metal through pores in the film. Improved life may be achieved by first imposing a harder noble metal film, eg, rhodium or platinum—iridium, on the substrate metal. For maximum adhesion, the metal of the intermediate film should ahoy both with the substrate metal and the soft noble-metal lubricating film. This sometimes requires more than one intermediate layer. For example, silver does not ahoy to steel and tends to lack adhesion. A flash of hard nickel bonds weh to the steel but the nickel tends to oxidize and should be coated with rhodium before applying shver of 1—5 p.m thickness. This triplex film then provides better adhesion and gready increased corrosion protection. 

Sihcone-based coatings are well suited for high temperature and high speed appHcations. They are flexible, tough, and resistant to thermal and oxidative deterioration. They have good surface resistance and are fungus- and flame resistant. However, they possess a high coefficient of thermal expansion and have poor adhesion. 

Titanium alkoxides are used for the hardening and cross-linking of epoxy, siUcon, urea, melamine, and terephthalate resins in the manufacture of noncorrodable, high temperature lacquers in the sol-gel process as water repellents and adhesive agents (especially with foils) to improve glass surfaces as catalyst in olefin polymeri2ation, and for condensation and esterification. 

Differences among the processes have a major impact on the use of the products. Products from a particular process or manufacturer may dominate one market, while products from a different process may be preferred in a different appHcation. Major uses include hot-melt adhesives for appHcations requiring high temperature performance, additives to improve the processing of plastics, sHp and mb additives for inks and paints, and cosmetic appHcations. 

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