Enamel properties

An apparatus for testing enamel with acid and alkaline liquids (and their vapours) was later proposed in an attempt to standardise corrosion ratings on an international basis. After surveying enamel properties and their relationship with resistance to liquids of different pH values, the concept of modifying the resistance by including specific elements in the glass structure has been outlined. ... 

All enamels had excellent adhesion, solvent resistance, and flexibility. Enamels made from LC diols Ib-lg were far superior to those made from control diols 2a-2g and 3a-3g in both hardness (5H-6H vs. H-2H 5H corresponded to about 20 KHN on a Tukon tester) and impact resistance (50 to >80 in-lb vs. 8 to 15 in-lb). Odd spacers lb and Id afforded the best properties in these formulations. Spacer variations did not measurably affect enamel properties in the control oligoesters. 

Table III. Enamel Properties with Varying HMMM...

Crosslinked Enamels. Properties of enamels made from LC diols optimized with slight variations in HMMM concentration gave 5H hardness (20 KHN Tukon tester) and >80 in-lb. impact resistance. The best properties obtainable for enamels made from non-LC diols were 2H hardness and 45 in-lb. impact resistance. 

Enamel Properties. Clear coatings were formed by crosslinking the PHBA-modified oligomers with a standard melamine resin. Baking at 175° was necessary to obtain optimal properties. The cured films were glossy and nearly transparent except for films made from 60/40 PHBA ratio polyol. Adhesion was excellent. 

Chem. Descrip. Linear sat. polyester resin Uses Polyester for corrosion-resist, primers and stamping enamels Properties Dens. 1.25 g/cm acid no. < 3 hyd. no. 7 100% soiids Dynapoi L 206 [Degussa AG/Coatings Coiorants]... 

Chem. Descrip. Epoxy resin sol n. (75% solids in 2-propoxyethanol) Uses Epoxy for RT-curing industrial maintenance coatings incl. clears, primers, masonry surfacers, and gloss and semigloss enamels Properties Gardner 5 max. color dens. 9.3 Ib/gal G-H vise. Z6 Seta flash pt. 132 F 75% NV EPON Resin 1002F [Resolution Perf. Prods.)... 

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. 

The main use of lead metaborate is in glazes on pottery, porcelain, and chinaware, as weU as in enamels for cast iron. Other appHcations include as radiation-shielding plastics, as a gelatinous thermal insulator containing asbestos fibers for neutron shielding, and as an additive to improve the properties of semiconducting materials used in thermistors (137). 

Du Pont produces this polymer under the trade names of Kapton, Pyrafin, Vespel, and Pyre-ML. The trade names refer to polyimides used for film, semiconductor coatings, mol ding applications, and wire enamel, respectively. They have exceUent thermal, electrical, and physical properties. 

Barium nitrate is prepared by reaction of BaCO and nitric acid, filtration and evaporative crystallization, or by dissolving sodium nitrate in a saturated solution of barium chloride, with subsequent precipitation of barium nitrate. The precipitate is centrifuged, washed, and dried. Barium nitrate is used in pyrotechnic green flares, tracer buUets, primers, and in detonators. These make use of its property of easy decomposition as well as its characteristic green flame. A small amount is used as a source of barium oxide in enamels. 

Dental abrasives range in fineness from those that do not damage tooth stmcture to those that cut tooth enamel. Abrasive particles should be irregular and jagged so that they always present a sharp edge, and should be harder than the material abraded. Another property of an abrasive is its impact strength, ie, if the particle shatters on impact it is ineffective if it never fractures, the edge becomes dull. Other desirable characteristics include the abiUty to resist wear and solvation. 

For conventional wet processing of sheet steel, the porcelain enamel frit is ball-milled using clay, certain electrolytes, and water to form a stable suspension. This clay-supported slurry of small particles is called the sHp and has the consistency of a heavy cream. The ingredients of the mill batch are carefully controlled. The amount and purity of all materials in the mill, including the clay and water, affect the rheological character of the sHp as well as a number of the properties of the fined enamel such as chemical resistance, reflectance, gloss, color, and abrasion resistance. 

Porcelain enamels meet a variety of performance characteristics required for different appHcations. The common characteristics of all enamels include good adherence to the substrate and good thermal expansion fit to the metal. Specific properties depend on usage for example, acid and alkaH resistance, hot water resistance, abrasion resistance, thermal shock resistance, high gloss, high reflectance, specific color, heat resistance, and cleanabihty. 

---