Chemical resistance colorants

In determining the chemical resistance, color changes of pigmented binder surfaces are measured after their exposure to various chemicals, such as water—sulfur dioxide or water—sodium chloride systems. These systems imitate the environment to which the colored articles could become exposed. 

For coatings, common evaluations are in regard to surface quality, chemical resistance, color, and weathering/light stability (discussed below). Gloss and... 

Key properties of alkyds are dimensional stability, colorability, and arc track resistance. Chemical resistance is generally poor. 

With sheet or pipe, multilayer coextmsion can be used. SoHd outer-soHd core coextmsion can place an ABS grade on the outside that has special attributes such as color, dullness, chemical resistance, static dissipation, or fire-retardancy over a core ABS that is less expensive or even regtind. 

Uses. Neopentyl glycol is used extensively as a chemical intermediate in the manufacture of polyester resins (see Alkyd resins), polyurethane polyols (see Urethane polymers), synthetic lubricants, polymeric plasticizers (qv), and other polymers. It imparts a combination of desirable properties to properly formulated esterification products, including low color, good weathering and chemical resistance, and improved thermal and hydrolytic stabiUty. 

Pigments and Extenders. Pigments are selected for use in house paints based on thek appearance and performance quaUties. Appearance includes color and opacifying abiUty. Performance quaUties include ultraviolet light resistance, fade resistance, exterior weatherabiUty, chemical resistance, as well as particle size and shape. Toxicity profiles and safety and health related properties are also important criteria in pigment selection. 

Iron Oxides. In addition to the black iron oxide, there are several natural and synthetic yellow, brown, and red oxides. As a class, they provide inexpensive but dull, lightfast, chemically resistant, and nontoxic colors. The natural products ate known as ocher, sieima, umber, hematite, and limonite. These include varying amounts of several impurities in particular, the umbers contain manganese. Their use is limited because of low chroma, low tinting strength, and poor gloss retention. 

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. 

Solvent-free high-build floor paints are available which can be readily applied with brush, roller or spray to a prepared concrete substrate to give a thickness of 0.10-0.20 mm per coat. Normally, two coats are applied and the first is often lightly dressed with fine sand or carborundum dust to give a non-slip, chemically resistant and durable colored floor, ideal for light industrial traffic conditions (for example, rubber-shod wheels). ... 

Polyester, thermoplastic TP polyesters have different grades. Polybutylene tereph-thalate (PBT) a crystalline polymer and an excellent engineering material. It has marginal chemical resistance but resists moisture, creep, fire, fats, and oils. Molded items are hard, bright colored, and retain their impact strength at temperatures as low as — 40°F (-40°C). Uses include auto louvers, under-the-hood electricals, and mechanical parts. 

Phenolic phenol formaldehydes (PFs) are the low-cost workhorse of the electrical industry (particularly in the past) low creep, excellent dimensional stability, good chemical resistance, good weatherability. Molded black or brown opaque handles for cookware are familiar applications. Also used as a caramel colored impregnating plastics for wood or cloth laminates, and (with reinforcement) for brake linings and many under-the-hood automotive electricals. There are different grades of phenolics that range from very low cost (with low performances) to high cost (with superior performances). The first of the thermosets to be injection-molded (1909). 

Chlorinated polyether is formulated particularly for products requiring, good chemical resistance. Other materials exhibiting good chemical resistance include all of the fluorocarbon plastics, ethylpentenes, polyolefins, certain phenolics, and diallyl phtha-late compounds. Additives such as fillers, plasticizers, stabilizers, colorants, and type catalysts can decrease the chemical resistance of unfilled plastics. Certain chemicals in cosmetics will affect plastics, and tests are necessary in most cases with new formulations. Temperature condition is also very important to include in the evaluation. Careful tests must be made under actual use conditions in final selection studies. 

When the highest resistance to corrosion and solvent fumes is needed, catalyzed paints are the answer. These come in two parts a clear or colored base finish and a catalyst. Since their pot life is limited (typically eight hours), they must be mixed just prior to use. Brochures with information on their chemical resistance can be obtained from companies that sell industrial finishes. Since the resistance to different chemicals varies from brand to brand, a planner should study several types to find one that will best suit the particular application. These finishes are of the high gloss type. For highest chemical resistance to fumes, a coat of clear finish should be applied on top of the colored one. While the vehicle in the finish is very resistant, the pigments may not be and therefore could discolor. 

PP is the lowest density plastic. It has fair-to-good impact strength and excellent colorability. It s translucent in thick sections, and it also has good chemical resistance. The properties can vary widely with different degrees of crystallinity. PP has good resistance to heat and low water absorption. That makes it a suitable material for many medical instruments that need. sterilization by steaming. 

GE introduced, in 2000, a new polyester carbonate based on resorcinol arylates called W-4. It is now marketed as Sollx. Sollx does not need to be painted, it offers good weather, chip, scratch, and chemical resistance and is being used as the fenders for the new Segway Human Transporter. It is also aimed at automotive uses including body panels. Sollx is coextruded into two layers clear and colored, to simulate automotive paint. It is then thermoformed and molded into the finished product. 

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