Resist adherence

Features Weather resist. adheres to all dean metal surfs. quick drying Properties Liq. 

Sheet aluminium can be given a colour by a similar process. The aluminium is first made the anode in a bath of chromic acid (p. 377) when, instead of oxygen being evolved, the aluminium becomes coated with a very adherent film of aluminium oxide which is very adsorbent. If a dye is added to the bath the oxide film is coloured, this colour being incorporated in a film which also makes the remaining aluminium resistant to corrosion. This process is called anodising aluminium. 

Adhesives. Acryhc emulsion and solution polymers form the basis of a variety of adhesive types. The principal use is in pressure-sensitive adhesives, where a film of a very low T (<—20 " C) acrylic polymer or copolymer is used on the adherent side of tapes, decals, and labels. Acrylics provide a good balance of tack and bond strength with exceptional color stabiUty and resistance to aging (201,202). AcryUcs also find use in numerous types of constmction adhesive formulations and as film-to-film laminating adhesives (qv). 

Reactions With Metals. AH metals react to some extent with the halogen fluorides, although several react only superficiaHy to form an adherent fluoride film of low permeabHity that serves as protection against further reaction. This protective capacity is lost at elevated temperatures, however. Hence, each metal has a temperature above which it continues to react. Mild steel reacts rapidly above 250°C. Copper and nickel lose the abHity to resist reaction above 400 and 750°C, respectively. 

Surface Fluorination of Polymers. Fluorocarbon-coated objects have many practical appHcations because the chemically adherent surface provides increased thermal stabiHty, resistance to oxidation and corrosive chemicals and solvents, decreased coefficient of friction and thus decreased wear, and decreased permeabiHty to gas flow. Unusual surface effects can be obtained by fluorinating the polymer surfaces only partially (74). 

It is difficult to process HPPE staple fibers mechanically because of so-called married fibers which are bundles of 4—6 fibers that firmly adhere to each other and resist separation by conventional processing. Although HPPE fibers like to adhere to each other, they exhibit poor adhesion to other materials. 

Industrial materials without sufficient scaling resistance frequendy fail after a short period of time as a result of rapid oxidation or hot corrosion, in conjunction with severe spalling owing to poor adherence of the scale to the metallic component. As a result, the permissible limits of metal loss often are exceeded and expensive, and premature replacement of parts is requited. Extensive efforts are made to develop alloys which are not simply strong at elevated temperatures but which also possess the adequate surface stabiUty. 

Lea.dAnodes. A principal use for lead—calcium—tin alloys is lead anodes for electrowinning. The lead—calcium anodes form a hard, adherent lead dioxide layer during use, resist corrosion, and gready reduce lead contamination of the cathode. Anodes produced from cast lead—calcium (0.03—0.09 wt %) alloys have a tendency to warp owing to low mechanical strength and casting defects. 

In a reducing atmosphere, molybdenum is resistant at elevated temperatures to hydrogen sulfide, which forms a thin adherent sulfide coating. In an... 

Aluminum and aluminum alloys are employed in many appHcations because of the abiHty to resist corrosion. Corrosion resistance is attributable to the tightly adherent, protective oxide film present on the surface of the products. This film is 5 —10 nm thick when formed in air if dismpted it begins to form immediately in most environments. The weathering characteristics of several common aluminum alloy sheet products used for architectural appHcations are shown in Eigure 30. The loss in strength as a result of atmospheric weathering and corrosion is small, and the rate decreases with time. The amount of... 

Fully Adhered. The substrate, ie, insulation, cover board, etc, that the single-ply membrane is to be attached to is either fuUy adhered or mechanically fastened to the deck. However, there are also appHcations where the membrane is adhered directly to the deck. The membrane is then adhered to the substrate. The typical method for adhering the membrane to the substrate is by applying a contact adhesive to the membrane and substrate, rolling the membrane into place, and brooming once the adhesive is ready. There are one-sided appHcations where the membrane is roUed directly into the adhesive that has been appHed to the substrate only. The membrane used in this appHcation method may be fleece-backed. FuUy adhered systems can be installed on any slope. The fuUy adhered appHcation offers a smooth surface that is easy to maintain and inspect, as weU as exceUent wind resistance on account of positive attachment. 

The prime installation method is mechanically fastened but fully adhered and ballasted appHcations can also be used. CSPE exhibits strong resistance not only to weathering but also to a broad range of chemicals and pollutants it is also inherently ozone-resistant. It can be produced in many colors and the sheet widths are typically 5—6.5 ft (1.5—1.65 m). The physical characteristics of a CSPE sheet have been described (17) (see Elastomers, SYNTHETIC-Cm OROSULFONATED POLYETHYLENE). 

CPA. Copolymer alloy membranes (CPAs) are made by alloying high molecular weight polymeries, plasticizers, special stabilizers, biocides, and antioxidants with poly(vinyl chloride) (PVC). The membrane is typically reinforced with polyester and comes in finished thicknesses of 0.75—1.5 mm and widths of 1.5—1.8 m. The primary installation method is mechanically fastened, but some fully adhered systems are also possible. The CPA membranes can exhibit long-term flexibiHty by alleviating migration of the polymeric plasticizers, and are chemically resistant and compatible with many oils and greases, animal fats, asphalt, and coal-tar pitch. The physical characteristics of a CPA membrane have been described (15). 

The greater portion of PVC is installed in the mechanically fastened roofing system a lesser portion is installed in fully adhered appHcations. Although PVC was once heavily used in ballasted roofing systems, there are only a small number installed in the 1990s. Fleece-back membrane is popular in the PVC constmction for both fully adhered appHcations as well as in appHcations where a separator sheet is needed. PVCs ate resistant to vafious weather conditions, bactefial growth, and industfial chemicals. These membranes ate chemically incompatible with bituminous materials. PVCs ate offered in a variety of colors. The physical characteristics of a PVC membrane have been described (15). 

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