Abrasive stability

Resistance to creep/stretch Stability of edges Resistance to abrasion Stability to vibration Dimensions of available supplies Ability to be fabricated Sealing/gasketing function... 

As Fig. 188 shows, antiaging agents exert a substantial influence on the abrasion stability of tread rubbers made from natural rubber, both in air and in nitrogen. The most effective combinations of antiaging agents proved to be santoflex AW, neozone D +4010, and neozone D +flectol N. 

Several ceramic cutting materials are compared, on the basis of the resistance they show against abrasive wear, in Figure 7.10. The Wooddell abrasion hardness measures the amount of work required to break down a unit volume of material. The data in Figure 7.10 indicate that, although alumina is certainly not the ceramic material of choice in terms of its abrasive stability, for economic reasons it remains a strong contender for the cutting tool market... 

As has already been mentioned, a further major disadvantage of wet-chemical finishes is the potentially doubtful long-term wash or abrasion stability. This is an issue especially for technical textiles, which may be subjected to mechanical, thermal, or chemical stress from natural or industrial... 

Figure 4.8.5 Histogram of abrasive stability of samples ( ) steel 45, (2) M02C electroplate [5], (3) W2C electroplate, and (4) ZrB2 electroplate...

Nitrile mbber finds broad application in industry because of its excellent resistance to oil and chemicals, its good flexibility at low temperatures, high abrasion and heat resistance (up to 120°C), and good mechanical properties. Nitrile mbber consists of butadiene—acrylonitrile copolymers with an acrylonitrile content ranging from 15 to 45% (see Elastomers, SYNTHETIC, NITRILE RUBBER). In addition to the traditional applications of nitrile mbber for hoses, gaskets, seals, and oil well equipment, new applications have emerged with the development of nitrile mbber blends with poly(vinyl chloride) (PVC). These blends combine the chemical resistance and low temperature flexibility characteristics of nitrile mbber with the stability and ozone resistance of PVC. This has greatly expanded the use of nitrile mbber in outdoor applications for hoses, belts, and cable jackets, where ozone resistance is necessary. 

Metal poHshes may contain emulsifiers and thickeners for controlling the consistency and stabilization of abrasive suspensions, and the product form can be soHd, paste, or Hquid. Liquid and paste products can be solvent or emulsion types the market for the latter is growing. Formulas for metal poHshes are Hsted ia Reference 12. A representative Hquid emulsion product may contain 8—25 wt % abrasive, 2—6 wt % surfactant, 0—5 wt % chelating agents, and 0—25 wt % solvent, with the remainder being water. The abrasive content ia an emulsion paste product is greater than that ia a solvent product. 

Plasma processing technologies ate used for surface treatments and coatings for plastics, elastomers, glasses, metals, ceramics, etc. Such treatments provide better wear characteristics, thermal stability, color, controlled electrical properties, lubricity, abrasion resistance, barrier properties, adhesion promotion, wettability, blood compatibility, and controlled light transmissivity. 

Such polyurethanes have excellent hydrolytic stability compared to water-reducible polyesters and superior abrasion resistance. In view of the importance of developing low solvent emission coatings, considerable effort is being devoted to new types of water-borne urethane resins (62,63). 

Resins are also used for permanent tooth-colored veneers on fixed prostheses, ie, crown and bridges. Compositions for this application include acryflcs, vinyl—acryflcs, and dimethacrylates, as well as silica- or quartz-microfilled composites. The resins are placed on the metallic substrates of the prostheses and cured by heat or light. These resins are inexpensive, easy to fabricate, and can be matched to the color of tooth stmcture. Acrylic facings do not chemically adhere to the metals and are retained only by curing the resin into mechanical undercuts designed into the metal substrate. They have relatively low mechanical strength and color stability, and poor abrasion and strain resistance they also deform more under the stress of mastication than porcelain veneers or facings. 

Acetal resins find a number of applications in gears, where they come into competition with the nylons. Acetal gears are superior to those made from nylon in fatigue resistance, dimensional stability and stiffness, whereas nylon gears in conditions of average humidity have greater resistance to impact fatigue and abrasion. 

Rider and Amott were able to produce notable improvements in bond durability in comparison with simple abrasion pre-treatments. In some cases, the pretreatment improved joint durability to the level observed with the phosphoric acid anodizing process. The development of aluminum platelet structure in the outer film region combined with the hydrolytic stability of adhesive bonds made to the epoxy silane appear to be critical in developing the bond durability observed. XPS was particularly useful in determining the composition of fracture surfaces after failure as a function of boiling-water treatment time. A key feature of the treatment is that the adherend surface prepared in the boiling water be treated by the silane solution directly afterwards. Given the adherend is still wet before immersion in silane solution, the potential for atmospheric contamination is avoided. Rider and Amott have previously shown that such exposure is detrimental to bond durability. 

Solid SBR is often prefened to natural rubber because of its better thermal oxidative stability, higher abrasion resistance and easier processability. Solid SBRs are generally grouped into three families according to the production method. 

Aminos. There are two basic types of amino plastics - urea formaldehyde and melamine formaldehyde. They are hard, rigid materials with good abrasion resistance and their mechanical characteristics are sufficiently good for continuous use at moderate temperatures (up to 100°C). Urea formaldehyde is relatively inexpensive but moisture absorption can result in poor dimensional stability. It is generally used for bottle caps, electrical switches, plugs, utensil handles and trays. Melamine formaldehyde has lower water absorption and improved temperature and chemical resistance. It is typically used for tableware, laminated worktops and electrical fittings. 

Articles made from polypropylene have good electrical and chemical resistance and low water absorption. Its other useful characteristics are its light weight (lowest thermoplastic polymer density), high abrasion resistance, dimensional stability, high impact strength, and no toxicity. Table 12-3 shows the properties of polypropylene. 

Synthetic rubbers (elastomers) are long-chain polymers with special chemical and physical as well as mechanical properties. These materials have chemical stability, high abrasion resistance, strength, and good dimensional stability. Many of these properties are imparted to the... 

Excellent mechanical properties, dimensional stability, chemical resistance (especially alkalis), low water absorption, selfextinguishing (when halogenated), low shrinkage, good abrasion resistance, very good adhesion properties... 

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