Bronze filler

Static friction decreases with an increase in load, and the static coefficient of friction is lower than the dynamic coefficient. The tendency to creep must be considered carefliUy in FEP products designed for service under continuous stresses. Creep can be minimized by suitable fillers. Fillets are also used to improve wear resistance and stiffness. Compositions such as 30% bronze-fiUed FEP, 20% graphite-filled FEP, and 10% glass-fiber-filled FEP offer high PV values ( 400(kPa-m)/s) and are suitable for beatings. 

Filler None MoSi Bronze Glass Fibre... 

The effect of load on filled and unfilled nylon is shown in Figure 12.3, and it is clear that the presence of the molybdenum disulphide filler conveys a similar relative improvement at all the loads tested. One successful commercial range of filled nylons are the Nylatrons, such as Nylatron GSM, a composite of molybdenum disulphide in nylon which has been extensively used in heavily loaded bearings in heavy industrial plant such as steel mills. In one crane application Nylatron bearings were reported to last twenty times as long as the bronze bearings which they replaced . ... 

Other experiments were carried out with filled PTFE material, using steam as fluidizing gas. Fillers were carbon black, glass fibres, and bronze. Important parameters are listed in Table 24.10. In the first three experiments, the inflnence of the temperatnre was investigated, in the following were other fillers nsed. 

Ampco-Trode [Ampco], TM for a series of aluminum-bronze arc-welding electrodes and filler rod containing 9.0-15.0% aluminum, 1.0-5.0% iron, balance copper, for joining like or dissimilar metals and overlaying surfaces resistant to wear, corrosion, erosion, and cavitation-pitting. 

Sil-Trode [Ampco]. TM for silicon bronze electrodes and filler rod for use in inert-gas welding. 

Typical fillers glass fiber, carbon fiber, graphite, metal powders (bronze), molybdenum sulfide, boron nitride, carbon black, Ni-Zn ferrite... 

Typical fillers graphite, glass fiber, bronze... 

Compounds, known as granular powders, are made with granular polytetrafluoroethylene resin. The choice and concentration of the filler depends on the desired properties of the final part. Glass fiber, bronze, steel, carbon, carbon fiber, and graphite are among the common filler materials. Up to 40% by volume of filler can be added to the resin without complete loss of physical properties. The impact of additives below 5% by volume of filler on the properties of compounds is insignificant. Above 40%, most physical properties of the compounds drop sharply. 

Bronze is the most popular metallic filler, although steel powder is occasionally used. Laige quantities (40%-60% by weight) of bronze reduce deformation under load and raise thermal and electrical conductivity of PTFE compounds. These two characteristics are beneficial to applications where a part is subjected to load at extreme temperatures. Transmission and air-conditioner compressor seals are two examples of such parts. Bronze is an alloy of copper... 

The volume fraction of the fillers in the compound depends on its specific gravity. A higher weight fraction of heavier fillers such as bronze can be incorporated than lighter additives like glass. Physical properties of the compound deteriorate with increase in the volume fiaction of the filler as illustrated in Fig. 3.4. 

Deformation under load of all filled polytetrafluoroethylene compounds decreases in comparison to unfilled resin, as seen in Table 3.13. Combinations of carbon and graphite reduce deformation the most at room and at elevated temperatures. The next effective filler in reducing deformation under load is bronze at 60% by weight. Hardness is increased by the addition of additives, particularly bronze, carbon, and graphite (Table 3.14). 

Polytetrafluoroethylene has excellent chemical resistance properties. The effect of incorporation of additives on chemical properties depends on the t) e of the filler and the specific chemicals. In general, chemical properties of filled PTFE compounds are not as good as those of the unfilled resin. Table 3.21 shows the effect of a number of chemicals on car-bon/graphite, glass, and bronze compounds. 

Polytetrafluoroethylene has a somewhat higher coefficient of expansion than other plastics. This differential expansion can result in leaking of joints when PTFE is combined with other materials. Addition of fillers such as glass, fiber, graphite, bronze, and molybdenum disulfide alters the coefficient of expansion of polytetrafluoroethylene compounds (Table 3.36). A compound containing 25% filler has a coefficient of expansion about half that of the unmodified resin. 

Compounds containing fillers are usually more sensitive to thermal decomposition due to the acceleration of thermo-oxidative reactions by a number of additives at elevated temperatures. Fillers could allow sintering compounds at lower temperatures due to an increase in the conductivity of the part. For example, a metal-filled PTFE compound (steel, lead, or bronze) has a significantly higher thermal conductivity than PTFE, which leads to rapid heating of the part. 

The thermal characteristics of NR-metal composites are close to the properties of metals, whereas the mechanical properties and the processing methods are typical of polymers.Thermally conducting, but electrically insulating, polymer-matrix composites are increasingly important for electronic packaging because the heat dissipation ability limits the reliability, performance and miniaturization of electronics.Thermal properties such as thermal conductivity, thermal dilfusivity and specific heat of metal (copper, zinc, Fe and bronze) powder-filled polymer composites are investigated experimentally in the range of filler content 0-24% by volume. ... 

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