Sizing Specific wear rate

Fig. 34 Specific wear rate (k) as a function of (a) tan delta at 25°C, (b) hardness, and (c) mean agglomerate size. Squares indicate PTFE-EPDM composites containing nonmodified PTFE and circles modified PTFE...

Similarly, a substantial decrease in the specific wear rate, w, can be observed in Si02-g-PAAM filled composites with the rise in filler content and all vv values are lower than those of untreated nano-SiOj-filled systems, although the untreated nanoparticles can also result in decreased w, with respect to the unfilled epoxy. Within the filler content range firom 2 to 6 vol.%, the wear resistance of epoxy is increased by a factor of about 20 by the addition of SiOj-g-PAAM. Bearing in mind the fact that 40 wt.% micron-sized SiOj (180 /tm) particles were needed to acquire a significant decrease in the wear rate of epoxy, the present systems are clearly characterized by a broader applicability. 

The importance of eliminating these contaminants can be understood by comparing the size of human hair (50 im diameter) and a bacterium ( 5 /xm) to a 1-jlm line such as used in a memory chip. To keep particulates from contacting the coating, all machines are maintained in dean rooms where air is filtered to remove contaminants also, people entering the room wear protective dothing that does not shed particulates into the air. The dean rooms are rated by the number of particles present in the air. A dass 100 rating indicates 100 or fewer particles >0.5 fim are present in 1 ft3 (2.83 x 10-2 m3 ) of air a dass 10,000 would have 10,000 or fewer 0.5 im partides. The exact specification depends on need, but class 100 rooms are in routine use. 

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