Nylon lubrication conditions

Laboratory tests and experience during use have demonstrated that the nylons have extremely good abrasion resistance. This may be further improved by addition of external lubricants and by processing under conditions which develop a highly crystalline hard surface e.g. by use of hot injection moulds and by annealing in a non-oxidising fluid at an elevated temperature (150-200°C for nylon 66). 

Fig. 4.28. Wear dependence (W) on sliding distance for self-lubricating materials (1) Nylon with M0S2 (2) acetal resin - - PTFE (3) GILES 80. Test conditions mating material S45C (surface roughness Ra = 3 xm) load 3 MPa velocity 0.167m/s (10 m/min)...

Figure 6.54 Stress vs. strain at various temperatures for conditioned EMS-Grivory Grilamid L 20 G—medium viscosity, lubricated Nylon 11 resin [3],...

Figure 6.96 Stress vs. strain at various temperatures for DuPont Zytel 70G-33L NC010—33% chopped glass filled, lubricated Nylon 66 resin (conditioned at 50% RH) [6].

In some cases very small molecules can act as lubricants. For example water is absorbed by nylon and plasticises the surface layers. So long as penetration of water is limited, the soft surface layer supported by the harder unplasticised substrate provides a low-friction system. This type of molecular interaction is related to two other aspects of polymer lubrication. First, at the molecular level of boundary lubrication wettability of the polymer by the lubricant may be of considerable importance. For example water does not wet rubber and does not provide effective boundary lubrication. However a water-alcohol mixture with a surface tension of 33 mJm" wets the rubber and, under boundary conditions, produces an appreciable reduction in friction. Secondly, in the choice of polymer lubricants there is the general problem of selecting fluids and additives that will not accelerate stress cracking of the polymer, cause excessive softening... 

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