Today's KNOWLEDGE Share
While in metals, wear is found to be strongly correlated with surface hardness (something not difficult to believe honestly), things are way more complex when it comes to plastics.
As shown in the attached classical graph, wear kinetics in polymers seems to correlate very well with the reciprocal of Stress@break X Strain@break.
Something known as the Ratner-Lancaster correlation.
So, for best performance, you want a strong polymer (which also means a very stiff one due to another typical correlation) with the highest elongation@break.
And guess what ? Elongation@break invariably decreases when elastic modulus goes up !
So this points to the fact that it is intrinsically very difficult to optimize the wear performance of polymers or find that elusive rare performer.
The result is that solutions are typically based on complex formulations using multiple fillers, some to increase strength, some to create a "slippery" transfer film mitigating the role of the typically lowish elongation at break.
source:Vito leo
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