Influence of Molecular Weight and Crystallinity of HDPE upon the Initial Friction and Transfer Behavior

Abstract

The influence of molecular weight, crystalline structure, and surface energy of high-density polyethylene (HDPE) upon initial friction and transfer behavior was studied on a pin-and-disk tribometer, at low speed (1.6 mm/s) 20°C and 12 percent relative humidity, using:

(a) Composite PE pins made from thin film (< 400 μm) of defined molecular weight, M_w (5.10⁴, 4.10⁵, 4.10⁶ g/Mole) and crystalline structure, controlled by the temperature of crystallization (120°C < T_c < 132°C), stuck onto a PE support (6 × 6 × 20 mm)

(b) Thoroughly polished, plasma-cleaned steel disks (Ra < 0.02 μm)

It was shown, that any increase in the PE surface energy (by plasma or chemical treatment) greatly influences the initial friction and transfer behavior.

Depending on the superficial cross-linking density, which is dependent upon the surface treatment, either transfer of polymer onto the metal, or the formation of metal-containing transfer particles on the polymer is promoted during the first few rotations. The influence of the crystalline morphology (spherulite or axialite) and M_w on friction is also described.

Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Hartford, Connecticut, October 18–20, 1983

Notes

Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Hartford, Connecticut, October 18–20, 1983