UHMWPE molecular structure analysis after turning operations and machinability with a standard off-the-shelf carbide tool

Abstract

Traditionally, ultra-high molecular weight polyethylene (UHMWPE) parts are manufactured by mass production processes, such as ram extrusion and compress moulding. However, the production of UHMWPE parts for arthroplasty is regularly unitary and performed by machining. Current literature on this material machining is scarce and there is no off-the-shelf turning tool specifically designed for polymer machining. The objective of this work was to evaluate the molecular structure of UHMWPE after turning operations and machinability with a standard off-the-shelf carbide tool through a basic experimental study. In this study, cutting force and cutting power were evaluated on face turning operations. Workpiece surface roughness measurements were taken considering the Ra parameter and the shape of the chip was observed. The degree of crystallinity was evaluated via Differential Scanning Calorimetry (DSC) and the molecular structure after machining via Fourier Transform Infrared (FTIR) spectroscopy. There were adopted one off-the-shelf carbide tool and parameters regularly recommended to metal turning. Cutting force and cutting power indicate that UHMWPE may be related to good machinability. However, the results of part surface roughness and shape of the chip lead to poor machinability. On this work, best UHMWPE machinability results was achieved for Vc = 600 m min−1, f = 0.2 mm rev−1 and ap = 1.25 mm. No significant changes were observed in the crystallinity of the chip samples according to DSC results. FTIR analysis detected hydroperoxide generation after machining with Vc = 600 m min−1 that requires further investigation.