TWI Industrial Member Report Summary 537/1995
S M Stevens
Polyetheretherketone (PEEK) is a high performance thermoplastic that has attractive service properties, (including exceptional chemical resistance and a high thermal stability,) and is therefore used in a variety of critical and hostile environments, in applications including chemically resistant coatings, and pump and aircraft components. As PEEK is a semicrystalline material, the crystallinity, molecular orientation and morphology are dependent on the processing history, including welding and these may influence the mechanical properties. This report describes work to generate data on the structural and morphological changes which occur when PEEK is welded. The effect of welding on the chemical resistance was not investigated.
Vibration welds were made at different pressures, and with a variety, of welding times, in order to produce welds with a range of mechanical properties. Fourier transform infrared (FFIR) microspectrometry, was used to measure the crystallinity and molecular orientation in these welds and transmitted light microscopy, was used to study their morphology. Tensile and tensile-impact tests were carried out, and the broken test specimens were examined by scanning electron microscope and transmitted light microscopy, to establish where failure occurred.