The effect of weld line on tensile strength of polyphenylsulfone (PPSU) in ultrasonic micro-moulding technology

Melting and processing polymers via ultrasonic vibration is now possible, but the weld line that results and the influence it may have on tensile strength has yet to be investigated. When producing products characterised by high mechanical strength, the parameters of the process should be considered in relation to the weld line on the parts. Here, four sets of process parameters (three using ultrasonic technology and one using the conventional process) were used to produce parts whose weld line strengths were then determined and compared. Amplitude values were found to significantly affect the V notch size and consequently the strength of the samples. Samples from parameters where the amplitude was high (90%, 100%) were characterised by a strength similar to that reached with conventional injection moulding technology. Moreover, the experiments showed that when using specific process parameters, the weld line strength is characterised by values akin to those of pure samples. Finally, the investigation revealed that this novel technology is a potential alternative to micro-injection moulding of high requirement polymers such as PPSU.