Near field ultrasonic welding of thermoplastics
Abstract (Summary)Engineering thermoplastics have found wide applications in automotive, aerospace, electronics, medical, and other domestic appliance industries. Therefore the joining of thermoplastics has become an important manufacturing operation. In near field ultrasonic welding the distance between the horn and the weld interface is less than 6mm. The near field ultrasonic welding of ABS and Polystyrene (PS) (amorphous) and Polyethylene (PE) and Polypropylene (PP) (semicrystalline) was studied. The ultrasonic wave propogation method was used to measure the storage (E') and the loss (E") moduli of the thermoplastics. The loss modulus was used to predict energy dissipation theoretically during ultrasonic welding. During welding the weld time, pressure, and amplitude of vibration were varied. Increasing the weld pressure did not bring about any significant improvement in strength. For PE and PP increasing the weld time resulted in an improvement in strength up to weld times of 1.5 seconds beyond which the strength levelled off. For ABS and PS the strength increased with increasing weld time up to weld times of 0.8 seconds; the effect of weld time beyond 0.8 seconds could not be studied because of machine overload. In general, it was found that the energy dissipated and the strength increase with increasing amplitude of vibration. Although there was some scatter in the data a good correlation between energy and strength was observed. The collapse or static displacement was also measured during welding. It too was found to increase with increasing energy dissipated and strength. Near field ultrasonic welding worked well and produced good bonds for both the amorphous and semicrystalline polymers. It was also observed that by monitoring energy dissipated and collapse during welding one could gain valuable information on weld quality.
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Date of Publication:01/01/1988