The effect of non-visible surface contamination on the quality of an ultrasonic weld

Final product strength is dependent on material properties after processing, which can include secondary operations, such as ultrasonic welding. In this paper, it is shown that non-visible surface contamination can have a profound negative impact on the quality of an ultrasonic weld. Acrylonitrile–butadiene–styrene (ABS) was contaminated with commonly used chemicals in the polymer processing industry. These included mold releases, cutting fluid, and lotion. The contamination was identified using Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR). The contaminated ABS was ultrasonically welded, then analyzed by pressure decay, tensile strength, cross-sectional microscopy, and scanning electron microcopy with energy-dispersive X-ray spectroscopy (SEM/EDS). Of the contaminates tested, the mold releases (FDA silicone and zinc stearate) had the largest negative effect on the weld, which was a 45% decrease in maximum load. Conversely, cutting fluid had the least effect; statistically, it displayed no difference in strength when compared to the non-contaminated samples.