Bonding durability of custom-made mouthpiece for scuba diving after water storage under pressure

The purpose of this study was to assess the behavior of laminated thermoforming materials in an underwater environment to understand the durability of mouthpieces for scuba diving. Two thermoforming materials, polyolefin (PO) and ethylene-vinyl acetate copolymer (EV), were laminated and stored in air, 37 degrees C water, and 37 degrees C water under 0.2-MPa pressure for 1 and 4 weeks . The load/ bonding width (bonding strength: BS) and displacement at the start of delamination (SD) and fracture (FR) were analyzed with 3-way ANOVA. BS values at SD and FR in air were significantly greater than those under the other conditions, and the BS at SD of EV was significantly greater than that of PO, though the effects of materials, duration and their interactions were not significantly different. The displacements at SD and FR were significantly influenced by the material. These results suggest that both materials can be employed for making a diving custom mouthpiece.