Effects of Natural Ageing on the Dimensional, Mechanical, and Thermal Properties of Diving Neoprene

This study examines the effects of natural ageing on thickness, flexibility, elongation, and thermal resistance of neoprene used in wetsuits. A natural ageing protocol was developed to simulate recreational diving conditions under controlled exposure. Thirty-three neoprene specimens representing 11 material types and three thickness categories were repeatedly immersed in seawater at 15 m depth for 45 min per cycle. Fifty immersion, cleaning, and drying cycles were performed, corresponding to 37.5 h of underwater exposure. Thickness decreased in the majority of samples (p = 0.00043; Cohen’s d = 0.64), while pre- and post-ageing values remained very strongly correlated (r = 0.9987). Flexibility decreased significantly (p = 0.000084; Cohen’s d = −0.74). Thermal resistance declined significantly (p = 0.00029; Cohen’s d = 0.66), with greater losses observed in high-performance neoprene. Elongation showed the greatest ageing-related change, decreasing by approximately 25% (p < 0.000001; Cohen’s d = 1.32). Thermal resistance was strongly associated with neoprene thickness, whereas thermal-resistance loss was not correlated with thickness reduction (r = −0.085). Overall, natural ageing affected dimensional, mechanical, and thermal properties through multiple degradation processes, highlighting the importance of long-term performance stability in neoprene material selection and wetsuit design.