Thermal and Mechanical Properties of Composite Materials for Depth-Independent, Ergonomic, and Segmented Cold-Water Diving Wetsuits

Navy divers are essential personnel for the operations of the fleet, supporting underwater ship maintenance, deep-sea salvage, and special naval warfare. Their effectiveness, however, is limited by heat loss in conventional wetsuits. Traditional neoprene wetsuits progressively lose insulating performance at depth because the increasing hydrostatic pressure compresses the neoprene’s closed-cell foam structure. To solve this problem, we developed a series of segmented wetsuits (K-suits) built by enhancing a neoprene undercoat with external pockets containing composite material plates made of incompressible hollow microspheres embedded in silicone. The K-suits significantly outperformed traditional 7 mm neoprene suits in field tests. Herein, we report on improved composites. A combination of 30 elastomers and additives was evaluated using American Society for Testing and Materials (ASTM) methods, including thermal conductivity testing (C518-21), compression testing (D575-91), slow-rate penetration testing (F1306-21), and custom impact testing. The results showed that multiple material combinations improve insulation, compressive strength, and resistance to puncture. Among all tested options, Sylgard 527 (S-527) with embedded 3M K1 glass microsphere had the best thermal insulation performance. Furthermore, its high flexibility makes it well suited for use in multilayer K-suits.