Abstract:

Objective This research aims to investigate the potential application of aerogel composite materials for enhancing the thermal insulation performance of dry diving suit liners underwater. Through meticulous experimentation conducted at both fabric and garment levels, this research aims to assess the thermal insulation capabilities, tailored for garment application. Employing sophisticated seam-sealing techniques, the behavior of these materials under compression in underwater conditions are to be simulated to evaluate alterations in thermal insulation performance. This comprehensive methodology seeks to elucidate the optimal utilization of aerogel composite materials, providing valuable insights into enhancing thermal insulation in diving suits, particularly in the challenging low-temperature, high-pressure environments often encountered during underwater operations.

Method Experimental samples consisted of various aerogel composite materials known for their lightweight and superior thermal insulation properties. These are in the forms of foam, nonwoven fabric, and flake-type aerogel composites, along with a conventional polyester fiber cotton, specifically the C-type Thinsulate from 3M Corporation, used in dry diving suit liners. Fabrication involved combining these materials into a three-layered fabric system, maintaining consistency in outer and inner layer materials. Testing methodologies included sweating hot plate experiments for thermal resistance assessment and simulated compression design to simulate underwater pressure conditions. Additionally, sweating manikin method and underwater human subject trials were conducted to evaluate insulation performance in practical scenarios.

Results Thermal performance analysis provided valuable insights into the behavior of various fabric systems. Significant thickness variations were observed among the samples before seaming, with flake-type materials displaying the highest initial thickness due to their relaxed state. After seaming, these materials experienced substantial thickness reduction, indicating their susceptibility to compression. Conversely, non-woven and foam-type materials exhibited minimal thickness variation, suggesting their resilience to compression by virtue of inherent elasticity and structural composition. Regarding thermal resistance, considerable diversity was noted among fabric samples pre-seaming, with flake-type materials demonstrating higher thermal resistance compared to others. However, post-seaming, the thermal resistance disparity diminished significantly. This reduction was particularly pronounced in flake-type fabrics, suggesting a decrease in insulation capacity due to fiber compression and air expulsion. Conversely, multilayer fabric systems comprising aerogel composites exhibited enhanced thermal resistance post-seaming, indicating their potential for improved insulation performance in underwater conditions. Furthermore, the evaluation of thermal clothing insulation performance yielded promising outcomes. Combining aerogel composite materials in drysuit thermal liners resulted in higher total thermal resistance compared to conventional polyester fiber cotton liners. Additionally, the multilayer fabric system composed of aerogel composites demonstrated superior thermal resistance under compression, suggesting enhanced insulation efficacy in underwater environments. During underwater dressing experiments, divers maintained stable core body temperatures above 37 ℃, despite the water temperature being 14 ℃ while experiencing decreasing skin temperatures over time. Notably, thigh skin temperature exhibited the fastest decrease, attributed to lower metabolic heat production and increased heat dissipation. Overall, the aerogel composite material thermal liner demonstrated excellent insulation performance, highlighting its potential for use in underwater garments. The findings emphasized the promising prospects of aerogel composite materials in enhancing insulation performance in underwater environments. These materials offer thinner and more effective thermal clothing solutions compared to conventional materials, paving the way for advancements in underwater garment design and performance.

Conclusion The study reveals the favorable suitability of selected aerogel composite materials underwater, with flake-type aerogel composites demonstrating optimal performance. Despite lower initial thermal resistance compared to C-type Thinsulate polyester fiber cotton in natural conditions, aerogel composites exhibit similar thermal resistance under compression, indicating their suitability for underwater high-pressure environments. Foam-type and non-woven aerogel composites show minimal thermal resistance differences before and after seaming, with foam-type materials exhibiting deformation-related variations. The assembled aerogel composite thermal liner demonstrates excellent insulation performance, maintaining core body temperatures above 37 ℃ during underwater experiments, thereby ensuring diver safety during subaquatic operations, despite the challenging water temperature of 14 ℃ encountered during these underwater experiments. The study provides valuable data for selecting and applying insulation materials in underwater high-pressure environments, offering new solutions for diver protection and influencing the development of underwater protective clothing.

Key words: dry diving suit, aerogel composite material, thermal insulation liner, thermal insulation performance, underwater insulation, cold protection