Film lowers the brutal heat of PPE suits

A new material would make personal protective suits more comfortable for healthcare workers.

The difference is a new desiccant film, which is biocompatible and non-toxic, has fast absorption rate, high absorption capacity, and excellent mechanical properties.

“Under room temperature of about 35 degrees C (95 F), a healthcare worker who dons a protective suit for one hour typically experiences a heat index of about 64 degrees C (147 F). This causes discomfort and prolong thermal strain can result in heat stroke and even death,” explains research team leader and assistant professor Tan Swee Ching of the department of materials science and engineering in the National University of Singapore College of Design and Engineering.

“Our novel composite moisture-trapping film achieves a cooling effect within the protective suit via evaporative cooling—by increasing sweat evaporation from the skin.”

Attaching a piece of novel composite film in a protective suit—for example at the back of the suit—could bring down the heat index by about 40%, lowering the likelihood of heat stroke.

The findings appear in the journal Small.

Medical protective suits have excellent antibacterial and waterproof properties. However, this high level of protection stops the venting of water vapor produced by evaporated sweat and impedes heat loss from the body. This is why users such as healthcare workers who need to don protective suits for long hours, especially in tropical environments, often report of occupational heat strain.

Thermal management solutions such as air-cooling garments with electrical fans or ingestion of ice slurry are impractical due to limitations such as bulkiness, heavy weight, and limited effectiveness. While advanced textiles and coatings are promising solutions, they are difficult to make and costly to produce.

The NUS team came up with a practical strategy to overcome the current challenges by leveraging the principle of evaporative cooling. Their solution involves using a super-hygroscopic composite film to control the humidity level in the micro-environment in the protective suit. When the moisture-trapping composite film absorbs water vapor within the protective suit, the humidity level drops. This in turn speeds up sweat evaporation from the skin. As a result, more heat is dissipated from the human body through sweating, providing thermal comfort for users such as healthcare workers.

To examine the effectiveness of their solution, the NUS team conducted tests in collaboration with researchers from Home Team Science & Technology Agency of Singapore (HTX), using a 20-zone “Newton” manikin within a climatic chamber.

With the composite film, relative humidity (RH) under moderate sweating condition dropped by about 40%—from 91% to 48.2% after one hour of sweating and to 53.2% after two hours of sweating. The team also found that within the first hour of sweating, the heat index or “felt air temperature” dropped significantly from 64.6 C (148 F) to 40 C (104 F) at air temperature of 35 C (95 F). At this level, while users still feel hot, the likelihood of getting heat stroke, heat cramps, and heat exhaustion is remarkably reduced.

“These experiments show that our moisture-trapping film effectively reduces the RH inside the protective suit, hence bringing the heat index down significantly and improving the thermal comfort for users,” Tan explains.

In another laboratory experiment, the research team also showed that body temperature (or skin temperature) could be significantly reduced by 1.5 deg C (2.7 F) through evaporative cooling. This further indicates that the composite film can potentially help users—such as healthcare workers, soldiers, or firefighters—relieve thermal stress, especially during strenuous activities.

Regeneration of the composite film is also more energy efficient, as it requires a lower temperature to release the trapped moisture. At 50 C (122 F), the composite film releases 80% of its water contents after 10 minutes and this reaches 95% after 40 minutes. Most hygroscopic materials regenerate at a temperature of more than 100 C (212 F), over a duration of more than an hour.

“From the findings of various studies in this project, we are hopeful that the moisture-trapping film can be embedded to Personal Protective Equipment (PPE) and/or Personal Protective Clothing (PPC) of the Home Team officers, to enhance thermal comfort and improve performance of the frontline officers,” says Ying Meng Fai, director of the Human Factors & Simulation Centre of Expertise at HTX.

Source: NUS

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