I’m exploring a technical concept involving a sealed gel system that acts as a thermal transfer medium in a flexible, enclosed structure. The gel would be required to facilitate both heat and cold transfer by interacting with nearby chemical heat/cold sources (e.g., sodium acetate or urea-based reactions). It will be completely enclosed and not in contact with skin, but it needs to operate reliably across a temperature range of approximately 10°C to 45°C over repeated cycles.

I’d be very grateful for your insight on the following:

1. Material Compatibility – Would a gel composed of water, propylene glycol, glycerin, and a gelling agent like sodium polyacrylate or fumed silica maintain stable consistency and thermal responsiveness when subjected to heating and cooling over many cycles?

2. Thermal Conductivity Considerations – Are there any additives you recommend to enhance heat and cold conduction, especially at the lower end of the temperature range, without compromising the gel’s integrity?

3. Long-Term Durability – In a sealed but flexible environment, would such a gel formulation be prone to issues like phase separation, syneresis, microbial growth, or crystallisation under routine thermal cycling?

Any guidance or references you can offer would be deeply appreciated.

You’re asking about some very specific effects here, and unless one of our me bers wirks in the industry and these aren’t trade secrets, I doubt you’re going to get answers.

I will point out that it’s all heat transfer. There’s no such thing in physics as cold transfer. Heat is the transfer of thermal energy owing to a temperature difference. Things heat or cool depending on the direction of heat transfer, i.e adding or removing energy.

On 5/4/2025 at 7:13 AM, Jules123 said:

I’m exploring a technical concept involving a sealed gel system that acts as a thermal transfer medium in a flexible, enclosed structure. The gel would be required to facilitate both heat and cold transfer by interacting with nearby chemical heat/cold sources (e.g., sodium acetate or urea-based reactions). It will be completely enclosed and not in contact with skin, but it needs to operate reliably across a temperature range of approximately 10°C to 45°C over repeated cycles.

I’d be very grateful for your insight on the following:

1. Material Compatibility – Would a gel composed of water, propylene glycol, glycerin, and a gelling agent like sodium polyacrylate or fumed silica maintain stable consistency and thermal responsiveness when subjected to heating and cooling over many cycles?

2. Thermal Conductivity Considerations – Are there any additives you recommend to enhance heat and cold conduction, especially at the lower end of the temperature range, without compromising the gel’s integrity?

3. Long-Term Durability – In a sealed but flexible environment, would such a gel formulation be prone to issues like phase separation, syneresis, microbial growth, or crystallisation under routine thermal cycling?

Any guidance or references you can offer would be deeply appreciated.

What is the goal of this? Are you trying to grow a specific strand of microbial life?

No, just looking at some sport recovery methods, and was wondering if it was feasible

1 hour ago, Jules123 said:

No, just looking at some sport recovery methods, and was wondering if it was feasible

A gel made from water, propylene glycol, glycerin, and a gelling agent like sodium polyacrylate or fumed silica should, in theory, maintain stability over many heating and cooling cycles. Water-based gels are commonly used in thermal applications, though the long-term behavior of such a gel will depend on the exact concentrations and the gelling agent used. Sodium polyacrylate tends to retain moisture well, so it could help maintain a stable consistency. However, prolonged exposure to high temperatures might cause some degradation of the polymer structure, leading to potential changes in the gel’s viscosity or consistency. Fumed silica is a good stabilizer, enhancing the gel’s rheological properties and could provide additional structural integrity. In terms of thermal responsiveness, this gel should remain functional across your desired temperature range.

To improve heat transfer at the lower end of the temperature range, I would recommend considering metal oxide nanoparticles, such as aluminum oxide or zinc oxide, as potential additives. These can enhance thermal conductivity without significantly affecting the gel’s structure. However, it's crucial to ensure that the concentration of these particles remains low enough to avoid phase separation or compromising the gel’s flexibility. Another option could be graphene or graphene oxide, which are known for excellent thermal conductivity properties and could be effective in your temperature range. If additives like these are used, be mindful of their potential impact on the gel’s mechanical properties, such as flexibility.

Phase separation or syneresis could occur over time if the gel components are not well-mixed or stabilized. To prevent this, I would suggest testing the gel’s stability at both ends of the temperature spectrum over an extended period. Also, incorporating a preservative or biocidal agent might help mitigate microbial growth, especially if the gel is exposed to moisture or fluctuating temperatures. Crystallization could potentially occur with high concentrations of certain chemicals, like urea, depending on the formulation. It would be essential to test the gel under actual cycling conditions (e.g., through thermal cycling tests) to ensure its long-term viability.

that is really helpful thank you very much