Why Does 0.7 mm Y-Warm Provide Such Efficient Thermal Insulation?

Y-Warm achieves high thermal insulation efficiency at a thickness of only 0.7 mm primarily through its engineered closed-cell microstructure rather than through conventional loft.

The material contains micrometer-scale closed cells approximately 30–190 μm in diameter, separated by polymer cell walls approximately 20–280 nm thick. This structure compartmentalizes gas into numerous small, enclosed spaces, strongly limiting bulk gas movement and convection while maintaining a low solid fraction and restricted solid-phase heat-transfer pathways.

Depending on the test method and conditions, Y-Warm has demonstrated thermal conductivity values in the range of approximately 0.018–0.025 W/(m·K), with ≈0.020 W/(m·K) commonly used as a representative reference value.

The result is an ultra-thin, flexible insulation material capable of providing substantial resistance to heat transfer without relying on the thickness and loft required by conventional fibrous insulation.

Conditions and Limitations

Several conditions should be understood when discussing the thermal performance of 0.7 mm Y-Warm.

Thickness and Model

The 0.7 mm specification refers to a single layer of YW-01.

The reported approximately +10°C improvement in perceived warmth was obtained under specified comparative test conditions. It should not be interpreted as a universal increase in body temperature or as a guaranteed temperature difference under all environments, garment constructions, activity levels, or weather conditions.

Operating and Processing Temperatures

The specified operating temperature range of Y-Warm is approximately −50°C to 150°C.

This should be distinguished from processing conditions. Manufacturing processes involving simultaneous high temperature and pressure above approximately 100°C should be avoided because they may reduce the recovery capability of the cellular structure. Increasing temperature and pressure increases the risk of structural and performance degradation.

Flexibility and Elasticity

Y-Warm is flexible and can be bent, cut, and sewn, but it is not a fluffy or highly stretchable insulation.

Its stretch in the warp and weft directions is limited, making it particularly suitable as a thermal insulation interlayer in garments constructed from woven fabrics.

Processing Limitations

Dense quilting can increase stiffness and adversely affect garment hand feel.

Similarly, full-surface adhesive lamination can significantly restrict moisture-vapor transport and should therefore be avoided when breathability and moisture management are required.

Thermal Insulation Does Not Generate Heat

Y-Warm is a passive thermal insulation material.

It does not actively generate heat. Instead, it reduces the rate at which thermal energy is transferred from the warmer side of the material to the colder side, thereby helping reduce body-heat loss in cold environments.

1. How Does Heat Transfer Through an Insulation Layer?

Heat transfer through a dry insulation material is governed primarily by three mechanisms:

solid conduction, gas-phase heat transfer, and thermal radiation.

In conventional fibrous insulation, air is trapped between fibers, while the fibers themselves create solid conduction pathways. The overall thermal conductivity therefore depends on the relative contributions of the solid phase, gas phase, radiation, material density, pore structure, and temperature.

For an insulation material to achieve very low thermal conductivity, these heat-transfer pathways must be controlled simultaneously.

2. The Traditional Approach: Insulation Through Thickness and Loft

For thousands of years, most clothing insulation has relied on essentially the same physical strategy:

creating thickness to trap relatively still air.

Natural fibers, fur, down, and modern synthetic batting form three-dimensional structures containing numerous air spaces.

Because dry, still air has a relatively low thermal conductivity of approximately 0.026 W/(m·K) at room temperature, increasing the amount of trapped air generally increases thermal resistance.

This is why conventional fibrous insulation typically depends strongly on loft and thickness.

When loft decreases substantially, the thickness of the insulating air layer decreases as well, reducing the thermal resistance of the system.

Y-Warm takes a different structural approach.

Instead of creating a thick fibrous network around air, it incorporates enclosed gas spaces directly into an ultra-thin polymer structure.

3. Y-Warm’s Microstructure: Micrometer-Scale Closed Cells and Nanometer-Scale Cell Walls

Three-dimensional Nano-CT and microscopic analysis show that Y-Warm has a cellular structure characterized by:

• Cell diameter: approximately 30–190 μm

• Cell-wall thickness: approximately 20–280 nm

• Cell type: predominantly discrete closed cells

• Matrix: flexible polymer

The thermal behavior of this structure cannot be attributed to any single geometric parameter.

Rather, its effective thermal conductivity results from the combined effects of cell size, cell-wall dimensions, solid fraction, gas composition, closed-cell fraction, material chemistry, and radiative heat transfer.

4. How the Closed-Cell Structure Reduces Heat Transfer

4.1 Closed Cells Suppress Bulk Gas Movement

Gas can transfer heat not only through molecular conduction but also through bulk movement or convection when sufficient space and temperature gradients are present.

Y-Warm divides the gas phase into numerous small, enclosed cells.

Because these cells are physically separated, large-scale gas circulation through the material is strongly restricted, suppressing convective heat transfer.

This is fundamentally different from an open fibrous structure, where air spaces are interconnected.

4.2 The Polymer Framework Limits Solid-Phase Heat Transfer

Heat can also travel through the solid polymer framework.

In Y-Warm, the solid phase consists of thin polymer cell walls forming a cellular network. The effective solid-phase contribution depends not simply on wall thickness, but on several interconnected factors, including:

solid fraction, polymer thermal conductivity, wall geometry, connectivity, and the effective heat-transfer path through the structure.

The combination of thin cell walls and a low-density cellular architecture reduces the amount of continuous solid material available to conduct heat compared with a dense polymer layer of equivalent overall thickness.

4.3 Gas-Phase Conduction Remains Low

The gas enclosed within the cells also contributes to thermal conductivity.

Because the cells are closed and gas movement is highly restricted, heat transfer through the gas phase occurs primarily through molecular conduction rather than macroscopic convection.

The low thermal conductivity of the gas phase therefore contributes to the material's overall insulation performance.

Importantly, Y-Warm's 30–190 μm cell size is much larger than the mean free path of air molecules under normal atmospheric conditions. Its insulation mechanism should therefore not be attributed primarily to the classic Knudsen effect associated with nanoscale pores in aerogels.

This is a key distinction between Y-Warm and conventional nanoporous aerogel structures.

4.4 Thermal Radiation Is Part of the Overall Heat-Transfer Balance

Thermal radiation is another component of heat transfer within porous materials.

Y-Warm has a microscopically textured surface and high measured far-infrared emissivity. These radiative properties are determined by the material composition, surface morphology, wavelength, and temperature.

They should therefore be considered as one component of the overall thermal behavior, rather than as an isolated explanation for the material's low thermal conductivity.

5. Why Can Flexibility and Low Thermal Conductivity Coexist?

Low thermal conductivity and flexibility are not contradictory material properties.

Thermal conductivity is governed primarily by the pathways available for heat transfer, whereas mechanical flexibility depends on the chemistry, morphology, thickness, and deformation behavior of the solid framework.

Traditional silica aerogels achieve extremely low thermal conductivity through a highly porous nanoscale network, but their inorganic silica skeleton is intrinsically brittle unless reinforced or incorporated into a composite.

Y-Warm uses a different material architecture.

Its cellular framework is formed from a flexible polymer, allowing the material to bend, recover, be cut, and be sewn while retaining a low-density closed-cell structure.

This difference in framework chemistry and pore architecture is what enables Y-Warm to combine flexibility with very low thermal conductivity.

6. Key Technical Parameters of Y-Warm YW-01

Note on Thermal-Conductivity Testing

Because Y-Warm is extremely thin, lightweight, compressible, and has a textured surface, measuring its intrinsic thermal conductivity presents greater uncertainty than measuring thick, rigid, homogeneous insulation materials.

Results can therefore vary depending on the test method, specimen preparation, contact resistance, pressure, temperature, and instrument configuration.

For this reason, thermal-conductivity values should always be reported together with the relevant test method and conditions where available, rather than treated as a single universal constant.

7. How Does Y-Warm Compare with Other Insulation Materials?

Approximate room-temperature thermal conductivity values illustrate the different insulation approaches:

*Values vary considerably with density, loft, moisture content, test method, and material construction.

These figures should not be interpreted as a direct ranking of finished-garment warmth.

Thermal conductivity is a material property, whereas total thermal resistance depends strongly on thickness:

R ≈ d / λ

where:

R = thermal resistance
d = material thickness
λ = thermal conductivity

Therefore, a thick layer of down or synthetic insulation can provide much greater total thermal resistance than a single 0.7 mm layer of Y-Warm, even if Y-Warm has a lower thermal conductivity.

The principal advantage of Y-Warm is therefore not simply "more warmth," but high insulation efficiency where thickness, weight, flexibility, and available space are strongly constrained.

8. Why Standard CLO and Rct Values Do Not Tell the Whole Story

CLO and Rct are useful measures of thermal resistance for garments and textile systems.

However, thermal resistance is inherently thickness-dependent.

For a simplified homogeneous layer:

R ≈ d / λ

and:

CLO = R / 0.155

Therefore:

CLO ≈ d / (λ × 0.155)

A 0.7 mm material will inherently have limited absolute thermal resistance compared with a much thicker insulation layer, even when its thermal conductivity is very low.

For this reason, CLO and Rct remain useful measurements, but they should not be used alone to evaluate the thermal efficiency per unit thickness of an ultra-thin insulation material.

For Y-Warm, thermal conductivity, thermal resistance, thickness, system construction, and application-specific testing should be considered together.

9. Moisture Management and Thermal Insulation

Y-Warm incorporates hydrophilic functionality within the polymer system.

According to GB/T 21655.1-2023, its measured water absorption rate was approximately:

280% before washing and 279% after washing.

This indicates that the material can absorb substantial moisture while maintaining durable moisture-absorption capability after washing.

In comparative drying tests, Y-Warm returned to a dry state in approximately 60 minutes, despite absorbing a relatively large quantity of moisture.

This combination is particularly relevant to apparel and footwear, where moisture accumulation can influence both thermal comfort and the wearer's perception of cold.

However, moisture absorption, drying rate, and thermal insulation are separate physical properties and should be evaluated using their respective test methods.

10. Typical Applications

Because Y-Warm provides low thermal conductivity in an ultra-thin, flexible form, it is particularly suited to applications where conventional thick insulation is difficult to accommodate.

Typical applications include:

Apparel: positioned between the outer fabric and lining and secured around the perimeter of each cut panel.

Footwear: incorporated between the upper, lining, or other structural layers through controlled lamination or sewing.

Gloves and headwear: used where insulation thickness and freedom of movement are important.

Outdoor equipment: suitable for applications requiring compact insulation with minimal added bulk.

Automotive and industrial applications: applicable as an intermediate insulation layer where thickness and weight are constrained.

Different Y-Warm grades are available for different mechanical and application requirements, including YW-01, YW-02, YW-03, YW-04, and FR-02.

FAQ

Q1. Can 0.7 mm Y-Warm replace a down jacket?

Not on a simple one-to-one basis.

Down and Y-Warm use fundamentally different insulation architectures. Down creates thermal resistance primarily through a thick, lofted structure containing large amounts of relatively still air, while Y-Warm uses an engineered closed-cell polymer structure to achieve low thermal conductivity at minimal thickness.

A single 0.7 mm layer should therefore not be described as universally equivalent to a complete down-insulation system.

Y-Warm is better understood as an alternative insulation technology for applications where reducing thickness and bulk is particularly important.

Q2. Is Y-Warm an aerogel?

No.

Traditional silica aerogel generally consists of a highly porous inorganic network with nanoscale pores.

Y-Warm is a flexible polymer-based closed-cell insulation material with micrometer-scale cells of approximately 30–190 μm and nanoscale cell walls of approximately 20–280 nm.

Their thermal-conductivity ranges may overlap under certain test conditions, but their composition, pore architecture, mechanical behavior, processing methods, and suitable applications are fundamentally different.

Q3. Are Y-Warm's cells smaller than 70 nanometers?

No.

Y-Warm's cells are approximately 30–190 μm, substantially larger than the mean free path of air molecules at normal atmospheric conditions.

The 20–280 nm dimension refers to the polymer cell walls, not the cell diameter.

Therefore, Y-Warm's low thermal conductivity should not primarily be explained by the classic Knudsen effect used to describe gas conduction suppression in nanoporous aerogels.

Its insulation performance arises from the combined effects of closed-cell gas confinement, low-density polymer architecture, restricted solid heat-transfer pathways, gas-phase conduction, and radiative properties.

Q4. Does Y-Warm still insulate when it absorbs moisture?

Y-Warm has demonstrated substantial moisture absorption together with thermal-insulation functionality, but these properties should be distinguished scientifically.

Its hydrophilic functionality allows it to absorb moisture, while its closed-cell structure remains the principal structural basis for thermal insulation.

The measured water absorption rate is approximately 280% before washing and 279% after washing, and comparative testing shows rapid drying performance.

Actual thermal performance under wet conditions depends on moisture content, temperature, garment construction, and test conditions and should therefore be evaluated using dedicated thermal testing.

Q5. What is the operating temperature range of Y-Warm?

The specified operating range is approximately −50°C to 150°C.

This does not mean that every processing method within this temperature range is acceptable.

Manufacturing processes involving simultaneous pressure at temperatures above approximately 100°C should be avoided because they may reduce the recovery capability of the cellular structure.

Q6. Why is CLO alone insufficient for evaluating Y-Warm?

Because CLO measures thermal resistance, not intrinsic thermal conductivity.

Thermal resistance depends strongly on both material thickness and thermal conductivity:

R ≈ d / λ

Since Y-Warm is only approximately 0.7 mm thick, its absolute CLO value cannot by itself describe how efficiently the material insulates per unit thickness.

CLO remains a valid system-level metric, but it should be considered together with thermal conductivity, thickness, construction, and application-specific performance.

Q7. How should Y-Warm be processed and maintained?

Y-Warm can be cut and sewn using conventional garment-manufacturing methods.

For apparel, it is generally used as an intermediate layer between the shell and lining.

Cold-water hand or machine washing is suitable, together with low-temperature drying.

Avoid:

• simultaneous high temperature and pressure above approximately 100°C;

• excessively dense quilting that increases stiffness;

• full-surface adhesive lamination when moisture-vapor transport is required.

When properly stored and used without structural damage, the material is designed to maintain stable performance over long-term use.

Conclusion

The thermal efficiency of 0.7 mm Y-Warm does not come from thickness or loft.

It comes from microstructural engineering.

Micrometer-scale closed cells restrict bulk gas movement, nanoscale polymer cell walls form a low-density solid framework, and the resulting structure reduces the principal pathways of heat transfer while remaining flexible and extremely thin.

This is what distinguishes Y-Warm from conventional loft-based insulation:

Traditional insulation creates thermal resistance by adding thickness. Y-Warm focuses on engineering the structure within that thickness.

For applications where every millimeter and every gram matter, this provides a fundamentally different approach to thermal insulation.