In the field of high-performance insulation materials, aerogels have attracted much attention due to their ultra-low thermal conductivity and ultra-thin insulation effect. In practical selection and engineering applications, many users focus on a key question: Does a lower aerogel density necessarily mean better insulation performance? What is the relationship between aerogel density and insulation performance?

This article will systematically analyze the relationship between aerogel density and insulation performance to aid in engineering selection and technical understanding.

I. What is Aerogel Density?

1️⃣ Basic Concepts of Aerogel Density

Aerogel density refers to the mass of a unit volume of aerogel material, usually expressed in kg/m³.

Compared to traditional insulation materials, the significant characteristics of aerogels are:

Extremely low density

Low solid content

Internal porosity can reach 90%–99%

Therefore, aerogels are often referred to as "one of the lightest solid materials in the world."

2️⃣ Common Aerogel Density Ranges in Engineering

In practical engineering, the density of common aerogel products (such as aerogel felts and aerogel boards) is typically:

150–250 kg/m³ (composite aerogel felts)

Special structure products may have lower or higher densities.

Lower density is not necessarily better; it is closely related to the application scenario.

II. Why Does Aerogel Have Excellent Thermal Insulation Performance?

To understand the relationship between density and thermal insulation performance, it is essential to understand the thermal insulation mechanism of aerogels.

1️⃣ Nanoporous Structure is Key

The interior of an aerogel consists of numerous nanoscale pores:

The pore size is typically smaller than the free path of air molecules.

Air convection is difficult.

The heat conduction path is significantly lengthened.

This means that the heat conduction of aerogels is primarily limited to solid-to-gas conduction.

2️⃣ Source of Extremely Low Thermal Conductivity

Thanks to its structural characteristics, the thermal conductivity of aerogels can typically be as low as:

0.015–0.020 W/(m·K)

far lower than:

Glass wool

Rock wool

Traditional insulation materials such as rubber and plastics

III. Relationship between Aerogel Density and Thermal Conductivity

1️⃣ The Relationship between Density and Thermal Conductivity is Not a Simple Linear Relationship

Within a certain range, the relationship between aerogel density and insulation performance exhibits the following patterns:

Too Low Density:

Insufficient solid skeleton

Insufficient structural strength

Easily collapses, negatively impacting insulation stability

Moderate Density:

Stable nanoporous structure

Effectively suppressed gas convection

Low thermal conductivity

Too High Density:

Increased solid content

Enhanced solid thermal conduction

The thermal conductivity actually increases

Therefore, there exists an "optimal density range" for aerogels.

2️⃣ Typical Performance in Engineering Applications

In engineering practice, the following can be observed:

Aerogel felt with a reasonable density exhibits the most stable thermal insulation performance.

Blindly pursuing ultra-low density does not continuously improve the thermal insulation effect.

IV. Comprehensive Impact of Aerogel Density on Insulation Systems

1️⃣ Impact on Thermal Insulation Performance

Reasonable density → Low thermal conductivity, stable performance

Excessively high density → Increased heat conduction paths, decreased thermal insulation

2️⃣ Impact on Mechanical Properties

Increasing density leads to:

Enhanced compressive strength

Improved tear resistance

More suitable for complex construction environments

Therefore, in pipes, equipment, and irregularly shaped parts, a balance must often be struck between density and workability.

3️⃣ Impact on Service Life

Structurally stable aerogels:

Not prone to pulverization

Not prone to collapse

Low long-term thermal conductivity degradation

This is one of the reasons why "extremely low-density products" are not chosen in engineering projects.

V. Density Selection Recommendations for Different Application Scenarios

| Application Scenarios | Density Selection Direction |

| Industrial High-Temperature Equipment | Medium to High Density |

| LNG Cryogenic Systems | Structurally Stable Density |

| Building Energy-Saving Retrofits | Lightweight Composite Type |

| Ultra-Thin Insulation Requirements | High-Porosity Stable Structure |

Density should be selected based on operating conditions, rather than simply pursuing the lowest possible value.

VI. Common Misconceptions

Common misconceptions in engineering and selection include:

❌ Lower density always means better insulation

❌ All aerogels have the same thermal conductivity

❌ Ultra-low density = High-end product

The correct understanding should be:

Structural design + density control + application environment jointly determine the insulation performance of aerogels.

The insulation performance of aerogels is closely related to density, but lower density is not always better. Within a reasonable density range, aerogels can maintain a stable nanoporous structure, thereby achieving extremely low thermal conductivity and long-term stable insulation effects. In engineering applications, aerogel products with appropriate density should be selected based on the usage environment and structural requirements.