In the field of high-performance insulation materials, aerogels have attracted much attention due to their extremely low thermal conductivity and ultra-thin insulation effect. In actual selection and engineering applications, many users will focus on a key question: Does the lower the density of aerogels, the better the insulation performance? What is the relationship between the density of aerogels and their insulation performance? 
This article will conduct a systematic analysis on the relationship between the density of aerogels and their insulation performance, aiming to assist in engineering selection and technical understanding. 
One, what is the density of aerogel? 
1️⃣ The basic concept of the density of aerogels 
The density of aerogel refers to the mass of the aerogel material per unit volume, usually expressed in kg/m³. 
Compared with traditional insulation materials, the notable feature of aerogels is: 
Extremely low density 
Low solid content 
The internal porosity can reach 90% – 99% 
Therefore, aerogels are often referred to as "one of the lightest solid materials in the world". 
2️⃣ Common density range of aerogels in engineering applications 
In practical engineering applications, the typical densities of common aerogel products (such as aerogel sheets and aerogel plates) are usually: 
150–250 kg/m³ (Composite Aerogel Sheet) 
Special structure products can be either lower or higher. 
Density is not necessarily lower is better; rather, it is closely related to the usage scenario. 
II. Why does aerogel have excellent insulation properties? 
To understand the relationship between density and insulation performance, one must first clarify the insulation mechanism of aerogels. 
1️⃣ The nano-porous structure is the core. 
The interior of the aerogel is composed of a large number of nanoscale pores: 
The aperture is usually smaller than the free path of an air molecule. 
It is difficult for air to undergo convection. 
The heat conduction path has been significantly lengthened. 
This limits the heat conduction mode of the aerogel mainly to solid conduction and 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) 
Much lower than: 
Glass wool
Rock wool
Traditional insulation materials such as plastics and rubber 
III. Relationship between the Density and Thermal Conductivity of Aerogels 
1️⃣ The relationship between density and thermal conductivity is not a simple linear one. 
Within a certain range, the density of aerogel and its thermal insulation performance follow the following pattern: 
Low density: 
Insufficient solid framework 
Insufficient structural strength 
It is prone to collapse, which in turn affects the stability of heat insulation. 
Moderate density: 
The nano-pore structure is stable. 
Gas convection has been effectively suppressed. 
The thermal conductivity is at a relatively low level. 
Excessive density: 
Increase in solid content 
Enhanced solid heat conduction 
The thermal conductivity has instead increased. 
Therefore, there exists an "optimal density range" for aerogels. 
2️⃣ Typical performance in engineering applications 
In engineering practice, it can be observed that: 
The aerogel batt with an appropriate density has the most stable insulation performance. 
Blindly pursuing extremely low density will not continuously enhance the insulation effect. 
IV. The Comprehensive Impact of Aerogel Density on the Thermal Insulation System 
1️⃣ Impact on heat insulation performance 
Optimal density → Low thermal conductivity and stable performance 
Excessive density → Increased heat conduction paths, reduced insulation performance 
2️⃣ Impact on mechanical properties 
An increase in density will result in: 
Increased resistance to pressure 
Improved tear resistance performance 
More suitable for complex construction environments 
Therefore, in pipelines, equipment, and irregularly shaped parts, it is often necessary to strike a balance between density and construction performance. 
3️⃣ Impact on service life 
Stably structured aerogel: 
Not prone to powdering 
Not prone to collapse 
Long-term thermal conductivity attenuation is minimal. 
This is also one of the reasons why "ultra-low-density products" are not chosen in engineering projects. 
V. Suggestions for Density Selection in Different Application Scenarios 
| Application Scenario | Density Selection Direction | 
| Industrial high-temperature equipment | Medium-high density | 
| LNG Low-Temperature System | Structurally Stable Density | 
| Building Energy Efficiency Renovation | Lightweight Composite Type | 
| Ultra-thin insulation requirement | High porosity stable structure | 
The density should be selected based on the working conditions rather than solely pursuing the lowest value. 
VI. Analysis of Common Misconceptions 
Common misunderstandings in engineering and selection include: 
❌ The lower the density, the better the insulation must be. 
❌ The thermal conductivity of all aerogels is the same. 
❌ Ultra-low density = High-end product 
The correct understanding should be: 
The insulation performance of aerogel is determined jointly by its structural design, density control, and application environment. 
The thermal insulation performance of aerogels is closely related to their density, but a lower density is not necessarily better. Within a reasonable density range, aerogels can maintain a stable nano-porous structure, thereby achieving extremely low thermal conductivity and long-term stable insulation effect. In engineering applications, the appropriate density of aerogel products should be selected based on the usage environment and structural requirements.