In the fields of building energy conservation, HVAC systems, and industrial pipeline insulation, rubber and plastic insulation materials are widely used flexible insulation products. Among them, the "thermal conductivity of rubber and plastic" is one of the core indicators for measuring its insulation performance and a crucial technical parameter that must be considered in engineering selection and energy-saving calculations. This article will systematically analyze the thermal conductivity performance of rubber and plastic materials to help users better understand their insulation capabilities and applicable scenarios.

I. What is the Thermal Conductivity of Rubber and Plastic Insulation Materials?

Thermal conductivity refers to the ability of a material to transfer heat per unit thickness and unit temperature difference. The lower the value, the better the insulation performance of the material.

In insulation engineering, thermal conductivity is usually expressed in W/(m·K).

The thermal conductivity of rubber and plastic insulation materials mainly reflects their ability to inhibit heat conduction under normal temperature or specified test conditions, and is an important basis for judging whether they are suitable for use in air conditioning pipes, chilled water pipes, refrigerant pipes, and other systems.

II. Structural Basis of Rubber and Plastic Thermal Conductivity

The relatively stable thermal conductivity of rubber and plastic materials is closely related to their internal structure.

1. Closed-cell foam structure is key.

Rubber and plastic are closed-cell insulation materials, composed of numerous independent, uniform microbubbles.

These bubbles are isolated from each other, preventing air from flowing freely within the material, thus effectively reducing:

The combined effects of heat conduction, heat convection, and heat radiation.

This is the fundamental reason for the relatively stable thermal conductivity of rubber and plastic.

2. Low contribution of gas thermal conductivity.

The pores of rubber and plastic foam mainly contain stagnant air or gases with low thermal conductivity. The thermal conductivity of gases is far lower than that of solid structures, inhibiting heat transfer at the microscopic level.

III. General Performance Range of Thermal Conductivity of Rubber and Plastics

Under normal application conditions, the thermal conductivity of rubber and plastic insulation materials is generally within a relatively stable range (based on standard test conditions):

Low thermal conductivity at room temperature

The thermal conductivity increases to some extent with temperature changes

Density, foaming uniformity, and formulation system all affect the final numerical value.

It should be noted that a lower thermal conductivity is not necessarily better; it should be comprehensively matched with the operating temperature, thickness design, and system operating conditions.

IV. Main Factors Affecting the Thermal Conductivity Performance of Rubber and Plastics

1. Foaming Density and Pore Structure

The more uniform the pore size and the higher the closed-cell rate,

The more complex the heat conduction path,

The more stable the actual insulation effect.

Inferior materials often exhibit large fluctuations in thermal conductivity due to pore wall cracks or excessive interconnected pores.

2. Operating Temperature Range

Rubber and plastics are mostly used in medium and low temperature environments. Within the recommended operating temperature range, their thermal conductivity performance is relatively stable.

When the temperature exceeds the design conditions, the material's thermal conductivity may change, affecting the overall insulation effect. 3. Thickness Design and Construction Quality

While the thermal conductivity of rubber and plastic is an inherent property of the material, the actual insulation effect also depends on:

Whether the thickness meets the calculation requirements

Whether the joints are tight

Whether there are construction problems such as compression or damage

V. Application Value of Rubber and Plastic Thermal Conductivity in Engineering

1. Energy Saving in HVAC Systems

In air conditioning chilled water pipes and duct systems, rubber and plastic materials can effectively reduce heat loss, reduce energy consumption, and improve system operating efficiency.

2. Preventing the Coexistence of Condensation and Heat Loss

Thanks to its closed-cell structure, rubber and plastic, while possessing a certain degree of thermal insulation, can also inhibit water vapor penetration, reducing the problem of decreased thermal conductivity caused by condensation.

3. Advantages of Flexible Construction

Compared to rigid insulation materials, rubber and plastic can maintain a continuous insulation layer in complex pipes and bends, making its thermal conductivity more easily utilized in actual working conditions.

VI. A Rational Comparison of Thermal Conductivity of Rubber and Plastics with Other Insulation Materials

From a Material Category Perspective:

Rubber and plastics belong to organic closed-cell insulation materials.

Rock wool and glass wool belong to inorganic fiber materials.

Aerogel belongs to high-performance nano-insulation materials.

While rubber and plastics do not have the lowest thermal conductivity, their overall performance is stable, their construction adaptability is strong, and their applicable scenarios are clearly defined, making them valuable for long-term application in HVAC and equipment insulation.

VII. How to Rationally View the Thermal Conductivity of Rubber and Plastics

In general, the performance analysis of the thermal conductivity of rubber and plastics cannot be evaluated in isolation from actual working conditions. Under suitable temperature ranges, reasonable thickness design, and standardized construction conditions, rubber and plastic insulation materials can stably perform their insulation function, making them a mature and reliable engineering insulation solution. During the selection process, it is recommended to consider the specific project requirements and make a comprehensive judgment from multiple dimensions, including thermal conductivity, usage environment, and construction conditions, rather than focusing solely on a single parameter.