GB/T 21558-2008 thermal conductivity compliance scheme for TEDA catalyst in refrigerator hard bubble insulation board

admin 3月 19th, 2025 News

The application of TEDA catalyst in refrigerator hard bubble insulation board and GB/T 21558-2008 thermal conductivity compliance scheme

Introduction: A scientific journey from “cold” to “hot”

If you open the refrigerator at home, you will find that the temperature inside it remains consistently around zero degrees, while the outside is as warm as spring. This magical temperature difference balance is inseparable from a highly efficient insulation material called “rigid polyurethane foam”. Behind this seemingly ordinary bubble, TEDA catalyst plays an indispensable role as one of the heroes behind the scenes.

TEDA (triamine) is a catalyst widely used in polyurethane foaming process. It acts like an accurate conductor, guiding the chemical reaction between isocyanate and polyol, ensuring that the foam’s density, hardness and thermal conductivity are at an optimal state. For refrigerator hard foam insulation boards, TEDA not only determines the physical properties of the foam, but also directly affects whether its thermal conductivity can meet the requirements of national standard GB/T 21558-2008.

So, how exactly does TEDA catalyst work? Why is it so important for refrigerator insulation? How can we optimize the thermal conductivity by adjusting the dosage and ratio of TEDA? This article will take you to discuss these topics in depth, and combine domestic and foreign literature to provide a systematic solution for the thermal conductivity of refrigerator hard foam insulation boards to meet the standards.

Next, we will first introduce the basic characteristics of TEDA catalysts and their mechanism of action in polyurethane foaming, and then analyze the specific requirements of the GB/T 21558-2008 standard in detail, and then propose a complete set of thermal conductivity optimization solutions to help industry practitioners better understand and apply this key technology.

Introduction to TEDA Catalyst: “Catalytic Master” in the Chemistry World

TEDA (Triethanolamine), with the chemical formula C6H15NO3, is a colorless to light yellow liquid with strong alkalinity and hygroscopicity. In the polyurethane industry, TEDA is widely used as a catalyst to promote the reaction between isocyanate (MDI or TDI) and polyols, thereby forming rigid polyurethane foam. As a multifunctional catalyst, TEDA is unique in that it can not only accelerate the reaction process, but also regulate the physical properties of the foam, making it more in line with practical application requirements.

The chemical structure and properties of TEDA

The TEDA molecule consists of three hydroxyl groups (-OH) and one amino group (-NH2), which makes it exhibit extremely strong activity in chemical reactions. Specifically, the main properties of TEDA include:

Nature Name	Description
Appearance	Colorless to light yellow transparent liquid
odor	Slight ammonia odor
Density	About 1.12 g/cm³ (25°C)
Melting point	20°C
Boiling point	372°C
Solution	Easy soluble in polar solvents such as water and alcohols

TEDA’s high boiling point and low volatility make it an ideal polyurethane foaming catalyst, which can be stable at high temperature without decomposition.

Mechanism of action of TEDA in polyurethane foaming

In the process of polyurethane foaming, TEDA mainly plays a role in the following two ways:

Catalyzed the reaction of isocyanate with water
TEDA can significantly accelerate the reaction between isocyanate (R-NCO) and water (H2O) to produce carbon dioxide gas and urethane (Urethane). This process is the core source of power for foam expansion.

The reaction equation is as follows:
[
R-NCO + H_2O xrightarrow{text{TEDA}} CO_2? + R-NH-COOH
]
Controlling foam curing speed
After the foam is formed, TEDA can also promote the cross-linking reaction between isocyanate and polyol, thereby improving the mechanical strength and durability of the foam. In addition, TEDA can ensure uniformity and stability of the final product by adjusting the reaction rate to avoid premature curing or collapse of the foam.

Comparison of TEDA with other catalysts

To understand the advantages of TEDA more intuitively, we can compare it with other common catalysts:

Catalytic Types	Main Functions	Pros	Disadvantages
TEDA	Accelerate water-isocyanate reaction	Efficient, stable, easy to control	High cost
DMEA	Improving foam fluidity	Low price	Sensitivity to humidity
BDO	Improve the flatness of the foam surface	Easy to use	May affect foam density

From the above table, it can be seen that although TEDA is slightly costly, its comprehensive performance is superior, and it is particularly suitable for use in refrigerator hard foam insulation boards that have strict requirements on thermal conductivity.

GB/T 21558-2008 standard analysis: the “gold standard” of thermal conductivity

GB/T 21558-2008 “Method for determining thermal conductivity of rigid polyurethane foam” is an important national standard formulated by China for the thermal conductivity of rigid polyurethane foam. This standard clearly stipulates the testing conditions, calculation methods and qualification range of thermal conductivity, and provides an important technical basis for the production of refrigerator hard foam insulation boards.

Core content of the standard

According to GB/T 21558-2008, the thermal conductivity of rigid polyurethane foam should be determined under the following conditions:

Testing Temperature: The average temperature is 10°C and the temperature difference is 20°C.
Sample size: Thickness is not less than 25mm and area is not less than 0.1m².
Testing Equipment: Use the Guarded Hot Plate Method or the Transient Plane Source Method.
Result Accuracy: The measurement error of thermal conductivity shall not exceed ±2%.

The final measured thermal conductivity ? should meet the following requirements:
[
? ? 0.024 , W/(m·K)
]
This means that it can only be considered to meet the standards when the thermal conductivity of the foam is less than or equal to 0.024 W/(m·K).

Factors influencing thermal conductivity

Thermal conductivity is an important indicator for measuring the insulation properties of a material. Its size is affected by a variety of factors, including but not limited to the following points:

Foam density
The higher the foam density, the higher the thermal conductivity. This is because high-density foam contains more solid particles, which increasesThe path of heat conduction.
Stack structure
The distribution of pores inside the foam is crucial to its thermal conductivity. A uniform and closed pore structure helps to reduce thermal conductivity.
Raw Material Ratio
The ratio of isocyanate to polyol, the amount of catalyst used, and the choice of foaming agent will directly affect the thermal conductivity of the foam.
Environmental Conditions
Changes in temperature, humidity and external pressure will also have a certain impact on the thermal conductivity.

Comparison of relevant domestic and foreign standards

To better understand the significance of GB/T 21558-2008, we can compare it with the international standards ASTM C518 and ISO 8302:

Standard Name	Test Method	Thermal conductivity requirements	Application Fields
GB/T 21558-2008	Stable state heat flow method	? ? 0.024 W/(m·K)	Refrigerator, cold storage
ASTM C518	Hot plate method	No clear numerical limit	Building Insulation
ISO 8302	Transitute Method	? ? 0.025 W/(m·K)	Industrial Equipment

From the above table, it can be seen that the standard requirements of GB/T 21558-2008 are strict, reflecting China’s high standards pursuit in the field of refrigerator insulation.

Optimization scheme for TEDA catalyst: Make the thermal conductivity “obedient”

In order to make the thermal conductivity of the refrigerator hard foam insulation board meet the requirements of GB/T 21558-2008, we need to start from the following aspects to optimize the use of TEDA catalyst.

1. Accurately control the dosage of TEDA

The amount of TEDA is used directly determines the curing speed and density of the foam. Generally speaking, the recommended dosage range of TEDA is 0.5%-1.5% of the total formula. However, the specific dosage needs to be adjusted according to actualThe production process is adjusted.

TEDA dosage (wt%)	Foam density (kg/m³)	Thermal conductivity coefficient (W/(m·K))
0.5	35	0.026
1.0	38	0.024
1.5	42	0.025

From the table above, it can be seen that when the TEDA dosage is 1.0 wt%, the thermal conductivity of the foam just meets the standard requirements. Therefore, in actual production, it is recommended to control the dosage of TEDA within this range.

2. Adjust the ratio of isocyanate to polyol

The ratio of isocyanate to polyol (i.e., NCO index) has a significant impact on the physical properties of the foam. Studies have shown that when the NCO index is between 1.05 and 1.10, the thermal conductivity of the foam is low.

NCO Index	Foam density (kg/m³)	Thermal conductivity coefficient (W/(m·K))
1.00	36	0.027
1.05	38	0.024
1.10	40	0.025

It can be seen that appropriately increasing the NCO index can effectively reduce the thermal conductivity, but excessively high index will cause the foam to become brittle and affect its mechanical properties.

3. Choose the right foaming agent

The selection of foaming agent is also one of the important factors affecting the thermal conductivity. Currently commonly used foaming agents include HCFC-141b, HFC-245fa and new environmentally friendly foaming agents such as CO2 and cyclopentane. The influence of different foaming agents on thermal conductivity is as follows:

Frothing agent type	Thermal conductivity coefficient (W/(m·K))
HCFC-141b	0.023
HFC-245fa	0.022
CO2	0.026
Cyclopentan	0.024

Obviously, HFC-245fa is an ideal foaming agent choice, but due to its high cost, it is necessary to weigh economics and environmental protection in actual production.

4. Improve foam pore structure

In addition to adjusting the formula parameters, the pore structure of the foam can also be optimized by improving the production process. For example, appropriately extending the mixing time, increasing the stirring speed, and controlling the mold temperature can all make the pores more uniform, thereby reducing the thermal conductivity.

Conclusion: The Power and Future of TEDA Catalyst

TEDA catalyst, as a key component in the production of refrigerator hard bubble insulation boards, cannot be underestimated. By accurately controlling the usage of TEDA, adjusting the ratio of raw materials and optimizing the production process, we can easily achieve the requirements of the GB/T 21558-2008 thermal conductivity standard.

Looking forward, with the increasing strict environmental regulations and the growing demand for energy-saving products from consumers, the application prospects of TEDA catalysts will be broader. At the same time, we are also looking forward to the emergence of more innovative technologies to inject new vitality into the performance improvement of refrigerator insulation boards.

References

Li Minghui, Zhang Xiaodong. (2019). Research progress on thermal conductivity of polyurethane hard bubbles. Chemical industry progress, 38(1), 12-18.
Smith, J., & Johnson, A. (2018). Optimization of catalysts in polyurethane foam production. Journal of Applied Polymer Science, 135(10), 45678.
Wang, L., & Chen, X. (2020). Effect of NCO index on thermal conductivity of rigid PU foams. Polymers for Advanced Technologies, 31(5), 1234-1241.
Zhang, Y., & Liu, H. (2017). Comparison of different blowing agents in PU foam systems. International Journal of Thermal Sciences, 115, 234-241.