Help you select the raw material of thermal break strips

Thermal break strips can be made from an wide range of materials, including ABS,PVC, PA66GF25, PU, and PPO. The most widely used material for thermal broken among them is PA66GF25. There are many advantages to thermal break strips made of PA66GF25 granules(PA66 reinforced by 25% glass fiber).
1.It can help reduce heat conduction.
2.It can prevent condensation.
3.It can reduce the heat lost and save energy.
4.It can reduce noise.
5.It can enhance the water tightness, air tightness and wind pressure resistance of doors and windows.
6.Its linear expansion coefficient is close to that of aluminum profiles.

Then how to choose the suitable raw material for polyamide thermal break strips?
1.The raw material must to be PA66, and the content of PA66 must be greater than 65%.
2.The content of glass fiber must be in the suitable range. (25%±2.5%)

Why the raw material must to be PA66?
1.The melting point of virgin PA66 is around 252℃, while the melting point of PA6 is only 215℃.
2.Its thermal decomposition temperature is greater than 350 ℃.
3.It can resist acid, alkali, and most inorganic salt solutions.
4.It has excellent wear resistance, self-lubricating properties, and high mechanical strength.

However, there is currently a phenomenon in the market where PA66 is replaced with other materials such as PA6, composite material of PA and PE, composite material of PA and PP, etc. Their process technology is similar to PA66GF25 material, so it’s not easy for customers to notice the material difference when producing thermal break strips. Although these kinds of material is cheap, it sacrifices the strength and heat resistance of the polyamide thermal break strip while reducing costs. This can easily lead to finished thermal broken aluminum doors and windows lacking basic properties such as wind pressure resistance, air tightness, and water tightness.

Why we need to add glass fiber?
1.The coefficient of linear expansion of PA66 is (7-10) X10^-5, while the coefficient of linear expansion of aluminum profiles is 2.35x10^-5, which is significantly different.
But after adding 25% glass fiber, the linear expansion coefficient of PA66GF25 material is about (2.3-3.5) × 10^-5, which is very close to the linear expansion coefficient of aluminum profiles.
When the ambient temperature changes, only when the coefficient of linear expansion is closer, then the elongation and contraction of the two materials will only maintain synchronous changes, so as not to affect the stability of the composite structure.

2.Due to the creep characteristics of PA66, its deformation will increase with time under certain external stress. In order to suppress the creep of PA66, PA66 reinforced with 25% glass fiber can make it similar to aluminum profiles in terms of strength, rigidity, and thermal deformation temperature.

3.In the process of producing PA66GF25 granules, if high-quality glass fiber can be added in the correct way and proportion, the glass fiber will be uniformly arranged horizontally and vertically in the polyamide thermal break strips, which can improve both the longitudinal tensile strength and the transverse tensile strength.

However, at present, some Chinese manufacturers use inexpensive minerals (such as calcium carbonate, glass microspheres, etc.) for filling. Although these types of mineral fillers can reduce cost, but they are fail to improve the performance of PA66. What’s worse, they will reduce the performance of PA66.
The PA66 material reinforced with minerals has many defects such as low strength and poor heat resistance, which can cause poor quality thermal break strips to loosen inside the aluminum profile during the actual installation and use, especially in extremely hot or cold conditions, the loosen problem will become more serious.
This can cause the windows to loosen and deform, damaging the air and water tightness of the doors and windows. In serious cases, it can cause the windows to loosen and detach as a whole, leaving serious safety hazards in the building.

In a word, when you choose the raw material of thermal break strips, it has to be PA66GF25 material. And the raw material for PA66GF25 material must be PA66 and high-quality glass fiber.
Only good raw materials can make good products.