1. Thermal stability basis of PET base film
PET (polyethylene terephthalate) itself has a certain thermal stability. The benzene ring structure in its molecular structure gives it high heat resistance. Within the normal temperature range, the PET base film can maintain good physical and chemical properties. Its glass transition temperature (Tg) is relatively high, generally around 70-80°C, which means that below this temperature, the PET base film can maintain good rigidity and dimensional stability. However, when the temperature gradually increases to approach or exceed Tg, the molecular segments of the PET base film begin to move, and its physical properties such as hardness and modulus will change. In Lamination adhesives for PET aluminum coated film, the thermal stability of the PET base film is the basis of the thermal stability of the entire film, which to a certain extent determines the initial performance of the aluminum-plated film when heated.
2. The influence of aluminum coating on thermal stability
The aluminum coating also plays an important role in the thermal stability of Lamination adhesives for PET aluminum coated film. Aluminum is a metal with high thermal conductivity. When heated, the aluminum layer can quickly conduct heat, which to a certain extent helps to evenly disperse the heat on the film surface and prevent local overheating. However, the aluminum layer and the PET base film have different thermal expansion coefficients. During temperature changes, internal stress may be generated due to the difference in thermal expansion. If the internal stress is too large, it may affect the adhesion between the aluminum layer and the base film, and even cause the aluminum layer to peel off. Under high temperature conditions, the aluminum layer may undergo oxidation. Although aluminum oxide can protect the internal aluminum layer to a certain extent, if the oxidation process continues or the oxide layer is damaged, it will also affect the thermal stability and other properties of Lamination adhesives for PET aluminum coated film.
3. Performance changes under high temperature environment
Under high temperature environment, the performance of Lamination adhesives for PET aluminum coated film will undergo a series of changes. When the temperature rises to a certain extent, the crystallinity of the PET base film may change, thereby affecting its mechanical properties. For example, the tensile strength may decrease and the elongation at break may increase. For the aluminum layer, high temperature may cause changes in the microstructure of the aluminum layer, such as grain growth, which may affect the optical properties of the aluminum layer, such as reduced reflectivity. At the same time, high temperature may also change the barrier properties of the aluminum-coated film. Due to the structural changes of the PET base film and the aluminum-coated layer, the barrier capacity for oxygen, water vapor, etc. may decrease, thereby affecting its protective effect in packaging and other applications.
4. Measures to improve thermal stability
In order to improve the thermal stability of Lamination adhesives for PET aluminum coated film, a variety of measures can be taken. In terms of material selection, a PET base film material with high heat resistance can be selected, or the PET base film can be modified, such as adding heat-resistant additives. In the aluminum plating process, the combination of the aluminum-coated layer and the base film can be optimized, such as improving the activity of the base film surface through pretreatment and enhancing the adhesion of the aluminum-coated layer to reduce the risk of aluminum-coated layer peeling due to internal stress at high temperature. In addition, during the application process, the chance of Lamination adhesives for PET aluminum coated film being directly exposed to a high temperature environment can be reduced by controlling the ambient temperature and adding a heat-insulating layer, thereby ensuring its thermal stability and related properties.
