Surface tension is the tension on any boundary along the surface of the liquid layer due to the imbalance of molecular attraction. The surface tension of a solid can be understood as surface energy, reflecting its ability to interact with other substances. The surface tension of pet silicone release film is mainly determined by the PET substrate and the silicone coating, among which the molecular structure and surface morphology of the silicone coating have a particularly significant impact on it. The low surface tension silicone coating gives the release film good release properties, making it difficult for the adhesive to adhere; while too high or too low surface tension will affect the spreading and transfer of the adhesive on the surface of the release film. Generally speaking, the surface tension of pet silicone release film needs to be controlled in an appropriate range to ensure that the adhesive can be evenly spread during the coating process and can be smoothly transferred to the target material during use.
Surface tension directly affects the interfacial force between the adhesive and the release film. When the surface tension of the release film is higher than that of the adhesive, the adhesive has good wettability on the surface of the release film and can be spread evenly, but it may remain due to excessive adhesion during transfer; on the contrary, if the surface tension of the release film is too low, the adhesive has poor wettability, and problems such as uneven coating and shrinkage are prone to occur, and insufficient adhesion may lead to inadequate transfer during transfer. In addition, the difference in surface tension will also affect the balance between the cohesion and adhesion of the adhesive during the transfer process. If the two are unbalanced, it may cause problems such as adhesive drawing, incomplete transfer or performance degradation after transfer, which seriously affects the processing and use of subsequent products.
Different types of adhesives (such as acrylics, rubbers, and silicones) have different surface tensions and rheological properties, and their compatibility with the surface tension of pet silicone release film is also different. For example, acrylate adhesives have relatively high surface tension and are suitable for use with release films with slightly higher surface tension to ensure good wettability and transfer effects; while silicone adhesives have low surface tension and need to be used with release films with low surface tension to avoid transfer difficulties due to excessive adhesion. Therefore, in practical applications, it is necessary to accurately select or adjust the surface tension of the release film according to the type, formula and use requirements of the adhesive to achieve the best adhesive transfer effect.
The surface tension of the release film can be effectively controlled by modifying the PET substrate or the silicone coating material. In terms of PET substrates, polar groups can be introduced by surface grafting, plasma treatment and other methods to increase the surface tension of the substrate; for silicone coatings, the surface tension of the coating can be reduced by adjusting the molecular weight and crosslinking density of the silicone polymer and adding functional additives (such as fluorinated surfactants). For example, adding a small amount of fluorinated polymer to the silicone coating can significantly reduce the surface energy and enhance the release effect; while amino grafting treatment on the surface of the PET substrate can improve its compatibility with polar adhesives and improve the transfer performance of the adhesive.
The coating process parameters have an important influence on the formation and stability of the surface tension of the release film. In the process of silicone coating, controlling the coating speed, temperature and pressure and other parameters can change the surface morphology and molecular arrangement of the coating, thereby affecting the surface tension. For example, appropriately increasing the coating temperature can promote the diffusion and cross-linking of silicone molecules, forming a more uniform and dense coating, and reducing the fluctuation of surface tension; adjusting the coating pressure can control the coating thickness and surface flatness, and optimize the uniformity of surface tension. In addition, the use of advanced coating technology (such as micro-gravure coating and slit coating) can achieve more accurate coating thickness control and surface morphology regulation, and improve the stability and consistency of surface tension.
Accurate detection and monitoring of the surface tension of pet silicone release film is the key to ensuring the quality of adhesive transfer. Commonly used surface tension detection methods include contact angle measurement method, surface tension meter test method, etc. Contact angle measurement indirectly reflects the level of surface tension by measuring the contact angle of the droplet on the surface of the release film; the surface tension meter can directly measure the surface tension value of the material. During the production process, a strict quality control system needs to be established to regularly test the surface tension of the release film, and adjust the material formula and process parameters in time according to the test results. At the same time, the adhesive transfer process is monitored online, and the effectiveness of surface tension regulation is verified by observing the coating state, transfer effect and final product quality of the adhesive to ensure the stability of product quality.
With the continuous improvement of product precision and performance requirements in the electronics, optoelectronics and other industries, higher requirements are also put forward for the surface tension regulation technology of pet silicone release film. In the future, surface tension regulation technology will develop in the direction of refinement, intelligence and greening. For example, develop a surface tension prediction and regulation system based on artificial intelligence, and realize the precise optimization of material formula and process parameters through big data analysis and machine learning algorithms; study new environmentally friendly surface tension regulation materials to reduce the use of organic solvents and harmful additives; explore the application of nanotechnology in surface tension regulation, and realize micro-regulation of surface tension by constructing nano-scale surface structures, so as to further improve the performance and quality of adhesive transfer.
