Phase Change Material (PCM) is a material that undergoes phase change within a specific temperature range and has significant heat storage or heat release capabilities. Therefore, it is widely used in construction, refrigeration, electronics, textiles, and New energy and other fields. The advantage of PCM is that it can balance the ambient temperature by storing and releasing heat, thereby greatly reducing energy waste, so it is regarded as a material with great development prospects.
PCM molding processes can be divided into two categories, namely microencapsulation and nano-coating. Below we will introduce these two molding processes in detail.
1. Microcapsule molding process
Microcapsules encapsulate liquid or paste PCM in a capsule with a diameter of several microns to several millimeters. Its main function is to prevent the fluidity of PCM, making it easier to control and apply. Microcapsule molding processes are divided into two types, namely physical encapsulation and chemical encapsulation.
1. Physical Encapsulation
Physical encapsulation is to mix the microcapsules and PCM evenly respectively, and mechanically encapsulate the PCM in the microcapsules. The advantage of this process is that it is low cost, simple and easy to implement, and is suitable for large-scale manufacturing. However, its disadvantage is that the thickness of the capsule shell is difficult to control, and it is not easy to achieve accurate control of the internal filling rate of PCM.
2. Chemical encapsulation
Chemical encapsulation is accomplished by preparing capsule materials, reacting PCM with those materials, and finally completing capsule molding. The advantage is that the capsule shell is thin, the filling rate is high, and the physical properties are more stable, but its reaction time is longer, which makes the cost higher and the production efficiency is not high.
2. Nano-coating molding process
Different from microcapsules, nanocoating uses nanotechnology to coat PCM on nanoparticles, giving it better heat transfer and adsorption. It is a new type of PCM molding process that is often used to prepare efficient thermal energy storage and release systems. Nano coating processes can be divided into three types, namely surface coating, internal coating and outer core coating.
1. Surface coating
Surface coating is to mix nanoparticles and PCM evenly, and then load PCM on the nanomaterial to prepare a new material for heat. The advantages of this process are its large surface area (approximately more than 100 times the volume of PCM) and large heat capacity, which can greatly improve heat storage efficiency.
2.Inner cladding
Internal coating is to coat PCM inside the nanomaterial. Nanomaterials with a large number of holes are prepared through composite materials, and then the PCM is moved inside these holes. This method is superior to surface coating because of its tighter structure and better temperature stability.
3. Outer core cladding
The outer core coating is a highly integrated heat release system that covers a large number of PCM and other auxiliary equipment to achieve stronger heat storage and release performance. This method is mainly based on the injection method of PCM and diffusing agent, and can quickly prepare an efficient and reusable PCM thermal storage material on polyethylene, silica gel and other frames.
To sum up, the PCM molding process can enable PCM to show better performance under different application conditions. With the development of nanotechnology, nanocoating will have more applications for PCM. At the same time, with the development of fluorine-free anti-corrosion technology and the discovery of new materials, more possibilities will emerge.
