For ETFE film, some people do not understand its process and technology. In fact, it is not difficult to understand and apply ETFE membrane materials, so we can start with the understanding membrane. The membrane material can be seen from the material composition:

1. Cellulose acetate: cellulose acetate (CA) membrane is cast in a mixture of cellulose acetate and cellulose triacetate. With the increase of acetyl content, salt interception rate and chemical stability increased and water flux decreased. Loeb-sourirajan's asymmetric structure is the use of a "doctor blade" (" doctor blade ") to cast a CA, ethanol or ether solution into a porous substrate (such as canvas), and the surface is formed by drying out a thin layer of the skin through the air. The dense epidermis on the larger pore layer is composed of a thin layer of about 0.2 mu m thick, and the total thickness of the membrane is about 100 mu m. The technique can also be used for the casting of tubular and hollow fibrous membranes.

The chemical stability of CA membrane is poor and hydrolysis occurs during operation, and its hydrolysis rate is related to temperature and pH conditions. Cellulose acetate membrane can be 0 ~ 30 ℃ in the temperature and pH 4.0 ~ 6.5 under continuous operation. These dongli membrane products may also be eroded by biological erosion, but they can eliminate biological erosion due to their ability to continuously expose themselves to a low-chlorinated environment. The result of poor film stability resulted in the decrease of membrane interception rate. However, the popularity of these materials is due to their wide availability and low prices.

2. Aromatic polyamide: the asymmetric aromatic polyamide (Aramid) film (Richter and Hoehn 1971) is pioneered in the form of hollow fiber. These fibers are spun from the solution of the solution. By controlling the evaporation of the solvent of spinning liquid, the dense epidermis of 0.1~ 1.0 mu m is formed on the outer surface of the fiber. The remaining fiber structure is a porous support structure of about 26 mu m thick. The salt intercepting occurs in the dense layer. In order to further improve the performance of entrapment of hollow fiber membrane used in brackish water desalination, on membrane using polyvinyl methyl ether (PT - A) the reprocessing, used for desalination with PT - A and tannic acid (PT - A) for post-processing.

Compared with cellulose film, aromatic polyamide membrane is characterized by excellent chemical stability. They can in 0 ~ 30 ℃ temperature pH4 ~ 11 pieces of continuous operation, and will not be eroded. However, if the aromatic polyamide membrane is continuously exposed to chlorine environment, it is susceptible to chlorine erosion. Therefore, it is important to remove chlorine from the feeding fluid they handle.

3. Film composite film: the work of North Star Research and Development Institute (located in Minneapolis), funded by the department of interior department of the interior of the interior department in the mid-1980s (Francis 1966; Rozelle et al. 1967 led to the development of film composite films. Universal Oil Products' Fluid Systems Division (Riley et al. 1967) introduced its commodity (membrane complex) membrane in the mid-1970s, while FilmTec introduced its FT30 composite membrane (Cadotte et al., 1980) in the early 1980s. In these membrane structures, the ultrathin grid layer is formed on the surface of microporous polysulfone (i.e., 0.2 mu m thick) on a porous fabric support body. The grid layer on the polysulfone is produced by the "in-situ" interfacial polymerization of polyamide or polyurea.

The advantages of the thin film composite membrane related to their chemical properties, its main features a larger chemical stability, operating under medium pressure was high water flux and salt intercept rate and resistance to erosion. They can in the temperature between 0 ~ 40 ℃ and pH2 ~ 12 continuous operation. Like aromatic polyamide, these materials have poor resistance to chlorine and other oxides.

The above images are domestic and foreign air inflation membrane application cases.