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Overview of Molecular Structure Characteristics of Cellulose Acetate Microporous Membrane

Issuing time:2023-08-14 10:34

Cellulose acetate membrane is a synthetic membrane used in a wide variety of applications, including water filtration, gas separation, and dialysis. It is extracted from cellulose, a natural polymer found in plant cell walls, through a chemical modification process called acetylation. The process involves replacing hydroxyl groups (-OH) in cellulose with acetate groups (-OCOCH3).

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The backbone of cellulose acetate membranes consists of repeating units of glucose molecules linked together by β-1,4-glycosidic bonds. This linear polymer chain is the main structural element forming the membrane, giving the membrane strength, stability, and resistance to enzymatic hydrolysis Properties, including the structural integrity of the membrane, play a crucial role in their performance in various industrial and biomedical applications.

The production of cellulose acetate membranes mostly adopts the acetylation process. During the acetylation process, the hydroxyl groups (-OH) in the cellulose chains are replaced by acetate groups (-OCOCH3), and these acetate groups are connected to the glucose units. On the carbon atoms, the chemical resistance of the film is enhanced for the cellulose molecules, and compared with unmodified cellulose, it is more resistant to the degradation of acid, alkali and organic solvents. This chemical resistance makes the cellulose acetate film suitable for Application of some harsh chemicals.

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When it comes to the acetylation process, there is a concept that is the degree of acetylation, which refers to the average number of acetate groups per glucose unit in the cellulose acetate membrane, which can vary according to the desired properties of the membrane, and can range from partial acetylation to acetylation (low degree of acetylation) to high degree of acetylation (high degree of acetylation); at the same time, the process of acetylation can improve the mechanical strength and stability of cellulose acetate membrane, enhance the resistance to mechanical stress, and make the membrane More durable and less likely to tear or break; also increases the thermal resistance of the film, allowing it to withstand higher temperatures without significant degradation.

Compared with some regular and symmetrical microporous membrane materials, cellulose acetate membrane has an amorphous structure and lacks long-range order or crystalline arrangement, which means that the polymer chains are arranged randomly instead of forming a crystalline structure. The shape-setting properties contribute to the flexibility and permeability of the film, as well as light transmission, etc.

In terms of porosity, the membrane structure contains interconnected pores or void spaces that allow certain molecules or ions to pass through while confining others based on their size, charge, and other factors. The size and distribution of these pores can be determined during fabrication. In-process control, which enables customization for specific applications, makes cellulose acetate membranes more versatile.

Hydrophilic/hydrophobic balance, the presence of acetate groups in the cellulose acetate membrane imparts a degree of hydrophobicity to the material due to the acetylation of the hydroxyl groups; however, the remaining hydroxyl groups in the cellulose backbone contribute to its Hydrophilicity, the balance between these hydrophilic and hydrophobic regions affects the interaction of the membrane with water and other polar or nonpolar substances.

Cellulose acetate membranes can have different molecular weights and molecular weight distributions depending on the manufacturing process. These characteristics will affect the mechanical strength, pore size, and permeability of the membrane. It also has strong biocompatibility, which means that cellulose acetate membranes The membranes are well tolerated by organisms and do not elicit an overt immune response, making them more suitable for various biomedical applications such as filtration in medical devices.

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In summary, the molecular structure of cellulose acetate membranes combines the inherent properties of cellulose and the advantages of chemical modification introduced by acetylation, which vary according to factors such as the degree of acetylation, membrane thickness, and manufacturing process, and these properties make cellulose acetate membranes widely used In filtration, dialysis, gas separation and other fields.

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