Degree of polymerization and alcoholysis of polyvinyl alcohol
Polyvinyl alcohol is obtained through the alcoholysis of polyvinyl acetate. Its degree of alcoholysis refers to the percentage of the number of vinyl alcohol units in the molecular chain to the total number of molecular structural units. The degree of polymerization of polyvinyl alcohol refers to the number of repeating units in the molecular chain, which directly affects the length and physical properties of the molecule. The different degrees of polymerization determine the different application fields and properties of polyvinyl alcohol. For example, polyvinyl alcohol with an ultra-high degree of polymerization is often used in applications requiring greater strength and durability, while polyvinyl alcohol with a lower degree of polymerization may be more suitable for applications requiring better solubility or flexibility.
For example: According to the chemical formula of polyvinyl alcohol (-C2H2O-)n, PVA 2488, -88 means that the degree of alcoholysis is 88mol%, and 24- means that its degree of polymerization is about 2400, so the ideal molecular formula of PVA2488 should be (-C2H2O-) 2400. The adjustment is approximately 2400*44=105600. Therefore, one is to measure the size of the formed skeleton, and the other is to measure the conversion rate into the desired product. Those two are different.
Polyvinyl alcohol (PVA) is the hydrolyzate of polyvinyl acetate. The solvent of PVA is water, but its solubility in water is largely affected by the degree of polymerization and is dominated by the degree of alcoholysis. Completely alcoholylated PVA has very little dissolution in water. When the alcoholysis degree is below 88%, it is almost completely dissolved at room temperature of 20°C. However, as the alcoholysis degree increases, the solubility decreases significantly. Solubility PVA is soluble in water. The higher the water temperature, the greater the solubility, but it is almost insoluble in organic solvents.
PVA solubility changes with the degree of alcoholysis and polymerization. .Partial alcoholysis and low polymerization degree PVA dissolve very quickly, while complete alcoholysis and high polymerization degree PVA dissolve slowly. As a general rule, the degree of alcoholysis has a greater impact on the solubility of PVA than the degree of polymerization.
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