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Discussion on water absorption of PVC film

by:LINYANG     2020-01-19

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The raw materials used to produce hard and soft polyvinyl chloride films are insoluble in water except emulsifier and a few stabilizers contained in emulsion polyvinyl chloride resin, also does not form hydrate substances. However, water molecules will be filled between polyvinyl chloride molecular chains, causing the film to expand, thicken and increase in shape. If the surface of the film is in contact with water for a long time, such as running water, a small amount of components will first be dissolved from the surface of the film and then from the inside of the film. After a long time, the dissolved amount can be weighed out. These dissolution components are not necessarily water soluble substances, such as plasticizers and stabilizers. Water-soluble components in the film (Such as emulsifiers or some stabilizers)Will accelerate dissolution.

In most cases, the expansion of various polyvinyl chloride films in water is reversible, I . e. the films will return to their original state after dehydration.

Table 3- What is listed in 18 is at 20℃ to 0 according to DIN53472. Water absorption data measured by various films with a thickness of 5mm.

The Hard film made of suspension polyvinyl chloride resin has good water resistance due to its high purity. The film made of emulsion polyvinyl chloride resin, since the resin contains emulsifier and stabilizer, it has slight water absorption. The impact-resistant Polyvinyl chloride resin and Polyvinyl Chloride Copolymer have slightly higher water absorption than the hard film prepared by suspension polymerization resin due to the relaxation of molecular structure.

PVC Films containing plasticizers have different water absorption due to different types and forgetting of plasticizers. The film will also dissociate some components into the water. Because water can move between polyvinyl chloride molecular chains; Therefore, when the film contains plasticizer that can strongly relax the polyvinyl chloride structure, water is easier to enter the inside of the film. The larger the amount of plasticizer contained in the film, the easier it is to absorb water.

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