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How to determine the chemical corrosion resistance of polyvinyl chloride films?

by:LINYANG     2020-01-27

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at present, there is no complete standard for determining the chemical erosion resistance of polyvinyl chloride films. The general method is to put the square or round sample into the chemical reagent and let it stand for 1, 2, 4, 8, 16 and 32 hours at normal temperature or high temperature, after each period of time, the weight, size, and changes in hardness, strength, bending strength or cold resistance are measured.

test according to different requirements. The specific operation is to wash the chemical reagent or its aqueous solution with distilled water first, and put the sample on the filter paper to absorb dry. If it is an oil-soluble reagent, use a glass rod or a scraper to remove oily substances, remove the rest with filter paper or wash with petroleum ether. The treated sample must be placed in an environment of 20℃ and Air relative humidity of 65% for 24 hours until constant weight before testing.

when recording the above test results, it must be noted that it is the result of testing a sample of a certain size. Since chemical action is first carried out on the surface of the object and then acts on the inside of the object, when the test results of a certain film sample are used to infer the chemical stability of films with other thicknesses, special care is needed, especially when the film is thin.

How to measure the chemical resistance of polyvinyl chloride film

The film without plasticizer has good stability for many chemicals, it has good chemical stability for most dilute and concentrated acid and alkali, grease, aliphatic hydrocarbon, alcohol or ozone. Substances with oxidation can destroy polyvinyl chloride resins, such as chlorine, concentrated nitric acid and concentrated sulfuric acid. Organic solvents with polar structures will expand or dissolve polyvinyl chloride films, such as esters, ethers, ketones, chloroalkanes and aromatics. What is discussed here is the situation at 20℃, which is more severe at high temperatures. Although PVC has good chemical resistance stability, it can still be used by individual chemicals--Especially solvents--The reason for this is its molecular structure. The molecules of PVC chain are combined with each other by weak paravalent bond force, so they cannot resist the invasion of polar solvent molecules. Polyvinyl chloride has no strong crystal structure, and polyethylene is stable to solvent just by virtue of crystal structure.

relaxation of intermolecular binding of polyvinyl chloride chain caused by internal plasticization or external plasticization will definitely reduce the chemical stability of polyvinyl chloride, and Pure polyvinyl chloride has the highest chemical stability.

The chemical stability of polyvinyl Chloride Copolymer and impact-resistant Polyvinyl chloride is worse than that of Pure polyvinyl chloride. The copolymer is in a solvent (As in Esters and ketones)It is easier to dissolve. Polyvinyl chloride films containing plasticizers are more sensitive to chemicals, and the higher the plasticizer content, the more sensitive they are. Inorganic acid ester plasticizer has the highest chemical stability among plasticizers.

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