Water soluble water-soluble mechanism of the membrane
Water soluble film film forming materials on the macro is hydrophilic substances, in its molecular structure of polar group has a lot of water.
Such as protein material is amino acid derivatives and polymers, the molecules contains a large number of hydrophilic carboxyl (
HnN -, n = 1 or 2)
, acyl amino (
Starch is a polysaccharide substance, also contain a small amount of protein substances (
It should be said that nitrogenous substances)
There is a lot of the base (, molecules in
PVA is poly vinyl acetate by the product of different degrees after alcoholysis, there is a tremendous amount of hydroxyl molecules (
And acyl (
< br / > < br / > the presence of these groups, make these material molecules and molecules of the combination of a strong role between key chain, large binding force, causing them to dissolve in water at room temperature and low temperature, these destructive need a certain amount of energy.
Starch as a result of the chain rigidity, under this combination may also form a gel, produce arrangement, association and crystallization (
Such as: < br / > < br / > protein film-former film adhesion strong, the luster nature, resistance to high temperature iron skin and polishing, good health, good air permeability and permeable, feel the nature.
Defect is hard film, extensibility is small, easy to fracture, water imbibition, not wet rub resistance.
< br / > < br / > the vast majority of the disadvantage of starch film, a film at low temperature and hard, brittle even;
The second is the difference in film transparency.
PVA membrane has good strength and flexibility, but has strong hygroscopicity.
< br / > < br / > so to get a satisfied with the quality of water soluble film, in theory to solve the following three problems: < br / > < br / > 1, increase the distance between molecules or adjust blocking material, in the guarantee that the water-soluble key in good condition, destroy or reduce the effect of intermolecular, let water molecules into the material smoothly between the molecules and soluble in water;
< br / > < br / > 2, after the formation of film performance is good, is not affected by the environment and does not affect the environment.
< br / > < br / > 3, can control and adjust the different solution temperature requirements.
< br / > < br / > for these three questions, often by of film-former chemical modification and physical modification agent solution.
To the protein material, low temperature or room temperature water solubility, need to be solved can use modification method to improve the film flexibility, gloss, water resistance and anticorrosive property.
< br / > < br / > by chemical modification of starch, starch is more appropriate, it can form a strong, clear and continuous thin film, film more than acidolysis starch or original uniform, shrinkage and burst the possibility of a smaller, thin film of water soluble is best, and the transparency of film.
< br / > < br / > for PVA, on the one hand, want to consider the alcoholysis degree problem of raw material, on the other hand, to solve the role of PVA molecules.
PVA under certain conditions, for example, Michael addition reaction with acrylamide to modification, implementation of the segmentation of the PVA, and increase solubility in water.
< br / > < br / > after solve these problems, but also solve the segmentation film-former molecules after absorbing water group (
Such as hydroxyl, carboxyl)
May lead to the absorption of moisture problem.
Some adjuvant components and film forming material and additive can occur between the chemical reaction, also can only physical union, water soluble film, improve the physical properties of film forming material, mechanical properties, process performance and soluble performance.