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Why the additive in plastic film has great influence on the composite strength?
Nov 27, 2018

The addition of additives in general thin film materials mainly involves three parameters: open, smooth and uniform.

Homogeneity refers to the non-uniformity and mobility of the distribution in the film, resulting in non-homogeneity of the smooth distribution in the film, leading to the packaging film breaking.The friction coefficient of the film is linearly related to the surface roughness.The size of the surface roughness is related to the type, quantity, particle size, shape and dispersity of additives, surface treatment and other factors.It has different effects on the bonding strength of the composite film.Strict control must be exercised.In film making, the general additive (3/10000) is of low smoothness when the content is less than 300ppm and can be used safely.At 500ppm, there is a certain risk for the compound peel strength.Do not dare to use above 800ppm, otherwise it will produce delamination phenomenon.

Common additives include: SiO2, TiO2, CaCO3, Al2O3, MgO, BaSO4, kaolin, etc., all of which are low molecular substances.With the increase of the added dose in the film, the friction coefficient of the film decreases, while the surface roughness increases.If the roughness is too large, the aluminum molecules in the ink, adhesive or vacuum aluminum plating may not be able to fill the sag on the surface of the film, forming a void and affecting the adhesion between the two. In serious cases, the ink, adhesive and aluminum coating may be separated from the film.In a certain range, the larger the surface roughness, the smaller the friction coefficient, that is to say, reducing the friction coefficient of the film surface is beneficial to printing and compounding, which is conducive to increasing the bonding surface between them and the plastic film and improving the adhesion between them.Generally, the friction coefficient of untreated films will be better around 0.4.As the additives are low molecular substances, over time or under the action of a certain temperature, the film will migrate to the outer surface, exudation, so that the ink film, film and the base film separated, the original adhesive state.In addition, due to the high heat sealing temperature, the additive of the film accelerates outward migration and gradually accumulates into a uniform thin layer on the film surface, making the hot sealing position easy to open and separate the layer.Generally, the thicker the film added more additives, the more serious the phenomenon of delamination, especially the CPE and CPP of over 60 mm.If the film additives too much, easy to produce quality problems, so that the ink film, film and aluminum film and the substrate completely separated.Therefore, when using K coating, M coating is often non-interference phenomenon is this reason.


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