PE film composite is not strong, that is, the composite strength is low, can not meet the requirements of customers, resulting in product scrap. Due to the particularity of PE film production process, low surface tension, high content of smooth agent and surface contamination may lead to weak composite.
Low surface tension.
PE film in the production of the surface tension value is very large, but with the passage of time, the surface tension value gradually decreased. Under normal circumstances, PE film can be stored for 3 to 6 months, but in the summer high temperature and humidity season storage period had better not exceed two months. Practice has proved that the surface tension value of PE film is closely related to the surrounding environment and the thickness of the film: the higher the ambient temperature and humidity, the faster the surface tension value decreases; The thicker the film, the faster the descent. Under normal circumstances, the surface tension of dry composite PE film must reach more than 38DYn/square meter before it can be used
Film surface contamination leads to the reduction of composite strength
PE film in the production process is generally very polluted, but one of the pollution is easily ignored, that is dyne pollution. Many PE film manufacturers have adopted their own configuration of dyne liquid to test the surface tension of the film. Dyne liquid typically use a mixture of ethylene glycol ether, which is a colorless transparent liquid, if carelessly onto the guide roller, due to its volatile slow, film after guide roll will be contaminated, the dyne immersion closely integrated with PE molecules on the PE film surface, composite, it does not and crosslinking adhesive molecules, cause local strength of composite is zero. This condition is extremely difficult to detect in prior examination.
Effects of additives
PE in the polymerization or PE film in the film, according to the different uses, generally need to add a certain amount of additives, such as antistatic agent, smooth agent, opening agent, etc.. These additives are not stationary after film formation or compound, especially for the lubricant. There are two reasons for the decrease of compound strength caused by the smooth agent.
PE film placed for a short time, the smooth agent will migrate to the surface of the PE film, forming a very thin layer of dense layer, this layer of dense layer blocked the bond between the adhesive and the PE film surface, resulting in the adhesive can not contact with the PE molecule, resulting in a significant reduction in the initial bonding force. The composite strength remains low even as the curing time increases. If we carefully understand the production of PE film resin, this phenomenon can generally be avoided. For special requirements must use high lubricant PE film, generally should not be placed for too long. If due to some reason caused by the prolonged use of PE film, in the compound before the best test or PE film in 60~70℃ temperature more than 8h, at this time the smooth agent will be partially ineffective, and then to compound generally will not appear the problem of low composite strength, but PE film has not had high smoothness.
(2). The initial adhesion of the composite is ok, but with the extension of curing time, the composite strength is lower and lower, and a layer of white powdery substance appears between the two layers. This is due to the production of PE film selection of high smooth PE raw materials, due to the high content of smooth agent in the film, in the process of high temperature (40~50℃) curing, the smooth agent molecular movement in the film intensified, a large number of these molecules to the membrane on both sides of the migration, with the extension of time, the amount of migration to the surface gradually increased, Its migration destroys the physical bonding process between the adhesive and PE molecules, and destroys the not very strong bonding force just formed. The longer the time, the stronger the destructive force and the lower the composite strength. In this case, generally adopt the method of increasing the curing temperature, accelerate the crosslinking speed of the adhesive, so that the reaction speed exceeds the migration speed of the smooth agent, in order to make up for the negative effects caused by excessive smooth agent in the PE film.
In the actual production process, when there is too much additives in THE PE film, it is recommended that the temperature of the hot steel roll should not be too high when compounding, because the high temperature is easy to lead to the migration of additives to the outside, resulting in the reduction of the peel strength. Generally, the temperature of the steel roll should be below 50℃. Auxiliaries more complex products for stripping can be obviously observed in the appearance of foggy.
In the process of production, in many cases, customers will meet all kinds of almost contradictory requirements, such as automatic packaging, which requires both high composite strength and low friction coefficient. This is a contradiction in itself, in order to solve this contradiction, generally adopt multi-layer co-extrusion membrane method, each layer according to the different use of different ingredients, respectively, to meet the different requirements of customers.
Zhongshan Jinjiuyuan Protective film Co., LTD is a self-adhesive temporary surface protective film manufacturer. Our company provides surface protection solutions for manufacturers of uncoated metal, plastic and decorative boards.
Article reprint please specify: Zhongshan Jinjiuyuan Protective Film Co., LTD http://www.kjyfilm.com