Influence of additives in PE film in dry compounding and solutions
Nov 11, 2022
When PE is polymerized or PE film is formed into a film, a certain amount of additives, such as antistatic agent, slip agent, opening agent, etc., are generally added according to its use. These additives are not stationary after film formation or compounding, especially slip agents. The slip agent is generally erucamide or oleic acid amide. There are two reasons for the decrease of composite strength due to slip agent:
When the PE film is placed for a short time, the slip agent migrates to the surface of the PE film, forming a thin dense layer, which blocks the bonding between the adhesive and the surface of the PE film, resulting in the inability of the adhesive to contact the PE molecules. , the composite initial tack is very low, with the increase of curing time, the composite strength does not change much, and the composite strength always remains very low or zero. If you carefully understand the resin situation of the PE film, this phenomenon can generally be avoided. For special requirements, high-smooth PE film must be used. Generally, it should not be placed for too long. If the PE film is used over time for some reason, it is best to do a small test before compounding or place the PE film at 60- At a temperature of 70°C for more than 8 hours, the slip agent will partially fail at this time. At this time, the composite strength will generally not be low, but the PE film does not have high slip.
The composite initial adhesion is acceptable, but as the curing time increases, the composite strength becomes lower and lower, and a layer of white powdery substance appears between the two layers. This is due to the selection of high-slip PE raw materials in the production of PE film. Due to the high content of slip agent in the film, during the high temperature (40-50 ℃) curing process, the molecular movement of the slip agent in the film is intensified. A large number of slip agent molecules migrate to both sides of the film, and as time goes on, the amount of migration to the surface gradually increases, and its migration destroys the physical bonding process between the adhesive and PE molecules, and the newly formed The weak bond is damaged, the longer the time, the stronger the damage and the lower the composite strength. In this case, the method of increasing the curing temperature is generally adopted to accelerate the cross-linking speed of the adhesive, so that the reaction speed exceeds the migration speed of the slip agent, so as to make up for the negative effects caused by too much slip agent in the PE film. influences.
In the production process, in many cases, various nearly contradictory requirements of customers will be encountered, such as automatic packaging, which requires both high composite strength and low friction coefficient, which is a contradiction in itself. Contradictions, the multi-layer co-extrusion film production method is generally adopted, and different ingredients are selected for each layer according to different uses to meet the various requirements of customers.
