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Does water-based pressure-sensitive adhesive have a proven application in paint protection film?

Jun 13, 2024

1. Types of pressure-sensitive adhesives

Pressure-sensitive adhesives are divided into water-based and oil-based pressure-sensitive adhesives according to different types of solvents, and oil-based adhesives are generally called solvent-based. Water-based pressure-sensitive adhesives are further subdivided according to the solute dispersion type, which includes water dispersion type and water emulsion type.

Does water-based pressure-sensitive adhesive have a proven application in car clothing?

What is a water-based pressure sensitive adhesive: A water-based polyurethane pressure sensitive adhesive is a class of adhesives that are sensitive to pressure. It has high peeling force and high peel strength, and is suitable for bonding between foam, paper and other materials.
Water-based pressure-sensitive adhesives contain surfactants, and if used on the car coating film, they will come into contact with water during use, which will affect the adhesive performance. The transparency and weather resistance of water-based pressure-sensitive adhesive are insufficient, and the car coating film is in contact with water, and the water adhesive cannot meet this aspect.

2. The conditions that need to be met for the car coating glue

 

The car coating has requirements for peeling force, peeling force, initial adhesion and cohesion are very high, aside from the light, most of the pure water-based pressure-sensitive adhesive can not be done for temperature aging, in addition, it is necessary to consider the aging performance, the adhesion between the glue and the substrate and the non-residual glue and so on.
Compared with many other pressure-sensitive tapes, the application scenario of car coating film is very different is that it is often exposed to the sun and rain, and many of the substrates are highly transparent, and the surface of the car paint is very smooth, and there can be no residual glue when it is torn off later, which is much higher than the requirements of PVC advertising stickers.
(1) Peel strength: Peel strength refers to the force required to peel off the adhesive line from a standard substrate at a constant rate and angle. How many N are needed for the peel strength of the car coat, as shown in the figure below:

Does water-based pressure-sensitive adhesive have a proven application in car clothing?

(2) initial tack: the initial tack is formed by the rapid "wetting" of the substrate by the pressure-sensitive adhesive under a small pressure, which is mainly determined by the activity of the chain segment, only when the activity of the chain segment is very strong, it can form good wetting with the rough surface of the substrate, and reach molecular level contact with the substrate molecules, in order to produce sufficient cementation strength by the interaction force between molecules. Decide whether the construction personnel can repeatedly construct and present a perfect construction effect.
(3) Cohesion: refers to the strength of the inside of the colloid, as a protective film of the colloidal cohesion must be very high, otherwise when the film is torn, the internal cracking of the colloid will cause residual glue.
(4) The test standards for aging performance are xenon lamp aging resistance, heat aging resistance, and moisture aging resistance.
(5) Adhesion of the substrate: the adhesion between the colloid and the substrate.
The reason for the occurrence of residual glue without adhesive: adhesion and cohesion are the decisive factors that determine whether the adhesive will remain on the surface of the car paint or take away the paint when the film is torn. Once the adhesion is less than the adhesion, glue will remain on the surface of the paint; Once the adhesion is greater than the cohesion, tearing off the film will also cause the bond between the glue molecules to break, and eventually lead to glue retention.
In general, if you want cohesion and adhesion to be greater than adhesion, you have requirements for the texture of the glue. At present, the market can meet this situation is the pressure-sensitive adhesive, the general pressure-sensitive adhesive adhesion< cohesion < adhesion, the use of pressure-sensitive adhesive to make invisible car clothing can greatly reduce the phenomenon of car paint retention. Among the pressure-sensitive adhesives, oil-based pressure-sensitive adhesives are the most in line with the requirements of car coating films, so most of the oil-based acrylic adhesives are used on the market now.

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