Cause analysis and countermeasures
1. Analysis of the mechanism of peel strength change over time and countermeasures
No matter how high the surface gloss is, there are many tiny holes that are unsightly visible on the surface of the object. Although the pressure-sensitive adhesive is cross-linked, it still has some deformation and fluidity, especially the polymer portion that is not involved in crosslinking. As time passes, the pressure sensitive adhesive gradually penetrates into the voids, forming an "anchor." In addition, when the protective film is attached, although the pressure is large, the contact area between the pressure sensitive adhesive and the surface of the material is not large, and the contact area gradually increases with time, and the force between the protective film and the protected surface is also increased. Gradually improve. Both effects increase the peel strength over time. In order to reduce the change of peel strength over time, the following measures can be taken:
1) adding a surfactant having a certain compatibility with the pressure sensitive adhesive;
2) using a pressure sensitive adhesive with a high gel fraction to increase the degree of crosslinking of the pressure sensitive adhesive;
3) reduce the amount of glue applied;
4) using a substrate having a higher hardness;
5) Copolymerization or grafting of acrylate monomers using long carbon chains.
2. Aging mechanism analysis and countermeasures
The main chain of the acrylate pressure sensitive adhesive is a saturated chain. The general thermal energy is difficult to break the main chain. The aging mechanism is mainly ultraviolet aging; the aging of the substrate is mainly ultraviolet aging. I have tested the tensile strength of PE film substrates after aging for 1 week at 80 °C and 30 W UV. The results show that the normal use temperature has little effect on the aging performance, while the effect of ultraviolet light is More
Big. However, under the dual action of heat and ultraviolet light, there is synergistic aging. Generally, the following measures can be taken to reduce the effects of ultraviolet aging:
1) adding an ultraviolet light absorber;
2) using a black substrate or an aluminized substrate;
3) Add TiO2 to the substrate.
3. Analysis and countermeasures for the compatibility mechanism of the surface material to be protected
Acrylate pressure sensitive adhesives are highly polar materials and are easily compatible with polar materials such as acrylates, polyesters, and polyurethanes, making it difficult to remove protective films. Sometimes small molecules that are not involved in cross-linking in the pressure-sensitive adhesive will be concentrated on the surface. If the surface between the protected surface material and these small molecules is large, small molecule migration will occur. The following measures can usually be taken to reduce the formation of such residual glue:
1) increasing the degree of crosslinking of the pressure sensitive adhesive;
2) If the surface to be protected is the surface of the paint, the surface of the paint should be fully cured and cooled.
Attach a protective film;
3) Use a rubber type pressure sensitive adhesive protective film.
4. Analysis of the mechanism of stretching effect and countermeasures
Since the elongation of the pressure sensitive adhesive and the substrate are different, the elongation of the pressure sensitive adhesive is generally smaller than the elongation of the substrate. When the protective film is stretched greatly, the pressure-sensitive adhesive reaches the extension limit, pulverizes, and falls off from the substrate, causing residual glue. The solution is generally to choose the right type of pressure sensitive adhesive, such as rubber pressure
Sensitive glue. Protective film made by co-extrusion process, because the pressure-sensitive adhesive layer is stretched
For materials with a long growth rate, the bond between the adhesive layer and the substrate is very strong and suitable.
Surface protection for stretch processing.
5. Mechanism analysis and countermeasures of viscoelastic effect
Pressure-sensitive adhesives are viscoelastic materials that undergo elastic deformation and plastic deformation under external force. When the force velocity is fast, the elastic deformation plays a major role; when the force velocity is slow, the plastic deformation plays a major role. If the protective film is quickly removed, the pressure-sensitive adhesive is elastically deformed, and the pressure-sensitive adhesive that is in contact with the protected surface is less than the surface-resisting adhesive. According to the principle of temperature and temperature equivalence, the effect of removing the protective film at a low temperature and quickly removing the protective film is similar. In order to avoid the above phenomenon, the protective film should be removed slowly at a certain temperature (greater than 15 °C) to avoid rapid operation at low temperatures. Japan's Sekisui has published a patent to create a protective film suitable for quick release, but no products are on the market.
1) The formation mechanism of the protective film residual glue has the peeling strength change over time, aging, compatibility, stretching effect, viscoelastic effect and the like.
2) For different reasons for forming residual glue, take certain measures to reduce the possibility of residual glue
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