Precautions for the use of solvent-free polyurethane adhesive
Solvent-free polyurethane adhesive, which I believe many people already know, because it has the characteristics of high viscosity, water resistance, cold resistance and high temperature resistance, has been applied to various fields, so let's take a look at the use of solvent-free polyurethane adhesive.
Solvent-free polyurethane adhesiveI believe many people already know this adhesive, because it has the characteristics of high viscosity, water resistance, cold resistance and high temperature resistance, and has been applied to various fields, so let's take a look at the matters needing attention in the use of solvent-free polyurethane adhesive.
Notice of solvent-free polyurethane adhesive:
1. Appearance treatment
One of the conditions for good bonding is the necessary treatment of the appearance of the substrate.Due to the influence of the weak interface layer such as grease and dust, the adhesive strength of the adhesive based on the weak interface layer is not easily improved. Chemical treatment is also required for substrates that do not match the apparent tension of the adhesive. Appearance treatment is one of the first steps to improve the bonding strength.
2. Clean degreasing
The appearance of some metal plastic substrates is often susceptible to sweat, oil, dust and other pollution, and the appearance of the plastic is related to the release agent, so the plastic and the adhesive layer only form a weak bonding interface.
For solvent-free polyurethane adhesive, the oil stain on the surface of metal or plastic has poor compatibility with polyurethane, while the presence of water will react with NCO groups in the adhesive to generate angry bubbles, which will reduce the contact surface products between the adhesive and the substrate and reduce the bonding force of the adhesive layer. Therefore, the surface must be cleaned and dried before bonding. It is usually washed with alkaline water containing a surfactant and an organic solvent and then washed dry, or washed directly with an organic solvent. For rusty metal, you usually start with sandpaper, right? wire brush to remove surface rust.
3. Rough treatment
The smooth appearance is usually ground to increase the contact area between the glue and the substrate. The adhesive penetrates into the depressions or pores on the surface of the substrate, and after curing, it achieves a "nail hook rod"-like condensation effect, which can firmly stick to the substrate all the way.
Commonly used methods include sandblasting, roughing of wood files, and sanding of sandpaper. But too rough will make the adhesive in the appearance of the penetration is affected, concave down easy to residue or produce angry bubbles, but will reduce the bonding strength. If sanding and other methods are easy to damage the substrate, it is appropriate to use adhesive coating, etching, corona treatment and other methods to change its appearance, so that it is easy to use solvent-free polyurethane adhesive bonding.
4. Chemical treatment of metal appearance
Metal appearance can be derusting, degreasing, micro-corrosion treatment, a lot of treatment agent available. This is typically an acidic treatment solution. Such as aluminum? aluminum alloy can be mixed with potassium dichromate/concentrated sulfuric acid/water (mass ratio is about 10/100/300), soak at 70-12 ℃ for 5-10min, wash, neutralize, wash again and dry. Iron can be mixed with concentrated sulfuric acid (hydrochloric acid) and water 1:1, soak at room temperature for 5-10 minutes, wash and dry. Or a mixture of potassium dichromate/concentrated sulfuric acid/water.
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