The good bonding effect of two-component

Simply put, the climatic conditions that affect the performance of adhesives mainly include two aspects: ambient humidity and temperature. Generally speaking, in spring and summer, especially the rainy season, the air humidity is relatively high and can even reach saturation, while in autumn and winter, the air is dry and the humidity is low. In terms of ambient temperature, summer is much higher than winter, with a difference of nearly 30-40 degree .

In order to analyze the causes of the above phenomena, it is necessary to understand the effects of moisture and temperature on adhesives. First of all, for two-component polyurethane prepolymer, moisture, like the main agent, can react with the NCO group in the curing agent. According to calculations, 1g of water can consume 26-32g of curing agent. In practice, water mixed into the working adhesive competes with the base agent as it reacts with the curing agent. However, no matter how much water is added to the reaction, the curing agent will undoubtedly be consumed, making it unable to react with the main agent in the original working ratio, resulting in incomplete curing and residual viscosity.

The viscosity and reactivity of adhesives are closely related to temperature. The viscosity values provided by the adhesive manufacturer are measured using a rotational viscometer at a standard temperature of 25 degree . The same adhesive exhibits lower viscosity values and good flow dispersion properties at high temperatures, while lower temperatures result in higher viscosity and poorer flowability. In addition, the cross-linking curing reaction between the two components of the adhesive is slow at low temperatures and rapid at high temperatures.

In response to this situation, when using two-component polyurethane prepolymer for bonding, it can be adjusted according to environmental changes.

1. If the air is humid and the temperature is high, increase the amount of curing agent by 10% to 20% to compensate for the consumption of moisture.

2. Regularly use dry cotton gauze or cloth to absorb condensed water droplets in the bonding machine to prevent them from falling into the bonding basin.

3. Unused working glue can be diluted with a small amount of solvent and then sealed and stored. If conditions permit, keep it in a small refrigerator. The next time it is used, it should be thawed in a sealed environment and mixed with newly prepared working glue.

4. When the temperature is low in winter, adding more solvent to prepare the working adhesive can reduce the viscosity of the system, improve flow and dispersion, and also reduce the generation of bubbles in the adhesive basin during operation. However, this will reduce the concentration of the working adhesive. If you do not want to change the concentration of the working adhesive, you can use a mixed solvent of acetone and ethyl acetate as a diluent in a ratio of 1:4 or 3:7.

5. When the temperature is low in winter, the temperature of the curing room can be slightly raised to ensure that the actual temperature can meet the requirements and avoid affecting the curing effect.