What are the effects of temperature changes on hot melt adhesives

temperature change of hot melt adhesive
hot melt adhesive is a thermoplastic material – or polymer – that usually becomes flexible at warm temperatures. On the contrary, during the cooling process, the hot melt adhesive solidifies and eventually forms a well-known long-lasting bond. Temperature and its variation patterns have a significant impact on the performance of hot melt adhesives.

The varieties of hot melt adhesives are almost countless. Therefore, temperature can affect them in many ways. Generally speaking, the most significant impact of temperature on hot melt adhesives is on their viscosity, strength, elasticity, and toughness or stiffness.

1. How does temperature affect the strength of hot melt adhesives? Although different types of hot melt adhesives have different levels of heat resistance, a good rule of thumb is that as the temperature rises, the strength of the hot melt adhesive will decrease because it loses the ability to firmly bond two substrates together. On the other hand, low temperatures usually do not have such an extremely adverse effect on the strength of adhesives. Usually, they cause some simple stiffness rather than damage their strength.

2. Stiffness, Heat and hot Melt: In most cases, the cooling and drying processes cause the adhesive to harden and form a strong bond. High temperatures applied to solid adhesives can still reduce the strength, stiffness or “toughness” of hot melt adhesives and cause the substrate to slip away when the adhesive fails. The safety issue here is obvious, as loose connections in buildings and heavy equipment can easily cause injuries and serious damage.

On the contrary, some adhesives become overly stiff and tough at high temperatures – that’s why it’s another important lesson to read and accurately understand which adhesive you are using. For adhesives designed to maintain flexibility, such as those used in environments where some “giving” is required, this increase in stiffness will reduce the effectiveness of the adhesive.

3. Temperature changes in the elasticity of hot melt adhesives: Due to changes in chemical composition, some components decompose, the adhesive crystallizes and becomes unstable, and the tendency of the adhesive to strain or break increases with rising temperature. This reduced elasticity may cause the adhesive to crack or break completely, which obviously makes the adhesive ineffective. This does not mean that flexibility is always what you want. Compared with adhesives with less elasticity, adhesives with excessive elasticity are more difficult to extrude, rotate, spray or coat.

4. Temperature and Viscosity Viscosity is a measure of a liquid’s resistance to flow. If the hot melt adhesive overheats and becomes too sticky, it may mean a serious risk of burns, severe confusion and an overall slowdown in the assembly process, as you have to stop and wait for the flowing adhesive to solidify. On the other hand, cold adhesives with insufficient viscosity to flow through the application tools are also not conducive to the assembly process.