Use of hot-melt pressure-sensitive adhesives at low temperatures
Hot melt pressure-sensitive adhesives generally have three types of interface damage, adhesive layer damage, and mixed damage at low temperatures. So what is the use of hot melt pressure-sensitive adhesives at low temperatures?
Generally speaking, the adhesive effect of pressure-sensitive adhesive depends on the interface adhesive strength and the cohesive strength of the adhesive itself.
Interfacial failure refers to insufficient adhesive strength between the pressure-sensitive adhesive and the surface to adhere. The failure of the adhesive layer is due to the low cohesive strength of the pressure-sensitive adhesive. When the force is applied, the adhesive of the damaged portion of the adhesive layer remains on the adhered surface.
Mixed failure refers to a mixture of the two types of failure described above. Generally, as the temperature decreases, the evolution law of pressure-sensitive adhesive failure is that the transition from adhesive layer failure to mixed failure eventually develops into interface failure.
The main reasons are as follows
1: The pressure-sensitive adhesive molecules have slow movement at low temperatures and it is difficult to quickly wet the adhered surface. At the same time, the modulus of the pressure-sensitive adhesive increases at low temperatures. When the same pressure is applied, the deformation of the adhesive is smaller, and the effective contact area is smaller than that at normal temperature. The bonding strength is low.
2: As a polymer product, pressure-sensitive adhesive requires sufficient time for its molecular movement. Generally, it needs to be cured for 72 hours at an appropriate temperature. The adhesive strength between the pressure-sensitive adhesive and the surface to adhere can reach the ideal adhesive strength. In this process, the temperature is also an important influencing factor, and the time required for the molecular to slow down at low temperatures to build up the strength also becomes longer.
The ambient temperature of many pressure-sensitive adhesives during construction is much lower than the normal temperature of pressure-sensitive adhesives. This is the main reason for the failure of a large number of unconventional pressure-sensitive adhesives in winter. It is recommended that you use low-temperature adhesives to complete winter applications. Bonding application. This type of glue can still maintain the ability of molecular movement at lower temperatures to ensure low-temperature performance.