Factors affecting the curing of hot melt adhesives

2021/03/27

1. The curing temperature is one of the important parameters in the curing process of the adhesive. If the curing temperature is too high, it is easy to cause loss of the adhesive or embrittlement of the adhesive layer, resulting in a decrease in bonding strength. If the curing temperature is too low, the matrix molecular chain will be hard, and the crosslinking density of the hot melt glue stick adhesive layer will be too low, and the curing reaction will not be completed. Therefore, during the curing process, the curing temperature must be strictly controlled. There is a specific curing temperature.

 

2. The curing time refers to the time required for curing during the bonding process under certain temperature and pressure conditions. The curing time of different adhesives is also different, such as instant curing, there are a-cyanoacrylate adhesives, hot melt adhesives have a few hours to cure, such as room temperature fast curing epoxy adhesives, second-generation acrylate adhesives, there are several Stupid curing time, such as epoxy polyamide glue. The curing time is also affected by the curing temperature and pressure. Advancing the curing temperature can shorten the curing time. Under lower curing temperature conditions, the curing time should be greatly delayed. If it is lower than room temperature, sometimes it will not cure for a few days.

 

3. Curing pressure refers to applying a certain pressure during the curing process, which is conducive to good adhesion between the glue layer and the adherend and guarantees the quality. Due to the different types of hot melt glue sticks, the pressure applied is also different. The contact pressure is divided into three situations: the contact pressure is cured by the pressure generated by the weight of the adherend, without applying pressure, such as epoxy resin glue, a-cyanoacrylate glue, second-generation acrylate glue, unsaturated poly Ester glue, polyurethane glue, etc. 0.1~0.3 MPa pressure is used for solvent-based adhesives, such as phenolic-acetal, phenolic-nitrile, epoxy-nitrile, epoxy-nylon, polyimide, etc. 0.3~0.5 MPa pressure is used for various adhesives and hot melt adhesives in film, powder, tube and granular form. The policy to increase stress is to increase its humidity.