Do you know PUR hot melt adhesive?
In recent years, the country's requirements for environmental protection are getting higher and higher, and environmentally friendly PUR hot melt adhesives have gradually replaced some solvent-based adhesives. PUR hot melt adhesives are widely used because they can provide high bonding strength for different substrates through covalent bonds, hydrogen bonds, secondary bonds, adhesion and cohesion, and transition layers. At present, the annual consumption of PUR hot melt adhesive is growing at a high speed. After recent years of research and development, the technology is becoming more and more mature.
In recent years, the country's requirements for environmental protection are getting higher and higher.PUR hot melt adhesiveGradually replace some solvent-based adhesives. PUR hot melt adhesives are widely used because they can provide high bonding strength for different substrates through covalent bonds, hydrogen bonds, secondary bonds, adhesion and cohesion, and transition layers. At present, the annual consumption of PUR hot melt adhesive is growing at a high speed. After recent years of research and development, the technology is becoming more and more mature.
PUR hot melt adhesive is a non-toxic, non-polluting one-component hot melt modified polyurethane adhesive, which is solid at room temperature and liquid when heated. It can be bonded with various substrates and has good adhesion. Good adhesion to plastic, metal, glass and other materials, good dustproof and waterproof effect, suitable for consumer electronics and other market applications; excellent heat resistance and solvent resistance; excellent high and low temperature resistance.
Good storage temperature 15~30 ℃, the original aluminum foil bag sealed. Storage at conditions outside this temperature range may adversely affect the performance of the product.
When curing, the NCO group mainly reacts with moisture or active hydrogen-containing substances to generate high-molecular-weight polymers with high cross-linking degree. The curing process can be divided into two stages:
1. Initial curing stage
PUR hot melt adhesive has an initial viscosity and can be cemented with the substrate through crystallization, molecular crosslinking and other colloidal methods. Most of the process at this stage is a physical process, so it is also called physical curing. The adhesive strength of the colloid at this time may be referred to as the tack strength.
2. Final curing stage
After the initial curing, with the continuous curing, the-NCO group in the colloid is completely reacted, the degree of crosslinking of the molecular chain is increased, and the molecular chain is further crystallized. Most of the processes at this stage are chemical processes, so this stage is also called chemical curing. After curing, the adhesive strength of the colloid is called the final strength. The physical curing of the PUR hot melt adhesive makes the prepolymer have a certain initial bond strength, and the chemical curing determines the final bond strength of the PUR hot melt adhesive.
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