PUR (Polyurethane Reactive), fully known in Chinese as moisture-curing reactive polyurethane hot melt adhesive. Its main component is isocyanate-terminated polyurethane prepolymer. PUR's adhesion and toughness (elasticity) can be adjusted, and it possesses excellent bonding strength, temperature resistance, chemical corrosion resistance, and aging resistance. It has become one of the important varieties in the adhesive industry and is now widely used in packaging, wood processing, automobiles, textiles, electromechanical, aerospace, and other fields of the national economy. PUR adhesive contains polar and chemically active urethane groups (-NHCOO-) or isocyanate groups (-NCO) in its molecular structure. It exhibits excellent adhesion to materials containing active hydrogen, such as porous materials like wood, leather, fabric, paper, ceramics, and smooth surface materials like plastics, metals, glass, and rubber.

Daily Operational Safety Precautions for PUR Hot Melt Adhesive machines:

Avoid using the PUR hot melt adhesive machine in the vicinity of volatile, explosive materials or gases. Flammable or explosive items must not be stored around the PUR hot melt adhesive machine or spraying equipment.

Do not operate the hot melt adhesive machine without suitable protective devices, proper insulation, or well-installed protective panels.

Only personnel trained specifically for this task are permitted to perform maintenance or disassemble the machine for repair.

Do not operate the PUR hot melt adhesive machine when the ambient temperature is below -20°C or above 80°C.

The area where the PUR hot melt adhesive machine is used must be free from rapidly flowing air. Exposure of the PUR adhesive drum and the melting platen to fast-flowing air can cause rapid cooling, adversely affecting the adhesive flow rate and wasting energy.

When replenishing PUR hot melt adhesive, check if the adhesive drum is deformed. Severely deformed PUR hot melt adhesive drums should be discarded to prevent damage to the machine's platen.

Whenever disassembling the hoses or adhesive gun of the PUR hot melt adhesive machine, any exposed PUR adhesive must be immediately sealed using silicone oil to prevent moisture-induced curing.

When the PUR hot melt adhesive machine is not used for extended periods, the circumference of the heated platen should be sealed with silicone oil to preserve the performance of the adhesive in the drum.

Precautions for Adhesive Change in PUR Hot Melt Adhesive Machines:

Before cleaning the PUR hot melt adhesive machine, the heated platen must first be separated from the adhesive drum. After separation, maintain the pressure in the lifting cylinder and cut off all power sources.

When separating the drum from the machine, the air pressure applied should be increased gradually from a low level. Under no circumstances should high-pressure gas be used directly for separation to prevent accidents.

After the platen is separated from the adhesive drum, and before cleaning the residual adhesive, the passage between the platen and the pump must be closed using the specific mechanism on the platen to prevent curing.

Personnel cleaning the heated platen must wear specialized high-temperature resistant protective clothing and high-temperature resistant gloves. Skin contact with the hot adhesive drum, molten PUR adhesive, heated platen, or other high-temperature components must be avoided to prevent burns.

The optimal method for drum separation is to introduce dried nitrogen into the 5-gallon adhesive drum. If compressed air must be used, it needs to be thoroughly dried. Regularly check the condition of the desiccant.

After the machine is separated from the adhesive drum, residual adhesive on the platen must be cleaned immediately and thoroughly. Do not use any hard tools during cleaning to avoid scratching the platen's non-stick coating.

For platens with special structures that cannot be cleaned thoroughly within a short time, dried nitrogen protection must be used during residual adhesive removal. The cleaning time must not exceed 10 minutes, and no hard tools should be used.

After cleaning the platen, immediately press it into a new PUR adhesive drum. Avoid leaving the platen exposed to air for extended periods. When pressing the platen into the new drum, the air pressure in the cylinder should be increased gradually, not directly set to high pressure, to ensure operator safety and prevent accidents.

When pressing the platen into the new drum, a small amount of silicone oil can be applied to the platen's sealing ring for lubrication, protecting the seal.

After the platen is pressed into the new drum, open the overflow valve to completely vent any residual air from the drum. Expel all adhesive containing air bubbles to prevent air-entrained adhesive from entering the pump and hoses.

After placing the platen into the new drum and venting the air, tighten the overflow valve. The pressure in the cylinder can then be appropriately increased for smoother operation.

After changing the adhesive, wait at least 20 minutes for the machine to heat up before starting the gear pump and motor. Starting them immediately can damage the polyurethane gear pump and reduce the machine's service life.