What Is Hot Melt Viscosity and How Does It Affect Application?
Viscosity is the resistance of molten hot melt adhesive to flow. The easy to pump in the application directly affects the shape of the outlet from the nozzle, the ability to wet the surface and the amount of penetration into the porous material. Therefore, viscosity should be read not alone, but with measurement temperature.
Why is the viscosity value supplied with the temperature?
Thermoplastic hot melt becomes more fluid as heated. It is not enough to see the value of cPs or mPa.s alone on TDS because the same product will show different viscosity at different temperatures; the measurement temperature should also be included in the comparison. Two products can be compared significantly under the same test temperature and similar method if possible.
Process effect of low and high viscosity
The lower viscosity surface can be quickly wet and create a thin film; but it can give you the risk of excessive absorption or uncontrolled flow in the porous material. It can provide higher viscosity space filling and form holding advantage on the right surface, but it can improve the pressure requirement and application force in small nozzle. The desired result is a balanced flow that makes the surface soaked enough but does not escape from the connection area.
Nozzle, aplicator and viscosity relationship
Dar orifis can limit the flow of long hose or low strong applicator in high viscosity product. The operator increases the risk of oxidation, smoke, carbonization and material damage when it increases more than the temperature to compensate this. So the equipment with adhesive should be selected as parts of the same system; melt rate, output capacity and nozzle geometry should be matched with the actual consumption goal.
How to diagnose viscosity problem?
Do not play with only temperature setting when irregular bead, tailing, distortion of the spraying pattern, excessive spinning or pumping is difficult. Verify tank, hose and applicator temperatures; check nozzle and filter cleaning; make sure the adhesive is the correct product and the right lot. Then create comparable data to the gram that comes out in a certain time.
Application control list
- Check the measurement temperature of viscosity value in TDS.
- Identify the need for porousity and space filling of the surface.
- Match target flow with nozzle diameter.
- Measure tank-hortum-repairing temperatures separately.
- Verify adjustment changes with gram/pcs and bond quality.
Conclusion
The correct viscosity is not only comfortable flowing adhesive; controlled gramm, means adequate soaking and stable application pattern. The best value is determined according to the application, surface and equipment triple.
Manstechnic approach
Manstechnic handles viscosity with nozzle, applicator capacity and line temperature profile as well as product selection.