Thermal Bonding

Thermal Bonding Calender Nip Pressure & Dwell Time Calculator

A calender nip is a few milliseconds long. Heat only travels a few microns in that time, which is why bonding is a surface event and roll temperature alone never explains a weak web.

Nip Calender
mm
N/mm
m/min
m
Thermal Polymer
°C
°C

PE sheath ≈130 °C, PP ≈163 °C, coPET ≈110 °C.

mm²/s

Polyolefins are close to 0.1 mm²/s.

Nip Dwell Time

— ms

Time any point of the web spends under the nip

Pressure & Heat

Nip Pressure
— MPa
Total Nip Force
— kN
Margin Over Melting Point
— °C
Thermal Diffusion Depth
— µm
Line Output
— m²/h

A negative margin over the melting point means the sheath never melts and the web leaves the calender unbonded. A very large margin melts the core as well, which makes the bond points brittle and the fabric tears at the dots.

Thermal Bonding Calender Nip Pressure & Dwell Time Calculator — free, with the formula and a worked example, at Textile School.