Recent Posts
- ANTEC Conference
- Not too technical
- Extrapolation, Comparison and Use of Polymer Melt Viscosity Data using curve fit data
- Melt disturbance onset from increasing line speed
- Viscosity driver of coextrusion melt disturbance
- Coextruding films without defects
- PVC-PET shrinkage and shrink labels
- The impact of polymer density on substrates
- FDA approval of a film
- Curl of coextruded films
Recent Comments
- rakatin on Substrate surface quality
- Eldridge Mount on Temperature profile on a chill roll
- Jimmy on Temperature profile on a chill roll
- Eldridge Mount on Reply to Jimmy's question
- juan on Dimensional stability considerations
Most Commented On
- Matte surfaces (4)
- Differences in film properties and manufacturing methods used to produce them (2)
- Dimensional stability considerations (2)
- Reply to Jimmy's question (2)
- Temperature profile on a chill roll (2)
Archives
Blog
Film Temperature estimation at strpping from the roll
March 10, 2008
To calculate the average temperature of a film being removed (or stripped)from a chill roll we can use the information we had in the last post from the calculation of the roll heat transfer coefficient from the water temperature change in the roll. Assuming we know or have recently calculated the roll heat transfer coefficient we can estimate the average temperature of the film exiting the roll. This is important to know as it will impact the tensile properties of the film and therefore the maximum tension we can apply to the film.
Knowing the heat transfer coefficient of the roll we can calculate the amount of heat being removed from the film by the water and therefore the temperature change in the film.
Q = Pmass (Tmelt - Tstrip)/Ac = h (Tpolymer-Twater)
And therefore
Tstrip = Tmelt - [h (Tpolymer-Twater) Ac]/ Pmass
The stripping temperature can be important to know for scale up of a process. For instance, if you are running with a current line speed and have reached a limit to the output due to a surface defect of film stretching (indicators of a film which is too weak or hot) then if you need to increase the output you can do so by improving the heat transfer to the roll. You can increase the heat transfer several ways but assuming you have and that you know the new value for h, then you can determine the new output limit by calculating the speed at which you reach the temperature at which the problem was noted in the first instance. Alternatively you could calculate the heat transfer coefficient you have to have to reach any particular speed. This lets you select the best roll technology for the upgrade to the line capacity
Posted by Eldridge M. Mount on March 10, 2008 | Comments (0)