dew point is also called the frost line, refers to the plastic by viscous flow state into the high elastic state boundary.
In the process of blown film, low density polyethylene (
LDPE)
From the squeeze when the mould is in the shape of the molten transparency.
After dividing die, by cooling air ring to
film bubble blowing area for cooling, cooling air blowing at must of viewpoints and speed just out from the plastic bubble, high temperature membrane bubble is in touch with cooling air, membrane bubble of heat will be taken away by the cold air, clear the decrease of the temperature to the low density
polyethylene (
LDPE)
Viscous flow temperature below, then make its cooling solidification and become blurred.
In blown film bubble is a transparent and we can see on the fuzzy boundary between points, and this is the dew point (
Perhaps the frost line)
。
in the blown film process, the discretion of the dew point of film must affect the function of.
Assume high dew point, located above the film after blowing bubble, blowing film is in liquid, huff just make film thinning, and molecular not being stretch orientation
, then the function is close to stretch film blowing film.
Instead, assume that dew point is lower, is blowing in the solid state, plastic under high elastic state at the moment, blowing like a transverse tensile, same in the molecular orientation effect, and then make the blowing film
function is close to the oriented film.
base function technical requirements
standard and tendency to
the width and thickness of the polyethylene film shall meet the requirements, bao hou uniform film, the thickness of the transverse and longitudinal tend to be small, and tend to be more evenly distributed.
there are more polyimide film
