The process that Dallas Plastics Corporation
utilizes to extrude its films is called blown film. This extremely efficient
and versatile form of extrusion is achieved by melting and pumping plastic
resin through an annular die (Figure 1).
Click here for larger view of Figure 1
The circular extrudate is then inflated to the desired size, formed and cooled by a
ring of air that blows onto the molten polyethylene, hence the name 'blown' film. The inflated
tube is then transported vertically by two nip rolls that pull the film upward through a
collapsing A frame, squeezing the air out and resulting in a flat tube.
Once the flat tube passes through the upper nip rollers, a secondary set of nip rollers
pulls the film downward through the tower (Figure 2)
while it continues to cool.
Click here for larger view of Figure 2
Finally, the flat tube is cut to the desired size and roll configuration and wound onto a
paper core (Figure 3).
Click here for larger view of Figure 3
Some of the advantages of blown film processing over
other forms of extrusion are (1) excellent size versatility,
(2) enhanced strength, shrink and barrier properties,
(3) inherently less waste, (4) ease of changeover, and
(5) natural tube shape readily forms into a bag, sleeve
or like configurations.
© 2000 Dallas Plastics Corporation
Dallas Plastics, Inc. (www.dallasplastics.com) is the highest quality supplier of POLYETHYLENE FILM, POLYETHYLENE, LDPE, HDPE, EVA, LLDPE, PLASTIC SHEETING, LAYFLAT TUBING, SLEEVE FILM, and DRAWTAPE.