Blown Film Extrusion Flashcards
This process can be used to form films and sheets
blown film extrusion
is a continuous process in which the polymer is melted, and the melt is forced through an annular die
blown film extrusion
the resulting tube from the step in BFE is then inflated into a ____ and cooled
bubble
are the most common polymers used
polyolefins
the creation of the bubble inherently stretches the film in the _____ direction
circumferential direction (transversal)
blown film is always _____ oriented
monoxial
_____ stretching can be further imparted to make the film biaxial
longitudinal
the film turns from molten to solid at the
frostline
6 steps in BFE
extruder, die, bubble cooling, collapsing form, nip rollers, slitting and winding
the most common die used in blown film extrusion is
spiral channel die
refers to the diameter at the die land opening
die gap
amorphous drawdown ratio
16:1
crystalline drawdown ratio
160:1
gauge variation in BFE can be up to
+/- 10 %
makes use of 2 air rings
dual lip design
4 ways to reduce wrinkling
add rollers, air collapsing frame, lower the bubble, use very tall towers
is a pair of rollers
nips
nips are made of
one metal, one rubber
moves film and stretches it
nips
allows you to cut tubes open and have a flat film
slitting
tubes produced in blown film can be used as
bags or pouches
3 types of process of winders
surface drive, center drive, surface-center drive
controls the tension
winder
too little tension will result to
telescoping
too much tension will result to
crushed core or center bagginess
is done after surface treatment as the effect wears out overtime
printing
a surface treatment that is used more often for films than flame treatment
corona discharge
