cast versus blown film
Click here to load reader
Embed Size (px)
TRANSCRIPT
Cast versus blown film
Ted Brink
polyamide-based
Page nr.11
Contentsfilm requirementspolyamide characteristicsblown versus cast film technologyconclusionscast versus blown film
Page nr.
Main applications PA-based films
cast versus blown film
Page nr.Food packaging - film requirementsoxygen barriermoisture barriergrease and fat resistantshrink performancepuncture resistancesealabilityprintabilitytransparency
cast versus blown film
Page nr.Main reasons to use polyamide
O2mechanical strengthbarrier propertiescast versus blown film
Page nr.Polyamide propertiesPA-typeMelting point [C]H2O permeability [cc/m2/atm/day]O2 permeability[cc/m2/atm/day]PA66255812PA62201512PA6.12215545PA6.661951614PA111904120PA121805190
cast versus blown film
Page nr.film productioncast versus blown film
Page nr.
In spite of significant differences, both technologies are used for similar applicationsblowncastcast versus blown film
Page nr.cast filmcast versus blown film
Page nr.
Plasticising unit DieCasting stationWinderAutomation system
Cast film linecast versus blown film
Page nr.Cast film basics
cast versus blown film
Page nr.Chill roll coolingefficient coolingtemperature controlled water or oilchill roll surface structure high gloss or embossedinfluences quenching rate and film surface
cast versus blown film
Page nr.
12
Chill roll temperature20 40 C for optimum thermoforming> 80 C for optimum dimensional stabilityuniform temperature gradient across the rollprevent morphological differences
cast versus blown film
Page nr.blown filmcast versus blown film
Page nr.
cast versus blown film
Page nr.Bubble coolingcooling medium: aircooling technologiesexternal bubble coolinginternal bubble coolingcooling influences:outputfilm morphologyambient air orchilled air
cast versus blown film
Page nr.
16
External bubble cooling
cooling from the outsidecommonly ambient air
cast versus blown film
Page nr.Internal bubble cooling (IBC)
IBC cools the bubble from the insidecool air injected (5 15 C)warm air removed ( 75 C)increased outputcast versus blown film
Page nr.cast blowncast versus blown film
Page nr.Blown versus cast film polymer viscosityblown film: requires melt strength high viscositycast film: less critical medium to even low viscositycast versus blown film
Page nr.Blown versus cast film cooling efficiencycooling medium blown film: airair not very efficient cooling mediumouter bubble coolinginner bubble coolingcooling medium cast film: chill rollcooling by water or oilchill roll temperature between 25 and 125 Ccooling efficiencydetermines outputcast versus blown film
Page nr.Blown versus cast film film morphologycooling rate determines morphologyslow cooling large crystalsfast cooling smaller crystals (crystals frozen-in)high quenching rate film remains (almost) amorphous
cast versus blown film
Page nr.Blown versus cast film film transparencytransparency related to morphologyslow cooling large crystals more hazefast cooling crystals less time to grow higher transparencyvery fast cooling low crystallinity highest transparencyfilms with low crystallinitymay show postcrystallizationcast versus blown film
Page nr.Blown versus cast film film stiffnessstiffness related to morphologyslow cooling higher crystallinity higher stiffnessfast cooling low crystallinity lower stiffnessfilms with low crystallinitymay show postcrystallizationcast versus blown film
Page nr.Blown versus cast film thermoformingcast films perform better than blown filmslower crystallinity easier drawing at lower stressfilm morphology determines thermoformingcast versus blown film
Page nr.Blown versus cast film curlingcurling may occur in nonsymmetrical filmsnonsymmetrical films have different polymersdifferent polymers have different crystallization rate
Alayer A and B liquidB
layer B crystallizeslayer A followsAB
layer A crystallizeslayer B cannot followBAcause for curlingcast versus blown film
Page nr.Blown versus cast film orientationdifference in MD and TD stretching determines orientationcast film:fixed widthuniaxial drawdownblown film:more balanced MD TD orientationtools: BUR and DDR
cast versus blown film
Page nr.Blown versus cast film process flexibilitycast film:die has fixed widthneck-inside trimblown film:adjustable bubble sizecast versus blown film
Page nr.Blown versus cast film gauge uniformitycast film: 2 % independent on film thicknessblown film: 10 % for thin films (< 20 m) 5 % for thicker films (> 20 m) cast versus blown film
Page nr.Blown versus cast film wastecast film:start-up ad shut-down wastechange-over wastewaste due to side trimsblown film:start-up ad shut-down wastechange-over wastewaste:cast film: 5 8 % blown film: < 5 %cast versus blown film
Page nr.Blown versus cast film costscast film:floor space neededhigher investment costsblown film:height neededlower investment costcast film requires higherinvestment than blown filmcast versus blown film
Page nr.Blown versus cast film PA6 versus PA6.66cast film:only PA6 is usedblown film:PA6.66 used more than PA6PA6.66 more transparent than PA6PA6.66 shows less curling than PA6PA6 blended with PA6I/6Tcast film: PA6blown film: PA6.66cast versus blown film
Page nr.Cast versus blown film - overviewPolymer related:required viscositymorphologytransparencystiffnessthermoform performancecurling
Machine related:cooling efficiencyprocess flexibilitygauge uniformityorientationwastecosts
some grey areascast versus blown film
Page nr.Cast versus blown film overview contdPropertyCast Blown Cooling efficiency++++Viscosity requiredMedium/lowHigh Transparency ++++Thermoforming performance++++Curling in non-symmetrical filmsLessMoreFilm orientationMoreLessTrim/scrapMoreLessGauge variation GoodMedium
cast versus blown film
Page nr.Cast versus blown film - summaryprocess:cast film: higher outputcast film: better gauge controlblown film: less floor space and investmentfilms:morphology differencefilm crystallinitycrystal sizeoptical propertiesthermoforming due to cooling rate
cast versus blown film
Page nr.More information and contact
Ted BrinkEmail: [email protected]: www.extrusionist.comTel.: +31 651109899Skype: ted.brink
cast versus blown film
Page nr.