Lamination Flashcards
Define lamination:
combine different plastic film materials (+ non plastic materials) => 1 material
2+ layers (at least 1 is plastic)
Purpose of lamination:
COMBINE properties of materials (mechanical properties, barrier, heat-sealing, printability, optical properties, stretch…)
What products usually use laminates for packaging? (3)
long shelf-life
$$$$ products (high profit margin)
sensitive products
methods of making laminates: (4)
adhesive lamination
extrusion coating
co-extrusion
vacuum metallization
What is the process of adhesive lamination? (4)
adhesive (solvent or water based) applied to one web
Cured (dried)
combine with uncoated web (heat + pressure)
continue until all layers complete
Adhesives can be ____ or ____ based
aqueous, solvent
Why is curing important in adhesive lamination?
dries; excess solvent can cause de-lamination
parts of the adhesive lamination machine: (3)
unwind/rewind rolls
adhesive applicator
nip and chill roller
____ coating is comon with PE, PP, PET paper
extrusion coating
What are advantages of extrusion coating vs adhesive lamination? (4)
- avoid handling (thin PE film handling is difficult)
- high temp impregnantes plastic into paper
- cheaper
- less pollution
What acts as the ‘glue’ in extrusion coating?
extrudate
What is co-extrusion?
2+ extrusion feeders into 1 head -> extrudate is combination
Advantages of co-extrusion: (3)
lower cost
less delamination
flexibility
What are some products obtained with co-extrusion?
thermoforming films/sheets, retortable films/sheets, flexible films
What is vacuum metallization?
metallized plastic film/paper (added metal material)
properties of metallized films: (4)
reflectance (metallic/shiny)
tougher
susceptor (microwave energy -> radiant heat)
better barrier
Pre-treatments required before vacuum metallization: (2)
mechanical treatment
primer coating
What is the mechanical treatment for vacuum metallization?
high voltage/frequency discharge
Corona (continuous arc) @ film surface -> introduce polar groups
-> clean, oxidize, activate surface = better adhesion
What is the ‘primer coating’ in vacuum metallization?
thin coat applied that attracts both layers (better adhesion)
What is the process for vacuum metallization? (3)
BATCH PROCESS:
- metal vaporized in vacuum chamber
- sprayed to apply to pre-treated material
- coated with varnish to seal/smooth
What films are used for vacuum metallization? (4)
PP (80%)
PET (15%)
PA (4%)
PVC, PVDC, PS (1%)
T/F: the most common plastic film in metallization is PS
FALSE: Least common (<1%)
What are the functions of various laminate layers? (inside -> outside) (5)
product compatibility heat sealability barrier mech. structure printability/abrasion resistance
Describe the laminated structure of a juice box (out -> in) (5)
- PE (outer protection)
- Printed paper (printable, strength)
- PE (puncture resistance)
- Aluminum (moisture/flavor barrier)
- PE (sealability, prevent metallic taste)
heat-seal depends on: (3)
melt temp
machine pressure
contact time
Ideal features for a heat-sealing layer: (3)
low melt temp
strong sealing properties
low cost
The best sealing materials? What is the downside?
Ionomers (Surlyn)
$$$$!
generally, the higher the seal ability, the (higher/lower) the cost
higher
An alternative to ionomers for heat sealing, that is slightly lower in seal ability and cost?
acid copolymers
common heat seal layers, worst to best heat sealability: (3)
LDPE
EVA (ethylene vinyl acetate)
Ionomer (Surlyn)
What are the major purposes of intermediate barriers? (3)
heat sealing
barrier
toughness/mech structure
major purpose of the outermost and inntermost layers?
outer: printability/abrasion resistance
inner: food contact (safe/nonreactive)
____ is comonly used as the outer barrier layer. what are its properties?
nylon
abrasion resistant/tough, but poor water barrier (*good gas barrier if DRY)
a nylon + LDPE laminate is considered a ____ barrier laminate
intermediate
What can be added to made an intermediate laminate into a high-barrier laminate?
Add a barrier layer between
ex: PVDC (excellent water/gas barrier)
Example of a low-barrier laminate
OPVC outer (breathable) - high water barrier but low gas barrier
LDPE/ionomer (coextruded) - low gas barrier
Saran-containing laminates are ____ barrier materials that are (flexible/rigid)
high barrier, flexible
2 examples of high barrier, semi-rigid laminate materials:
How are they produced?
PVC/EVOH/EVA
PVC/EVOH/surlyn
co-extrusion
2-layered laminates are usually ____barrier, and are (flexible/rigid)
medium barrier, flexible
materials commonly used to increase barrier properties: (3)
Saran
EVOH
Foil
Give the structure/materials of a non-shrink bag:
PA/PET outer (strength, O2 barrier)
LDPE/ionomer/EVA inner (moisture barrier, heat seal)
Give the structure/materials of a shrink bag:
nylon outer (strength)
PVC/PVDC (gas barrier)
EVA/surlyn inner (moisture barrier, heat seal)
2 machinery types for forming packages:
VFFS (vertical form-fill-seal)
HFFS (horizontal form-fill-seal)
Which is faster, VFFS or HFFS?
HFFS
Describe the process of VFFS:
unwind laminate forming & draw down (form package) product feed (fill package) longitudinal sealing jaw -> cross seal & cut off
T/F: VFFS is larger than HFFS systems
false: more compact
compare HFFS vs VFFS:
HFFS: Faster, multi-tunnel systems, horizontal fill
VFFS: slower, compact, vertical fill
Describe the process of HFFS:
unwind laminate forming plow (forms film) product deposited (filled) form seam -> pouch close/seal
What types of seals are used in VFFS? (2) What is used for HFFS? (2)
VFFS: fin seal, lap seal
HFFS: 3-side seal pouch, gusseted bottom
various forms of packages made by VFFS or HFFS:
bags, pouches/stand-up pouches, tear seams, dispenser, re-sealable bags
re-sealable zippers for ready-made foods are usually made of _____ in order to ____
PP withstand retort (heat-stable)
resealable closures types:
PP zipper
adhesive (ex: cookies)
What are specific packaging requirements for coffee/milk powder? What is the solution?
degassing (gas release from coffee)
protection from O2, heat, light, moisture (preserve flavor/quality)
solution: metallized PE (stiff, strong, barrier, opaque, seals, vacuum)
What packaging is used for coffee concentrate, and why?
PE/Al/PE/Al/PE (multilayer)
seals, lightweight, protect from light & O2
What packaging is used for pizza, and why?
PET/PVDC/PE(or ionomer)
PET: strength,
PVDC: high barrier against gas/moisture/oil
PE/Ionomer: seals
What packaging is used for fresh meat? Why?
PE/PA/PE or PET/PVDC/PE
PE/PET: water barrier
PA/PVDC: strength/barrier
PE: seals
Why does sausage have different packaging material requirements than fresh meat?
Different composition (less moisture, more fat)
What packaging is used for sausage? Why?
PE/OPA
water barrier, strength, oil resistant, seals
What packaging is used for fresh pasta? Why
PE/PVC
strength, moisture barrier, seal
What packaging is used for cheese? Why?
PET/PE/PVDC
strength, moisture barrier
seal
barrier (odor), oil resistant
What packaging is used for baked goods? Why?
PVDC/PET(or PP)/PE
barrier, seal
What packaging is used for freeze-dried goods?
48ga PETE 60ga extruded PE 28ga Aluminum 60ga extruded PE 40ga LLDPE freshlock zipper
