Lecture 7: Lamination

Question 1

what are 3 layers in lamination? what are each of their functions?

Answer 1

1. PA: toughness, resilience, abrasion, printability
2. PVDC: barrier
3. PE: heat sealant layer

Question 2

define lamination

Answer 2

• a combination of different plastic films into one material
• at least 2 layers
• at least 1 of the layers is plastic

Question 3

what is the objective of lamination?

Answer 3

combine properties

• mechanical (tensile strength, stiffness, etc…)
• barrier (O2, water vapour, light)
• heat sealing
• printability
• optical (haze, clarity)
• stretch
• machinability

Question 4

what are examples of applications of laminates?

Answer 4

• extend shelf life
• products with high profit margin
• v sensitive pdts

Question 5

what are 4 methods of making laminations?

Answer 5

1. adhesive lamination
2. extrusion coating
3. co-extrusion
4. vacuum metallization

Question 6

describe adhesive lamination

Answer 6

adhesive (can be solvent or water based) applied to one web and combined w/ another

Question 7

describe the steps in adhesive lamination

Answer 7

• aqueous or solvent based is applied
• cured (dried) to take away excess solvent which would cause de-lamination
• coated web combined w/ uncoated using heat/pressure

Question 8

how does the type base of the adhesive change requirements of the lamination?

Answer 8

the type changes w/ heat requirements and bond strength

Question 9

what paper is extrusion coating used for?

Answer 9

common w/ PE, PP, PET paper

Question 10

what are advantages of extrusion coating over adhesive lamination?

Answer 10

• handling thin films of PE is difficult
• extrusion temp impregnantes plastic into paper
• cheaper
• less pollution

Question 11

what is the function of extrudate in extrusion coating?

Answer 11

acts as a glue

Question 12

what is co-extrusion?

Answer 12

two or more extrusion feeders into one head

Question 13

what are advantages of co-extrusion?

Answer 13

• lower cost
• less delamination
• flexibility

Question 14

what does vacuum metallization produce?

Answer 14

metallized plastic film or paper

Question 15

what are properties of metallized films?

Answer 15

• reflectance
• tougher
• susceptor: converts microwave E into radiant heat
• better barrier: but possibility of pinholes to moisture, flavour, light, gas

Question 16

what pre-treatments are needed before vacuum metallization?

Answer 16

• mechanical treatment: high voltage and high frequency discharge
• corona (continuous arc) is generated at film surface. This introduces polar groups which (1) cleans, oxidizes, activates surface and (2) gives better adhesion
• primer coating: thin coat attracts both layers

Question 17

describe the vacuum metallization process?

Answer 17

• metal is vapourized in vacuum chamber, then sprayed
• batch process
• mostly uses PP (80%), PET, PA
• coated w/ varnish to seal for a smooth surface

Question 18

what is the functionality of the laminate layer (from outside to inside)

Answer 18

• printability/abrasion resistance
• mechanical structure
• barrier
• heat sealability
• pdt compatibility

Question 19

what are the functions of the layers (from outside to inside) in a juice box?

Answer 19

1. PE: outer protection
2. printed paper: printability and strength
   3: PE: improves puncture resistance of foil
3. aluminum foil: barrier to moisture and flavour
4. PE: improves foil and heat sealability

Question 20

heat seal depends on what (3)

Answer 20

1. melt temp
2. machine pressure
3. contact time

Question 21

what are desirable properties of heat sealing layers?

Answer 21

• low melt temp
• strong seal
• low cost

Question 22

what is high sealing ability associated with?

Answer 22

high cost

Question 23

what is the film with highest seal and cost

Answer 23

ionomer (surlyn)

Question 24

what are common heat-sealing layers? what are their best properties?

Answer 24

LDPE: low T, fast seal, cheap cost

EVA (ethylene vinyl acetate)

ionomer (surlyn): seals through crumbs and grease

Question 25

what are examples of intermediate barriers?

Answer 25

nylon (outer barrier layer that is abrasion resistant) with LDPE (heat sealing)

Question 26

what is an example of high barrier laminates?

Answer 26

nylon (poor water but high gas barrier)
with PVdc (water and gas barrier)
LDPE (heat sealing layer)

Question 27

what is an example of a low-barrier laminate?

Answer 27

OVPC (outer breathable layer with high water but low gas barrier)
with LDPE (low gas barrier)

Question 28

what are 2 machines for forming packages?

Answer 28

1. VFFS: vertical form fill seal

2. HFFS: horizontal form fill seal

Question 29

describe VFFS

Answer 29

• compact and slower

steps:

1. product feeds into machine
2. goes through a longitudinal sealing jaw
3. film is cross sealed and cut off
4. used for package

Question 30

describe HFFS

Answer 30

• faster
• multi tunnel system

steps

• forming plough
• side seam
• fillers
• close and seal

Question 31

what are types of VFFS seams?

Answer 31

fin and lap

Question 32

what are types of HFFS seams?

Answer 32

3 side seal pouch

gusseted bottom

Question 33

for coffee packaging, what are

a) problems/needs
b) solutions

Answer 33

problems

• degassing
• protection from O2 (oxidation) and heat, light moisture (loss of flavor)

solution: metallized PET/PE which is
- stiff/strong
- good barrier to gas
- protects from O2
- protects from liht and moisture
- seals
- can be vacuum packed