Unit 2 - Closures

Question 1

Who are the 3 main users of closures, and give an example of each

Answer 1

• Supplier closures
  
  • Include base of steel cans and closed end of tubes
• Fillers closures
  
  • Bottle caps and heat-seal films
• Consumer closures
  
  • Re-closeable lids etc.

Question 2

Name the 5 main types of closures

Answer 2

1. Glued / taped
2. Stitched / stapled
3. Folded / twisted
4. Mechanical
5. Heat-sealed

Question 3

What do stitched / stapled closures rely on?

Answer 3

Rely on tear strength of the substrate

Question 4

What do folded / twisted closures rely on?

Answer 4

Rely on dead-fold characteristics of materials and the accuracy of cutting / creasing operations for cartons

Question 5

Name the 4 ways in which mechanical closures are applied

Answer 5

1. Threaded
2. Seamed
3. Clamped
4. Pushed on

Question 6

How are threaded closures applied and removed?

Answer 6

Twist on and twist off

Question 7

What materials can threaded closures be made from?

Answer 7

Metal or plastic

Question 8

Name the 3 types of machinery that can apply threaded closures

Answer 8

1. Single head
2. Linear head
3. Multi-head capping machinery

Question 9

Name the two types of threaded closures and describe them

Answer 9

1. Continuous - rotation draws the threads of the cap onto the container by at least 360° to make the seal
2. Interrupted - closure descends until a liner forms a seal, with typically less than 90° rotation; can also be called a lug closure

Question 10

Give the 2 types of neck used with threaded closures and state what materials they are used with

Answer 10

1. Symmetrical - designed for glass bottles
2. Modified buttress - designed for plastic

Question 11

Name the 3 ways to achieve a seal with a threaded closure

Answer 11

1. Wadded closure
2. Wad-less closure
3. Plastisol liner

Question 12

Describe a wadded closure

Answer 12

1. The wadding conforms to the irregularities of the container top to provide a seal between the rim and the closure
2. Usually made from pulpboard or expanded plastic lined with PE
3. Held in place by friction fit

Question 13

Describe a wad-less closure

Answer 13

1. Seal is made between the pack and the cap, so the dimensions are critical
2. Inside of the cap has a lip which fits securely over the neck of the bottle enabling the seal

Question 14

Describe a Plastisol liner

Answer 14

1. A suspension of PVC particles in a liquid plasticiser - it flows as a liquid and can be poured into a heated mould
2. When heated to 177°C, the plastic and plasticiser mutually dissolve in each other, which give a flexible plastic when cooled

Question 15

Describe how an induction seal is applied

Answer 15

• Screw threaded closure is applied to the container to a set torque and then the capped container is passed between induction coils
  
  • The aluminium foil layer in the wad in heated via electromagnetic field transferring energy to metallic laminate and the heat seal coating on the foil is softened and adheres to the rim of the container (like a milk or condiment bottle)
  • There is no contact between the sealing coils and the closure

Question 16

What happens when an induction seal is opened?

Answer 16

On opening, the foil diaphragm remains sealed to the container, giving tamper evidence and maintaining preservation

Question 17

Name and describe the two types of induction seals

Answer 17

1. Two-piece liner - heat melts the wax, which is absorbed by the pulpboard which releases the aluminium layer to adhere to the container; the pulpboard remains in the cap
2. One-piece liner - the backing remains on the foil layer

Question 18

What are twist on / twist off closures made from?

Answer 18

Heavy gauge, lacquered or printed steel

Seals via flowed-in plastisol liner

Question 19

Give 3 advantages of twist on / twist off closures

Answer 19

• Withstands heat processing
• Tamper-evident pop-up button
• Fast application with typically less than 90° rotation

Question 20

What material are twist on / twist off closures usually applied to?

Answer 20

Used mainly on glass jars

Question 21

What do twist on / twist off closures require to work?

Answer 21

Requires clean thread area

Question 22

Give a disadvantage of twist on / twist off closures

Answer 22

Can be difficult to remove

Question 23

How do twist on / twist off closures provide tamper evidence?

Answer 23

Filled in a steam environment to draw a vacuum, created by the steam filling the headspace then condensing creating a vacuum to give a concave lid button

Question 24

Describe the composition of a press on / twist off closure

Answer 24

• Printed metal shell with no threads
• Flowed-in soft liner
• During heat processing, liner conforms to container threads

Question 25

Give 3 advantages of press on / twist off closures

Answer 25

1. Tamper evidence via pop-up button 2. High speed 3. High throughput

Question 26

Describe a pry off / lever lid and one requirement

Answer 26

- Required the lid to fit accurately to the container body in order to be leakproof - The rim of the container is used as a level point

Question 27

Describe seamed closures and where they are used

Answer 27

- Formed by the mechanical folding of metal and require a sealing compound - They are used where microbiological integrity is critical and so tolerances are very tight

Question 28

Describe the composition of a crown cork closure

Answer 28

- Heavy gauge tinplate with preformed liner or plastisol - Crimped glass bottle finish - Other developments include twist off crowns which use a lighter tinplate

Question 29

Describe roll on pilfer proof (ROPP) closures

Answer 29

- Aluminium shell, punched from printed and lacquered sheets with no threads - Liner inserted for sealing - Usually applied to glass bottles - Capping machine rolls threads into sidewall of shell

Question 30

Give an advantage and a disadvantage of ROPP closures

Answer 30

- Provides tamper evidence - Collar can be difficult to remove

Question 31

What 3 materials can push in / push on closures be made from?

Answer 31

1. Metal 2. Cork 3. Plastic

Question 32

What three things do push in / push on closures rely on?

Answer 32

1. Friction fit (dimensional accuracy) 2. Extensibility of materials 3. Compressibility of materials

Question 33

Describe heat seal closures

Answer 33

- Made by softening thermoplastic materials, such as PE, using heat and pressure - Seal can be made permanent or peelable depending on materials and processing conditions

Question 34

Describe how an ultrasonic seal is formed

Answer 34

- Uses mechanical vibration to create heat - the movement creates friction along molecular chains and contact points for both the substrate and sealing film; it is this friction which melts the materials together - Heat is developed internally rather than by traditional conduction from external layers - A voltage is supplied to an ultrasonic generator which converts this to a mechanical vibration; a sonotrode transmits this to the film

Question 35

Give 6 advantages of ultrasonic seals

Answer 35

- Low thermal loads so film shrinkage can be eliminated - No burning hazards - Cold weld tools ensure faster cooling and increased stability of the tool - Less cleaning - Shorter heating and cooling phases - Smaller sealing lines which saves packaging materials

Question 36

Give 2 disadvantages of ultrasonic sealing

Answer 36

- High cost - Loss of effectiveness with crystalline materials as the crystals dampen the ultrasonic pulse

Question 37

Name 3 things that a good ultrasonic seal depends on and why

Answer 37

- Time - too long will result in slow line speed; too short will lead to a poor seal - Temperature - too low and no seal will form; too high will result in over-melting - Pressure - too low and no seal will form; too high and the sealing layer will be squeezed out

Question 38

Give 3 things that can be designed into closures

Answer 38

1. Tamper evidence 2. Child resistance 3. Dispensing and measuring

Question 39

Describe 3 qualities of tamper evident closures

Answer 39

- Must provide visible evidence that pack has been breached - Relies on customer recognising that something is different - No agreed standard for tamper evidence

Question 40

Describe 3 qualities of child resistant closures

Answer 40

- More closely regulated - international standards for single use and reusable systems; BS EN 28317 - Must be usable by adults - especially the elderly - Usually have two features to be operated at once - for example, push and turn

Question 41

Give a disadvantage of dispensing and measuring closures

Answer 41

How you reclose with residual product needs to be considered