Unit 2 - Fibre Flashcards

Question

Describe how moisture content affects fibre packaging performance

Answer 1

- Cellulose fibres absorb moisture and swell as they are hygroscopic: therefore, testing should be carried out after sample conditioning (23°C at 50% RH) - Change in the moisture content will affect the dimensions, the stiffness, the strength, and flatness - Fibres swell across the width and increase in size in the cross direction - Coatings can give an exaggerated effect as the moisture is preferentially absorbed into the uncoated side of the paper

Answer 2

- Tensile (pulling force) required to produce a rupture in a strip of paper - Measured in both MD and CD and is measured in kN/m - Indicative of fibre strength, fibre bonding, and fibre length

Answer 3

- Indicates behaviour of paper in various end-use situations such as web-runability, toughness, and the ability to absorb shocks - Important factors are fibre length and inter-fibre bonding - Longer fibres improve tear strength as the fibres can distribute stress better - Measured in both MD and CD and is expressed in mN

Answer 4

- Measure of force required to bend paper / board through a specified angle - this is a measure of flexural rigidity - Stiffness is defined as the bending moment (g-cm) needed to deflect the free end of a 1.5in wide vertically clamped sample 15° from its centre line when load is applied 50mm away from the clamp - Measured in MD and CD

Answer 5

- Done via Cobb test to determine water absorption over 60 seconds and is expressed in g/m^2 - Can effect the strength and propensity to curl - Results are dependent on water temperature so a standard of 23°C is used

Answer 6

- Measured using the Gurley method and is defined as the resistance to the passage of air when a pressure difference exists between the 2 sides - The time for a given volume of air to flow - Air resistance is an indirect indicator of degree of pulp beating, fibre compaction, and the amount of filler used in the production process - Vital when vacuum handling is used

Answer 7

- How much pressure a paper can tolerate before it ruptures - Measured as the maximum hydrostatic pressure required to rupture the sample by constantly increasing the pressure applied through a rubber diaphragm on a 1.2in diameter samples

Answer 8

1. Surface smoothess 2. Surface strength 3. Surface absorption 4. Surface tension 5. Whiteness 6. Opacity

Answer 9

- Also called the wax pick test and is a measure of the surface strength (or resistance to picking) - Picking occurs due to the poor internal bonding strength - Tested using a series of graded wax sticks (Dennison test) - when the wax has set, it is peeled off and the degree of fibre adhesion to the cold wax in measured (only for uncoated samples) - An acceptable pick level is #6 - For coated grades, the IGT pick test is used, where a tacky ink is applied and moved at an increasing speed - An acceptable IGT is >300

Answer 10

Affects how ink ‘wets out’ on the paper surface

Answer 11

Determines how resistant a paper is to losing printed inks

Answer 12

- Paper is made from cellulose wood fibres - mostly from north European softwood trees - Virgin hardwoods: most common species are birch and eucalyptus; they have short fibres which helps to give a smooth surface - Virgin softwoods: from coniferous trees such as pine and spruce; have long fibres which give high strength due to the greater surface area and fibrillation of fibres; however, if they are used on their own then they would produce a sheet with poor smoothness and poor printability - Recycled fibres are also used (which will have clays and calcium carbonate in) - Every time a fibre is recycled, it gets shorter resulting in a paper with higher density, lower bulk, and weaker physical strength

Answer 13

1.Logging / debarking 2. Pulping 3. Refining 4. Bleaching 5. Final preparation

Answer 14

1. Trees are harvested and transported to a pulp mill where they are de-barked 2. Bark is used as fuel (known as hog fuel) 3. Logs are reduced to chips

Answer 15

1. Only produced from softwood pulps 2. Physical grinding of wood chips to form a slurry with water 3. Softens the lignin but does not remove it - this residual lignin actually increases strength of the paper 4. It is a fast method and is used for low-grade paper 5. Type 1: thermo-mechanical (TCP) 1. Used in integrated mills 2. Uses 2+ rotating discs with bars machined into the surface 3. The distance between the discs is adjusted to make the correct pulp quality 4. The discs rotate in opposite directions which grinds the woodchips into fibres - this is called fibrillation 5. Called thermo-mechanical because a lot of heat is generated as steam which is used to soften the chips 6. Produces pulp with better bulk and strength properties 6. Type 2: chemi-thermo-mechanical pulp (CTMP) 1. Same as TCP but with chemicals added, such as sodium metabisulphite, to improve brightness of the pulp

Answer 16

1. Digestion of wood chips with chemicals and temperatures of 160°C 2. Process dissolves and removes 95% of the lignin and does not shorten fibres 3. More expensive and slower than mechanical pulping, but gives a strong final paper 4. Type 1: elemental chlorine-free (ECF) 1. Uses chlorine dioxide and ozone in a multi-stage bleaching process 5. Type 2: totally chlorine-free (TCF) 1. Also multi-stage but only uses ozone 2. The Kraft process is used to cook the fibres and separate them - this produces an unbleached pulp 3. Produces longest and strongest fibres

Answer 17

Developed in response to ban of elemental chlorine bleaching - dioxins and furans produced are linked to cancers

Answer 18

1. Size 2. Starch 3. Bactericides 4. De-foaming agents 5. Colours 6. OBA - optical brightening agents 7. Fillers

Answer 19

1. Controls water absorption and ink penetration 2. When added at the wet end, it is an emulsion of rosins 3. When added at the dry end as a surface application, it is mostly a polyurethane and starch emulsion

Answer 20

1. When added at the wet end, it is used to improve the internal ply-bond strength (in the z-direction) 2. Usually in the form of Farina (potato starch) 3. Ply-bond strength is important as a good carton crease relies on partial delamination of the internal plies 4. When applied at the dry end, it can improve printability in uncoated grades and reduce linting - usually maize starch

Answer 21

1. Used at the wet end as temperatures are high in paper mills which can lead to bacteria growth - starch also contributes to this 2. Starch makes bacteria grow which is not good for food contact and can cause runability problems 3. Bromine is used to instantly kill bacteria and no residual is left in the water

Answer 22

1. Usually a silicone emulsion - traditionally mineral oils or paraffin 2. Needed as air bubbles can disturb formation or lead to ‘skips’ in coatings

Answer 23

1. Complex and very expensive alternative to fluorescent whitening agents (FWA) 2. Used in the wet end or as a coating

Answer 24

1. Added to reduce cost and give properties such as printability, brightness, opacity, and dimensional stability 2. They fill the interstices of the paper to give a smooth finish and greater ink receptiveness 3. They interfere with fibre bonding, giving a softer feel, but reducing strength 4. Usually China clay (Kaolin), chalk, and titanium dioxide

Answer 25

1. In an integrated mill, pulp is transferred directly to the papermaking machine 2. In a non-integrated mill, pulp arrives in the form of sheets which are then mixed with water in a machine called a hydrapulper

Answer 26

1. A mechanical process which bruises and splits fibres to increase their flexibility - this is called fibrillation which increases the surface area of the fibres and controls fibre length distribution 2. Primary refining is done in a disc refiner then secondary refining is done in a conical refiner 3. The higher surface area means more hydrogen bonds can form and give more interlocking 4. A better fibre length distribution means better uniformity and printability 1. Fibres can be put through a fractionator so only fibres of the correct length are used

Answer 27

If the paper needs to be white, the pulp is bleached with chlorine-containing compounds or hydrogen peroxide

Answer 28

1. Additives are put into the pulp (now called Furnish) 1. Sizing agents such as rosins to control water and ink absorption 2. Starches and gums for burst and tensile strength, stiffness, and pick resistance 3. Clay and chalk for brightness and better printability 2. Pulp then goes through screening to ensure there are no contaminants 3. Then diluted to reach the required consistency 1. >1% for paper 2. 0.2 - 0.2% for board

Answer 29

1. Wet end - Head box - Slice lip - Wire (also called Fourdrinier table) - Press 2. Dry end - Heated cylinders / air dryers -Surface finishing processes

Answer 30

Paper pulp with 97-99% water content onto a moving belt where water is drained

Answer 31

The forming wire is a continuous loop of plastic mesh which acts as a sieve to allow water to drain which leaves an even layer of fibres on the surface

Answer 32

The headbox ensures sufficient turbulence in the thin stock so that it is evenly dispersed and delivered at an even pressure to the slice across the full width of the machine

Answer 33

The slice is used to control the size of a slot band and is divided into many sections, each about 20cm wide

Answer 34

- On the wire, water is removed by a combination of gravity and creating a pressure differential using table rolls on slower machine and high speed foils on faster machines - the foils create a downdraft to help draw water down - You know all water has been removed when you can see a dry-line across the sheet

Answer 35

Picks up the sheet onto a continuous felt belt 75%

Answer 36

- The sheet then continues to the secondary pressing where the water content is now low enough that it can no longer be suctioned out; water must be squeezed into the felt belts by hydraulic rolls - at this point, only one felt is used - The water content is now approximately 50%

Answer 37

- Next is the drying cylinders which is the most energy-intensive and costly part of the process - Sheet passes through many drying rolls to reduce the moisture content to 8% - On some machines, there is an MG cylinder between the drying cylinders which are up to 5m wide and have a highly-polished surface - Sometimes also sizing press in the middle which applied a size solution to control picking and water absorption

Answer 38

- Some machines have a final coating station to apply a pigmented coating for good printability - Usually water-based so are dried using a combination of infra-red and hot air units

Answer 39

- May also be a calendering unit which helps to smooth the paper and ensure an even thickness across the web - Pressure of 700kg/cm^2 and 300°C - Smoothness is caused by a differential speed difference

Answer 40

Thicker board

Answer 41

- A series of cylinders that each have a forming wire and a vat containing dilute paper stock - The wet sheet forms on the cylinder as it comes out of the vat and it couched off onto a felt belt on the underneath - this happens at every vat, each ones adding roughly 30gsm over 8-10 vats

Answer 42

Inverform - Designed due to speed limitations - The formers are inverted so each layer is put on top of the previous one - This is used in all modern machines

Answer 43

- Two sheets are formed separately then bought together in their wet state - There is a top and bottom felt to help drain water - As fibres are layered down, there is less fibre bonding than Fourdrinier

Answer 44

Pope reels

Answer 45

- Slit to customer widths with as little waste as possible - Uses two circular knives which are at the top and bottom - The top knives are sacrificial and act in a scissor action - A bad quality slit can cause fibrous debris - Rewind is formed of rollers which each run faster than the last to ensure the sheet remains taught

Answer 46

- For carton production, most printing presses are sheet-fed lithography - The cutting heads use two rotary knives which cut in a scissor action - Cut sheets are carried down the machine by tapes running over rollers to the delivery ‘lay-boy’ where they are placed on a pallet

Answer 47

1. GSM 2. Thickness 3. Moisture content

Answer 48

1. Inter-ply bond strength 2. Cobb 3. Smoothness

Answer 49

1. Printing and decoration 2. Cutting and creasing 3. Gluing

Answer 50

Stored under controlled conditions and allowed to stand for 48 hours to acclimatise

Answer 51

Offet lithography

Answer 52

- The printed sheet is cut and creased to the shape of the carton blank using a flat die or rotary cutting dies - Sharp knives produce cuts - Blunt knives produce creases

Answer 53

- Embossing can be carried out during the die-cutting process - Achieved by shallow knives - Either aesthetic or functional such as braille

Answer 54

- Foil blocking is only for decoration - Foil is fed in on a carrier layer which is then peeled away to leave the foil attached to the board

Answer 55

- Cartons are typically glues down the vertical side seam (straight line gluing) - May also be glued at the base for easier construction (glued crash locks) - They are pressed between 2 blankets to ensure the adhesive has bonded - The major creases are usually folded through 160° to ensure they don’t resist carton erection

Answer 56

1. Blister packs 2. Carded skin packs

Answer 57

- Composed of a rigid, thermoformed plastic shape which is attached to a paperboard backing card - they usually are adhesive bonded together - The backing card can be perforated to give a convenient opening feature - Sliding designs provide repeat and easy access to the product and require no heat-sealable coatings

Answer 58

1. Cost 2. Mouldability 3. Impact resistance 4. Scuff resistance 5. Low-temperature 6. Clarity

Answer 59

- PVC (polyvinyl chloride) performance varies depending on the formulation - Compatibility with adhesives should be evaluated - Can have a slight blue or yellow cast - Require low temperature performance - PET (polyethylene terephthalate) is fairly cost-effective and offers superior performance - Polystyrenes have excellent clarity but low impact resistance unless a special high-impact grade is used

Answer 60

Majority are 0.12-0.18mm in thickness

Answer 61

- Board must be selected according to the weight of the product being packed - Usually between 500-800µm in thickness - Suitable thickness can be achieved by doubling a lighter sheet - this is particularly useful for reinforcing pegboard holes

Answer 62

Most blister packs are flat and do not require the board to have good folding properties

Answer 63

1. Receptive to print 2. Good internal bond strength to resist ply separation 3. Porous so a vacuum can draw through the board to create the conforming skin 4. Stiff so it doesn't curl or delaminate

Answer 64

- After printing, the board is coated with a heat-sealable top coat and the blister is attached by the application of heat - Printing inks must be able to withstand the temperature - A properly-sealed pack will show fibre tear

Answer 65

1. Coated chipboard 2. Double white-lined stock 3. Solid bleached board

Answer 66

- Made by placing the product on a flat board sheet, then draping a heated plastic film over it - A vacuum is created to draw the film down around the product and a heat-activated adhesive bonds to the board

Answer 67

- They are more economical than blister packs as no special tooling is required - the product is the mould - Process is also easily adapted to small or large runs - It also immobilises the packaging for security

Answer 68

TetraPak and Combibloc Milk and fruit juice

Answer 69

- Usually tube-style cartons made from polyethylene-coated board - The coating is heated on the filling line to seal the pack

Answer 70

- Usually made from 3 overlapping spiral winds of recycled paper overlayed with bleached or natural Kraft paper - Inner wind can be laminated with foil or polyethylene to provide a barrier and liquid resistance - Usually have a round body but it is possible to make them rectangular

Answer 71

- Made by rolling a rectangle of paper to the desired number of layers - Bodies can be round, oval, or oblong and are difficult to make watertight, so most are for dry products - Containers are formed by printing a flat blank, then forming the shape around a mandrel using glue to form an overlap seal, then the ends are beaded and the end is added

Answer 72

Paperboard, metal, or plastic

Answer 73

Cushioning (especially for small electrical goods)

Answer 74

- Produced from waste paper - Can be coloured for aesthetic effect - Can be waxed for moisture resistance

Answer 75

- Stock preparation - The pulper combines pulp and water to provide stock of approximately 4% solids - 1% of these are resins which help bind the final pack together - Colour may be added as required - Wet forming section (rotary) - A forming die is immersed in a vat of stock and a vacuum system attracts fibre into the screen of the die; water is drawn away through the die, leaving a shaped pulp product - Drying section - Transferred to the drying section when it contains 75% water - Recycling hot air drying is used to reduce moisture content to approximately 8%

Answer 76

They are used when high-quality is required and good rigidity is needed for product protection

Answer 77

- Made from board and cover pages - Board is cut and creased with a score wheel - The base and lid are made and the corners stayed - this means reinforced - Pre-cut paper is used to cover the lid and base

Answer 78

Re-used for long-term storage such as jigsaws

Answer 79

1. Not suited to high-speed production 2. Manufacture is labour-intensive 3. Expensive

Answer 80

Kraft paper in a reel-fed process using semi-extensible paper, and can hold up to 32kg

Answer 81

- The inner tube is formed and the side-seam is glued - The outer tube is formed around the inner tube, then the seam is glued and both tubes are attached to each other - This multi-wall tube is cut, and the bottom is folded and glued

Answer 82

- Produced by running 1-4 plies of paper together to form a tube - The paper is off-set slightly so each ply bonds separately when adhesive is applied

Answer 83

- Self-opening sack - with our without paper handles - Sewn and open-mouth - with our without plastic handles - Roll-bottom - for pet food and granular products - Pinch-bottom - bottom is rolled twice to give a sift-proof bottom for powder products - Block bottom - gusseted and allows sack to stand up on the shelf - Valve sacks - for chemicals and fine powders

Answer 84

- Consists of a layer of fluted paper (roughly 105gsm) sandwiched between 2 layers of paper (roughly 125gsm each) - This gives high strength but using less materials - Accounts for 56% of fibre packaging in the UK - Formed of four main material categories: Kraft, test, chip, and fluting

Answer 85

- Brown Kraft is naturally brown in appearance and the shade can vary depending on mill location, fibre source, and the pulping process - White top Kraft was developed to have a good appearance with high strength but at a lower cost than traditional bleached Kraft; there are two main types: - White top liner - a top skin of bleached fibres on a natural fibre base - Coated white Kraft - a white coating (usually Kaolin) on a white top kraft or bleached fibre base - White mottled Kraft (sometimes called oyster) is made in the same process as white top liners but the skin of white is randomly distributed to give a mottled appearance - Bleached Kraft has slightly less strength but are rarely used nowadays - Birch-faced Kraft is where the top ply is made from birch fibres which are bleached using oxygen

Answer 86

- **Test liner 1** - Predominantly recycled fibres - Have a Ring Crush Test value similar to Kraft paper - Most often used as inner liners - **Test liner 2** - Predominantly recycled fibres - Have a RCT value that is 90% of that of Kraft - **Test liner 3** - Predominantly recycled fibres - Have a RCT value that is 75% of that of Kraft - Vary in colour and appearance from one source to another - Sometimes dyed and most often used as inner liners

Answer 87

- Manufactured from recycled fibres and are usually unsized - Used as inner or centre liners - Usually dyed brown or undyed grey - Can also be called ‘container middles’

Answer 88

- Recycled fluting - Made from 100% recycled fibre and usually sized - Semi-chemical fluting - Manufactured from hardwood pulp with some softwood and recycled fibres - Used for heavy-duty packaging and high humidity conditions

Answer 89

How many peaks per length of board

Answer 90

How high the peaks are

Answer 91

A fluting is mostly used in the USA for applications requiring high impact strength e.g. refrigerator packaging

Answer 92

C and B fluting is used for some transit packaging or display packaging for canned goods

Answer 93

- Paper is first conditioned to ensure the correct moisture content to prevent bowing and curling which could jam machinery - Flutes are formed using the ridges of the corrugator rolls with steam and pressure - Following this, a starch adhesive is applied to the tips and combined with a liner to produce a single-face corrugate - This is repeated until the desired wall type is achieved - Anything more than a single-face cannot be coiled and so is slit into sheets for carton blanks to be cut from

Answer 94

A case in which all cuts and scores are in straight lines - these require no special tooling

Answer 95

Vertically

Answer 96

- Long side flaps meet in the centre of the box - Uses the minimum amount of board in its construction

Answer 97

- Long side flaps totally overlap - Provides additional protection but uses more material

Answer 98

- Both axis flaps meet in the middle of the box - Good protection for the product - Requires extra tooling to die-cut the short side panels which increases the cost of production

Answer 99

Any case with angled or curved creases or cut-outs requires die-cutting

Answer 100

- Flat bed die - All knives and blunt strips are laid out on a flat blank - Rotary die - A curved die that is wrapped around a cylinder

Answer 101

- Advantages - More complex designs - Dimensionally more accurate - Disadvantages - Higher cost as each design needs a separate die

Answer 102

- Cutting knives must remain sharp otherwise you get swarf - this are bits of corrugate that are left attached - This will fall into the machine and jam it

Answer 103

3-point scoring uses a 1.1mm thick rule and is used for B, E, and smaller flutes

Answer 104

5-point scoring uses a 1.5mm thick rule and is used for A, C and double-wall corrugates

Answer 105

Include flexographic, screen, and offset lithography

Answer 106

A lot of redundant stock if the design needs to be changed

Answer 107

- After cutting, the cases are usually pre-folded and glued (usually the side joint) - Other conversion may include stitching (stapling) or taping to assemble the joints - Produces the most secure closure and is used for heavy-duty transit cases - As this method uses metal, it is not food contact approved and cannot be used for food products

Answer 108

1. Viscoelasticity 2. Moisture resistance 3. Mullen burst strength 4. Edgewise compression strength 5. Flat crush test 6. Porosity 7. Surface friction 8. Glue seam strength 9. Print quality / print adhesion 10. Product resistance

Answer 109

Corrugate is manufactured using tension and pressure which will revert to its original state over time (the crease will reduce in quality)

Answer 110

- An increase in moisture content quickly reduces the compression resistance - For each 1% increase in moisture content, the compression resistance falls by 10-15% - Treatments can either be in the paper itself or applied as a coating - Thermoset resins and waxes can provide wet strength

Answer 111

Uniform force is applied and is recorded when the liner fails

Answer 112

Fluting style

Answer 113

- Performance in printing and assembly machines - Measures resistance of fluting to failure - Is called the Concora test when done on fluting alone

Answer 114

- Often called Gurlen porosity test and measures airflow though corrugated material - Critical for vacuum handling systems

Answer 115

Relates to food stability on pallets

Unit 2 - Fibre Flashcards

(142 cards)