Week 1: History/Background & Functions
Packaging: Components which are “required” for a hybrid of functional needs that contain, protects/preserves, transports and informs/sells.
functional needs is the balance of the technical ( contain, protect, measure, dispense, preserve, store, etc.) and the marketing/business side ( promote, motivate, sell, communicate, inform, display, etc.)
change is inevitable and driven from:
– societal need / demand (ex: Tylenol package tampering circa 1982)
– availability / scarcity ( natural cork depletion -> synthetic corks)
– evolution & improvement ( glass milk jug -> carton -> plastic jug -> bag in box)
History / Evolution:
Earliest of packages: wrap of leaves or animal skin, naturally hollow piece of wood or gourd, nut shell, etc.
Increased use of tools and trading among peoples increased packaging use and choices: Fabrication of crude sacks, bags, baskets evolved into clay pots and fired clay, glass objects have been noted from ~ 2500 BC, wood barrels, paper and up to today’s use of plastics and composites.
Industrial Revolution led to an industrial society which created consumer demand, which accelerated the demand for packaging improvements. Bulk delivery to point of sale required some method of containing portion for single sale – use of wrapping paper became common. Imprinting on the wrapping became common.
Central Processing evolved as well, increasing efficiency and reclaim possibilities.
(cotton example: fibers to thread, linters to chemicals/papers, hulls to animal feed, oil from seed to frying, etc.)
1877 Quaker Oats brand image appeared.
Plastics: 1856 – first plastic based upon cellulose was made (non-packaging application)
1907 phenol formaldehyde plastic was discovered (Bakelite)
1911 DuPont chemists perfected the cellulose casting process (cellophane)
Packaging has two primary industries : supply side that produces packages / materials; and the use / converting side that makes final products.
Environmental: 4 R’s Reduce, Re-use, Recycle, Recover
Chapter 2: Levels of Packaging
Primary Secondary Distribution Package Unit Load
Contain Function – consider product and its physical form / nature.
Protect & Preserve Function – shocks, loads/forces, compression actions, etc. as well as the atmosphere control needs. Preserve function is mostly related to time sensitive items, ex. food products.
Forms of change: internal biological deterioration, external biological deterioration, abiotic deterioration ( chemical or physical changes)
Pathogens are critical design consideration.
clostridium botulinum botulism
claviceps purpurea ergotism
aspergillus flavus aflatoxin poisoning
Micro organism types:
Mesophyllic prefers ambient conditions 20-45˚C (68-113˚F)
psychsophilic prefers cool conditions 10-25˚C (50-77˚F)
thermophilic tolerates heat, will propagate 30-75˚C ( 86-167˚F)
Aerobic needs oxygen to propagate
anerobic propagates only in the absence of oxygen
Principle environmental factors regulating microorganism growth:
– temperature – moisture
– acidity (pH) – nutrient source
Approaches to extending shelf life:
– reduced temperature – thermal processing – water reduction/extraction
– chemical preservation – modified atmospheres – irradiation
Bacteria & molds stop developing -8˚C (18˚F)
chemical & microorganism activity stops -18˚C (0˚F)
peak ice crystal formation temperature 0 to -5˚C (32 to 23˚F)
beef color w/ O2 and fish challenges discussion
Thermal Processing – treatment depends upon:
– microorganism to be destroyed
– acidity (pH) of the food
– physical nature of the food
– heat tolerance of the food
– container type and its dimensions
Hot filling –
Ultra High Temperature –
Normal canning –
Retortable pouch –
Water Reduction – elimination of moisture below microorganism support levels: heat, salt or sugar. equilibrium relative humidity ≡ erh = atmospheric humidity condition under which the moisture gain or loss is zero. water activity, Aw is the usual expression.
example: erh = 50% => Aw = 0.5
low erh or Aw foods / products need moisture barriers
Chemical Preservation – use varies widely & strictly controlled by country specific laws.
– many are acids which lower pH.
– some kill bacteriostats, i.e. kill bacteria.
– salt application and/or smoking of item.
– oxygen absorbers & anti-oxidants in the packaging materials.
Modified Atmosphere Packaging (MAP)
– oxygen is usually reduced or eliminated.
– CO2 in high concentrations is a natural bacteriostat, and is highly soluble in water.
– nitrogen: inert negligibly soluble in water, tasteless
Gasses within the package must be balanced in the design of the package to avoid equilibrium partial pressure being established over time.
Fruits and vegetables – respiration continues: consumes oxygen and produces moisture and CO2. requires ventilation (low barrier films).
Irradiation – radiation energy with shorter wavelengths, causes an ionization process, usually with water. Cobalt 60 is the common source used for gamma rays on food. Cannot make items radioactive, but the Cobalt 60 must be utilized with all precautions involving radioactive hazards. Controversial on food in some countries. Labeling requirements vary. Also used on medical devices, packaging materials, and personal care products.
Transport Function – transporting is regarded as hazardous to the product or the package contents: packaging is designed to protect the product. Understanding of the distribution chain is essential to packaging success.
Inform / Sell Function – pure communication.
Fundamentally required: Food labeling laws required:
– product name – ingredients
– quantity – nutritional analysis
– address or contact method – batch / lot info
Demographics & psychographics also impact:
– selected materials – shape and size
– color – typography or fonts
– icons and known symbols – illustrations
Chapter 3 : Graphic Design
Blending of technical functions with the inform consumer functions: goal is to persuade and “claim” attention from other packages/products.
Needs to be balanced with actual product & performance.
Who is the targeted receiver of the communication?
Demographics: Grocery Products Manufacturers of Canada (GPMC) study:
– Laissez faires (18%)
– mature moderates (17%)
– three squares (21%)
– fat phobics (22%)
– trend trackers (22%)
What is the purchase intent? durable goods, impulse item, staple item, seasonal, gift, etc.
Use & Application Features:
– opening & re-close features – dispensing and measuring aides
– instructions & cautions – disposal method or secondary uses
– storage method – use quantities
– overall attractiveness
Retail and Merchandising Methods: mail order, self serve, shelf display, warehouse outlet, hanging or pegboard, department stores, vending machine, door to door, street vendor, specialty stores, etc. Each will impact the design of the package.
Brand Names – separate class in the marketing area . $50 MM for establishing a new “national” brand name.
Color and the perceived product performance : emotional based.
Graphic Design Basics:
– Shape – Size (actual or perceived)
– Color – Texture (actual or perceived)
– Tone -Lines
– Icons & Symbols
Also consider: Balance and unity
Direction and dominance
Typography and Fonts
Week 2: Chapter 4 – Printing & Decorating
Objective of printing: create visibly identifiable image consistently for a large number of units.
Printing Plate creates the ability to separate image and non-image areas.
Printing includes flexography, lithography, and gravure.
Decorating includes all special methods, including screen printing, stamping, embossing, pad printing, laminating, and coatings.
Color-based upon the electromagnetic spectrum, visible light is about midway on the scale:
Sound AM TV infrared red violet ultra X-rays Gamma
Radio | visible |
700 nm 400 nm
Þ decreasing wavelength with increasing powerÝ
Human eye – receptors , provides ability to sense several million colors.
Additive Synthesis: Blue + Green = cyan ù
Red + Blue = magenta ú primary printing colors
Red + Green = yellow û
White: all receptors equally stimulated
Black: no stimulus
Subtractive Synthesis: absorption of certain light wavelengths from white light yields a different color appearance.
Hue: named color , position in the spectrum.
Value: lightness or darkness of a color.
Chroma: how strongly colored a sample is, AKA saturation.
Tinting – Adjusting lighter with more white.
Toning – Adjusting darker with more black.
Brightness – white standard: pure magnesium dioxide º 100
For a package substrate, its brightness is key because ink is transparent and the resulting non-absorbed light is reflected back to the observer. Intensity is related to reflected (vs. absorbed) light.
Color perception is highly subjective due to : observer, light levels, object itself.
– international standard for illumination º 5000°K (outdoors @ noon)
– object: surface texture, gloss, geometry, adjacent colors, etc.
– Observer: emotions & preferences, along with fatigue and after images combine to impact perceived colors. Colorimeters and densitometers remove human factors from color matching and identification.
CMYK KºKey color, can’t get a clean black color from CMY so use K.
Artwork: Drawing, illustration, or graphic effect imparted to a substrate.
printed matter: – line art
– halftone art
– process-printed art
which one used impacts printing plate preparation.
line art: solid monolithic laydowns of a single hue. examples: diagrams, illustrations, illustrations with solid blocks of color. Simplest and least expensive. Requires a plate for each color, which requires registration.
PMS # => Pantone Matching System Number ( has ~ 1000 #’s which results in exact matches about 50% of the time).
Halftone, single color: uses patterns to crate a scale of color saturations. Illusion of the image is created via blending the ink pattern with the blank background of the substrate showing through (“tricks the eye”). The smaller the pattern, the better the resolution and the sharper the image appears. Screens are used to project the image onto the printing plates, with screens being defined by the resolution in dots per inch (dpi).
the substrate, image or illustration type, and printing method dictate screen size, i.e. finer screens ( higher dpi) for smoother substrates.
Process printing: Uses halftone technology for each color to be printed via a separate plate. Registration of the plates is critical.
Component colors are “separated” into photo negatives for making plates.
Super imposing without control or design would result in Moiré (mow ray) patterns, which is an optical perception issue. To reduce the chances of this occurring Magenta is at 75˚, yellow is 90˚, and cyan is at 105˚ from vertical.
Preparation for Printing:
Design of the image or pattern is laid out in what is called a mechanical layout drawing. Some key design requirements include:
– direct image or reverse image
– treatment of UPC (universal product code)
– color bleed areas (see examples)
– gluing locations or any other hidden portions
– press tolerances that need “trapping”
– special colors or inks that need separate plates (fluorescent, metallic, very bright greens or oranges, etc.) note dark browns usually require a separate plate due to heavy “laydown” if not done as a separate color.
Proofing: creating actual sample of the final printed image without the full cost of printing plates, press runs, etc.
Fuji or Match prints
Trap: overlapping of the ink “dots” to eliminate substrate showing through.
litho – 100 μm (0.004 inch)
flexo – 350 μm (0.014 inch)
gravure – 175 μm (0.007 inch)
– crosses for alignment
– tonal scales
– gray balance charts
Note: Reference specimens are usually saved for print quality and color tolerances from the first acceptable press run.
Printing Methods: all use form of a “plate” to transfer inks
Relief – Flexography variations, letterpress & offset letterpress (flexo)
Planographic – lithography or offset lithography (litho or offset)
Gravure – rotogravure, intaglio (gravure or roto)
Common features of presses:
– an accurate material feed system that presents the substrate in register
– ink reservoir(s) or fountain with a supply method
– ink metering system for control of laydown
– ink configuration system (printing plate)
– transfer point: location where substrate is pressed into contact with ink(s)
– drying system
Press can be web fed (faster with greater output) or sheet fed (for stiff, non-bendable objects).
Which type of printing to select depends upon:
– volume or number of impressions needed.
– substrate type
– physical shape of the substrate
– art type and desired effect
– special packaging process or use conditions (chemical or thermal)
Relief Printing- raised surface holds the ink for transfer, i.e. standard office rubber stamp.
Flexography – 60-120 dpi (needs to be a fairly “fluid” ink , low viscosity)
– sensitive to pressure changes at the impression point.
– pressure changes appear as color changes in the finished work.
– copy with fine details or large areas of solid block colors should be avoided.
Letterpress & offset letterpress (subset of flexography)
– usually used for tags or labels
– uses a thicker or more paste like ink
– printing plates are usually made of hard plastic or metal, cost more than std. flexo but last longer
– gives finer screen pattern
– cylindrical objects can be direct printed using letterpress or offset letterpress (overlap of the pattern leaves a “darker” margin). drawn & ironed metal cans, round plastic tubes, metal or plastic collapsible tubes can be printed with offset or letterpress.
– inks are cured by heat or ultra violet.
– usually simple line art or halftone art. look for fine unprinted line between color areas.
Lithography – 133-150 dpi based upon the differences between oil & water.
– Aluminum alloy plates contain oil receptive areas and water receptive areas.
– usually ( not always ) sheet fed.
– Offset litho most common printing method for carton stock, paper labels for cans and bottles.
– paper needs to be somewhat water resistant, clean surface with tight anchorage of fibers and coatings, which if not then image will be marred.
– litho on plastics in not reco’d
– ink is still “wet” when exiting printing press, requires good “trapping” over wet inks.
– water based UV varnish is used to “coat” the image allowing further handling before complete drying of image.
Gravure or Rotogravure – ink well approach: metal cylinder is etched with recessed cells that hold ink. Depth of cell determines the amount of ink that is held.
– low viscosity ink is flooded over the surface of the plate and then “doctored” off, leaving each cell with it’s pre-determined volume of ink.
– usually web or roll stock fed.
– substrate surface must be very smooth.
– sometimes electrostatic charging is used to assist ink transfer.
– allows very thick ink laydown.
– always uses a dot pattern, which makes fine lines and pin striping difficult to achieve.
– cylinders are more costly and take longer to manufacture, but last for several million impressions (vs. ≤ 1 million for other two methods), best for high volume web applications.
See tables in text for:
– pro’s and con’s of each type
– press configurations and applications
– ink thickness achieved
Other Printing Techniques and/or Applications
Screen Printing- uses easy and economical screen over which ink is spread, uses a lot of ink (i.e. very heavy coverage), made of plastic or metal mesh.
Reflective Metallic – reflective gloss comes from metal surface of Aluminum foil or metallized substrate, usually applied only to roll goods (web fed), has high cost for large areas, small areas use hot stamping. Moisture and gas barrier forms with use of Aluminum.
Heat Transfer & Hot Stamping- hot stamping requires heated die with image on it, heat transfer (popular for plastics) uses overall heated die with the image detail pre-applied to the carrier.
Pad Printing – uses a flat gravure plate called a cliché which is inked and a highly flexible pad to make a conforming transfer medium, extremely useful for irregular shapes.
Embossing – physically deforms the substrate to impart the image in the structure.
Protection of Printing – coatings applied over the printed image, usually a UV cured gloss coat with good gloss and shine (semi-gloss or dull also available).
Reverse printing is also used where an additional layer will act as a backer sheet in a laminate structure.
Laser Marking – burns material away to produce the image, high speed but limited in font sizes.
Ink Jet Printers – use electrical changes to deflect the sprayed ink droplets into forming the images desired.
Printing Inks – “typical inks” contain:
Pigments – ingredients that provide color.
Vehicle – component that binds pigment particles and adheres them to the surface, usually a resin or a derivative of a resin.
Solvents – used to fluidize components and delay resin solidification.
Additives – agents for wetting, drying, anti-oxidation, viscosity control agents, tackifiers (for increasing adhesion), etc.
Inks “solidify” by:
– Evaporation of solvent or water.
– Absorption of solvent or water.
– Chemical reaction.
– heavy metal components in some pigments is an issue: lead, mercury, bismuth, antimony, chromium, cadmium are used, but need to be reduced or eliminated.
– resin components and related solvents are being regulated. Water based options are increasing in performance and in cost. More options being developed.
– Vegetable based inks are being developed and growing in application.
– Art work design will impact the printing choices along with details about the item to be printed / decorated.
– Printers will have good input into cost and final quality.
– Methods of printing are constantly competing with each other, rapid and significant improvements are ongoing.
– Remember the 4 R’s of environmental loading concerns.
Week 3: Paper and Paperboard
– Usually composed of plant fibers formed into a matted or felted sheet.
– Fiber sources: rags ( linen), bagasse (sugar cane), cotton, straw, wood to cellulose fiber.
Paper board, boxboard, cardboard, carton board are all used to describe heavy paper stock.
– 2 most common methods to quantify a paper is caliper (thickness) and grammage (weight or basis weight)
Paper or Board classification: depends upon the system of units –
ISO = material greater than 250 gms/ sq meter is paper board (~51 #’s/ 1000 sq ft)
US standard practice calls anything thicker than 300 μ m (0.012in) is paper board
Things that impact paper properties:
– fiber source
– extraction method and preparations for making
– machine upon which paper is made
– treatments given to the finished paper
Fiber Length is very key to paper properties (especially in packaging): the longer the fiber, the better for entangling and the stronger the finished product which yields higher tensiles, tear, fold and puncture strengths.
Table 5.1 has average fiber sizes for wood sources.
Eucalyptus example. Recycle impact on fibers and contents / inclusions
Down side of longer fiber is courser texture and print quality impact from lack of smoothness.
Formation = evenness of the fiber distribution across the sheet as it is formed.
Short fibers are more consistent and result in a smoother texture with tradeoffs in strength, etc. hence the blending of fibers is sometimes used.
Wood components: cellulose (cell wall structure), lignin (natural adhesive), carbohydrates, rosin like substances (esp. softwoods).
Separation methods: Mechanical, Chemical, and combinations of the two
Common treatments: beating , bleaching
Result is stock or furnish to send to paper machine with additives.
Additives: sizing agents, starches/gums, and wet strength resins.
Paper Machine Types
Fourdrinier: pulp pumped onto wire or moving screen. Limited in thickness capability.
Cylinder machine: screen on outside of a drum rotates from a pulp bath , dewatering fibers and pushing sheet onto the felt. Allows multiple stations and can be different furnishes in different layers.
Twin wire machine: uses two wires/screens to trap the fiber mat and dewater from both sides simultaneously.
Depositing fibers onto a moving belt tends to align the fibers yielding differences in properties : MD & CD. Paper is anisotropic material i.e. properties are different depending upon direction.
Directionality of paper is critical to package designer ( esp. in corrugation and boxes).
Cylinder machines 4:1 MD to CD Fourdrinier machines 2:1 MD to CD
wet end 35 % to 55% dry reel target is 2 to 4% (watch bone dry conversions)
Dry End treatments: Calendering, Coatings, Polishing, others
– coating adhesion and printing properties
– sizing, water resistance, and adhesives.
-variations in papers and boards (run to run and mill to mill)
Week 4 Paper Board Cartons (Chapter 6)
Folding Cartons – Tube style or tray style
– Tube- High speed
– includes milk cartons (heavily sized polyethylene coated) & juice boxes (paper/foil/poly laminated)
-Tray – example: beverage carrier for bottles
Set-up boxes- storage space empty = storage space full
advantages: upscale image durable for storage
Tubs, trays, & Liquid Resistant Boxes
Tubs – ice cream & frozen foods: Formed with paper endseals
Trays – frozen entrées : flat sheets with gusseted corners
Dual ovenable paperboard trays
Paper is hygroscopic: impacts laminating, warpage and buckling.
Equilibrium moisture content is usually quantified approaching from the lower humidity side (bone dry) due to hysteresis in the paper.
23°C & 50% R.H. is International Standard
Paper is also Hygroexpansive and viscoelastic
Over long periods paper fibers move, distort, or “creep”. This also allows set to be an impact to carton running with age of the carton.
Paper Characterisation Methods: ASTM & TAPPI
Back to cartons….
Design considerations: – product requirements
– retailing factors
– production requirements
– consumer needs
– other needs
– Style of the carton itself
– self contained or will another package be inside?
– single entry or repeated entry?
– need for security features?
– weight of particular product an issue?
– is sift proof construction required?
– type of packaging operation?
– vertical or horizontal?
– retail orientation?
– any particular machinery restrictions?
Carton layouts are normally shown from the outside or printed surface, except for sample manufacturing ( i.e. hand cut sample), then the drawing is reversed to show proper construction , particularly for scoring.
Board selection is mainly driven by : -structural requirements
– printing and decorating needs
(Slides and discussion)
Corrugated Fiber Board (chapter 15)
Mullen burst test original requirement for completed box performance.
1991 dual classification allowing ECT was introduced
UFC – Uniform Freight Classification
NMFC – National Motor Freight Classification
Stamp on the “bottom”
Regular Slotted Container – RSC
mottled white or oysterboard from layer of bleached kraft
solid bleached kraft liner board used for preprint.
Recyle fibers and impacts: thickness and water properties.
Flutes: A C B E
flutes/meter 100 -120 120-140 145-165 280-310
Take up factor 1.54 1.42 1.32 1.27
Finished board is described from the outside of the box to the inside of the box.
(Corrugator machine cutaway overhead)
Adhesives – usually starch, sometimes with other additives
Once Board is hard via heat and curing, it must be handled in sheet form
slit and cut to length.
scoring is frequently done on the corrugating machine.
Balance and unbalanced construction of single wall board
(overhead on corrugation testing procedures)
ECT is utilized where warehouse stacking strength is critical
Mullen test is utilized were environment that package will see is rugged and/or subject to puncture.
McKee formula for approximating box compression strength:
Compression strength, kN = 5.87 * ECT * √BP * T
where : ECT = edge crush test, kN/m
BP = inside box perimeter, m
T = combined board thickness, m
Week 5 : Corrugate (cont.’d)
Fiberboard characterization tests:
-Mullen Burst: pressure at which inner liner or facing ruptures ( related to paper tensile strength).
-Edgewise Compression Test (ECT) relates to McKee formula. Note: only applies to RSC’s, and only those with perimeter to depth ratio of 7:1 or less.
McKee Formula (again!)
Box Compression strength, kN = 5.87 * ECT * √(BP *T)
Where: ECT is Edgewise Compression Test, kN/m
BP is box perimeter, inside, m
T is combined board thickness, m
(Slide on Box dimensions and names)
– Flat Crush Test – Water Take-up Test (Cobb)
– Combined Weight of Facings – Puncture Test (Beach or GE for triple wall)
– Thickness of Corrugated Board – Pin Adhesion
– Gurley Porosity – Ply Seperation
– Flexural Stiffness – Coefficient of Friction (0-0.3 too low)
NMFC & UFC rules are for reference only, can’t effectively be utilized as package “design tool”. Table 15.4 is a good guide for selecting corrugate specifics when in the initial design phase of the box.
Flutes: (usually C or B )
E & F are available, but limited in economics to replacing 30 point carton board.
A flute has ~ o.25 inch flute dimension and typically is no longer available.
B flute is typically used where internal product supports the load.
C flute is used where container bears most or all of the weight in stacking.
Table 15.6 summarizes flutes and characteristics.
Box Design Variations:
RSC- slits & cuts, scores are all straight lines in MD & CD only.
Die Cut Designs – angled cuts or scores, curves or internal cut outs. More accurate, but die process causes strength losses. Can be rotary or flatbed die cut.
Bliss Box- style used for produce and items requiring internal support. Allows for triangular corner supports as well. Requires a special erecting machine, and increases the inventory of boxes on hand.
knock down flat (KDF) or wrap-around styles (show samples)
Dimensions: always in this order Length*Width*Depth
Use inside dimensions, greater of the flap opening dimensions is the Length, the other is width. Depth is the inside dimension between the upper/top and lower/bottom flaps.
Top Loading uses greatest area of board, but has the largest opening for loading.
End Opening uses the least area of board, but has the smallest opening.
Scoring: corrugate folds by collapsing in on self, so tolerances are needed to allow for material utilized in each score. How much allowance depends upon the box design, flute of the board, materials, and scoring wheel utilized.
(slide on score to score dimension)
Table 15.8 in text contains scoring allowances for boards of various thicknesses.
Chapter 14: Flexible Laminates
Laaminate – noun used for combined structure of two or more materials to form a single structure with the combined properties of all individual components.
structural – strength, elongation, puncture & abrasion resistance, etc.
performance – machinability, sealability, environmental suitability, etc.
barrier – moisture, gas, odor, UV light, etc.
aesthetics – clarity, feel, opacity, appearance, etc.
Aluminum: easily alloyed with copper zinc magnesium, manganese, chromium + others
bauxite à Aluminum oxide à Aluminum
4 kg 2 kg 8kW 1 kg
recycling only requires 5% of the original processing energy
~1/3 wt of steel with ~ 40 to 60% of strength
Foil is rolled Aluminum less than 152.4 micro meters (0.006 inch), and all foil is supplied at 0 Temper, which is the softest and most workable.
Metals in general talk: work hardening & workability- metal is work hardened if rolled cold (lower temperatures than in molten state), which produces a much stiffer metal. If it gets too stiff, the ability to work it is reduced. Annealing reduces the stiffness and increases workability. Workability and hardness need to be balanced to deliver the desired temper. Metal temper is designated by the Rockwell 30 – T hardness tester and is given as a number. The Rockwell guage measures the penetration of a hardened steel ball into the sheet surface.
Back to Aluminum….two modes of manufacture casting of ingots ( with annealing between rolling passes, or continuous casting where it is taken straight from melting furnace and ends up in a coiled roll of foil.
Rolling of foil is a form of extrusion: metal entering a roll nip encounters combined forces of downward pressure and in the machine direction.
– thickness is reduced thru each roll nip pass.
– conservation of volume concept: if width is controlled and thickness is reduced, what happens to length?
Work rolls are usually ground and highly polished, resulting in a very bright/shiny surface on the foil side that touches the work rolls.
Foil that is under 25 micro meters (0.001 inch) is usually passed through the nip back to back for 2 sheets at a time. Foil to foil face of each has a dull matte or satin finish.
Corrosion: a natural oxide layer forms on surface of Aluminum which can resist mild acids which are typical of most foods. Mildly caustic as well as strong acid or base will corrode Aluminum, need to consider laminated or coated stock for some application.
Attributes of Aluminum Foil in packages:
– Appearance – Barrier properties (gas & light) – Friability
-Dead Fold – Formability – Hygene
– Conductivity (elect. & heat)
Foil coatings: decorative, protective, sealing. Coatings above 25 micro meters (0.001 inch start to become a factor in performance of the foil.
See Table 14.2 in text for common coatings and performance in various applications.
Reflectance and light behaviours require special considerations for graphics designs on foils. Frequently primers are required before foils can be printed, and cover coats are used to protect printing from scuffing. Embossing can be used when inks and laquerer cannot.
Thin foil is subject to pinholes. Laminating with other components minimizes the pinholes.
Flex cracking is caused in the forming process of a package. Heavier laminates (thicker materials) can reduce the formation of flex cracks. Need to always watch forming, folding and creasing functions which might make the resulting transmission rates unacceptable.
Vacuum Metalizing : (see slide on metalizing process)
thickness of Aluminum deposited = web speed, wire feed rate, melt boat temperature. usually equals ~ 1/1,000,000 inch.
Vacuum metalization improves properties of plastic films.
Vacuum metalization doe not improve properties of paper.
See Table 14.3 for examples of metalized film applications.
Laminate Structures & Physical Properties:
Besides balancing overall cost, need to consider strength (tensile), resistance to tear propogation, puncture resistance, and elongation. Start with considering product weight and/or physical characteristics; then consider process impacts (i.e. retort needs); then consumer uses & preferences.
Side discussion about friction: Coefficient of Friction, CoF – static and dynamic
sometimes they are equal, sometimes static is greater, dynamic is never larger than static.
CoF is critical for some use equipment and not as important for others.
Make certain that methods of measurement and units are understood for CoF.
CoF 0.12 – 0.2 slippery
0.25 – 0.35 high
Body and Dead-Fold Properties: stiffness, shape holding properties, overall body of the laminate. Fillers can be added to increase these properties.
Tear Properties: needed to aid opening. Polyester & polypropylene propagate tears, polyethylene does not. Sometimes foil or paper aid opening, or notches for starting are used.
Thermoformability: usually nylon based, use a film with heat sealing capability and add coatings for additional strength and barrier properties. Rigid cups are usually made from materials 380 μmeters (0.015 inch) thick, vs typical films of 10 μmetersto 50 μmeters (0.0004 to 0.002 inch).
Temperature ranges of use are also key properties of laminates to be considerd.
Machines and package application examples: VFFS & HFFS.
Week 7 ( no class week 6): Completion of Laminates and Flexible Films Topic
Application for packaging materials:
VFFS – vertical form fill seal
HFFS – horizontal form fill seal
Also : Flow Wrapping– utilizes technology from both VFFS & HFFS
Laminating is nearly exclusively web fed ( roll to roll type processing).
Wet bonding- use of adhesives (implies paper is included in the structure).
Dry Bonding- adhesive is evaporated to leave bonding agent behinc.
Hot – melt bonding- thermal activation is used for the actual bonding function.
Extrusion- high pressure heads and extrusion dies combine materials into one.
Coatings: hundreds of methods of applying coatings to the web in a laminating machine.
Gravure and extrusion coating are the two predominate types used.
Overhead of Gravure coating
Overhead of Extrusion laminating
Overhead of Wet bond laminator
Overhead of Dry bond laminator
Laminate Specifications: full specification is matched very closely to the machine that it will be run on (converted to final package on or simply converted). The more complex of a machine that is utilized for converting, the more critical the specification of the laminate will be.
Barrier properties: usually refers to moisture and oxygen transmission avoidance or reduction. Usually expressed in transmission rate over a given area of material for 24 hours at standard atmospheric pressure and temperature.
Aesthetics: clear or opaque requirements. Metallic shine requires foil or metallizing the material.
Printing: typically gravure or flexographic. Frequently reverse printed on the inside of the film. Sometimes over coated to reduce the impacts of abrasion to the printed message area.
Sealability: ranges in complexity from waxes to LDPE to Ionomers (Surlyn) to acrylic polymers (Nucrel). Usually matched to process that the film will be converted on which sets parameters of time and pressure, leaving temperature as the adjustable setting.
Sample of near burnthrough on coffe bag where temperature is too high.
Custom features: coatings for gloss or gloss reduction, anti-static, friction adjustments, etc.
Ordering details vary by supplier, but usually entail basis weight, or thickness & density, number of impressions or repeats, etc. Most critical detail is the unwind detail relative to any printed artwork.
Standard unwind overhead.
Examples of laminates overheads