Plastic as a PackagingMaterial

What are plastics?➢Plastics may be defined as any group of substance, of natural or synthetic origins, consisting chiefly of polymers of high molecular weight, that can be moulded into a shape or form by heat & pressure.

➢They usually consist of large molecules of organic materials which arebased on certain building block molecules, undergo a process known aspolymerization, a plastic or long chain polymer is produced.

➢Other material such as accelerators, initiators, solvents & catalyst canbe added during polymerization to improve the characteristics.

Advantages➢Light weight➢Reduced volume (warehousing & distribution cost reduction)➢No corrosion problems➢Good resistance to mould & bacteria.➢Generally inert chemically, but be wary of “solvents”➢Usually have good impact strength; difficult to break, if breakageoccurs fragments tend to be less hazardous than glass.➢Wide design & decorative possibilities.

Disadvantages➢No plastic is totally impermeable to moisture, gases etc.➢Most plastics permit some passage of light. Even highly pigmented

plastics & those with UV absorber are likely to let certainwavelengths through.

➢Many are difficult to clean or are liable to attract dust & dirtunder unfavorable conditions.

➢May be permeable to, or subject to attack by, organic substances,particularly solvents.

➢Subject to adsorption or absorption according to formulationingredient.

➢Light weight & thin wall section may require specificproduction line handling.

➢Fully effective closing systems are sometimes difficult to achieve.➢Certain designs may show panelling or cavitation

Types of Plastics1) Thermoplastic Polymers-These are heat softening materials which can be repeatedly heated,

made mobile & then reset to a solid state by cooling.- Under conditions of fabrication they can be moulded by temperature& pressure.

-Eg. Polyethylene, PVC, polystyrene, polypropylene, nylon, polyester

2) Thermosetting Polymer-These are polymers produced by a polymerization process involving a curing or vulanisation stage during which the material becomes ‘set’ to a permanent state by heat & pressure.

-Further heating leads to decomposition of the plastic.-Eg. Phenolics, melamine, urea, alkyds, epoxides, certain polyesters &

polyurathanes, cross linked polymers.

Plastics Used For Packaging1. High Density Polyethylene (HDPE)

Characteristics:▪Low – cost▪Moderately flexible▪Stiffer and has better▪Chemical resistant▪Poor clarity

barrier properties

▪Translucent in natural state and can betinted with any opaque color.

▪Odorless and tasteless

Advantages▪Low-cost▪Good moisture barrier▪Not attack by most solvent

Disadvantages▪Poor barrier for oxygen & other gases▪Odors and flavors are sometimes lost▪Perfume or flavoring oil can transpire rapidly▪Stress-crack in the presence of some product

Applications▪For thin-wall blow- moulded containers▪ Injection moulding of closures▪Rotational moulding for large containers such ascarboys▪Industrial and consumer bags and thermoformedtrays

2. Low Density Polyethylene (LDPE)

Characteristics:

▪Odorless and tasteless▪Easily blended with such copolymers▪

▪

▪

▪

▪

▪

Highly resistant to most solventPoor barrier for gasesSoftening temperature is around 210ºFEasily pigmentedGood transparencyTranslucent and waxy in thick-walled container

Advantages

▪Flexible

▪Moisture barrier

▪Tough

▪Chemical resistant

▪Light weight

▪Low cost

▪Heat sealableDisadvantages

▪Not practical for rigid container and flexible packages

▪Problem in flavors and odors

▪Stress cracking

▪Not recommended for oily products

Applications:

▪

▪

▪

▪

Use in squeezable tubes and bottles

Wrappers and bags for different products

Thermoformed into trays, frozen food containersCoating material for bottle cartons, bacon

wrappers and paperboard milk containers

3. Linear Low Density Polyethylene (LLDPE)

Characteristics:

▪Low-cost

▪

▪

▪

▪

▪

Light weight

Superior toughnessRigid Flexible Moisture barrier

Chemical and stress-crack resistant

Advantages:

-

-

-

-

Good tensile strength

Puncture resistance

Good impact and tear properties

Stress cracking and warding resistance

Application:

- For large-sized bagging and wrapping

operations

4. Polypropylene (PP)

Characteristics:

▪

▪

▪

▪

▪

▪

Heat and chemical resistance

Tough & rigid

Resist oil and greases

Stress-crack resistance

Fairly good barrier to moisture

High melting point

and gases

Advantages

▪Light weight

▪Low-cost

▪Less shrinkage

Disadvantages

▪Low impact strength

▪Sharp melting point

Applications:

▪Widely used in closures of all kinds

▪Suitable for some boil-in-bag packages and containers

▪Standard plastic in moulded container

5. Polyvinyl chloride (PVC)

Characteristics:

▪Crystal clear

▪

▪

▪

▪

Low in impact strength

Tough and has good puncture resistance

Good barrier properties (moisture

Retains odors and flavors

and gases)

Advantages

▪Relatively inexpensive

▪Tough

▪ clear

Disadvantages

•Corrosive when overheated

•Yellows when exposed to heat

•Scratches easily seen

or UV light

Applications:

•Blister packaging for pharmaceutical and capsules

•Garment, box and pallet load wrapping applications

6. Nylon

Characteristics:

•

•

•

•

Structurally strong

Relatively low moisture absorption

Good dimensional stability

Heat sealability

Advantages

•Clear

•Good barrier properties to gases

•Excellent stability at both high and low temp.

Disadvantages

•Can be oxidized causing nylon to lose strength

Applications:

• Co-extruded with poly-olefins to enhance packaging

• Coating on paperboards, papers and foils

properties

•Extrusion-blow-molded containers for hard to-hold chemicals

7. Polyester (Polyethylene Tetraphthalate)

Characteristics:

•Excels in strength, toughness and clarity

•Resistant to weak acids, bases and most solvents

•Not good barrier for gases

Advatages

•Fairly stiff material

•Excellent transparency

•Excellent heat, low

•temperature and water resistance

•Excellent oil, chemical and solvent resistance

•Excellent barrier to aroma and Flavor

Disadvatages

•Poor seal property

•High cost

8. Polystyrene (PS)

Characteristics:

•Crystal clear and very hard, brittle and rigid•

•

•

•

Low melting point (190ºF)

Poor impact strength

Not good barrier for moisture or gases

Odorless and tasteless

Advantages

•Clear and light weight

•Low in cost

•Easily molded, thermoformed and extruded into film

•Accept printing, metallizing and hot-stamping

Disadvantages

•Slight tendency to shrink

•Discolor in strong sunlight

•Can craze and become cloudy

•Builds up static changes Easily

•Applications:

•Bottles for pharmaceutical tablets and capsules

• In molded forms for close containment of fragile products

9. Polycarbonate

Characteristics:

• Good clarity, impact strength, ductility and low controllable mold shrinkage

• Sterilizable and tolerates gamma radiation

• High-priced material

Advantages

•Great clarity, toughness and high softening

•Dimensionally stable and processable

•Odorless and non-staining

temp.

Disadvantages

•High- cost

•High permeation of moisture and gases

•Sensitive to oxygen and carbon dioxide

Plastic Processing :1. Injection Molding- Grains of polymer are mixed and heated by a screw in a molding

machine and injected under a high pressure into a cool mold.

MOVING

ivtOLTEN

STATIONARY PLATEN HOPPER

MOLDING

2. Compression Molding

-

-

-

powdered resin is put into a heated mold

mold closes under high pressurePlastic cures in a minute, then molds open.

;- .·.;

..

·'·

FORCE

PLUG

....COMPOUND

CAVITY

.•

....... :•

�.. I>

•

-·

MOLD LOADED

3. Rotational Molding

- also called rotomolding or rotational casting

- Produces seamless, hollow parts of uniform thickness and

without the internal stresses that can be created during

conventional molding or thermo forming

4. Blow Molding

- similar to glass making and

either a single or two stage

process for producing bottles

a. Extrusion Blow Molding

used

- continuously extruded

tube of softened polymer trapped between two halves of mold and inflated by compressed air to the shape

of the mold.

b. Stretch Blow Molding

- a preform is injection or extrusion

- reheated to produce biaxial orientaton of the molecules and finally stretch blown

c. Injection Blow Molding

- polymer is injection molded around a blowing stick , then

transferred to blowing mold.

- compressed air is used to form final shape of container

5.Thermoforming

- film is softened over a mould, and a vacuum and/

or pressure is applied

HeaterClamp

,II

21

(al

Typical Technologies of Converting

To give new processing to yield new value on the rolls that are

wound thin substrates which are plastics film sheet, paper, foil and cloth.

1. Coating

- Thin membrane that is coated liquid on the film sheet

- Process of applying one or more layers of polymer latices or polymer melt to the surface of a substrate

2. Laminating

-made multiple layers by adhesives and extrusion molten resin

3. Printing-to express conveyance of eye information and ornament

4. Metallizing- metals are vaporized and adhere to substrate

5. Embossing

- of set of concave-convex design to substrate by embossing roll

- to make soft-feeling and mat surface

6. Slitting- film sheet is continuously slit constant position width of the

product for secondary processing

7. Winding- is of set purpose to adjust edge of roll product and get rid

rejective part.

Constituents in Plastic•Plasticizers

•Fillers, Extenders, Lubricants

•Stabilizers

•UV absorber

•Slip additives/ anti-slip additives

•Anti-blocking agents

•Colourants-pigments & dyes

•Antioxidants

•Internal release agent

•Inhibitors (mould or bacteria inhibitor)

•Toughening agents- impact modifiers

•Flame-retarding agent eg- opacifiers, whitening agnet

Plasticizers• Plasticizers improve the flow properties of material,increases softness & flexibility, & are found mainly inpolyvinyl chloride (plasticised PVC) and the cellulosics.• The most common PVC plasticizers are phthalate esteres, phosphate esters, sebacate & adipate esters, polymeric

plasticizers.

Fillers•Filler is an inert solid substance•Eg- carbon black, chalk or calcium carbonate, china clay, silica & magnesium carbonate

•The maximum limit of filler is upto 1:1 ratio , after which

binding power with the plastic is lost.

the

Toughening agent/ impact modifiers

•A few plastics which tend to be naturally brittle require an

improvement in both Their drop (impact) strength & their top

loading (compression) strength.

•In the case of polystyrene ,rubber is widely used as an impact

modifier.• Rigid PVC, when used as container may suffer weaknesswhen subjected to 3-4 feet drop test & hence 15% of methylmethacrylate butadiene styrene (MBS) copolymer is added to

improve impact strength.

Lubricants• lubricants may be added either as an additive or at the

fabrication stage as a processing aid.

•In general lubricants prevent adhesion with metal part.

•Lubricants may also improve the flow & thereby lower the temperature of the moulding operation.

•Eg in silicone polydimethyl siloxane may be used in

LDPE & HDPE films to improve flow.

•Lubricants may be solid, such as waxes, stearates or

liquid such as liquid paraffin.

Stabilizers

Stabilizers increase the stability of plastic either during processing

or during the moulded life of the material

•

• Stabilizers are frequently used to combat the combined effects

heat & light.

UV Absorber

UV absorber may be used for two reason:

To protect the plastic from UV degradation

To prevent the product degradation due to UV rays passing

through the plastic.

of

•

1.

2.

• Chemically UV absorber may be based on substituted phenols or

bezophenones.

Eg- 2-hydroxy-4-n-octoxybenzophenone, & other benzophenones

Iron oxide & carbon are also used.

•

•

.

Slip additives•Slip additives are widely used for films either made or used on relatively High speed equipment where any non-slip or drag properties might be detrimental to out put.•The most used slip additives are oleamide & stearamide, since they operate at the film surface they can be physically

removed by abrassion.

Anti-slip additives•These were primarily developed to provide good bonding for palletsied loads of plastic sacks & bag

•Without the additives plastic sacks would tend to destack

& slide off when the pallet is moved or jerked.

Anti-blocking agent•Both reel wound & sheet stacked materials may be difficult to separate due to blocking

•This may be caused by the smoothness of two surfaces giving rise

surface adhesion.

•It can be prevented by incorporation of finely divided silica or diatomacous earths eg. Mica

Antioxidants•Used to prevent oxidative degradation of certain plastics

to

•Polymers may be subject to various forms of oxidative attack

all stages of their life cycle.

•Eg. BHT,BHA

ColourantsDyes & pigments are used

during

Extenders•These are somewhat similar to fillers

•They are used as lower cost substitute for plastic

Internal release agent•These agents are somewhat similar to lubricants

provide release, particularly from metals eg mould

• zinc , calcium & magnesium stearate.

in that they

Inhibitors•Used to prevent microbial growth

•

•

•

•

•

•

•

•

•

Plastic CollapsibleAdvantages:

Tubes

Low In Cost,

Light In Weight, Durable, Flexible Pleasant To Touch,

Unbreakable, Leak Proof,

Odorless & Inert To Most Chemicals

Able To Retain Their Shape Throughout

Unique Suck Back Feature

Their Use

Disadvantages

Permeation Of Gases

Plastic Closures•The closure is an integral part of the pack, hence the word ‘pack’ covers the both the container & the closure system.•The pack is only as effective as the closure employed, a successful marriage between container & closure is essential to the product shelf life & its acceptance during use.• These are plastic devices which are used to prevent the contents from escaping and allow no substance to enter

the container.

3.Roll-on closures

4.Friction closures

5.Press on closures

•

•

•

•

•

Blister PackAdvantages

Excellent environmental protection

Pleasing & efficacious

User convenience

Child resistance

appearance

Tamper resistance

Blister Material•Polyethylene

•Polystyrene / Polypropylene

•PVC

•Polyvinylidene Chloride

•Polychlorotrifluoroethylene

Plastic PouchAdvantages

•Ease of handling

•Used for unit dosage

Materials used:

•Polyethylene

•EtIhllylIetne

•Polyester

Vinyl Acetate