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 are
based on certain building block molecules, undergo a process known as
polymerization, a plastic or long chain polymer is produced.
Other material such as accelerators, initiators, solvents & catalyst can
be added during polymerization to improve the characteristics.
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 breakage
occurs fragments tend to be less hazardous than glass.
Wide design & decorative possibilities.
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 certain
Many are difficult to clean or are liable to attract dust & dirt
under unfavorable conditions.
May be permeable to, or subject to attack by, organic substances,
Subject to adsorption or absorption according to formulation
Light weight & thin wall section may require specific
production line handling.
Fully effective closing systems are sometimes difficult to achieve.
Certain designs may show panelling or cavitation
Types of Plastics
1) 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
-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 Packaging
1. High Density Polyethylene (HDPE)
Low – cost
Stiffer and has better barrier properties
Translucent in natural state and can be
tinted with any opaque color.
Odorless and tasteless
Good moisture barrier
Not attack by most solvent
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
For thin-wall blow- moulded containers
Injection moulding of closures
Rotational moulding for large containers such as
Industrial and consumer bags and thermoformed
2. Low Density Polyethylene (LDPE)
Odorless and tasteless
Easily blended with such copolymers
Highly resistant to most solvent
Poor barrier for gases
Softening temperature is around 210ºF
Translucent and waxy in thick-walled container
Not practical for rigid container and flexible packages
Problem in flavors and odors
Not recommended for oily products
Use in squeezable tubes and bottles
Wrappers and bags for different products
Thermoformed into trays, frozen food containers
Coating material for bottle cartons, bacon
wrappers and paperboard milk containers
3. Linear Low Density Polyethylene (LLDPE)
Chemical and stress-crack resistant
- Good tensile strength
- Puncture resistance
- Good impact and tear properties
- Stress cracking and warding resistance
- For large-sized bagging and wrapping
4. Polypropylene (PP)
Heat and chemical resistance
Tough & rigid
Resist oil and greases
Fairly good barrier to moisture and gases
High melting point
Low impact strength
Sharp melting point
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)
Low in impact strength
Tough and has good puncture resistance
Good barrier properties (moisture and gases)
Retains odors and flavors
•Corrosive when overheated
•Yellows when exposed to heat or UV light
•Scratches easily seen
•Blister packaging for pharmaceutical and capsules
•Garment, box and pallet load wrapping applications
•Good barrier properties to gases
•Excellent stability at both high and low temp.
•Can be oxidized causing nylon to lose strength
• Co-extruded with poly-olefins to enhance packaging properties
• Coating on paperboards, papers and foils
•Extrusion-blow-molded containers for hard to-hold chemicals
7. Polyester (Polyethylene Tetraphthalate)
•Excels in strength, toughness and clarity
•Resistant to weak acids, bases and most solvents
•Not good barrier for gases
•Fairly stiff material
•Excellent heat, low
•temperature and water resistance
•Excellent oil, chemical and solvent resistance
•Excellent barrier to aroma and Flavor
•Poor seal property
8. Polystyrene (PS)
•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
•Clear and light weight
•Low in cost
•Easily molded, thermoformed and extruded into film
•Accept printing, metallizing and hot-stamping
•Slight tendency to shrink
•Discolor in strong sunlight
•Can craze and become cloudy
•Builds up static changes Easily
•Bottles for pharmaceutical tablets and capsules
• In molded forms for close containment of fragile products
• Good clarity, impact strength, ductility and
low controllable mold shrinkage
• Sterilizable and tolerates gamma radiation
• High-priced material
•Great clarity, toughness and high softening temp.
•Dimensionally stable and processable
•Odorless and non-staining
•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.
2. Compression Molding
- powdered resin is put into a heated mold
- mold closes under high pressure
- Plastic cures in a minute, then molds open.
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 used
either a single or two stage
process for producing bottles
a. Extrusion Blow Molding
- 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
- film is softened over a mould, and a vacuum and/
or pressure is applied
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
- 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
-made multiple layers by adhesives and extrusion molten resin
-to express conveyance of eye information and ornament
- metals are vaporized and adhere to substrate
- of set of concave-convex design to substrate by embossing roll
- to make soft-feeling and mat surface
- film sheet is continuously slit constant position width of the
product for secondary processing
- is of set purpose to adjust edge of roll product and get rid
• Plasticizers improve the flow properties of material,
increases softness & flexibility, & are found mainly in
polyvinyl chloride (plasticised PVC) and the cellulosics.
• The most common PVC plasticizers are phthalate esteres,
phosphate esters, sebacate & adipate esters, polymeric
•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 the
binding power with the plastic is lost.
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
• Rigid PVC, when used as container may suffer weakness
when subjected to 3-4 feet drop test & hence 15% of methyl
methacrylate butadiene styrene (MBS) copolymer is added to
improve impact strength.
• 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 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 of
heat & light.
• UV absorber may be used for two reason:
1. To protect the plastic from UV degradation
2. To prevent the product degradation due to UV rays passing
through the plastic.
• Chemically UV absorber may be based on substituted phenols or
• Eg- 2-hydroxy-4-n-octoxybenzophenone, & other benzophenones .
• Iron oxide & carbon are also used.
•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.
•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.
•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 to
•It can be prevented by incorporation of finely divided silica or
diatomacous earths eg. Mica
•Used to prevent oxidative degradation of certain plastics
•Polymers may be subject to various forms of oxidative attack during
all stages of their life cycle.
Dyes & pigments are used
•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 in that they
provide release, particularly from metals eg mould
• zinc , calcium & magnesium stearate.
•Used to prevent microbial growth
Plastics used for pharma packaging
•Plastic Collapsible Tubes
•Freedom Of Design
•Extreme Resistant To Breakage
Plastic Collapsible Tubes
•Low In Cost,
•Light In Weight,
•Pleasant To Touch,
•Unbreakable, Leak Proof,
•Odorless & Inert To Most Chemicals
•Able To Retain Their Shape Throughout Their Use
•Unique Suck Back Feature
•Permeation Of Gases
•The closure is an integral part of the pack, hence the
word ‘pack’ covers the both the container & the closure
•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
• These are plastic devices which are used to prevent the
contents from escaping and allow no substance to enter
Types of closures
5.Press on closures
•Ease of handling
•Used for unit dosage
•Ethylene Vinyl Acetate
•Cracks and breaks anywhere in the container
•Any spot at heel or shoulder
•Rough cut off at finish, leading to leaky closure
•Weld lines that permit stress cracking in contact with product.
•Below minimum weight
•Any dimension outside of limit
•Rough or orange peel surface
•Blotchy or incomplete printing
•Plastic trim in boxes delivered with closures
•Improper identification of cases.
Evaluation of Plastic