1. Basic of Polyester
• Polyester (PET) is the short form of Polyethylene
terephthalate
• PET has various use in various applications for
bottle, yarn for making clothes and FILM
• The basic Raw material for PET is crude oil
• Invented By British chemists, John Rex
Whinfield and James Tennant Dickson,
2. Properties of PET
• Molecular formula(C10H8O4)n
• Density1370 kg/m3
• Young's modulus(E)2800–3100
• MPaTensile strength(σt)55–75 MPa
• Elastic limit50–150%notch test3.6 kJ/m2
• Glass temperature75 °C
• melting point260 °C
• Vicat B170 °C
• Thermal conductivity0.24 W/(m·K)
• linear expansion coefficient (α)7×10−5/K
• Specific heat (c)1.0 kJ/(kg·K)Water
absorption (ASTM)0.16
• Refractive Index1.5750
3. Method of making Polyester
• PET resin can be formed by two different
reactions.
• The starting material for the first reaction is
Terephthalic Acid which can be converted in a
condensation reaction with Ethylene Glycol to
form Bis(hydroxyethyl)-terephthalate and Water
(TPA - Route).
• The other possibility is to start the condensation
reaction with Di-m ethyl- terephthalate and
Ethylene Glycol to achieve Bis(hydroxyethyl)-
terephthalate and Methanol (DMT - Route). In
the next step,
• The PET is formed by transesterification and
gives some amount of Ethylene Glycol back,
which can be used in the first step again.
4.
5. Flow chart of Polyester film Making
• FLOWCHART for boPET processing
7. BOPP
The abbreviation BOPP stands for Bi-axially
Oriented Polypropylene. By stretching the film,
i.e. by orienting the macro-molecules of the
polypropylene, it’s properties are altered as
follows.
8. Properties of Polypropylene
Molecular Formula: (C3H6)x
Density: Amorphous (0.85 g/cm3)
Crystalline (0.95 g/cm3)
Melting Point: 165°C
PP is a crystalline solid produced by polymerization of propylene monomers.
9. PP HOMOPLYMER:
Steps followed in producing PP homopolymer:
•Washing out the catalyst/drying of solvent(only for slurry
process)
•PP powder, additives, granulating
•PP granulate
The following reaction agents are put into the reactor:
•Propylene as a monomer to achieve polymerization.
•Hexane as a solvent.
10. Molecular Weight:
•The hydrogen constituent in the process is responsible for the
mean molecular weight, which in turn determines the melt
viscosity and thus the ability of the melt to flow through the die.
•The capability of the melt to maintain it’s form upon leaving the
extruder die is improved by increasing the molecular weight.
MFI (Melt flow index):
•Indicates the flow property of the polymer melt and is related with
the molecular weight of the polymer.
•Polypropylene is tested for MFI usually at 230 degrees C with a
testing weight of 2.16 kg. For BOPP production process a MFI of
1.5-3.5 g/10min is chosen. The numerical value of MFR is
inversely proportional to the viscosity.
11. •The iso-tactic portion influences the crystallinity, though
crystallinity is also influenced by cooling rate.
•Crystallinity affects the density of the polypropylene. For a
crystallinity of 30-60%, the density is 0.91kg/cm3 and the melting
point of the PP homopolymer is 165-175 degree C.
Additives:
•They are added to the PP powder to form granulates
•Anti-oxidation agents and thermo-stabilizers to prevent the
degradation of molecules during further processing.
•Calcium-stearate or hydrotalcid serves to neutralize non-washed
out catalyst deposits. Catalyst deposits like chlorine compounds
affect the which affect the roll surface. Calcium stearate also acts
slip agent.
12. PP Copolymer
•Is produced by polymerizing together propylene, ethylene –P-E-
P-E-P-E-P-P-E-P-P-E-P-P-E- (Random Copolymer).
•The ethylene portion of the random copolymer is 3-5%.
•The ethylene portion determines the melting pt. of the copolymer.
•Higher the percentage of ethylene , lower is the melting point.
Though, a very high percentage of ethylene may cause increase
in haze.
•Generally the melting point of copolymer is 138 degree C. The
MFI of random copolymer is appox 5-7 g/10min
13. ADDITIVES
Masterbatch is a PP granulate with additives introduced into the
homopolymer, copolymer system through a dosing system.
Additives in masterbatch form guarantees homogenous
distribution in the granulate and also the film.
The additives are added subject to application:
Slip agents
Anti-statics agents
Anti-blocking agents
SLIP Agents are applied in order to obtain a smooth-slipping film
with low coeff. of friction. It also improves the extruder output
capacity while decreasing extruder power input.
14. •Erucamide is a chief agent in anti slip additives.
•For plain film 250-750 ppm of slip agent is added, while for
coextruded film 1000-2000 ppm of slip agent is added to
homopolymer and 1000ppm for copolymer.
•1-2 weeks of migration time is required to make the slip agent
effective on the film’s surface.
Anti-Static Agents are used to reduce electrostatic charge on the
film.This is tested by finding out the half-life of the accumulated
charge to get discharged.
•The agent is bipolar , so while migrating to film surface , the
unpolar portion stays with the PP, while the polar portion attaches
humidity.
15. •Anti-blocking agents are used to prevent blocking of film on
winder which is caused by the following reasons.
•Short-polymer chains migrate to the film surface and get pasted
with the other film.
•If the film surface is too smooth, great adhesive strength
originates between two films.
•Therefore anti-blocking agents like silicic acid agents are added
to artificially roughen the film surface. 2 and 4 μm particle size of
silicic acid in a concentration of 200-1000ppm is added.
•Thinner film requires more antiblocking agent. Silicic acid is
chosen since it is amorphous, has high refraction index, and is a
soft material.
•Since this is an inorganic product, it doesn’t migrate and is fully
effective right after migration.
•The store-up of water, facilitates easier discharge of electrostatic
charge from the film. These are especially for co-ex film with a
concentration 300 ppm. Appropriate migration is required, 1-2
weeks
