Transcript File

COMMODITY PLASTICS
CORPORATE TRAINING AND PLANNING
Polypropylene
Introduction
Preparation of Polypropylene
Structure Property Relationship
Tacticity
Properties of isotactic PP
General properties
Additives for isotactic PP
Processing Considerations
Processing techniques
Grading of PP
Applications
Modification
of Polyolefins
CORPORATE TRAINING AND PLANNING
Polypropylene
Introduction
n CH2=CH
Polymerization
CH2-CH
H3C
n
CH3
Polypropylene (PP) is a linear polymer, composed of
repeating units of isopropane.

The main attractive features of PP are
Exceptional flex life,
Good surface hardness,
High chemical resistance,
Good stability in boiling water,
Excellent electrical property
Long-life integral hinge application.
CORPORATE TRAINING AND PLANNING
Preparation of Polypropylene

PP is prepared by using Ziegler type catalyst –
titanium tri chloride with aluminium tri ethyl,
aluminium tri butyl, or aluminium di ethyl chloride
in
naphtha under nitrogen atmosphere to
form
slurry
consisting of 10% catalyst and 90% naphtha.

The molecular weight can be controlled by using hydrogen
as a chain transfer agent.

In suspension process, propylene is charged into the
polymerization vessel under pressure while the catalyst
and the reaction diluent are metered in separately.
CORPORATE TRAINING AND PLANNING
Ziegler Natta Polymerization
 Polymerization reactions especially of olefins and dienes catalysed
by organometallic compounds is known as coordination
polymerization.
 The first step in polymerization is the formation of a monomer –
catalyst complex between the organometallic compound and the
monomer.
R
H2C
H2C
+
Mt
Organo metallic
catalyst
H2C
H2C
CH
CH
H2C-R
CH
CH
Mt
Diene monomer
CH2
Monomer catalyst complex

Here Mt indicates metals like Ti, Mo, Cr, Ni.

In the formation of monomer – catalyst complex, a
coordination bond is involved in between a carbon atom of the
monomer and the metal of the catalyst. Hence the
polymerization effected by such catalyst systems is
called coordination polymerization.
CORPORATE TRAINING AND PLANNING

Ziegler Natta catalysts are such type of catalyst as
existed in coordination polymerization.

It comprises of two components as against single
component organo metallic component and other
consisting of halides of IV-VIII group
elements
having transition valences.

The co-catalysts are organo-metallic compound such as
alkyls, aryls and hydrides of I-IV metals.

The commonly used catalysts and co-catalysts are
Titanium chlorides (both tri and tetrachlorides) and
triethyl aluminium i.e. Al(C2H5)3, diethyl aluminium
chloride Al (C2H5)2Cl.
CORPORATE TRAINING AND PLANNING

Aluminium alkyls acts as the electron acceptor and the
titanium halide acts as electron donor. Therefore these two
forms a coordination complex which is necessary for
coordination polymerization.

The formed complex is insoluble in the solvent .

Many structures are proposed for these complexes
R
R
Al
Cl
Ti
R
Cl
Cl
Cl
Cl
Cl
Al
Ti
Cl
Cl
Ti
R
Cl
R
R
Cl
CORPORATE TRAINING AND PLANNING
R


From the active centre, the chain reaction propogates and
form a solid surface of catalyst complex phase and the
monomer is complexed with metal ion of the active centre
before it inserts into growing chain.
When catalyst and co-catalyst components are mixed , there
occurs a chemisorption of the aluminium alkyl (electro
positive in nature) on the Titanium Chloride solid surface,
resulting in the formation of an electron deficient bridge
complex as
R
R
Al (C2H5)3
Co-catalyst
+
Al
TiCl3
catalyst
Cl
Ti
R
Cl
An active centre
CORPORATE TRAINING AND PLANNING
Cl

The monomer is attracted towards Ti-C bond (C from alkyl
group R)in the active centre. When it forms a π -complex
with Titanium ion. The rate of reaction is influenced by the
electrons present in the active centre.
R
R
Al
R
Cl
Ti
Cl
ACTIVE CENTRE
+
CH2=CHCH3
R
Cl
Cl
R
Al
Ti
R
Cl
PROPENE
CH2=CHCH3
CORPORATE TRAINING AND PLANNING
Cl
The bond between R and Ti opens up producing an
electron deficient Ti and a carbanion at R.
CH
R
Al
R
3
R
Cl
Ti
Cl
R
CH
CH2
Cl
Al
CH2=CHCH3
Cl
Ti
The Titanium ion attracts the π electron pair of monomer
and forms a sigma bond. While the counter ion attracts
electron-deficient centre of the monomer. The monomer
is then inserted into a transition state ring structure.
CORPORATE TRAINING AND PLANNING
This transition state now gives rise to the chain growth at the metal
carbon bond regenerating the active centre.
Repeating the whole sequence with addition of a second monomer the
structure of resultant chain growth as
CH3
R
H3C CH
CH
H3C
H2C
Al
CH-CH2 R
H2C
Ti
+ CH2=CHCH3
Al
Cl
Ti
Cl
The monomer insertion is repeated in this manner and orientation of the
substituent group of monomer is always taken from the metal ion end
resulting a stereo regular polymer.
CORPORATE TRAINING AND PLANNING
Flow Diagram
Propylene
alcohol
water
Solvent
Catalyst
catalyst
preparation
Alcohol
solvent
degasssing
Atactic
polymer
catalyst removal
hexane
polymerization
centrifugation
waste-water
removal
Solvent,atactic and
alcohol recovery
water
PP
CORPORATE TRAINING AND PLANNING
Metallocene Polymerization

Metallocene polymerization is catalyzed by metallocenes.

It allows to make polymers of very high molecular
weights in comparision to Ziegler Natta catalyst.

Metallocene polymerization is also good for making
polymers of very specific tacticities.

A metallocene is a positively charged metal ion
sandwiched between
two
negatively
charged
cyclopentadienyl anions.

Cyclopentadienyl anoin is made from cyclopentadiene.
CORPORATE TRAINING AND PLANNING


In Cyclopentadienyl most of the carbon atoms has one
hydrogen atom but one carbon atom has two hydrogen
atoms. One of those two hydrogen atoms are acidic
which separates very easily.
So, the carbon atom is left with only one hydrogen atom
with an extra pair of electrons.
H
H
H
C
C
H
C
C
C
H
H
H
H
C
C
C
H
Cyclopentadiene
C
C
H
H
Cyclopentadienide anion
CORPORATE TRAINING AND PLANNING
H



The ring in anionic form is very stable.
These cyclopentadienyl ions have a charge of –1.When a
cation like Fe with a +2 charge comes along , two of the
anions forms an iron sandwich called as ferrocene.
When a metal with a bigger charge is
involved, like zirconium with a +4 charge,
the Zirconium will bond to two chloride
ions to balance the charge, -1 charge on
each to give a neutral compound.
Cl
Zr
Cl
bis- Chlorozirconocene
CORPORATE TRAINING AND PLANNING

In Zirconocences extra chlorine ligands can not be
adjusted in between the cyclopentadienyl rings.

To make room for the chlorines, the rings tilts with
respect to each other.
This tilting happens whenever a metallocene has more
ligands than just the two cp rings.

CORPORATE TRAINING AND PLANNING

In bis- Chlorozirconocene each
cp ring has aromatic ring fused to
it. The two-ring system fused to a
phenyl ring is called an indenyl
ligand.

There is an ethylene bridge that
links the top and bottom cp rings.

These two features make this
compound a great catalyst for
making isotactic polymers.

The bulky ligands pointed in
opposite directions guide the
incoming monomers so that they can
only react when pointed in the right
direction to give isotactic polymers.

The ethylene bridge holds the two
indenyl rings in place.
CORPORATE TRAINING AND PLANNING


To make Zirconocene complex catalyze a
polymerization, a co- initiator methyl allumoxane
(MAO) is added to it.
The chlorines of zirconocenes are
labile that means they like to fall off
of the zirconocene.MAO replace H C
them with some of its methyl
Zr
groups. The methyl groups can fall
off too. When one of them falls off H C
a complex is formed.
3
CH2
CH2
3
alpha - agostic association
+
Zr
H
H
C
H
The positively charged zirconium is stabilized because
the electrons from the carbon-hydrogen bond are
shared with the zirconium to form a α-agostic
association
CORPORATE TRAINING AND PLANNING

Zirconium still lacking in electrons. The bonding is
satisfied by the olefin monomer. In Propylene, carboncarbon double bond is having electrons to share, so it shares
a pair with the zirconium to satisfy the bonding.
+
Zr
H H
C H
H
H3C C C
H
H
CORPORATE TRAINING AND PLANNING
+
Zr
H H
C H
H
H3C C C
H
H
The precise nature of the complex between the zirconium
and the propylene is complicated. This compexation
stabilizes the zirconium but not for long.
When this complex forms, it rearrange itself into a new
form. The electrons in the zirconium-methyl carbon bond
shift to form a bond between the methyl carbon and one
of the propylene carbons.

The electron pair that had been forming the alkenemetal complex shifts to form an outright bond between
the zirconium and one of the propylene carbons.
CORPORATE TRAINING AND PLANNING
 As can be seen in the picture, this happens through a four
membered transition state. Also zirconium ends up just
like it started, lacking a ligand, but with an agostic
association with a C-H bond from the propylene
monomer.
H H
C H
+
Zr
H
C
H
H3C C
H
+
Zr
H
+
Zr
H
H H+
C H
H
C
H
C
CH3
H H
C H
H
C
H
C
CH3
+
H H
Zr
C
H C
CH3
CORPORATE TRAINING AND PLANNING
H H
C H

Another propylene monomer react just like the first one.
H3C
H3C
C
H
C
H
H
H
C
C
H
H
H H
Zr
C
H
H C
CH3 C H
H
+

+
Zr
H H
C
C
H CH
3
H
C H
H
The propylene coordinates with the zirconium , then the
electrons shuffle.
CORPORATE TRAINING AND PLANNING
H3C
H C
H
C
H
+
H H
Zr
C H
C
H CH C H
3
H
H
H3C
C
+
Zr

H
C
H
C
H
H
C
H
CH3
H
C
H H
When second propylene monomer has added to the chain,
the methyl groups are always on the same side of
polymer chain which leads to an isotactic polymer.
CORPORATE TRAINING AND PLANNING

The propylene monomer always approaches the catalyst with
its methyl group pointed away from the indenyl ligand.
H
+
Zr
H2C=C
CH3

CH2
CH2
H3C
If the methyl group were pointed towards the indenyl
ligand, the two would bump into each other keeping the
propylene from getting close enough to the zirconium to
form a complex. So, only when the methyl group is pointed
away from the indenyl ligand, the complex of ziroconium
with propylene is
formed
CORPORATE TRAINING AND PLANNING

When the second monomer is added it approaches from the
other side and its methyl group away from indenyl ring .
+
CH3-CH2-CH- Zr
CH3


CH2
CH2
H3C
C=CH2
H
The methyl group is pointed up rather than down.
This is so because the second propylene is adding from the
opposite side as the first,it must be pointed in the opposite
direction if the methyl groups are to end up on the same
side of the polymer chain.
CORPORATE TRAINING AND PLANNING
Structure Property Relationship
CH2-CH
n
CH3
 PP is a linear polymer with little or no branching.
 Methyl group in the chain leads to increase in melting point
and chain stiffening.
 The tertiary carbon atom provides a site for oxidation so that
the polymer is less stable than PE in the presence of oxygen.
 Methyl group leads to products of different tacticity.
 Commercial polymers are usually about 90-95% isotactic.
CORPORATE TRAINING AND PLANNING
Tacticity
H
Isotactic
H
C
H
C
H
C
H
H
Syndiotactic
C
Atactic
H
C
CH3
C
H
C
H
C
H
H
C
CH 3
H
H
C
CH 3
H
H
C
C
H
CH3
H
H
C
H
C
H
H
C
C
H
H
H
H
CH3
C
C
H
H
CH3
CH3
H
H
C
CH3
H
H
CH 3
C
C
CH 3 C
H
H
CORPORATE TRAINING AND PLANNING
H
Properties of isotactic PP
Compare to Polyethylene

It has lower density (0.90 gm / cc).


It has a higher softening point and hence a higher
maximum service temperature.
Articles can withstand boiling water and can be
subjected to steam sterilizing operations.

It has a higher brittle point.

It is more susceptible to oxidation.
Atactic PP

Atactic PP is an amorphous some what rubbery in nature.

Commercial polymer is usually 90-95% isotactic and
rest is blocks of atactic and syndiotactic structures.
CORPORATE TRAINING AND PLANNING
Properties of Polypropylene
Name
Specific gravity
Value
0.90
Unit
--
Tensile Strength
Tensile modulus
Flexural modulus
35.5
1380
1690
MPa
MPa
MPa
Elongation at break
Impact Strength (Izod )
35-350
37
%
J/m
Hardness
HDT (under 1.82 MPa load.)
Glass transition temperature
R100
55
5
--°C
°C
Melting point
Dielectric Strength
164
24-28
°C
CORPORATE TRAINING AND PLANNING
KV/mm
General Properties
Chemical properties
 No solvent affects PP at room temperature. Polypropylene
will dissolve in Decaline at 130°C.
 Aromatic and chlorinated solvents often swell polymer at
elevated temperature.
 Strong oxidizing acids slowly attacks the resin (fuming
HNO3).
CORPORATE TRAINING AND PLANNING
Electrical properties
 PP is an excellent insulator due to its non-polarity.
 It is used in many molded products, as well as in winding
coils and transformers.
Flammability
 PP burns slowly and can be identified by an odour of
crude oil.
 Flame–retardant grades
electrical applications.
are
available
CORPORATE TRAINING AND PLANNING
for
specific
Mechanical properties
 Commercial grades of PP is tough and having good impact
resistance.
 PP becomes more brittle than many other thermoplastics at
zero temperature.
Weathering properties
 Standard grades have shorter life when exposed to the
outdoor.
 Discoloration, colour fade and crazing occur in products
not stabilized with anti oxidants or carbon black.
CORPORATE TRAINING AND PLANNING
Additives for Isotactic PP
Fillers
 About 3% of PP compounds are filled with talc.
 Talc filler improves stiffness and heat deformation resistance.
 Talc filled PP compounds are used in heater housings, car
mounting components and several domestic appliances.
 Talc filled PP sheet is used as an alternative to carton board.
CORPORATE TRAINING AND PLANNING

In comparison to the talc filled grades the CaCo3 filled
grades claimed to have
Higher impact strength.
Brighter colour.
Higher thermal stability.
Improved fatigue strength.
Lower stiffness and tensile strength.
CORPORATE TRAINING AND PLANNING
Rubbers


Particularly butyl rubber is used to reduce the brittleness of PP.
Rubbers are used because of their
Reasonable price.
Good weathering properties.
Negligible
toxicity
easy
processability
and
reprocessability.
Pigments

The selection of pigments for PP follows the same
considerations as for PE because of the higher processing
temperature and lesser resistance to oxidation, selection does
require more care.CORPORATE TRAINING AND PLANNING
Carbon black


To improve the resistance to UV light, carbon
black is used as a light screener.
Hindered amine UV stabilizers (HALS) are used to
improve the UV resistance of PP material.
Antioxidants


Antioxidants are necessary for prevention from
adversity of oxidation.
For optimum processing stability a single
antioxidant of the phenol alkane type, for e.g.,
1,1,3 –tris (4 hydroxy - 2 methyl, 5 – t – butyl
phenyl) butane, tends to give the best results.
CORPORATE TRAINING AND PLANNING
Processing Considerations

Processing of Polypropylene is similar to Polyethylene,
particularly high-density polyethylene.

Flow properties
additives present.

Unfilled grades generally considered as easy flow.

Flow Path: wall thickness ratios of 175:1 are possible on
1mm wall thickness sections.

Thermal stability is quite good in the absence of oxygen
so that there is no need to purge with another material when
shutting down. CORPORATE TRAINING AND PLANNING
depend
on
molecular
weight
and
Processing techniques
Injection Molding



Recommended processing temperatures are in the
range of 210 to 275°C.
Injection pressures are of 150 to 180 MPa depending
on the grade of the material.
Because of crystallanity there is high molding
shrinkage and is reasonably uniform in all directions.
CORPORATE TRAINING AND PLANNING
Pipe Extrusion

PP-R has less heat conductivity compare to PE,
therefore needs longer time to melt.

This requires longer L/D ratio 30:1.

The melt temperature is recommended to be 220230°C.
CORPORATE TRAINING AND PLANNING
Manufacturing Process of BOPP Film
BOPP film is manufactured with the blown method.
Molten resin is extruded from a circular die to form a thick tube.
The tube is stretched with air pressure at controlled temperature
to achieve transverse orientation and simultaneously pulled by
take off nips to achieve machine direction orientation.
CORPORATE TRAINING AND PLANNING
Grading of Polypropylene
MFI (gm/10
min)
3-5
9-11
Grade
16
11
1.9
Extrusion coating grade
General purpose injection grade
Bottle grade
Blown film grade
Cast film grade
CORPORATE TRAINING AND PLANNING
Trade Names
Haldia Petrochemicals Ltd, India
IPCL, India
Reliance, India
Exxon Mobil, US
Mitsui petrochemical, Japan
Mobil Chemical, US
Sumitomo, Japan
Mitsubishi , Japan,
- Halene PP
- Koylene
- Repol
- Escorene
- Sunlet PP
- Bicor PP
- Esprene
- Noblen
CORPORATE TRAINING AND PLANNING
Applications
Automotive

PP is used in bumpers, steering wheel covers,
profiles, consoles, door pockets, radiator grills,
spoilers, rubbing strips, fenders, wheel arches, truck
linings, mud flaps, seat covers, plumbing, integral hinges,
accelerator pedals, glove boxes and air- intake noise
suppressors.
Packaging

PP is used in packaging for goods wrapping, sleeping
bags, films for packing tobacco products, candy,
cosmetics, contact lens cases, first aid cases, drums and
jerry cans, tool boxes, cheese wrap, electrical capacitors,
synthetic turf, clothing inner liners, wiping clothes, films
for textile goodsCORPORATE
and medicines.
TRAINING AND PLANNING
Electrical / Electronics

PP is used in cable connectors and fittings, cable and
wire coatings, industrial lights, transformer housings,
insulators for electrical fencing, aerial parts, switch gears,
radio and TV housings, capacitors, coil forms, control
knobs etc.
Appliances

PP is used in dish racks, pump housings, door
handles, air cleaners and washing machine parts,
bleach
and detergent dispensing units, agitators, tub liners, housing
for appliances, valve and control assemblies, drain tubes,
PP silverware baskets.
CORPORATE TRAINING AND PLANNING
Household

PP is used in buckets, thermo flask cases, strainers and
chairs, baby feeding bottle warmers, microwave oven trays,
labels for soft drink bottles, canvass for luggage, air
conditioner parts, floor and ceiling pans, dehumidifiers,
room humidifiers, knife sharpeners, can openers, hair
dryers, coffee makers.
CORPORATE TRAINING AND PLANNING
Applications
Multilayer PP coating for Offshore applications
Car Dashboard and Bumper
Coffee Maker and Toaster
PP furniture
CORPORATE TRAINING AND PLANNING
Modification of Polyolefins





Ethylene-vinyl acetate (EVA) copolymer.
Ethylene-ethyl acrylate (EEA) copolymer.
Ethylene-methyl acrylate (EMA) copolymer.
Ethylene-acrylic/methacrylic acid copolymer.
Ethylene-propylene copolymer.
CORPORATE TRAINING AND PLANNING
Ethylene–Vinyl acetate (EVA) copolymer.

Both filled and unfilled EVA copolymers have good
low temperature flexibility and toughness.

EVA with 15-20 mol % Vinyl acetate content are
rubbery copolymers.

About 28% Vinyl acetate content are used in hot–melt
adhesives.

EVA films are used for liquid packaging, frozen foods,
meat wrap, ice bags, drum liner.

Molded and extruded EVA resins are use in flexible toys,
bumper pads, hose , gasketing.
CORPORATE TRAINING AND PLANNING
Ethylene–acrylate copolymers

Ethylene–ethyl acrylate (EEA) and ethylene–methyl
acrylate (EMA) copolymers with up to 20% weight EA,
MA content respectively are commercially available.

EEA resins have higher thermal stability and can
withstand higher processing temperatures than EVA.

EMA resins yield blow film with rubber like limpness
and extremely high dart-drop impact strength. They find
useful applications in extrusion coating, co-extrusion and
laminating applications.
CORPORATE TRAINING AND PLANNING
Ethylene–acrylic/methacrylic acid copolymers (EAA/EMa)

Copolymers up to 6.5% acrylic acid and 15% by
weight of methacrylic acid are used for melt processing
applications.

The acid group promotes excellent adhesion to
various substrates and increases abrasion resistance and
stress cracking resistance

These resins are extrusion coating onto aluminium foil
for pouches, for composite toothpaste tubes, wire and
cable applications, blown or extruded films for
packaging of food and other products and various
lamination applications.
CORPORATE TRAINING AND PLANNING
Ethylene–Propylene Copolymers




Two main types of ethylene (E) propylene (P) resins
are EPM and a terpolymer (EPDM).
Rubbers which are rich in either ethylene or propylene
have higher tensile strength and elongation at break (%) in
the unvulcanized state than those rubbers which contain
equal amounts of E and P.
EPM rubbers can be vulcanized only by peroxides or
high energy radiation.
In EPDM the third monomer has two double bonds; one
enters the polymerization process and the other C=C
bond remains as a side chain available for vulcanization
with sulphur/accelerator systems.
CORPORATE TRAINING AND PLANNING