Download - Polyurethane By. Muhammad . shafiq randhawa
Polyurethanes
Muhammad Shafiq Randhawa
Technical Consultant Polyurethane [email protected]
Cell #00923334114187Skyep=taha.shafiq87
Polyurethanes
History of Polyurethanes
• Dr. Otto Von Bayer (1937)
•IG Farben Industries•Rigid and flexible foams•TDI and polyols
•Attempts to reduce natural rubber use
What are Polyurethanes?
•Polyurethane
•Polyurethane polymers are traditionally and most
commonly formed by reacting a di- or
polyisocyanate with apolyol. Both the isocyanates
and polyols used to make polyurethanes contain on
average two or more functional groups per molecule.
•Types of polyurethane•1.Flexible Polyurethane Foam•2.Rigid Polyurethane Foam•3.Coating,Adhesives,Sealants and Elastomers(CASE)•4.Thermoplastic polyurethane (TPU)•5.Reaction Injection Molding (PIM)•6.Binders•7.Waterborne Polyurethane Dispersions (PUDs)
Polyurethane Structure
Polyurethane Monomers
• Polyurethanes consist of different block co-polymers•MDI- 4 4'-diphenylmethane diisocyanate• TDI- Toluene-2,4-diisocyanate
Polyurethane Monomers
Polyols- hydroxy terminated polyether, polyester, polyolefins, and glycols
Polyurethane Reactions
•Multiple types of reactions make up different end products of polyurethanes•Polyurea reactions are important for spandex production
Raw Materials
Components of Polyurethanes • Isocyanates• Polyol • Catalysts• Silicon surfactant• Fire retardant• blowing agent
Isocyanates;
Different Isocyanates are used for the
synthesies of polyurethane. Toluene
diisocyanate (TDI) was the first mass produced
isocyanate. It was used for rigid and flexible
products before the development of Methyl
phenyl diisocyanate (MDI) in the early 1960s.
TDI is still used in most flexible foam and many
elastomers and coatings. The TDI production
process yields two difunctional isomers
. The series of multifunctional aromatic or aliphatic isocyanates are used in polyurethane foams. The detail information about synthesis and reactions of isocyanates can be studied in the literature. Polyurethane is commercially produced by the phosgenation of amines. The solution of amine and phosgene are mixed to form a slury of amine hydrochloride and carbamic chloride then by heating the amine salts react with excess phosgene.
Parameter Value
Colour Dark brown
Viscosity (CPS) 170-250
Specific Gravity at 25
degree centigeade
1.24
NCO content 32
Specification of Crude MDI
Molecular Weight 174.163
Density (g. per cm3) @20°C (68°F)
1.21
Viscosity (cs) @100°C (212°F) 0.8
Freezing/Melting Point Range T100 (°C)
21.5-22.0
Freezing Point 2,4-isomer (°C)
15.0
Boiling Point @10mm Hg (°C) 121
Flash Point, COC (°C) 132
Acidity, as HCI (%) T100 <0.0130
Specification of TDI
Polyols
During the initial development of polyurethanes, polyesters were the most commonly used type of Polyols. Since unsaturated polyesters were found unstable for use in polyurethanes, completely saturated polyesters containing terminal hydroxyl groups rather than carboxyl groups are used many Polyols are available to the polyurethane formulator. The size, functionality, and starting materials determine the properties of the final product.
Rigid polyurethanes are formed by low molecular weight polyol.
Flexible polyurethane are make from the higher molecular weight polyols, castor oil, trihydroxy fatty triglyceride, is an example of naturally occurring polyol.
Polyester polyols are prepared by step growth or condensation polymerization. Formation of polyester chains is a random process and leads to broad distribution of molecular weights. Bifunctional monomer make the linear polymers.
Adipic acid used where flexibility is required, The Phthalic anhydride is used for those requiring rigidity, Dioles include ethylene glycol, 1.4 butandiol. And 1,6- hexandiol The polymerization has the characterstics of a chain reaction, whose chemistry is presented by initation, propagation and termination steps. Propylene oxide (PO) and ethylene oxide(EO) , are low price epoxides produce by the oxidation of proplylene and ethylene.
Polyols
•Polyols are the major component of rigid polyurethane. Rigid polyurethane foam can be manufactured by standard polyether base and polyester base polyol.
Type of PU average
molecular
weight
OH no(mg
KOH/gram)
Average
functionalit
y
Viscosity
at 25
degree
centigrate
(CPS)
Acid
number
Density(gm/cm)
Rigid foam 930 350-390 6.2 1500-
3000
1.0 1.1
Shoe sole 2000 58-62 2.1 700-1000 0.4 1.15
Elastomers 2000 50-58 2 500-800 1 1.17
Soft coating 2750 38-45 2 700-800 1 1.12
Hard coating 2450 250-270 11.3 17000 4 1.24
Flexible foam 2400 57-63 2.7 1000-
1200
1.3 1.15
Catalysts
Catalyst is the important additive. It is control the reaction rate and also control the balance between polyol and isocyante reactions. and blowing in order to attain the desired foam properties. Amine and Tin are two good catalyst used. Formation of transient complexes between polyol and isocyanate are formed due to catalyst.
Tertiary amines can catalyze both in gelling and blowing reaction and are usually called the blowing catalysts, Reaction rate of both gelling and blowing process depend on catalyst structure.Amine catalyst are control the both these parameter.Tin catalyst are more reactive and use in less quantity but it is use for gelling reaction, so it is called the gelling catalyst. .
Surfactant
•It is important additive in polyurethanes to get
homogenous foam with low density,
•Surfactant help in good mixing during foaming.it can
prevent bobbles from collapse and stabilize the cell
structure. Branching chains can be introduced to
either silicone or polyether and different end group
can be cooed in to chain end.
Blowing agent
Different blowing agents are used to form gas bubbles in the reaction mixture Firstly water was used as a blowing agent then it was rejected due to high boiling point and open cell foam is produced which was not good for insulation. In insulation we need low thermal conductivity material but the polyurethane which is manufactured by water has high thermal conductivity. Now CFCs, HCFCs, Pentanes, HFCs are use as blowing agent in rigid PU foam these gases are responsible for excellent insulation properties
CFCs gases were phased out due to environmental problems. In japan & Europe CFCs-11 was substituted by HCFCs 141b are Pentanes. middle East Asia and Africa CFCs-11 is still used.
Blowing
agent name
Molecular
weight
gm/mole
Boiling point
In centigrade
Liquid
Density at 20
degree C
Ozone
depletion
potential
CFC-11 137.4 23.8 1.49 1
HCFC-141b 116.9 32.2 1.24 0.11
HCFC-22 86.5 -40.6 1.21 0.055
HCFC-142b 100.5 -9.8 1.10 0.065
Physical properties of different blowing agents
Breakdown of the PU Industry
Economics
•The PU industry was estimated to produce 13.65 million tons of plastic in 2010 and is expected to grow to 17.95 million tons by 2016•The PU industry is expected to grow from $33
billion in 2010 to $55.5 billion in 2016.
Processing Machineries
Rigid PU processing machines1) Spray foam machine
2) Discontinuous PU panel
3) Continuous PU panel
Shoe Grade PU
Flexible PU
ApplicationsApplications
Building and Construction
PU Pipes
Wall insulation
Water cooler
Refrigerator
Appliances and Hot pots
PU shoes
Bibliography
1.http://www.pslc.ws/macrog/urethane.htm
2.http://www.8linx.com/cnc/polyurethane_foam.htm
3. http://www.essentialchemicalindustry.org/polymers/polyurethane.html
4. http://sunilbhangale.tripod.com/pu.html
5.http://www.poliuretanos.com.br/Ingles/Chapter1/132comercial.htm
6.http://www.plastemart.com/Plastic-Technical-Article.asp?LiteratureID=1674&Paper=global-polyurethane-market-PU-foams-thermoplastic-elastomers
7.J.M. Buist. Developments In Polyurethane-1; Applied Science Publishers LTD, UK, 1978.