1. Recycling Of
Polyurethane Foam
Wastes
RONAK VAGHANI: 11POL1006
GUIDE: DR. ANAGHA S. SABNIS
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2. What are PU foams?
PU
Foams
Polyol
Isocyanate
Catalysts
Blowing
Agents
Surfactants*
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3. Where are they used?
Rigid PU foams:
◦ Refrigeration
◦ Thermoware like Casserole
◦ Industrial Insulation
Flexible PU foams:
◦ Automotive Car Seating
◦ Foam Mattresses, Pillows
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4. Why do they need to be recycled?
Global Consumption of 17.5 Million MT of Polyurethane.
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 Waste Disposal
 Non Bio-Degradable.
 Adverse Effects like
Flammability.
 Effect of Blowing agents
on the environment.

5. Disposal
techniques
Recycling
Landfill Incineration
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6. How can we recycle them?
Methods of Recycling:
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Mechanical Chemical
Thermo-
Chemical
Biological

7. Physical/Mechanical Methods
Grinding
 Used as filler in new PU foam
 Average particle size is 50 μm
 Recycle content of 7-10 %-wt.in the new
foam
 Cost savings of around 2.7-2.8 %
Toyota made mudguard by addition of 10% wt.
powder (Reduction of 4-5% cost)
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8. Mechanical Methods…
Adhesive Pressing.
Scrap PU particles are surface coated with a
binder and bonded in a heated press.
Production of mats, carpet underlay, sports
hall floor parts and automotive sound
insulation.
PU foam scrap can be rebonded by mixing
scrap particles (size ~1 cm) with di-isocyanate
MDI followed by form-shaping at 100-200°C,
30-200 bar
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9. Mechanical Methods…
 Compression/Injection Molding
Molding at temperatures and
pressures high (180°C, 350 bar)
enough to generate the shear forces
needed to flow the particles
together, without the need for
additional binders.
SRIM (structural reaction injection
molding)
Mainly used in Automotive parts.
I.M. carried out for crosslinked PU.(
with addition of thermoplastics)
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10. Chemical Methods…
Glycolysis:The purpose is to recover the polyol.
In the process, three phases are obtained:
an upper phase which contains the polyol
 a bottom phase which has the sub products of the reaction and the excess of glycol
a third phase which is in the middle and it is formed by the polyurethane unreacted.
Choosing the right reagent and degradation condition can get high quality
polyol, not only with low reaction temperature and short reaction time, but also
with higher degradation efficiency
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11. Chemical Methods…
Glycolysis
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T=180-220⁰C

12. Chemical Methods…
Conventionally catalysts
used are
Amines [DEA (Diethanolamine)]
Alkoxides (Titanium n-butoxide)
Hydroxides( NaOH)
Polyols are used as a solvent
system(DEG)
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13. Advances in Glycolysis
Microwave Assisted Glycolysis: pentaerythritol with (glycerine+ NaOH)
Scraps of flexible PU foam with above ingredients was put it in microwave oven at180⁰C and
800W.
Split phases appeared after complete foam digestion. The upper phase contained recycled polyol,
and the lower phase was a brown liquid with highly functionalized oligomers, amines and unreacted
degradation reagents and showed potential for application in rigid polyurethane foam formulation.
Easy to process, rapid, eco-friendly and amine-free polyol was achieved in high yields and purity.
New Catalysts
Potassium and calcium octoates
They lead to the complete degradation of the polymeric chain at low reaction time and the recovery
of the polyol in high concentration.
Main advantage: amount of octoate used represents only 15% by weight of the DEA needed.
Low cost of octoates.
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14. Chemical Methods…
Hydrolysis:
Under the action of water vapour in 250-340°C, polyurethane is degraded into diamine, polyol and
CO2 in high pressure.
Catalyst used is an alkali metal hydroxide.
Initially, Superheated steam @200⁰C was used, takes 15mins to obtain Volume Reduction factor of
30.
Now, We use superheated steam@288 ⁰C with 5% virgin material to obtain excellent polyol.
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15. Chemical Methods…
Amine Method:
Researcher Xue degraded the rigid polyurethane foams with fatty amine (such
as diethylenetriamine, triethylenetetramine).
The main reaction included the fracture of carbamate base, urea base, biuret
base and urea base formic acid ester base, and the generation of polyol,
multiple amine and aromatic compounds in the degradation process.
Reaction can happen at low temperature.
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16. Chemical Methods…
Phosphate Ester Method
Degradation reaction can happen in 142 °C without catalyst. Troev K. speculated that alkylation
reaction, free radical reaction and ester exchange reaction happened between polyurethane and
phosphate
Also used are phosphoric acid ethyl ester, triethyl phosphate, chlorine ethyl triethyl phosphate,
which degraded the microporous polyurethane elastomer at 180 °C, the degradation product
was liquid, containing phosphorus element or phosphorus and chlorine element oligomer
These products can be used as non-reactive additives to improve the flame retardant
performance
Only used in packing, applications need further study.
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17. Thermochemical Methods
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18. Thermochemical Methods…
Pyrolysis
Pyrolysis of a PU foam was analysed using TGA up to 450°C (in nitrogen, 5-20 K/min heat-up)
and a “pyroprobe” pyrolysis reactor at 500 - 800°C (in nitrogen, heat-up ~300 K/s) plus a
secondary reactor .
Decomposition of the PU to a mass loss of~95% occurred between 230 and 380°C.
The tests in the “pyroprobe” set-up yielded gas mixtures containing at 500°C large fractions of
toluene, benzene, methyl 1,4-pentadiene, ethane +ethylene, propylene and butadiene, at 900°C
mainly benzene, ethane + ethylene, and methane.
Also, ammonia (NH3), pentene and the semi-volatiles 5-hexen-1-ol and 1, 6-hexane diol were
found in significant amounts in the products, as also some hydrogen cyanide (HCN), aniline
(aminobenzene), benzonitrile and naphthalene, at levels depending on temperature.
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19. Thermochemical Methods…
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 Gives syn gas.
 Takes place in oxygen
@1200-1500⁰C, 20-80 bar.
 Residence time of few
seconds gives 98-99%
conversion.
 Benefit :chlorine (from
CFCs) is bound by the
ammonia formed (from PU
nitrogen) to form
ammonium chloride
(NH4Cl).
 Gasification

20. Biological Degradation
Microbial degradation of polyurethanes is dependent on the many properties of the polymer
such as molecular orientation, crystallinity, cross-linking and chemical groups present in the
molecular chains which determine the accessibility to degrading-enzyme systems
Involves 2 classes of enzymes belonging to the esterase and protease families.(both
membrane-bound and extracellular)
Microbial degradation of polyester polyurethane is hypothesized to be mainly due to the
hydrolysis of ester bonds by these esterase enzymes.
Enzymes: human neutrophil elastase and porcine pancreatic elastase.
Bacteria: Delftia acidovorans TB-35 (Polyester), Staphylococcus epidermidis(Polyether)
Fungi: Aspergillus terreus (Polyester), Chaetomium globosum( Polyether).
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21. Other Methods
Prevent the release of CFC into the atmosphere.
During shredding, the CFCs released must be trapped, after which they can be
destroyed.
The extraction of blowing agents CFC-11 and HCFC-141b from rigid PU foams
using supercritical CO2 (sc-CO2) can be done due to very high diffusivity of the
sc-CO2 through the polymer.
Extraction efficiencies
>99% -sc-CO2 and (slightly less efficient) sc-CO2/C3H8 mixtures, shorter time.
40% with liquid CO2 and 14% removal with N2 , longer time.
The extracted gases are then trapped and the PU can be stored for further
processing.
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22. Conclusion
Methods conserving cost and energy have to be found
Large Scale Processing should be feasible.
More R&D in Biopolymers and suitable replacement of PU is much needed.
The existing methods are capable of a high yield but that is not observed on an
industrial scale.
Innovative methods need to publicized well for world wide PU Industries.
Market for recycled products has to be established. It doesn’t end at recycling,
but optimum use of the end product of recycling has to be carried out.
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23. Thank You
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