Environmental Improvement
Potential of Flexible Polyurethane Foam for Aviation Applications
—
A Case Example Analysis
Carl-Christoph Höhne*, Ronny Hanich, Ana Salles, Peter Brantsch, Thomas Reichert
all Fraunhofer-Institute for Chemical Technology ICT, Joseph-von-Fraunhofer Str. 7, 76327 Pfinztal, Germany
* carl-christoph.hoehne@ict.fraunhofer.de
1 Höhne C-C, Hanich R, Kroke E. Intrinsic flame resistance of polyurethane flexible foams: Unexpectedly low flammability without any flame retardant, Fire Mater. 2018, 42, 394.
Acknowledgements: Nathália Freire Monteiro and Lin Zhang are greatly acknowledged for their support.
These research activities receive supporting funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 807091, 807083, 945549 and 945521. This publication reflects only the author’s views and the European Union is not liable for any use that may be made of the information contained therein.
Introduction
The analysis of environmental impacts of aviation should include the full life cycle of an aircraft and its parts and should go beyond use-phase emissions. Environ- mental impacts of the manufacturing stages e.g. related to consumption of
resources, pollutions and the use of hazardous materials like environmentally toxic chemicals as well as environmental impacts of end-of-life scenarios for an aircraft must be considered. Based on a case example on polyurethane flexible foams (PUR-FF) for aircraft seating cushions, an analysis of the environmental impacts supported by the life cycle assessment methodology has been
conducted. This analysis covers the production of polyurethane flexible foams with a particular focus on three perspectives being: (a) use of biomaterials
instead of fossil based material, (b) reduction and replacement of hazardous chemicals like heavy metal catalysts and flame retardants, (c) use of recycled polyol obtained by chemical solvolysis of flexible polyurethane foam.
Use of Biomaterials
PUR foams using polyols produced from different renewable resources are studied. Significant impact disadvantages of bio-based polyols are the water
consumption and eutrophication by e.g. the land use change for the plantation, such as deforestation, and use of fertilizers during the cultivation of the oil plants:
Reduction & Replacement of Hazardous Chemicals
Typically, tin(II) catalysts are used with an amount of 0.1 % in PUR foams. Modern PUR foams use amine-based catalysts, which are less environmentally harmful.
Due to the low catalyst amount of 0.1 %, the substitution of the tin(II) catalyst has a low environmental impact compared to the environmental impact of the entire PUR foam formulation. However, on a global A220/ A320 fleet-level, 33 tons of tin(II) catalysts might be avoided by using modern PUR foam formulations. Modern PUR foams are also able to pass the aviation flame retardant requirements without any flame retardant [1] - leading to a flame retardant saving of 1,750-3,500 t.
In comparison with fossil-based polyether polyol, four out of five bio-based
polyols show a higher Eutrophication Potential (EP). The EP of polyol produced from palm oil is nearly half as high compared to fossil-based polyol. However, palm oil is often cultivated in deforestation areas of rain forest e.g. obtained by fire clearance. Low fertilization, which leads to a low EP during the cultivation period, is assumed. From an overall environmental-related point of view,
deforestation has to be avoided. On the base of the EP, polyols produced from soybean or rapeseed seems to be suitable polyols for eco-friendly PUR foams.
Use of Recycled Polyol
Chemical recycling technologies enables the recovery of the polyol fraction of a PUR foam. Concerning the use of bio-based polyols, the recovery of the polyol fraction is important as the amount of PUR foam product from the
cultivated seeds is significantly increasing - reducing oil plantation land use:
Conclusions
For ecoDESIGN, several environmental indicators have to be considered, especially during the production stage and the end-of-life stage of an aircraft.
Within this eco-screening, the procedure to achieve this deep ecological understanding is shown by three case examples of PUR-FF for aircraft seating cushions.
0 1 2 3 4
0 50 100 150 200
Water Pollution / m3/kg GWP / kg CO2 eq./kg
Fossil based PUR Foam vs.
100 % Recycling Polyol based PUR Foam Primary Energy Demand (PED) / MJ/kg
Ecotoxicity / CTUe/kg
Chemical Recycling Process:
Recycling polyol is obtained by recycling process in technical scale.
Solvent recovery and thermal recovery are currently not taken into account.
-18%
-38%
-1.5%
+118%
Increased Material Efficiency
5.5
1.5
0x Chemical Recycling Loop
10x Chemical Recycling Loops
kg PUR per kg Polyol
Thought experiment: From 1 kg polyol about 1.5 kg of PUR foam are
produced. If the PUR foam is recycled ten times (this means eleven PUR foam generations), with an assumed polyol recovery of 95 % and the recycled polyol is used with 75 % in the next PUR foam generation, the PUR foam amount produced from one kg of polyol increases to 5.5 kg PUR foam.
Assumption for A320:
• 6 kg PUR Foam per Seating Structure
• approximately 60 Seating Structures per a/c
• 6x exchange of all Seating Structures per a/c life time
2 t PUR Foam per a/c over life time
Global: 35.076 t PUR-FF per A220/320 fleet
https://magazin.lufthansa.com/xx/de/airbus-a320-200-2/sitzplan-airbus-a320-200/
https://www.airbus.com/aircraft/market/orders-deliveries.html (August 2021)
16239 Tin(II) Catalyst
Flame Retardant
Typically 5-10 % Flame Retardant in an a/c PUR foam formulation:
Hazardous Materials
Tin(II) Catalyst
Typically 0.1 % tin(II) catalyst in an a/c PUR foam formulation:
1,750-3,500 t
Flame Retardant Savings 35 t Tin(II) Catalyst Savings
Polyol from Palm Oil shows lowest
Eutrophication Potential (EP). Soybean Polyol shows medium EP.
Global Warming Potential (GWP) of Palm Polyol is high due to deforestation. Soybean Polyol shows lowest GWP.
Soybean Polyol is selected for the PUR foam
Eco Screening
GWP / kg CO2 eq/kg
Palm
Soybean (Hyd.) Soybean (Epo.) Rapeseed
Castor REFERENCE Soybean (Hyd.)Palm
Soybean (Epo.) Rapeseed
Castor REFERENCE
Primary Energy Demand / MJ/kg
2.1
11.1
11.1
9.2
42.4
2.2 0.4
1.2
1.5
2.1
1.3
3.4 2.5
12.3
12.6
11.3
43.7
5.6
seed to oil / petrol to crude oil oil to polyol
TOTAL
EUTROPHICATION POTENTIAL [g Nitrogen eq/kg]
Palm (Epoxidation)
Soybean (Hydroformylation)
Soybean (Epoxidation)
Rapeseed (Epoxidation)
Castor (Hydroformylation)
Reference: Polyether polyol (fossil based)
Eutrophication Potential / g Nitrogen eq/kg
Further information:
https://www.cleansky.eu/eco-design
