Steve PickeringSchool of Mechanical, Materials and Manufacturing Engineering

Routes to Recycling or Disposal of Thermoset Composites

Presentation Outline

• Need to Recycle

• Problems in recycling thermoset composites

• Recycling/Disposal Processes– mechanical recycling

– thermal processing

• Future Prospects

Need to Recycle

Pressure from legislation

• EU Directives

• Landfill

• End-of-Life Vehicles

• Waste Electrical and Electronic Equipment

• Construction and Demolition Waste

Recycling Heirarchy

• Prevent waste

• Reuse product

• Recycle material

• Incineration• with material and energy recovery

• with energy recovery

• without recovery

• Landfill

Does not measure recycling quality

(environmental benefit)

Problems in Recycling Thermoset Composites

• Technical Problems •Thermosetting polymers can’t be remoulded

• Long fibres

• Mixtures of materials (different compositions)

• Contamination

• Costs

• Collection and Separation

Recycling Processes for Thermoset Composites

Powdered fillers

Fibrous products (potential

reinforcement)

Combustion with energy

recovery (and material

utilisation)

Fluidised bed process

Pyrolysis/Gasification

Chemical products, fibres and

fillers

Clean fibres and fillers

with energy recovery

Thermal Processes

Mechanical Recycling

(comminution)

Mechanical Recycling

Size reduction • Coarse primary crushing

• Hammer milling followed by grading to give:

• Powder

• Coarser fractions (reinforcement rich)

All scrap material is contained in recyclate (incl. different polymers, contamination, paint….)

Mechanical Recycling

Recycling into new composites• Powdered recyclate useful as a filler

(up to 25% incorporated in new composite)

• Coarser recyclate has reinforcement properties

(up to 50% substitution of glass fibre)

Several companies have been founded to commercialise recycling – ERCOM (Germany), Phoenix Fiberglass (Canada)

Mechanical Recycling

Recycling into other products• Compounding with thermoplastics

• Production of reinforcement with recyclate core to allow resin flow during impregnation

• Using recyclate to provide damping (noise insulation)

• Alternative to wood fibre

• Asphalt

Thermal Processing

Combustion with Energy and Material Recovery • Calorific value of thermosetting resins ~ 30 MJ/kg

• Co-combustion with municipal waste in mass burn incinerators

• Co-combustion in cement kilns

• Co-combustion with coal in fluidised bed

Thermal Processing Combustion with energy recovery

• Calorific value depends on inorganic content (10 - 30 MJ/kg)

• Filler effects: • CaCO3 1.8 MJ/kg (+800 C)• ATH 1.0 MJ/kg

• ‘Cleaner than coal’• Bulky ash remaining

Cement manufacture

• energy recovery from polymer

• glass and fillers combine

usefully with cement minerals

• fuel substitution limited to <10%

by boron in E-glass

Potential savings <£20/tonne of GRP used

Thermal Processing Combustion with energy and material recovery

Thermal Processing Combustion with energy and material recovery

Fluidised Bed Coal Combustion

• (Limestone filled composites)

• energy recovery from polymer

• limestone filler absorbs oxides of

sulphur from coal

• commercial trial undertaken

Thermal Processing – Fluidised Bed Process

Cyclone

Air Inlet

Electric Pre-heaters

Fibre

Scrap CFRP

Recovered FluidisedBed

Air distributor

plate

300 mmAfterburner

Clean flue gas To energy recovery

Fan

Fluidised Bed Processing Materials and Energy Recovery

Fluidised

Bed

Scrap

FRP

Separation of fibres

and fillers

Recovered

FibresRecovered

Fillers

HeatRecovery

Recovered

Energy

Clean Flue Gas

Secondary

Combustion

Chamber

Fibres and fillers carried in gas flow

Fluidised Bed Operation• Temperature: 450 to 550 deg C• Fluidising air velocity: up to 1.3 m/s• Fluidising medium: silica sand 1mm

• Able to process contaminated and mixed composites eg: double skinned, foam cored, painted automotive components with metal inserts

Recovered Glass Fibres

Properties

• Strength: reduced by 50% (at 450 C)

• Stiffness: unchanged

• Purity: 80%

• Fibre length: 3 to 5 mm (wt)

Reuse of Recycled Glass Fibre Moulding Compounds

•Moulding - virgin glass fibreMoulding - virgin glass fibre

•Moulding - 50% recycled glass fibreMoulding - 50% recycled glass fibre

Moulding Compounds

• Only effect is 25% reduction in impact strength

• no change to processing conditions

• demonstrator components produced

Outline Process EconomicsGlass Fibre Recycling

Commercial Plant Schematic (5000 tonnes/year)

Outline Process EconomicsGlass Fibre Recycling

5,000 tons/year Capital £3.75million

Annual costs: £1.6 millionAnnual Income: £1.3 million

Breakeven throughput: 10,000 tons/year

Fluidised Bed Process

Cyclone

Air Inlet

Electric Pre-heaters

Fibre

Scrap CFRP

Recovered FluidisedBed

Air distributorplate

300 mmAfterburner

Clean flue gas To energy recovery

Fan

Carbon Fibre Properties

•Tensile strength reduced by 25%

•Little change in modulus

•No oxidation of carbon fibres

00.5

11.5

22.5

33.5

44.5

Virgin 450 deg C 550 deg C

Fibr

e S

treng

th

[GP

a]

Carbon Fibre Properties Fibre Quality

• Fibre surface quality similar to virgin fibre

• Clean fibres produced

~200mm~200mm

100mm100mm

100100mm

Recovered Fibre Composite

0

50

100

150

200

250

RecoveredFibre A

RecoveredFibre B

VirginCarbon

Virgin Glass

Tens

ile s

treng

th [M

Pa]

0

2

4

6

8

10

12

RecoveredFibre A

RecoveredFibre B

VirginCarbon

Virgin Glass

Tens

ile m

odul

us [G

Pa]

• Fibres made into polycarbonate composite

StrengthStrength StiffnessStiffness

ReactorScrap feed Condenser

Hot gases

Solid and Liquid

Hydrocarbon Products

Combustible Gases to heat reactor

Solid Products (fibres, fillers, char)

Pyrolysis Process

Thermal Processing

Thermal Processing

Pyrolysis Processes • Heating composite (400 – 800°C) in absence of air to give

• hydrocarbon products – gases and liquids

• fibres

• Some char contamination on fibres

• Hydrocarbon products potential for use as fuels or chemical feedstock

• Low temperature (200°C) catalytic pyrolysis for carbon fibre

Gasification – limited oxygen – no char, fuel gases evolved

Thermal Processing

Products from Pyrolysis (450°C)

Polyester Composite (30% glass fibre, 7% filler, 63% UP resin)

6% Gases: CO2 & CO (75%) + H2, CH4 …….

40% Oils hydrocarbons, styrene (26%)…….

15% Waxes phthalic anhydride (96%)…..

39% Solids glass fibre & fillers (CaCO3), char (16%)

What is best Recycling Route??

• Established hierarchy and ELV Directive favour mechanical recycling techniques – but are these the best environmentally??

• Detailed Life Cycle Analysis needed to identify environmental impact

• Recent project in Sweden (VAMP18) has considered best environmental and cost options for recycling a range of composites

Prospects for Commercial Success?

• ERCOM and Phoenix – viable levels of operation not

achieved

• Recyclates too expensive to compete in available markets

• Need to develop higher grade recyclates for more

valuable markets

• Legislation and avoidance of landfill are new driving forces

Value in Scrap Composites

• Energy value of polymer £ 30/tonne

• Value of polymer pyrolysis products

Maleic Anhydride, Bisphenol A £1,000/tonne• Value of filler £ 30/tonne• Value of glass fibre £1,000/tonne• Value of carbon fibre £10,000/tonne

New Initiative

• EuCIA (GPRMC) initiative

• ECRC (European Composites Recycling Concept)

• Scheme to fund recycling to meet EU Directives

• A guarantee that composites will be recycled

Conclusions

• A range of technologies is under development• material recycling

• thermal processing

• Key barriers to commercial success are markets at right cost

• Need for environmental analysis to identify best options

• Future legislation is driving industry initiatives

Recycled Carbon Fibre Life Cycle Analysis

• Energy use for

recovery process is

10% of virgin fibre

production

• 40% to 45% energy

reduction observed for

recovered fibre

composites

-50

0

50

100

150

200

Carbon Fibre Production Fluidized Bed Recovery

Ene

rgy

(MJ/

kg)

Coal Crude Oil Lignite Natural Gas Other Recovered

-50

0

50

100

150

Virgin Carbon FibreComposite

Equivalent Stiffness Equivalent Strength

En

erg

y (M

J/kg

) Coal Crude Oil Natural Gas Lignite Other Recovered Energy

Fluidised Bed Process