Thermoplastic and Thermosetting Polymers for Composites

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Thermoplastic and Thermosetting Polymers for
Composites

• Dr Ian Hamerton
• Chemistry
• School of Biomedical and Molecular Sciences
• University of Surrey

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Outline of Presentation

• Definition of a Composite
• Thermosetting polymers
• Thermoplastic polymers
• Thermoplastic processing
• Use of Composites in Aerospace
• Performance Criteria
• Application of LCA to composites
• Conclusions
• Questions

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• Composite
• A multi-phase material in which the properties
  of a continuous phase (matrix) are enhanced by
  distributed sheet-like, fibrous or particulate
  fillers

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Common Thermoset Polymers

• Epoxy (common, industry standard, versatile)
• Vinyl esters (composition, cost properties
  between epoxies and unsaturated esters)
• Unsaturated polyesters (cheapest, good properties
  at lower temperature, large components/volume
  production)
• Phenolics (lower mechanical properties, retain to
  high temperature, no toxic flammables)
• Polyimides (expensive, but high performance)
• Bismaleimides (good hot/wet properties, brittle,
  cheaper than some polyimides)
• Cyanate esters (low loss properties, relatively
  expensive)

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Selected high performance thermosets
Polyimides
Bismaleimides
Cyanate esters

• Epoxy

Phenolics
Unsaturated polyesters
Vinyl polyesters
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Thermosetting Polymers

• Can offer
• Variety of physical forms and viscosities
• Wide choice of curing systems
• Latitude with processing conditions
• Low cure shrinkage
• Good chemical resistance
• Good mechanical properties
• Good fibre/reinforcement adhesion
• Thermal stability over wide temperature range
• Good resistance to moisture
• But
• Often limited outlife
• Usually need to be toughened
• Pose significant recycling problems

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Selected high performance thermoplastics
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Thermoplastic Polymers

• Will soften above Tg for shaping and harden in
  this form on cooling
• Can offer
• Better resistance to moisture and various
  industrial solvents than thermosets
• Superior flexural and impact properties to
  thermosets
• But
• Poorer abrasion and dimensional stability to
  thermosets
• No apparent advantage in static properties or
  fatigue
• Higher processing temperatures than most
  thermosets (generally above 300oC)
• Compression strength may be inferior

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Thermoplastic matrices

• Tg/oC Tproc/oC
• Poly(amide-imide)a 275 345-355
• Polyarylethersa 220-260 310-345
• Polyethersulphonea 220 300-310
• Poly(arylene sulfide)a 200-210 345
• Polyetheretherketonec 140-145 340-350
• Polyphenylenesulfidec 85-95 330
• Poly(arylene ketone)c 200-210 370-415
• Polyimidea,c 250-280 350-360
• Tg Glass transition temperature a
  amorphous
• Tproc Processing temperature
  c crystalline

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Thermoplastic processing methods

• Autoclave consolidation
• Press forming (rubber assisted punch or hydro
  forming)
• Double diaphragm forming
• Pultrusion
• Roll forming
• Filament and tape winding

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Aerospace Applications

• Combinations of thermoplastics and thermosets

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Aerospace Applications
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Trade offs as composite
Property T/sets T/plastics Formulations complex
simple Melt viscosity very low high Fibre
impregnation easy difficult Prepreg
tack good none Preprepg drape good none to
fair Prepreg stability poor excellent Processing
cycle long short to long Processing
T/P low/moderate high Fabrication
cost high potent. low Mech. Properties fair to
good fair to good (-54 to 93oC, hot/wet) Environ.
Stability good unknown Solvent
resistance excellent poor to good Damage
tolerance poor/good fair/excellent Database very
large small
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LCA should address

• Initial preparation
• Formulation
• Processing
• Lifetime(s)
• Recycling potential

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Conclusions potential hotspots

• Thermosets
• High monomer cost
• Long processing cycle
• Storage of prepreg (refrigeration)
• Repair (poor damage tolerance)
• Poor recycling potential
• Thermoplastics
• High melt viscosity/impregnation
• High polymerization temperatures

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Any Questions?