thermoplastic and thermosetting polymers for composites dr ian hamerton chemistry school of...
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Thermoplastic and Thermosetting Polymers
for Composites
Dr Ian Hamerton
Chemistry
School of Biomedical and Molecular Sciences
University of Surrey
2
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
3
Composite
A multi-phase material in which the properties of a continuous phase (matrix) are enhanced by distributed sheet-like, fibrous or particulate
fillers
4
Common Thermoset PolymersEpoxy (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)
5
Selected high performance thermosets
N
O
O
Epoxy
O
O
O
O
O
OH
OH
OH
OH OH
OH
N
O
O
Unsaturated polyestersVinyl polyesters
Phenolics
NCO
Polyimides Bismaleimides Cyanate esters
6
Thermosetting PolymersCan 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
7
Selected high performance thermoplastics
Ar Ar'
O O
** n
Poly(ether ether ketone)s
* O Ar O Ar' *n
Poly(aryl ether)s
* O Ar O Ar'
O
*n
Poly(arylene ether ketone)s
N
O
O
Ar
O
N Ar
H
N
H
Ar N
O
OO
Poly(amide-imide)s
N
O
O
ArN
O
O
Polyimides
* O Ar SO2 Ar' *n
Poly(ether sulphone)s
Ar S ** n
Poly(arylene sulphide)s/ Polyphenylsulphide
8
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
9
Thermoplastic matrices
Tg/oC Tproc/oCPoly(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
10
Thermoplastic processing methods
• Autoclave consolidation• Press forming (rubber assisted
punch or hydro forming)• Double diaphragm forming• Pultrusion• Roll forming• Filament and tape winding
13
Trade offs as compositeProperty 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/goodfair/excellent
Database very large small
14
LCA should address:
• Initial preparation
• Formulation
• Processing
• Lifetime(s)
• Recycling potential
15
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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