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 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)

5 Selected high performance thermosets Epoxy Unsaturated polyesters Vinyl polyesters Phenolics PolyimidesBismaleimidesCyanate esters

6 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

7 Selected high performance thermoplastics

8 Thermoplastic Polymers Will soften above T g 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 300 o C) Compression strength may be inferior

9 Thermoplastic matrices T g / o C T proc / o C Poly(amide-imide) a Polyarylethers a Polyethersulphone a Poly(arylene sulfide) a Polyetheretherketone c Polyphenylenesulfide c Poly(arylene ketone) c Polyimide a,c T g = Glass transition temperaturea = amorphous T proc = 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

11 Aerospace Applications Combinations of thermoplastics and thermosets

12 Aerospace Applications

13 Trade offs as composite PropertyT/setsT/plastics Formulationscomplexsimple Melt viscosityvery lowhigh Fibre impregnationeasydifficult Prepreg tackgoodnone Preprepg drapegoodnone to fair Prepreg stabilitypoorexcellent Processing cyclelongshort to long Processing T/Plow/moderatehigh Fabrication costhighpotent. low Mech. Propertiesfair to goodfair to good (-54 to 93 o C, hot/wet) Environ. Stabilitygoodunknown Solvent resistanceexcellentpoor to good Damage tolerancepoor/goodfair/excellent Databasevery largesmall

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

16 Any Questions?