Thermoplastic and Thermosetting Polymers for Composites Dr Ian

Thermoplastic and Thermosetting Polymers for Composites Dr Ian Hamerton Chemistry School of Biomedical and Molecular Sciences University of Surrey

Outline of Presentation • • • Definition of a Composite Thermosetting polymers Thermoplastic processing Use of Composites in Aerospace Performance Criteria Application of LCA to composites Conclusions Questions 2

Composite A multi-phase material in which the properties of a continuous phase (matrix) are enhanced by distributed sheet-like, fibrous or particulate fillers 3

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) 4

Selected high performance thermosets Polyimides Bismaleimides Cyanate esters Epoxy Vinyl polyesters Phenolics Unsaturated polyesters 5

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 6

Selected high performance thermoplastics 7

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 300 o. C) • Compression strength may be inferior 8

Thermoplastic matrices Poly(amide-imide)a Polyarylethersa Tg/o. C 275 220 -260 Tproc/o. C 345 -355 310 -345 Polyethersulphonea 220 300 -310 Poly(arylene sulfide)a 200 -210 345 Polyetherketonec 140 -145 340 -350 Polyphenylenesulfidec 85 -95 330 Poly(arylene ketone)c 200 -210 370 -415 Polyimidea, c 350 -360 Tg = Glass transition temperature Tproc = Processing temperature 250 -280 a = amorphous c = crystalline 9

Thermoplastic processing methods • Autoclave consolidation • Press forming (rubber assisted punch or hydro forming) • Double diaphragm forming • Pultrusion • Roll forming • Filament and tape winding 10

Aerospace Applications • Combinations of thermoplastics and thermosets 11

Aerospace Applications 12

Trade offs as composite Property T/sets Formulations complex Melt viscosity very low Fibre impregnation easy Prepreg tack good Preprepg drape good Prepreg stability poor Processing cycle long Processing T/P low/moderate Fabrication cost high Mech. Properties fair to good (-54 to 93 o. C, hot/wet) Environ. Stability good Solvent resistance excellent Damage tolerance poor/good Database very large T/plastics simple high difficult none to fair excellent short to long high potent. low fair to good unknown poor to good fair/excellent small 13

LCA should address: • Initial preparation • Formulation • Processing • Lifetime(s) • Recycling potential 14

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 15

Any Questions? 16