Thermosetting and Thermoplastic Polymer Matrices for Composites

Transcription

1 Thermosetting and Thermoplastic Polymer Matrices for Composites Dr Ian Hamerton Reader in Polymer Chemistry Chemistry Department Faculty of Engineering and Physical Sciences and Surrey Materials Institute

2 Bibliography During the preparation of this lecture, I consulted:

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4 Context Last Workshop

5 Context Last Workshop

6 In the Meantime

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8 787 Materials Usage

9 Airbus Materials Usage

10 Airframe Manufacture

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12 Introduction to Thermosets Thermoset based composites account for about 60% of the total composites market (ca. 7 Mt p.a. worldwide) More than 80% [by weight] of market consists of glass fibre reinforcement in unsaturated polyester resin matrices High performance fibres and resins account for a smaller proportion but relatively more valuable sector of the market ne of the most important current trends is the increasing adoption of high performance composites into commodity market sectors.

13 Polymer Resin Matrices THERMSETTIG RESIS Chemosets Liquid resin thermally cures to solid SMC, BMC Paste or solid thermally cured THERMPLASTIC RESIS Melt - freeze process Solid at room temperature

14 Principal Thermoset Resins Vinyl polyesters Unsaturated polyesters Epoxy Phenolics H H H H H H Polyimides Bismaleimides Cyanate esters C

15 Thermoset Resin Matrices Unsaturated polyesters many variants (hot/cold cure), cheap, versatile, limited high temp/environmental capability, good properties at lower T g, large components, volume production, market leader in commercial sector Vinyl esters - cost/properties between epoxies and unsaturated esters Epoxy - common, aerospace industry standard, versatile, higher cost Phenolics old established system, lower mechanical properties, retain to high T g, no toxic flammables (Good FST) Polybenzoxazines new family, similar to phenolics in many respects Bismaleimides good hot/wet properties, brittle, cheaper than some polyimides Polyimides expensive but high performance, difficult to process Cyanate esters low loss properties, intermediate T g, relatively expensive, epoxy blends

16 Processing Thermoset Composites CURE Transform from liquid or paste to infusible solid on thermal cure Cannot be re-melted Cure always exothermic [heat produced] There is sometimes a gaseous by-product FRMULATI Usually at least two reactants Chemically unstable once mixed = finite useable life [ shelf life, pot life, out life ] Proportions need to be carefully controlled

17 Cure of Thermoset Composites Many based on condensation polymerisation Resins for composites specially formulated to reduce or eliminate condensation by-products e.g. water, ammonia or C 2 Unsaturated polyesters cured via addition polymerisation of vinyl monomer [styrene] Styrene vapour - environmental hazard (subject to strict emission controls) Epoxy resins/bmis/benzoxazines/cyanates formulated to eliminate condensate

18 Processing Thermosets 1 VISCSITY Formulation, cure temperature CURE TEMPERATURE Function of formulation CURE RATE Controlled by formulation [e.g. % initiator] Cure temperature : HT FAST, LT SLW EXTHERM Extent function of resin formulation Rate depends on cure rate - too fast overheat

19 Epoxy Resins DEGREE F CURE & EXTHERM/TIME - EPXY RESI K = 127 o C MAX RATE F HEAT EVLUTI DEGREE F CURE RATE F EXTHERM ARBITARY UITS TIME - min 0.000

20 Processing Thermosets 2 SHELF LIFE Formulated thermosets have limited shelf life may require refrigerated storage. PT LIFE, UT LIFE Time when of workable viscosity at room temperature PRCESSIG WIDW Time available to infiltrate or consolidate [low viscosity required.] before gelation arrests flow. Time will be lower at higher temp. but initial viscosity will be lower!

21 Typical Phenolic Mechanical Properties H H H H H H Unfilled casting Moulding (wood flour filled) Moulding (cotton fabric filled) Laminate (paper filled) Specific gravity Tensile strength (MPa) Flexural strength (MPa) Compression strength (MPa) Impact strength, Izod (J/m) Water absorption (mg)

22 Polyimides Discovered in 1908 Commercialised in 1950s In-chain polyheterocyles H Imide Few acyclic polyimides known Cyclic imide properties range of applications Ar Polyimides high temperature polymers * * n

23 Cyanate Ester Resins CH 3 H 3 C CH 3 H Cyanate functional group CH 3 m.p. 79 o C, T g = 270 o C CF 3 H H 3 C CH 3 m.p. 106 o C, T g = 255 o C CH 3 CF 3 H m.p. 87 o C, T g = 273 o C m.p. 29 o C (supercooled liquid), T g = 258 o C CH 3 CH 3 CH 3 CH 3 n m.p. 29 o C (supercooled liquid), T g = 192 o C liquid and solid, T g = o C

24 Commercial Bis-Benzoxazines CH 3 CH 3 Araldite Araldite Araldite S LME LMB 6457

25 Semi-crystalline polymers better at HT and environment. Thermoplastic Resins PRCESS RUTE All are processed by melt-freeze route Always solids at room temperature Very viscous in liquid state May be remelted or softened repeatedly! MELTIG TEMPERATURE Ranges from 100 o C for PE to 400 o C for PEEK GLASS TRASITI TEMPERATURE T g Usually ~ 150 o C below MP Determines upper use temperature CRYSTALLIITY

26 Thermoplastic Resins CMMDITY THERMPLASTICS Polyethylene Polypropylene Polyester* * ot same as thermosetting polyester ARMATIC THERMPLASTICS Polyether sulphone Polyether amide Polyimide Polyamide imide Polyether ether ketone EGIEERIG THERMPLASTICS Polyamides [nylons] Polysulphones Polyphenylene sulphide Polycarbonate

27 Thermoplastic Polymers * Ar Ar' * n Poly(aryl ether)s * Ar S 2 Ar' * n Poly(ether sulphone)s Ar S * * n Poly(arylene sulphide)s/ Polyphenylsulphide Ar Ar' * n * * Ar Ar' n * Poly(ether ether ketone)s Poly(arylene ether ketone)s H H Ar Ar Ar Ar Poly(amide-imide)s Polyimides

28 Thermoplastic Polymers C C CH 3 C CH 3 C C n PEI Aromatic Thermoplastic Amorphous Crystalline H C C C Ar n PAI PES PEI PAI PEEK PPS Epoxy Specific gravity Modulus (GPa) Strain to failure (%) Fracture toughness (kj m -2 ) T g ( C)

29 Processing Thermoplastics Main consideration is the high melt viscosity eed to fully wet and infiltrate the reinforcement Main process routes: GMT [Pressing or stamping hot T/P preform] Injection moulding [discontinuous fibres] Pultrusion Co-mingling technologies Most processes mould a hot charge into cold tooling Thermoplastics allow post-forming operations Potentially easier to recycle

30 Processing Trade ffs 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

31 Property Trade ffs Property T/sets T/plastics Fabrication cost high potentially low Mech. Properties fair to good fair to good (-54 to 93 o C, hot/wet) Environ. Stability good unknown Solvent resistance excellent poor to good Damage tolerance poor/good fair/excellent Database very large Small

32 LCA 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 polymerisation temperatures

33 Thank you for listening - Any Questions? The Queen of Hearts, CFA Voysey for Minton, ca. 1930