ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 1 Review of Polymers ver. 1ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 2 Overview • What is a polymer? • Why are polymers good? • Types / examples • Crystallinity • Melting properties • Heat transfer • Fluids • Behavior during processingME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 3 Just one word: plastic • The Graduate: 1967ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 4 Globalization of Barbie • 1959 – Invented; Japan • 1960’s – Hong Kong • 1980’s – Philippines, Malaysia, Thailand • 1990’s – Indonesia • 2000’s – ChinaME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 5 Commodity Production • 34.8 million metric tons of plastics produced in US in 2010 – Density of plastic = 1 gm/cm3 • 69.7 million metric tons of steel produced in US in 2010 – Density of steel = 8 gm/cm3ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 6 Polymers • poly = many • meros = units • long-chain hydrocarbons – 1,000 - 10,000 units long – 104 - 106 gm/gm-moleME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 7 Why are polymers good? • Light • Corrosion resistant • Strong • Easily formed into complex, 3D shapes – no further machining necessary • Good filters – water / gas - permeable / impermeable • reverse osmosis • oxygenatorsME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 8 Types of polymers • Thermoplastics – can be melted and solidified repeatedly • Thermosets – react to polymerize during forming – cross-linked networks – can’t be remelted – decompose with too much heatME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 9 Types of polymers • Elastomers – large, recoverable, elastic deformations – soft – low glass transition temperatures – partially cross-linked networks – can be thermoset or thermoplasticME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 10ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 11 Bakelite • Leo Baekeland – 1863–1944 – first synthetic polymer (1907) – made from phenol and formaldehydeME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 12 Polyethylene (PE) • trash bags, electrical insulation • thermoplasticME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 13 Polypropylene (PP) • margarine tubs, food containers • thermoplasticME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 14 Polystyrene (PS) • coffee cups (styrofoam) • clear plastic boxes • thermoplasticME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 15 Polyvinylchloride (PVC) • credit cards • pipes • thermoplasticME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 16 Polycarbonate (PC) • Lexan • thermoplasticME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 17 Polymethylmethacrylate (PMMA) • Lucite, plexiglas • thermoplasticME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 18 Polytetrafluroethylene (PTFE) • Teflon • bearings • coatings • thermoplasticME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 19 Polyester (PET) • bottles • carpets • thermoplasticME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 20 Epoxy • adhesive • composite matrix • thermosetME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 21 Rubber – vulcanization (1844) • elastomer • thermoset Charles Goodyear 1800-1860 Vulcan Roman god of fireME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 22 Bonding • Leads to all mechanical properties • Primary – covalent (C-C, C-O, C-H, C-N) – along chain, interchain • Secondary – van der Waals – hydrogen – ionic – interchainME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 23 Bonding • Thermoplastics – covalent along chain – secondary between chains – 2D structure • Thermosets – covalent along and between (cross link) chains – 3D networkME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 24 Bonding • Elastomers – partially cross-linked – 2.5 D networkME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 25 Crystallinity • Short range order (1,000s of Å) • Amorphous – PS, PC • bulky side groups prevent packing • Semi-crystalline – PE, PP • small or no side groups allow packingME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 26 Crystallinity • Tightly packed • Rigid • Large secondary bonds crystal region amorphous regionME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 27 Crystallinity • Spherulites (PP) • Platelets (PE)ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 28 Effects of crystallinity • Increased stiffness – matrix reinforcement • Increased solvent resistance – large secondary bonds prevent solvent molecules from entering • Crystallinity can go from 0 to 90+%ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 29 Melting properties mechanical property temperature Tg Tm amorphous semi-crystalline glassy rubberyME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 30 Transitions Material Tg (oC) Tm (oC)PE -120 137PVC 87 212PP -18, -10 176PS 100 noneME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 31 Pressure – Volume – Temperature (pvT) diagramME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 32 Polycarbonate pvT diagramME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 33 Viscoelastic Behavior • Fast loading or cold = acts like elastic • Slow loading or hot = acts like a viscous fluid • Example: Silly PuttyME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 34 Old Glass WindowME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2011 35 Behavior • Polymers do not follow a linear stress-strain rate curve