MSE 201-Polymers 1 General Overview of General Overview of Polymers (Unit 1 Polymers (Unit 1– 5b) 5b) • Polymer Classifications • Concept of Mole. Wt. • Polymerization routes • Polymer crystallinity Introduction Introduction • Recall polymer (macromolecular) Recall polymer (macromolecular) definition definition – Covalent linkages of many repeating Covalent linkages of many repeating monomer units. (polymer or chain monomer units. (polymer or chain molecules or polymer chains) molecules or polymer chains) – Very high MW (e.g., MW of PS = 300,000 Very high MW (e.g., MW of PS = 300,000 (cf. MW of small molecules) (cf. MW of small molecules) – Recall Lecture 1 Recall Lecture 1
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MSE 201-Polymers 1
General Overview of General Overview of Polymers (Unit 1Polymers (Unit 1––5b)5b)
definitiondefinition–– Covalent linkages of many repeating Covalent linkages of many repeating
monomer units. (polymer or chain monomer units. (polymer or chain molecules or polymer chains)molecules or polymer chains)
–– Very high MW (e.g., MW of PS = 300,000 Very high MW (e.g., MW of PS = 300,000 (cf. MW of small molecules)(cf. MW of small molecules)
–– Recall Lecture 1Recall Lecture 1
MSE 201-Polymers 2
IntroductionIntroduction
•• Chemical properties defined by Chemical properties defined by monomer propertiesmonomer properties
•• Physical properties are UNIQUE Physical properties are UNIQUE and changeable (large size, and changeable (large size, interactions, chain flexibility, interactions, chain flexibility, M M == xxMoMo).).
•• 10 < n, 10 < n, xx, D.P. < 10,000 (where , D.P. < 10,000 (where MMoo == 100)100)
MSE 201-Polymers 3
Concept of Molecular Concept of Molecular Weight DistributionWeight Distribution•• ExplainExplain
Class Practice ProblemClass Practice Problem
•• If a particular type of PE has a If a particular type of PE has a degree of polymerization of 10 degree of polymerization of 10 000, what is its molecular 000, what is its molecular weight? (atomic masses of C weight? (atomic masses of C and H are 12 & 1)and H are 12 & 1)
MSE 201-Polymers 4
Molecular vs.Molecular vs. MicrostructuralMicrostructuralEngineeringEngineering
•• Different properties by joining Different properties by joining monomers in different ways (cf. monomers in different ways (cf. metals)metals)–– cfcf: Metals can only be heat: Metals can only be heat--treated or treated or
workwork--treated but their molecules (& treated but their molecules (& crystals) are fixed forever crystals) are fixed forever ((microstructuralmicrostructural engineering)engineering)
–– MicrostructuralMicrostructural eng. also possible eng. also possible with polymer (structurewith polymer (structure––property property relations to be discussed later)relations to be discussed later)
–– Illustrate overIllustrate over
Schematic of Polymer Schematic of Polymer ChainsChains
•• FIBERS (explain high strength FIBERS (explain high strength & stiffness**)& stiffness**)–– Nylon or PA; Polyester (PET); Nylon or PA; Polyester (PET);
Rayon (modified cellulose**)Rayon (modified cellulose**)–– Clothing, upholstery, etc.Clothing, upholstery, etc.
MSE 201-Polymers 8
Usage, Usage, cont’dcont’d
•• COATINGS & FILMS (many types)COATINGS & FILMS (many types)–– Paints, structural adhesives,Paints, structural adhesives, HMPSA'sHMPSA's, ,
varnish, lacquers)varnish, lacquers)–– typically polymer typically polymer emulsionsemulsions
•• Emphasize complex structure of Emphasize complex structure of polymers/ benefits (fortuitously polymers/ benefits (fortuitously polymers can be used without inpolymers can be used without in--depth knowledge of structure)depth knowledge of structure)
•• OptionalOptional Reading (Chap. 1, Rodriguez,1996)Reading (Chap. 1, Rodriguez,1996)–– (Importance & other e.g.s)(Importance & other e.g.s)
Polymerization RoutesPolymerization Routes
•• 2 broad classifications 2 broad classifications (chain vs. step) W.J.(chain vs. step) W.J. CarothersCarothers et alet al–– ADDITION (or "Chain")ADDITION (or "Chain")
�� Chain reactions involving an Chain reactions involving an unpaired electron or an ionunpaired electron or an ion
�� Common with DOUBLECommon with DOUBLE––BONDED compounds, e.g., PEBONDED compounds, e.g., PE
•• Polymers crystallize differently Polymers crystallize differently from simplefrom simple cystallinecystalline solidssolids–– XRD patterns are less sharpXRD patterns are less sharp–– Small crystallite size (100 A)Small crystallite size (100 A)–– Polymer chains much larger than Polymer chains much larger than
materialmaterial–– carbons are 109° to each other (tetrahedral bond carbons are 109° to each other (tetrahedral bond
angle for spangle for sp33 hybridizationhybridization–– “zigzag” structure“zigzag” structure
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MSE 201-Polymers 18
Polymer Crystal ModelsPolymer Crystal Models
•• Chain folded Chain folded Chain folded Chain folded modelmodelmodelmodel -- crystals crystals are actually small are actually small platelets of platelets of interwoven interwoven polymer chainspolymer chains
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Polymer Crystal ModelsPolymer Crystal Models•• In many bulk In many bulk
polymers polymers crystallized crystallized from the melt, from the melt, these platelets these platelets often arrange often arrange themselves in themselves in radiating radiating patterns to formpatterns to formspherulitesspherulitesspherulitesspherulites..
•• PE, PP, PE, PP, PVC,PTFE, PVC,PTFE, nylon crystallize nylon crystallize in this mannerin this manner
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MSE 201-Polymers 19
Melting and Glass Melting and Glass Transition Transition TemperaturesTemperatures
•• Temperature at which melting (or glass Temperature at which melting (or glass transition) occurs is determined as it is for transition) occurs is determined as it is for glasses: Specific. vol. vs. T.glasses: Specific. vol. vs. T.
Tm
Spec
ific V
olum
e
TgTemperature
A. Amorphous B. Semicrystalline C. Crystalline
AB
C
End of Lecture, Unit 1–4b
• READ • Class notes and Callister 2000, • pp. 446-469, 482-486, 496-512