1. Rubber: History,Rubber: History,
Properties and StructureProperties and Structure
Katrina CzenkuschKatrina Czenkusch
Physical Chemistry of MacromoleculesPhysical Chemistry of Macromolecules
April 9, 2009April 9, 2009

2. Definition of Rubber/Definition of Rubber/ElastomerElastomer
““A material that can be stretched to atA material that can be stretched to at
least twice its original length and willleast twice its original length and will
retract rapidly and forcibly to substantiallyretract rapidly and forcibly to substantially
its original dimensions upon release of theits original dimensions upon release of the
force.force.””
Rosen; p389Rosen; p389

3. Natural Rubber: Where?Natural Rubber: Where?
Hevea brasiliensisHevea brasiliensis
–– Most common sourceMost common source
–– Responds to wounding by producingResponds to wounding by producing
more latexmore latex
–– Produces cisProduces cis--1,41,4--polyisoprenepolyisoprene
–– Native to Amazon RainforestNative to Amazon Rainforest
GuttaGutta--PerchaPercha
–– Produces transProduces trans--1,41,4--polyisoprenepolyisoprene
–– Native to MalaysiaNative to Malaysia
Rubber Plantations in MalaysiaRubber Plantations in Malaysia
Pictures: http://en.wikipedia.org/wiki/Natural_rubber

4. Rubber in PrehistoryRubber in Prehistory
60 million BC60 million BC –– EuropeEurope --
rubberrubber--producing plantsproducing plants
First millennium BCFirst millennium BC –– MexicoMexico ––
First evidence of theFirst evidence of the
Mesoamerican ballgameMesoamerican ballgame
66thth centurycentury –– Mexico and CentralMexico and Central
AmericaAmerica –– Aztecs/MayansAztecs/Mayans
–– BallsBalls
–– Dipped Feet to make shoesDipped Feet to make shoes
–– Coated FabricsCoated Fabrics
Pictures: http://en.wikipedia.org/wiki/Mesoamerican_ballgame

5. Rubber and EuropeRubber and Europe
First European exposureFirst European exposure
–– Columbus supposedly watched aColumbus supposedly watched a
Mesoamerican ballgameMesoamerican ballgame
–– Early explorers learned nativeEarly explorers learned native
waterproofing techniqueswaterproofing techniques
Charles Marie de la CondamineCharles Marie de la Condamine
and Francois Fresneauand Francois Fresneau
–– Popularized rubber in FrancePopularized rubber in France
starting mid 1730starting mid 1730’’ss
–– Discovered first solventsDiscovered first solvents
–– Wrote about propertiesWrote about properties
Picture: http://en.wikipedia.org/wiki/Charles_Marie_de_La_Condamine

6. VulcanizationVulcanization
18391839
–– Goodyear and HancockGoodyear and Hancock
–– Mixed natural rubber, sulfur and white lead on a hotMixed natural rubber, sulfur and white lead on a hot
stovestove
–– Rubber wasRubber was ‘‘curedcured’’ of all its defectsof all its defects
18461846
–– AlexanderAlexander ParkesParkes invented a coldinvented a cold--cure process usingcure process using
sulfur chloride gas in solutionsulfur chloride gas in solution
[ ]n
[CH3
R'R + S8
S
CH3
R
2
R
3
S
S
CH3
R
R
1
2-8 Sulfurs
]
][

7. Natural Rubber the Real StoryNatural Rubber the Real Story
18601860 -- Williams (UK)Williams (UK)
–– Decomposed naturalDecomposed natural
rubber to isoprenerubber to isoprene
18791879 -- BouchardatBouchardat
(France)(France)
–– Repolymerized isoprene toRepolymerized isoprene to
make rubbermake rubber
19101910 –– PicklesPickles
–– Rubber is made of longRubber is made of long
chains of isoprenechains of isoprene
CH2
CH2
CH3
CH3
R'R [ ]n
Isoprene
cis-Polyisoprene

8. Origins of Rubber ElasticityOrigins of Rubber Elasticity
Energy elasticityEnergy elasticity –– elongation resultingelongation resulting
from rotation around single bonds and thefrom rotation around single bonds and the
straining of bond angles and lengthsstraining of bond angles and lengths

9. Statistics of Ideal Rubber ElasticityStatistics of Ideal Rubber Elasticity
Ideal rubberIdeal rubber
Slope of the stressSlope of the stress--strain curve or Youngstrain curve or Young’’s Moduluss Modulus
–– ρρ = density= density
–– R = Gas ConstantR = Gas Constant
–– T = temperatureT = temperature
–– Mc = number average molecular weight of the networkMc = number average molecular weight of the network
chainschains
–– αα = extension ratio, l/l= extension ratio, l/l00
–– l/ll/l00 = current length/unstretched length= current length/unstretched length
E=
ρRT
Mc
(2α+ α-2)

10. Deviations from IdealityDeviations from Ideality
Under predicts modulus forUnder predicts modulus for αα > 1.5> 1.5
Chain endsChain ends
Stress induced crystallizationStress induced crystallization

11. Butadiene RubberButadiene Rubber
PolybutadienePolybutadiene
–– First synthesized in 1910 by S. LebedevFirst synthesized in 1910 by S. Lebedev
–– Very durable but cis/trans issuesVery durable but cis/trans issues
–– Side walls of truck tires and golf ballsSide walls of truck tires and golf balls
–– Modern day use is as copolymerModern day use is as copolymer
CH2
CH2
cis-1,4-PBD 1,2-PBD
trans-1,4-PBD
R
R
2
CH2

12. And its copolymersAnd its copolymers
Buna N/ Buna NNBuna N/ Buna NN
–– Butadiene andButadiene and
acrylonitrileacrylonitrile
–– Increased acrylonitrileIncreased acrylonitrile
increases stiffness andincreases stiffness and
oil resistanceoil resistance
Buna SBuna S
–– Butadiene and styreneButadiene and styrene
–– Increased styreneIncreased styrene
leads to stiffer rubberleads to stiffer rubber
R
R
N
[ ]
R
R[ ]

13. The War YearsThe War Years
Japan captured Pacific Rubber plantationsJapan captured Pacific Rubber plantations
US synthetic rubberUS synthetic rubber
–– 19391939 –– 2000 tons/yr2000 tons/yr
–– 19451945 –– 830,000 tons/yr830,000 tons/yr
–– Butyl rubberButyl rubber
German synthetic rubberGerman synthetic rubber
–– BeforeBefore –– 22,000 tons/yr22,000 tons/yr
–– MiddleMiddle –– 100,000 tons/yr100,000 tons/yr

14. Butyl RubberButyl Rubber
Copolymer of 98% isobuteneCopolymer of 98% isobutene
–– 2% isoprene or butadiene2% isoprene or butadiene
–– Cationic polymerizationCationic polymerization
–– Air impermeableAir impermeable
–– Inner tubes for tiresInner tubes for tires
CH2
CH3
CH3
R
R
1
CH3
CH3R
+
n

15. Thermoplastic ElastomersThermoplastic Elastomers
Rubbers which canRubbers which can
be melt processedbe melt processed
afterafter ““crosslinkingcrosslinking””
Immiscible blockImmiscible block
copolymerscopolymers
–– Form matrix ofForm matrix of
rubbery polymer withrubbery polymer with
spheres of hardspheres of hard
segmentssegments
–– Most common:Most common:
StyreneStyrene--ButadieneButadiene--
Styrene (SBS)Styrene (SBS)
Pictures: http://en.wikipedia.org/wiki/Copolymer

16. Requirements to make a RubberRequirements to make a Rubber
High Molecular WeightHigh Molecular Weight
–– Rubber elasticity is due to the coiling/uncoiling of chainsRubber elasticity is due to the coiling/uncoiling of chains
Use temperature must be above TgUse temperature must be above Tg
–– To allow for molecular motionTo allow for molecular motion
Amorphous in its unstretched stateAmorphous in its unstretched state
–– Crystals would hinder coiling/uncoilingCrystals would hinder coiling/uncoiling
Chains tied together to prevent flowChains tied together to prevent flow
–– Traditionally through crosslinkingTraditionally through crosslinking
–– Hard/Soft DomainsHard/Soft Domains
–– EntanglementsEntanglements
All polymers above Tg act as rubbers due to entanglementsAll polymers above Tg act as rubbers due to entanglements
However, when the entanglements break, the polymer will begin toHowever, when the entanglements break, the polymer will begin to
flowflow

17. Rubber: History,Rubber: History,
Properties and StructureProperties and Structure
Katrina CzenkuschKatrina Czenkusch
Physical Chemistry of MacromoleculesPhysical Chemistry of Macromolecules
April 9, 2009April 9, 2009

18. ReferencesReferences
GoritzGoritz, D., Muller, F. H.,, D., Muller, F. H., SietzSietz, W.;, W.; ““TemperatureTemperature--induced andinduced and
StressStress--induced Crystallization in Oriented Polymersinduced Crystallization in Oriented Polymers””,, Progress inProgress in
Colloid and Polymer ScienceColloid and Polymer Science; Springer Berlin/Heidelberg, 1977; Springer Berlin/Heidelberg, 1977
Herbert, Vernon;Herbert, Vernon; AttilioAttilio BisioBisio;; Synthetic RubberSynthetic Rubber, Greenwood Press,, Greenwood Press,
19851985
HiemenzHiemenz, Paul C.; Lodge, Timothy P.;, Paul C.; Lodge, Timothy P.; Polymer Chemistry 2Polymer Chemistry 2ndnd ed.,ed.,
CRC Press; 2007CRC Press; 2007
James, Hubert M.,James, Hubert M., GuthGuth, Eugene;, Eugene; Theory of the Elastic Properties ofTheory of the Elastic Properties of
RubberRubber; J. Chem. Phys.; J. Chem. Phys. 11,11, 455 (1943)455 (1943)
LoadmanLoadman, John;, John; Tears of the TreeTears of the Tree, Oxford University Press, 2005, Oxford University Press, 2005
Rosen, Stephen L.;Rosen, Stephen L.; Fundamental Principles of Polymeric MaterialsFundamental Principles of Polymeric Materials
22ndnd ed.ed., Wiley, Wiley--Interscience Publication, 1993Interscience Publication, 1993
Solo, Robert;Solo, Robert; Research and Development in the Synthetic RubberResearch and Development in the Synthetic Rubber
IndustryIndustry; The Quarterly Journal of Economics;; The Quarterly Journal of Economics; VolVol 68, No.1 (1954)68, No.1 (1954)

19. From Curiosity to ProductFrom Curiosity to Product
(1820(1820--1840)1840)
T. HancockT. Hancock
–– Pickling MachinePickling Machine –– produceproduce
homogeneous rubberhomogeneous rubber ‘‘doughdough’’
–– SpreaderSpreader –– the standardthe standard
coating machine used todaycoating machine used today
M. FaradayM. Faraday
–– Established empirical formulaEstablished empirical formula
of natural rubber (Cof natural rubber (C55HH88))

20. Natural Rubber ProductionNatural Rubber Production
Wild ProductionWild Production
–– Amazon River and its tributariesAmazon River and its tributaries
–– AfricaAfrica
18761876 -- H. WickhamH. Wickham
–– Sent 70,000 Hevea seeds to BritainSent 70,000 Hevea seeds to Britain
–– 2397 germinated2397 germinated
–– Plants sent to Singapore, India, MalaysiaPlants sent to Singapore, India, Malaysia
–– Foundation of the eastern rubber plantations (1895)Foundation of the eastern rubber plantations (1895)
19131913--19141914 -- Plantation rubber exceeds wildPlantation rubber exceeds wild