I need a script/simple explanation of this lesson for my presentation. Thank you! Properties of PolymersThe properties of the polymers are usually governed by its structure. One such importantproperty of polymers that is being analysed is the glass transition temperature. The glass transitiontemperature (Tg) is the temperature range where a polymer chain gains segmental motion. Theflexibility of the polymer chains depends on (1) the presence of stiffening and flexibilizing groupsincorporated in the polymer backbone and (2) the presence of functional groups attached to thepolymer backbone. These functional groups attached to the polymer backbone is called pendantgroups. For example, polyethylene terephthalate (PET) has a higher glass transition temperature thanpolyethylene adipate. The terephthalic acid moiety in polyethylene terephthalate (PET) isconsiderably an inflexible unit. Furthermore, the terephthalic acid moiety stiffens the polymerbackbone and restricts polymer chain mobility. On the other hand, the adipic acid moiety inpolyethylene adipate is flexible; thus, making the polymer backbone chains more freely mobile. Theeffect of pendant groups in the glass transition temperature is very evident by comparing the glasstransition temperatures of low density polyethylene (LDPE) and polyvinyl alcohol (PVA). PVA has arelatively higher glass transition temperature than LDPE attributed to the presence of the hydroxylgroup (-OH) which can form strong hydrogen bonds with other polymer chains. Whereas in LDPE,each polymer chains can only interact with each other via the much weaker London dispersion forces.The glass transition temperature of polymers also increase due to polymer backbone symmetry andthe presence of crosslinks. Adding aditives such as plasticizers, on the other hand, decreases theglass transition temperatures of polymers.Table. Approximate glass transition temperatures (Tg) for selected polymersGlass TransitionTemperature (Tg)PolymerChemical StructureонPolyethylene Adipate223PolyethyleneTerephthalate (PET)342ннLow density-148polyethylene (LDPE)H HPolyvinyl Alcohol (PVA)358НоAnother important property of polymers is its melting temperature. Melting temperature (Tm)is the temperature range in which the whole polymer chains become mobile. Synonymous to Tg, themelting temperature is higher for polymers having stiffening groups in the backbone and pendantgroups that may form stronger intermolecular forces of attraction.

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perature (Tg) is the temperature range where a polymer chain gains segmental bility of the polymer chains depends on (1) the presence of stiffening and flexibili rporated in the polymer backbone and (2) the presence of functional groups atta mer backbone. These functional groups attached to the polymer backbone is cll ps. For example, polyethylene terephthalate (PET) has a higher glass transition temp ethylene adipate. The terephthalic acid moiety in polyethylene terephthalate siderably an inflexible unit. Furthermore, the terephthalic acid moiety stiffens t kbone and restricts polymer chain mobility. On the other hand, the adipic acic ethylene adipate is flexible; thus, making the polymer backbone chains more freely ct of pendant groups in the glass transition temperature is very evident by comparin sition temperatures of low density polyethylene (LDPE) and polyvinyl alcohol (PVA). tively higher glass transition temperature than LDPE attributed to the presence of t p (-OH) which can form strong hydrogen bonds with other polymer chains. Wherea n polymer chains can only interact with each other via the much weaker London disper glass transition temperature of polymers also increase due to polymer backbone sy presence of crosslinks Adding additives such as plasticizers on the other hand de

2nd Edition

ISBN:9781133958437

Author:Ball, David W. (david Warren), BAER, Tomas

Publisher:Ball, David W. (david Warren), BAER, Tomas

Chapter22: Surfaces

Section: Chapter Questions

Problem 22.19E