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The truth about super glue

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Xue Rong Kok

on 8 April 2010

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Transcript of The truth about super glue

The Truth About Super Glue Background
adhesives have been around for a long time Since 1900s... Conventional wisdom super glue generally perceived to be stronger than white glue

but is this necessarily so? Objectives Examine chemistry behind adhesives
What makes super glue so "super"?
Debunk myth that super glue is significantly stronger than white glue in terms of internal strength
Popularity of super glue likely due to other factors such as faster setting (hardening) time

Contents How adhesives work Adhesion
Cohesion Focus on chemistry: Cohesion Chemical bonds within adhesive
Chemical bonds within polymer chains (thermoplastic vs thermoset) The showdown: White glue vs super glue

Result: Not much difference in terms of cohesive strength!

Application of this knowledge

Limitations and conclusion 1. Adhesion
2. Cohesion Cohesion: Intermolecular forces within adhesive itself

Adhesion: attraction of two different substances resulting from forces between them Mechanisms of adhesion Mechanical

Diffusion

Covalent bonding
Dispersive adhesion
Electrostatic adhesion Cyanoacrylate Polyvinyl acetate (PVA) However...adhesion involves many mechanical and physical forces



Focus on cohesion Chemical bonds within adhesive polymer Chemical bonds between polymer chains (thermoset vs thermoplastic) PVA Methyl-cyanoacrylate All C-C covalent bonds, with equal bond energy (348kJ/mol)
No identifiable difference in this aspect PVA Methyl-cyanoacrylate Cures through solvent evaporation
polymer chains held together by secondary Van der Waals forces
thermoplastic melt when heated, resolidify when cooled
Linear/branched
Secondary intermolecular bonds
Do not melt when heated, but may decompose
Cross-linked i.e. chemically bonded Thermoplastic Thermoset Cures through anionic polymerisation
Though poly(methyl cyanoacrylate) made up of longer chains, it is still thermoplastic due to absence of cross-links Our findings Hence, super glue not necessarily stronger than white glue, at least where cohesion is concerned
Apparent difference in strength likely to come from mechanical adhesive abilities
Eg: super glue not significantly stronger in terms of temperature resistance (similar glass transition temperatures)
Applications Chemical examination reveals super glue sets faster than white glue white glue more user-friendly and safer for handicraft; flexible super glue more suitable for mending broken objects Rapid setting duration = chemical advantage over white glue

Is what makes super glue "chemically super"? Kok Xue Rong U091317X
Wang Huan U095623U Limitations and conclusion Still need better understanding of adhesion to determine overall strength of adhesive
Yet, while strength is important, it is not typically the determining factor
Possibly explains why super glue is still highly regarded in general adhesive flows into pores and crevices and hold them through interlocking occur when adhesive and adherents are mobile and soluble in each other
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