Farley, Paul S.;
(1992)
The preparation, characterization and hydrolysis of epoxidized natural rubber.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The double bonds in NR can be partially epoxidized using peracids and mild experimental conditions. More forcing conditions result in hydrolysis and the ring-opening of epoxy groups. The epoxidation of NR latex concentrates using performic acid generated in situ from hydrogen peroxide and formic acid has been studied intensively; variability in the reaction is consistent with the presence of adventitious iron and the intervention of Fenton's Reagent. The determination of epoxy groups in ENR by a range of analytical techniques has been examined and conflicting results in the literature have been resolved. The fractionation of ENR by molecular mass and particle size in latices has yielded further evidence for epoxidation being a random chemical reaction. However, there is conflicting chemical evidence for a non-random process. The acid-catalysed hydrolysis of ENR results in ring-opening and the preferential formation of tetrahydrofuran rings and/or ether crosslinks. The products of hydrolysis are determined by the concentration of epoxy groups and acid and the activity of counter-ions. Intermolecular ether bonds in ENR have been characterized. The formation of crosslinks can be monitored by 13C-NMR spectroscopy via the concentration of pendant alcohol groups. Model studies have demonstrated that ring-expansion results in the exclusive formation of tetrahydrofuran rings. Cis- and trans-epoxy groups are formed during the uninhibited autoxidation of NR and ENR in an apparent trans:cis ratio of 1.4:1.0. This result is consistent with the exclusive formation of epoxy groups by the addition of peroxyl radicals to double bonds.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | The preparation, characterization and hydrolysis of epoxidized natural rubber |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10122695 |
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