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|Title: ||Synthesis and properties of anionically grafted thermoplastic elastomers|
|Authors: ||Young, John A.|
|Issue Date: ||1981|
|Publisher: ||© John Armstrong Young|
|Abstract: ||Through the use of a sec-butyllithium.N,N,N',N'-
chelate complex it was possible to anionically graft a conventional
unvulcanised rubber, SBR (solprene 1204), with vinyl aromatic monomers such
as styrene, o(-methylstyrene and vinyltoluene. By choosing suitable
solvents and reaction conditions high yields were obtained. Grafting
efficiencies, determined from the amounts of homopolymer present in the gel
permeation. chromatograms of the products, were found in the 60 to 100& range.
Grafting efficiencies for the o(-methylstyrene only systems were generally
found at the lower end of this range whereas the grafting efficiencies for
the other JBR graft copolymers were usually greater than 80%. Possible
reasons for these differences are discussed.
Characterisation of the graft copolymers, in terms of molecular weight
and composition, was carried out using gel permeation chromatography,
membrane osmometry and nuclear magnetic resonance techniques. Because it
was found, via ozonolysis and gel permeation chromatography, that graft
molecular weight was the same as that of the homopolymer produced as a
result of inefficient grafting, the presence of this latter species in the
products was used as a means for readily determining the molecular weight
characteristics of the grafts. The number of grafts per polymer chain was
calculated from the amount of 'active' initiator added.
Dynamic mechanical studies' of moulded and solvent cast samples of the
SBR graft copolymers have shown that a phase separated structure exists.
The position and shape of the high temperature tan b damping peak did,
however, suggest that the hard phase was a mixed phase containing a small
amount of SBR. The ultimate properties of the graft copolymers were
comparable with those of vulcanised SBR. Compression set values, measured
under standard conditions, were poor compared to conventional vulcanisates.|
|Description: ||A Doctoral Theses. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Chemistry)|
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