353255[1].pdf (8.86 MB)
Studies of the oxidative degradation of butyl rubber in tyre inner tube
thesis
posted on 2010-11-29, 10:15 authored by Ekbal Awad Hatam HatamTyre inner tubes made of butyl rubber have been found to have poor
heat resistance when used in the environment of Iraq. Research
investigations were undertaken to establish the causes of the
problem: these consisted of examining the individual contributions
of oxidative scission processes in both rubber hydrocarbon and the
various processing oils. The principal method used to monitor the
degradation processes was ageing in hot air using the reduction in
strength for the rubber and change in chemical composition of the
processing oils.
This preliminary study established that the processing oil made in
Iraq was found to be of different composition from the common European
rubber processing oils and contributed considerably to the poor life
of the butyl inner tubes. Analysis of the oil from Iraq identified
the presence of trace amounts of copper (3 ppm) known, from the
literature, to adversely affect the resistance of many rubbers to
elevated temperatures and, as found in this work, to also degrade
butyl rubber.
Replacement of the butyl rubber by chlorobutyl rubber overcame the
problem of inner tube degradation and an antioxidant system based on
a combination of an acetone/diphenylamine (ADPA) plus mercaptobenzimidazole
(MBI) with MgO was found effective in minimising chlorobutyl
inner tube degradation. However, unexpectedly, the research also
established that trace quantities of copper were useful as stabilisers
in enhancing the heat ageing properties of chlorobutyl rubber and the
addition of a particular copper salt (copper sulphatel in small
proportions (3 ppm) as an anti-degradant was found beneficial. Another method studied to improve the resistance of halogenated
butyl rubber to heat induced oxidative degradation tried to use
ZnO as the curative, as recommended by the manufacturers of chlorobutyl
rubber; however it was found that with this technique higher
degradation was obtained in chlorobutyl than with the standard ZnO/
sulphurless curing system (i.e. ZnO/TMTDin proportions 5:1 phr).
It was concluded from these studies that:
1. Reducing the oil level in butyl inner tubes from 25 phr to
15 phr enhances heat ageing properties of the rubber. Factory
trials confirmed this finding.
2. Adding a copper inhibitor (ZDC) in the proportions 1-2 phr in
butyl inner tubes was found successful in minimising oxidative
degradation.
3. The existence of elemental copper in a chlorobutyl inner tube
rubber formulation in the proportion 3 ppm improved the rubber
properties at elevated temperatures.
History
School
- Aeronautical, Automotive, Chemical and Materials Engineering
Department
- Materials
Publisher
© E.A. HatamPublication date
1984Notes
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.EThOS Persistent ID
uk.bl.ethos.353255Language
- en