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Abstract:
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The primary objective of this investigation has been to develop more efficient and
low cost adhesives for bonding various elastomer combinations particularly NR to NR,
NR/PB to NR/PB, CR to CR,NR to CR and NR to NBR.A significant achievement of the investigation was the development of solventless
and environment friendly solid adhesives for NR to NR and NR/PB to NR/PB particularly
for precured retreading. Conventionally used adhesives in this area are mostly NR based
adhesive strips in the presence of a dough. The study has shown that an ultra accelerator
could be added to the dough just before applying it on the tire which can significantly
bring down the retreading time resulting in prolonged tire service and lower energy
consumption. Further latex reclaim has been used for the preparation of the solid strip
which can reduce the cost considerably.Another significant finding was that by making proper selection of the RF resin,
the efficiency and shelflife of the RFL adhesive used for nylon and rayon tire cord dipping
can be improved. In the conventionally used RFL adhesive, the resin once prepared has to
be added to the latex within 30 minutes and the RFL has to be used after 4 hours maturation
time maximum shelf life of the RFL dip solution being 72 hours. In this study a
formaldehyde deficient resin was used and hence more flexibility was available for mixing
with latex and maturing. It also has a much longer shelf life. In the method suggested in this study, formaldehyde donors were added only in the rubber compound to make up the
formaldehyde deficiency in the RFL. The results of this investigation show that the pull
through load by employing this method and the conventional method are comparable.
This study has also shown that the amount of RF resin with RFL adhesive can be partially
replaced by other modifying agents for cost reduction.Cashew nut shell liquid (CNSL) resin can
be employed for improving the bonding of dipped nylon and rayon cord with NR.Since
CNSL resin cannot be added in the dip solution since it is not soluble in water, it was
added in the rubber compound. The amount of wood rosin in the rubber compound can be
reduced by using CNSL resin.Another interesting result of the investigation was the use of CR based adhesive
modified with chlorinated natural rubber for CR to CR bonding. Addition of chlorinated
natural rubber was found to improve sea water resistance of CR based adhesive. In the
bonding of a polar rubber like nitrile rubber or polychloroprene rubber to a non polar
rubber like natural rubber, an adhesive based on polychloroprene rubber was found to be
effective. |