Natural rubber (NR) used in this study, SMR-20, was supplied
by Tecnopolimeri srl, Russia. A tri component system consisting of
resorcinol, formaldehyde resin and Silica was used as bonding
system. The resorcinol component used is known as Cohedur-RS,
supplied by Morgan Chem., Egypt; the resin was octylphenyl
formaldehyde of grade (HR-0417), produced by Shinktady, England;
and hexamethylene tetramine (HMT) acts as a methylene group
donor, supplied by Bayer AG, Germany