ืdevelopment of more durable tubeless tires with the air retaining
innerliner chemically bonded to the body of the tire. Tire innerliners are by far the largest application for halobutyl today. Both chlorinated (chlorobutyl) and brominated (bromobutyl) versions of
halobutyl are commercially available, and are extensively used
for the said purpose [4,5].
The authors have successfully reported a judicious blend of
chlorobutyl rubber (CIIR) and natural rubber (NR) along with using
an optimization technique to design a formulation to improve the
mechanical and gas barrier property [6]. The important factors
affecting properties were rubber ratio, and carbon black (CB) and
processing oil concentration.
In the present work, a 90:10 blend ratio of CIIR and 50 mol%
epoxidized natural rubber (ENR50) by weight was used. Natural
rubber is modified by partial epoxidation of the unsaturations
present in it and the epoxidized form has certain advantages over
the natural rubber in certain applications.
The advantages of ENR arise from the fact that epoxidation
raises the glass transition temperature by approximately 1 C for
every mole percent epoxidation. Strength and fatigue properties
are, however, still high as ENR is capable of strain induced crystallization. Property changes with increasing level of epoxidation
include: an increase in damping; a reduction in swelling in hydrocarbon oils; a decrease in gas permeability; an increase in absorption of microwave energy; an increase in silica reinforcement;
improved compatibility with polar polymers [7]; reduced rolling
resistance and increased wet grip [8]. Since ENR was blended with
CIIR so it was expected that the gas barrier property would be
enhanced over previously used CIIR/NR blend in the same rati