The aim of this paper is to demonstrate that the stressestrain behavior of natural rubber reinforced with
short pineapple leaf fiber (PALF) can easily be manipulated by changing the cross-link density and the
amount of carbon black (CB) primary filler. This gives more manageable control of mechanical properties
than is possible with conventional particulate fillers alone. This type of hybrid rubber composite displays
a very sharp rise in stress at very low strains, and then the stress levels off at medium strains before
turning up again at the highest strains. The composites studied here contain a fixed amount of PALF at 10
part (by weight) per hundred rubber (phr) and varying carbon black contents from 0 to 30 phr. To change
the cross-link density, the amount of sulfur was varied from 2 to 4 phr. Swelling ratio results indicate that
composites prepared with greater amounts of sulfur and carbon black have greater cross-link densities.
Consequently, this affects the stressestrain behavior of the composites. The greater the cross-link density,
the less is the strain at which the stress upturn occurs. Variations in the rate of stress increase
(although not the stress itself) in the very low strain region, while dependent on fillers, are not
dependent on the crosslink density. The effect of changes in crosslinking is most obvious in the high
strain region. Here, the rate of stress increase becomes larger with increasing cross-link density. Hence,
we demonstrate that the use of PALF filler, along with the usual carbon primary filler, provides a
convenient method for the manipulation of the stressestrain relationships of the reinforced rubber. Such
composites can be prepared with a controllable, wide range of mechanical behavior for specific high
performance engineering applications.