Tensile stress relaxation of short‐coir‐fiber‐reinforced natural rubber composites

Abstract

ABSTRACT:The stress relaxation behavior of natural rubber (NR) and its composites reinforced with short coir fibers under tension was analyzed. The rate of stress relaxation was a measure of the increase in the entropy of the compounds: the higher the rate was, the greater the entropy was. At lower strain levels, the relaxation mechanism of NR was independent of strain level. However, the rate of relaxation increased with the strain level. Also, the strain level influenced the rate of stress relaxation considerably in the coirreinforced NR composites. However, the relaxation mechanisms of both the unfilled compound and the composite were influenced by the strain rate. The rate of relaxation was influenced by fiber loading and fiber orientation. From the rate of stress relaxation, we found that fiber-rubber adhesion was best in the composite containing fibers subjected to a chemical treatment with alkali, toluene diisocyanate, and NR solutions along with a hexaresorcinol system as a bonding agent. In this study, the stress relaxation curves could not be viewed as segments with varying slopes; however, a multitude of inflection points were observed on the curves. Hence, we propose neither a two-step nor three-step mechanism for the coir-fiber-reinforced NR composites as reported for some other systems.

Stress-relaxation behavior of lignocellulosic high-density polyethylene composites

“…6 Geethamma et al studied the relaxation response of short-coir-fiber-reinforced natural rubber and concluded that the strain level, fiber loading, and fiber orientation influence the rate of stress relaxation in the composites. 7 Using composites under life cycle loads is problematic, because the long-time decay of stress should be interpreted and data should be acquired along extensive periods of time which is a tedious process. Therefore, principles such as Boltzmann and time-temperature superposition are invoked to evaluate the long-term viscoelastic behavior of materials by utilizing shortterm data and constructing master curves.…”

Tensile Stress Relaxation Studies of TiO2 and Nanosilica Filled Natural Rubber Composites

“…Bhagawan et al observed an increase in stress relaxation with increase in short jute fiber content in an NBR matrix. 25 The stress relaxation behavior of natural rubber reinforced with coir fibers was studied by Geethamma et al 26 The introduction of particulate fillers in rubber generally results in an increase in relaxation rates. According to the theory of "strain amplification", 27 due to the inextensibility of the filler, the strain in the polymer phase of a filled material is greater than the overall strain.…”

Mechanical properties of thermoplastic elastomeric blends of chitosan and natural rubber latex

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