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Krispon
ADVANCING SCIENCE
© The Author, 2021. This article is published with Creative Commons attribution licenses (CC-BY, http://creativecommons.org/licenses/by/4.0/)
at krispon.com.
Volume-1, Issue-2, 2021 7
Received: 07 Dec 2020/ Accepted: 20 Mar 2021/ Published: 31 May 2021
DOI: https://doi.org/10.5281/zenodo.4876604
Development of specialized natural rubber composites using nano silica and
short nylon fiber for tyre side wall component
Leny Mathew
1
, Sunil K Narayanankutty
2
1
Central Institute of Plastics Engineering & Technology, IPT, Kochi, 683501, Kerala, India
2
Department of Polymer science & Rubber Technology, Cochin University of Science & Technology, Kochi-22, Kerala, India
Corresponding author: Leny Mathew (drlenycipet@gmail.com)
This work was presented at the International Conference on Natural Polymers (ICNP-2019) held during 6-8, December 2019 at Mahatma
Gandhi University, Kottayam, Kerala, India.
Introduction: Short fibers can be incorporated directly into the rubber compound along with other additives, the resulting
composites are amenable to the standard rubber processing steps of extrusion, calendering and the various type of molding
operations such as compression, injection and transfer molding (1). Properties of short fiber elastomer composite critically
depend upon the interfacial bonding between fiber and the matrix (2-6) The role of silica is to improve wetting of the fiber
surface (7-10). As small particles have higher surface area, nanosilica can be more effective in improving wettability of the
fibers.
Sreeja et al. studied the cure characteristics and mechanical properties of natural rubber / short Nylon 6 fiber composites (11).
The reinforcement of rubbers using particulate fillers such as carbon black or precipitated silica has also been studied at length
(12-15). Murtyet al. (16) also reported the effect of particulate fillers on the processing characteristics and physical properties
of jute fiber reinforced natural rubber composites. In all these studies they have used conventional precipitated silica with
particle size in microns (17-21). As small particles have higher surface area, nanosilica can be more effective in improving the
properties of the hybrid composites.
Methods: Nano silica was synthesized by precipitation method using sodium silicate and dilute hydrochloric acid under
controlled conditions. The synthesized silica was characterized by Scanning Electron Microscopy (SEM), Transmission
Electron Microscopy (TEM), BET adsorption and X-Ray Diffraction (XRD). The performance of this synthesized nanosilica
as a reinforcing filler in natural rubber (NR) compound was investigated. The commercial silica was used as the reference
material. A new hybrid rubber composite prepared by the utilizing short Nylon fibers which is a waste product from fiber
industries. These composites combine the rigidity of the fiber and the elasticity of the rubbers. The fiber can be incorporated as
one of the compounding ingredients during the mixing process. The cure, mechanical, ageing, thermal and dynamic
mechanical properties of n.anosilica / Nylon 6 short fiber / Natural Rubber hybrid composites were studied.
Short nylon fiber content varies from 0,10, 20 & 30 phr and nanosilica content varies 3,6, &9 phr for the compounds A,B,C,D
respectively and E for commercial silica.Natural rubber-100 phr, Zinc oxide-5 phr, Stearic acid-2 phr, N-(1,3-
dimethylbutyl)N
’
-phenyl-p-phenylenediamine) -1 phr, CBS-0.6 phr, TMTD- 0.2 phr and sulphur-2.5 phr were common to all
mixes.
Results & Discussions: The minimum torque increases with fiber loading and nanosilica content for all the mixes,
indicating that the processability becomes more energy intensive by the introduction of fiber and silica. Scorch time increases
with silica content and decreases with fiber loading for all the mixes. The delayed start of cure reaction in the presence of
silica may be attributed to the possible interaction of the silica with the accelerators, making it unavailable for cure reaction.
Cure time increases with fiber content and silica loading for all the mixes This may be due to the interaction of silica with the
accelerators. Cure rate increases with fiber loading and decreases with silica content. Increase in cure rate with fiber content is
due to the accelerating effect of nylon fiber on the cure reaction. Decrease in cure rate with silica content may be due to the
interaction of silica with the accelerators. The differential torque is a measure of the extent of the cross link formation and the
filler–matrix interaction. The higher values for the nanosilica compounds indicate that the matrix is more restrained. The
tensile strength increases with fiber content with an initial minor drop at 10 phr fiber loading. This drop may be due to the
dilution effect of the fibers at lower loadings (22, 23). At higher fiber loadings, however, the reinforcing effect takes over,
resulting in an improved ultimate strength. At any fiber content the tensile strength is higher for the nanosilica filled samples.
This may be attributed to better chances of interaction between the fiber and the matrix through silica surface. Silica is also
known to improve the wetting of short fibers in natural rubber matrix (22). There is a drastic fall in the abrasion loss with
increasing fiber loading. A stiffer matrix has lower abrasion loss. In this case the presence of strong interfacial adhesion