By Dr Arup K Chandra
Nano materials are key to the sustainable growth of rubber, tyre and auto-component industries. Major advances are being made in the usage of nano materials and other nanocomposites which can greatly improve the efficiency and performance of products in these industries.
World population is growing. The urban and middle-class populations are growing even faster. People aspiration and mobility, and as a result, the number of vehicles on the road are increasing day by day. This is depleting the resources on this earth very fast and creating an uncertainty for the sustainability in the future.
In order to overcome this, we have to reduce materials usage. Nano-materials and Nano-technology promise more for less. It offers ways to create smaller, cheaper and lighter devices that can do more using less energy and materials.
Rubber and tyre manufacturers are conducting more and more investigation and developments for manufacturing different components based on nano composites to achieve sustainability for our future generation. Various developments taking place in polymer nano composites will be a major deciding factor in future.
Nano materials are a class of new-generation materials, which have at least one dimension in the order of nano meter and within 100 nm. This new class of material has varying shapes ranging from isotropic needle-like, particulate sphere or sheet-like structure.
Uniform dispersion of these nano-sized particles can lead to ultra-large inter-facial area between a polymer and the fillers. This large inter-facial area between the polymer and filler due to nanoscopic dimension differentiates Polymer Nanocomposites (PNC) from traditional composites.
Development of nano rubber
Nano rubber was developed jointly by professors Werner Obrecht and LANXESS. It is defined as nano rubber because it is characterised by a chemical nano structure whereby the rubber particles have a dimension of 40-65 nm. The nano rubber has been designed with a highly cross-linked particle core and consequently the particle morphology is not destroyed by high shear when added to polymer.
Additionally, due to a high degree of core cross-linking, the compounding ingredients such as oil, sulphur and accelerators are not absorbed by the core. Moreover, owing to chemical composition and cross-linking density, the particle core exhibits a specific Tg, which influences temperature-dependent damping characteristics of vulcanizates (rolling resistance, wet traction).
More precisely, when the nano-rubber particles are dispersed in a conventional polymer matrix, they form a separate phase in the continuous phase of the polymer matrix and hence behave exactly like filler but after vulcanization, they are co-cured with polymer matrix.
Uses of fillers
Fillers are one of the key ingredients to tyre and rubber industries. Reinforcing fillers such as carbon black and silica individually or in combination with special chemicals are incorporated into the tyre /rubber to enhance the mechanical properties.
Fillers are used in polymers for a variety of reasons — cost reduction, processing improvement, density control, optical effects, thermal conductivity, control of thermal expansion, electrical properties, magnetic properties, flame retardancy and improved mechanical properties, such as stress–strain properties, hardness, tear resistance etc.
Each filler has different properties and these in turn are influenced by the particle size, shape, particle morphology and surface chemistry. Amorphous silica, carbon black and clay are the most widely used particulate fillers in polymer industry to achieve the performance requirements in various engineering applications.
Degree of improvement of these performance requirements by these particulate fillers in polymer-filler composites mainly depends on size of disperses filler, polymer-filler interaction , morphology of the fillers and the quantity of the filler added to the matrix.
The addition of nano-fillers increases mechanical, thermal, electrical, optical, air permeability and flame retardancy exponentially at exceptionally lower filler dosage. As a result, it is possible to produce lighter weight tyre with improved rolling resistance at the same time with extended life. The reduction of filler will reduce the specific gravity and heat generation, which can lead to improvement of the performance of different tyre compounds and ultimately result in better fuel-efficient tyre.
That’s why polymer / layered silicate (one of the most important types of nano fillers) nano-composites have gained strong momentum in achieving material properties desired for tyre applications. The application of nano-composite / nano-materials like nano zinc oxide, carbon nanotube will help tyre industry to a great extent in future.
(The article is based on a presentation made by the author at a seminar held in connection with the ISO-TC-45 meeting in Kuala Lumpur recently)