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Natural Rubber (NR) has been effectively used for various industrial applications. Invention of pneumatic tyres and inner tubes in late 1840’s and the expansion of the automobile industry resulted in a greater demand for NR. However, the properties and the cost of the products manufactured from NR were not attractive until the use of carbon black as reinforcing filler.
Since then, carbon black is the most common and widely used filler for rubber compounds used for tyres and tubes etc. Excellent reinforcing effect imparted by carbon black greatly upgrades the mechanical properties of rubber compounds and makes many applications possible from the rubber. In addition to carbon black, there are inorganic fillers such as silic, clay, and calcium carbonate used as reinforcing and non-reinforcing fillers for rubber compounds.
Synthetics
There had been acute shortage of NR during the World War 1. The Germans knew that the rubber supply was becoming severely inadequate for war- time uses, as did the rest of the world. In World War I, the British naval blockades kept Germany away from getting NR from Southeast Asia.
As a result, and due to high prices of NR at that time, Synthetic rubber (SR), which is produced from petroleum by-products, was developed as a potential substitute to NR. Nevertheless, at present, both natural and synthetic rubber have become unbeatable engineering materials as they can be converted to useful products with good mechanical, thermal and barrier properties for various industrial applications.
Nanotech
In the 21st century, the term “nanotechnology” also referred to as “nanotech” has become a hot topic among scientists, engineers and industrialists. It is common thinking among scientists that nano-science and nanotechnology are enabling to produce new and promising materials and applications across all disciplines of science and technology.
Therefore, it is believed that next industrial revolution will be based on nanotechnology. Effects of nanotechnology have already begun to appear in some fields such as electronics, healthcare, energy, environmental and polymer technology.
Nano-science and nanotechnology is to discover novel behaviours and properties of materials with dimensions at the nano scale which ranges from 1-100 nanometres (nm) and to control and manipulate the nano scale material into useful products/structures.
Materials that are in nano metre scale are extremely smaller than anything we see under conventional microscopes. A nano metre is one-billionth of a metre (i.e. 10-9 m) and approximately 10 times larger than the size of hydrogen atom. The size of nano metre scale is very small in comparison to micro scale materials. To elaborate further, it is like the size ratio between nano particle and a foot-ball, which is same as the size ratio between foot-ball and the earth planet.
Rubber industry
In the recent past, in addition to thermoplastic materials, rubbers have also demonstrated as very promising engineering materials for various industrial applications.
Although, rubber nanocomposites have showed slow progress in comparison to thermoplastic nanocomposites, a number of recent studies revealed that rubber nanocomposites have a good commercial potential for various applications.
Therefore, it is crucial that we explore the superiority of this novel technology for use in the rubber industry by developing rubber nanocomposite materials with unique properties.
Three major advantageous of rubber nanocomposites over conventional rubber composites are given below:
1) Lighter weight due to low loading level of nano particles
2) Improved material properties (i.e. mechanical, thermal, electrical) and new functionalities (antimicrobial, barrier, flame retardant)
3) Easy processing in comparison to conventional composites
Applications
Presently thermoplastic cups are used in estates for field latex collection. Development of new latex collecting cup with nano- structured surface which provides a zero adhesion of latex to the latex collection cup and with antibacterial properties would be an advantage in improving the quality of field latex.
Preservation of field latex is another area where nanotecnology can be applied successfully. Application of preservatives eg. ZnO and TMTD at nanoscale to field latex would enhance the effectiveness of the preservative system.
Nanotechnology has potential applications in latex dipping. A point to remember when working with nanomaterials is the vast increase in surface area to volume which results as the particle size of the material is reduced to nanoscale.
In latex technology, several physical phenomena are dependent on surface area, for example the extent of reinforcement and surface absorption of materials. One of the consequences of the large surface area of any nanofiller is it’s effect on latex stability.
Another practical application of this technology has been the blending of an aqueous dispersion of vermiculite with butyl rubber latex. The composite latex has an exceedingly low permeability, and is used in the manufacture of tennis balls.
Besides these, we would expect many other benefits and openings for the rubber products sector if this technology is developed further.
Challenges
Nano particles and nanocomposites are the trend in polymer technology today. They show surprisingly enhanced material properties and novel functionalities which cannot be seen in conventional fillers and composites. However, commercial applications of rubber Nanocomposites are yet to gain real momentum, at present, since there are a few unresolved issues that need to be resolved in order for successful conversion of these novel materials into commercial artifacts.
Most of the rubbers are not compatible with nano particles and, as a result, dispersion of these particles into nano scale within the rubber matrix is a difficult task. Therefore, development of new and effective methods to achieve homogeneous dispersion of nano particles such as layered silicates and carbon nanotubes in rubber matrix is a challenge, since the degree of dispersion is one of the key factors to enhance the material performances.
Although rubber nanocomposites exhibit remarkable improved material properties, cost/performance ratio of some rubber nanocomposites is commercially unattractive since some nano particles (e.g. carbon nanotubes, metallic nano powders) are relatively more expensive.
This is one of the major obstacles to commercialize these rubber nanocomposites. However, it is expected that the cost of nano particles will come down with the development of new process technologies.
In addition, there are few other specific problems in applying this novel technology for certain rubber products, for example tyres. Replacing carbon black with nano scale layered silicates, which impart remarkable reinforcement at low loading levels, is not economically attractive for the tyre industry, at the present stage of development.
The rubber nanocomposites based on layered silicates require large volume of rubber in order to keep the total volume of the final product unchanged. All these need to be looked into.
Conclusion
The rubber industry might have been the first one to use nano-technology on a large scale, without even knowing it, because the term nano-technology did not exist then. The use of carbon black to reinforce rubber in fact is an application of nano-technology. It has been known for a long time that smaller particle sizes of carbon blacks lead to higher reinforcement of the rubber .This has to do with the active surface of the material which increases rapidly with decreasing size of the particles.
Nowadays, all over the world nano-technology is a hot item. In almost every field people expect much of it. Apart from the use of carbon blacks, in the rubber industry the influence of nanotechnology is still limited. Generally spoken, reduction of particle sizes to nano dimensions will make the added materials more reactive. This applies not only to carbon blacks but also to activators, accelerators and other compounding ingredients.
Increasing the reactivity means that the same effect can be achieved by the use of less material. So the quantities of chemicals in a rubber product can be reduced which is a good thing for the environment. Whether such a reduction of the quantities of chemicals will also lead to a reduction in costs is doubtful because the prices of nano chemicals are much higher than those of the common ones.
In plastics, the use of nano particles produces an increase in strength, aging resistance and permeability properties. The use of nano-particles in relation to controlled release of anti oxidants and UV stablilizers is presently being investigated. Experiments with nano clay in Natural Rubber did show already that the use of such materials indeed leads to an increase in stiffness and some improvement of the permeability properties. Furthermore it is claimed that nano-technology can play an important role in fire resistance of plastics and rubbers. All of this will, of course, require further research. Therefore, considering the present economical situation, the heavy competition in the rubber and plastics industry and the relative conservative nature of the rubber industry it is not soon to be expected to have results in this area. However, we are convinced that in the long run some positive effects of nano-technology will become visible also in applications with Natural Rubber.
Recognizing the importance nanotech in technological advancement in various disciplines of science, the Government of Sri Lanka has already established a separate Institute of Nanotechnology, under the Ministry of Science and Technology. This is an area of the technology to be watched with interest over the next few years.