Rubber Nanocomposites
by Nagesh Potluri, Ph.D. in Core Competencies Posted on 10/22/2020 11:37 AM
Industrial rubber products comprise of automobile tires, inflatable rafts, conveyor belts, and hoses. Growing demand from the automotive industry and the rise in rubber products are the key drivers. Global Industrial Rubber Products Market is Estimated to Reach US$ 151 Billion by 2025.
Relentless efforts have been dedicated to improving rubber compounds' mechanical and other physical properties using fillers for reinforcement-a typical example of rubber reinforcement results in the improvement of wear and abrasion of tires using carbon black. The absence of fillers in rubber compounds will lead to less than optimum service life to the tires. In addition to the tensile properties, adding fillers into rubbers will improve abrasion resistance, hardness, rupture energy, resistance to crack growth, tear-fatigue properties, and thermal aging behaviors. Uniformly dispersed filler particles, and the strong physical and chemical interactions with the rubber matrix polymer will improve mechanical properties.
While carbon black and silica have been the conventional fillers for rubbers, nanofillers such as CNT (Carbon Nanotubes), Graphene, and nano-silica have shown enormous promise reinforcing rubber in the last two decades. Ruber nanocomposites are amorphous polymer matrices that contain fillers as reinforcements at nano dimensions (1 billionth of a meter). The molecular-scale nanofillers uniformly dispersed in rubber matrices offer a large surface area for strong interfacial bonding with the rubber matrix. The strong interfacial adhesion manifests in an unexpected enhancement of physical properties and hitherto known properties in rubbers.
A wide variety of fillers such as nano-sized carbon black particles, nano-silica, colloidal metal oxides, carbon nanotubes (CNTs), Graphene, nano-diamonds, expanded graphite, fullerenes, metal thiophosphate, molybdenite (MoS2), halloysite nanotubes (HNTs), layered silicates (clay) have shown to impart improved mechanical properties. Morphology of the fillers plays an essential role in harnessing other exciting attributes. Nano-fillers like double hydroxide, graphene nanoplatelets, and vermiculite with layered morphology have shown, 20- 30 folds increased gas barrier properties in butyl rubber.
The synergistic combination of CNTs and Graphene has been shown to impart multifunctionality, such as electrical and thermal conductivities. Strong Vander Waals forces of attraction make nano-particles stay in stable agglomerated structures. In contrast to thermoplastic materials with distinct melting points, rubbers don't melt sharply and have higher viscosities and difficult to flow. The unique rheological properties of rubbers add additional challenges in achieving the uniform distribution of the nano-fillers. The introduction of agglomerated nano-particles into rubbers create stress concentration points and result in inferior properties. Even if one reaches uniform distribution, nanofiller can't latch on to the rubber matrix because of the lack of functional groups in their pristine state. Therefore, it is crucial to create functional groups on the nano-filler to realize the optimum performance. For achieving viable applications of nano-fillers, three criteria have to be fulfilled: 1) Functionalized, 2) De- agglomerated, and 3) uniformly dispersed into nanoscale dimensions.
An in-depth understanding of functionalizing, dispersing, and processing the nano-reinforcements into rubber matrices is necessary to apply rubber nanocomposites to real-world products. Also, cost-effectiveness, safe handling, know-how related to the toxicity of the nanomaterials is required. Through a holistic understanding of the supply chain, regulations, and 1.5 decades of practical experience in all aspects of commercialization of nanocomposites, ChemPrise will be your trusted partner to assist you in taking the rubber nanocomposite solutions to the marketplace.
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