Quick Guide To Nanofillers, Nano-composites, Polymer Nano-composites
What is Nanofiller?
Nanotechnology could bring another revolution to the world of material science much like biotechnology or genetechnology has already done. Nanofillers are defined as fillers with particle sizes in the 1–100 nm range. Such fillers, e.g., carbon blacks, synthetic silicas, and precipitated calcium carbonate, have been around for a long time; however, their primary particles form bigger, stable secondary particles through agglomeration, so ultimately they cannot be classified as nanofillers.
When the diameters of polymer fiber materials are shrunk from micrometers to submicrons or nanometers, there appear several unique characteristics such as very large surface area to volume ratio (this ratio for a nanofiber can be as large as 103 times of that of a microfiber), flexibility in surface functionalities and superior mechanical performance (such as stiffness and tensile strength) compared to any other known form of the material. Major current applications are packaging films and rigid containers, automotive and industrial components.
Classification: Nanofillers can be classified into three types:
1. Nanoscale dimension (nanoplatelet)
2. Nanoscale dimension (nanofiber)
3. Nanoscale dimension (nanoparticulate)
Nanofillers with appropriate physical and dimensional properties can be selected depending on application requirements. Carbon nanotubes (CNTs) have been considered to be novel among the various nanofillers and are used extensively because of their exceptional properties. They exhibit an excellent combination of mechanical, thermal, and electrical properties not found in previous materials. There are two main types of CNTs:
- Single-walled carbon nanotubes (excessively expensive)
- Multiwalled carbon nanotubes (feasible alternative for various applications)
As the name depicts they are distinguished by the number of rolled cylinder-shaped graphene sheets in the CNTs.
Polymer Nanocomposites
A polymer nanocomposite is a composite with a combination of polymer matrix (which could be thermosetting or thermoplastic) with some nanomaterial. They are a new alternative to conventionally filled polymers. Because of their nanometer sizes, filler dispersion nanocomposites exhibit markedly improved properties when compared to the pure polymers or their traditional composites. These include increased modulus and strength, outstanding barrier properties, improved solvent and heat resistance and decreased flammability. Even after knowing so many performance improvements the number of real-world applications for polymer nanocomposites is very limited. There are number of potential factors such as:
- Selection of nanofillers to combine
- Quantity of nanofillers selection
- Process for proper incorporation of nanofillers in polymers
Classification of Polymer Nanocomposites
According to fillers
1. Carbon nanotube-based nanocomposite CNT: CNT polymer composites are synthesized as a promising material for industrial devices with advanced applications such as supercapacitors, sensors, electromagnetic absorbers, photovoltaic cells, photodiodes and optical limiting devices. CNTs are used for electroactive materials in supercapacitors which have lower specific capacitances than in the case of activated carbon. The combination of CNTs with metallic oxides or conducting polymers results in higher specific capacitance value compared to CNT materials in supercapacitor applications. CNTs, on the other hand, show an important disadvantage which leads to their limited usage in commercial supercapacitors is their high price.
2. Layered double hydroxides (LDHs): LDHs exhibit great potential in a wide range of applications in environmental, energy, catalysis, and biomaterials related fields, including heavy metal removal, radionuclide capture, organic contaminants purification, oil pollution elimination, hydrogen generation, supercapacitors, batteries, solar cells, catalysis, and biomaterial fabrication.
3. Cellulose nanoparticles: Cellulose is the most abundant, renewable, and sustainable biopolymer on earth. It is present in plants, tunicates, and some bacteria. Depending upon the source of the cellulose and the method of production, a CNF displays similar morphologies but several dimensions. Typically, a CNF and a CNC have typical diameters of 2–100 nm and between 2 and 30 nm, respectively. The attractive properties of nanocellulosic materials such as biodegradability, biocompactibility, renewability, low density, high strength, good stiffness, low thermal expansion, and high aspect ratio make them suitable for biomedical applications.
According to matrix polymer
1. Polyolefin based: Polyolefins are today the most used thermoplastic materials thanks to the high technology and sustainability of the polymerization process, their excellent thermomechanical properties and their good environmental compatibility, including easy recycling and nanocomposites have recently offered new exciting possibilities.
2. PVC based: PVC formulation typically contains a number of different additives, and exists in rigid and flexible forms.PVC nanocomposites are obtained mainly by in situ polymerization, solution based or mixing techniques. The resulting products show improvement of most important properties of poly(vinyl chloride) such as thermal, mechanical, rheological, flammability, antibacterial, etc.
3. Nylon based: Nylon is synthetic, aliphatic or semi-aromatic polyamides. It can be melt-processed into fibers, films or different desirable shapes. The composites of nylon are mostly applied in the automobile industry. There are different types of nylon, which differ with monomer, for commercial purposes such as nylon 6, 11, 12, 6/6, 6/10, 6/12, etc. The popular nylons used are nylon 6 and nylon 6/6 in which is used in textile industry. The polymer can be also used in coating of metal objects, molding and tubing extrusion.
4. PET based: PET is an excellent commercial thermoplastic polymer, which is in use for very wide scope such as textile/industrial yarn, film, injection mold and bottle, and the various fillers have been applied to solid additives incorporated into the PET polymer in order to modify its mechanical, thermal and chemical properties.he nano size fillers are attracting a great deal of attention, because the properties of filled polymers can be taken much beyond their intrinsic values.
5. TPU based: TPU are a commercially important class of thermoplastic elastomers, which have an inherent nanostructured morphology. Significant changes of thermal, mechanical, surface, flame retardant and barrier properties of TPUs have been achieved by their combination with different nanoparticles. A large interfacial surface between TPUs and nanoparticles has led to the possibility for new properties to be created. Properties of TPU-based nanocomposites strongly depend on the preparation method, the type and content of hard and soft segments in the TPUs, the type and content of nanoparticles, and intensity of interfacial interactions between the polymer matrix and nanoparticles.
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