Vegetable oil-based polymer nanocomposites

Abstract This chapter describes vegetable oil-based polymer nanocomposites. It deals with the importance, comparison with conventional composites, classification, materials and methods, characterisation, properties and applications of vegetable oil-based polymer nanocomposites. The chapter also includes a short review of polymer nanocomposites of polyester, polyurethanes and epoxies based on different vegetable oils and nanomaterials. The chapter shows that the formation of suitable vegetable oil-based polymer nanocomposite can be considered to be a means of enhancing many of the desirable properties of such polymers or of obtaining materials with an intrinsically new set of properties which will extend their utility in a variety of advanced applications. Vegetable oil-based shape memory hyperbranched polyurethane nanocomposites can be sited as an exampie of such advanced products. 

Key words vegetable oil-based polymer nanocomposites, preparation of poiymer nanocomposite, properties of polymer nanocomposites, appiication of polymer nanocomposites. 

It has been shown in earlier chapters that in most cases vegetable oil-based polymers exhibit inferior properties compared to analogous petroleum-based polymers. Even though the performance characteristics can be improved by blending and interpenetrating network formation with other polymers and by the formation of conventional composites with natural and/or synthetic fibres, the improvements are not sufficient to meet the requirements of many advanced applications. In addition, the base polymers lost their characteristics of light weight, and transparency (in case of 

Nanocomposites are a class of advanced multifunctional materials which provide a unique combination of physical, thermal, mechanical, barrier, optical, electrical and biological properties. A combination of two or more phases containing different compositions or structures, where at least one of the phases is in the nanoscale, is known as a nanocomposite or nano hybrid material. One of the components must possess at least one dimension (length, width or thickness) in the nanometre range. When the polymers are of biological origin (e.g. plant products such as seed oils) the nanocomposites may also be treated as nano-biocomposites . 

Almost all types of vegetable oil-based polymer nanocomposites, that is clay/polymer nanocomposites, carbon nanotubes/polymer nanocomposites, metal nanoparticles/polymer nanocomposites (metals such as Ag, Cu, Fe and their oxides) are found in the literature. These have several advantages over their respective pure polymers, or conventional polymer composite systems, and thus have the potential to meet the current demand for advanced polymeric materials. 

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Vegetable oil-based nanocomposites are used in many advanced applications. These materials have great significance in the current scenario of advanced materials. The main significance of vegetable oil-based polymer nanocomposites, such as petroleum-based polymer nanocomposites, are as follows. ... 

Thus vegetable oil-based polymer nanocomposites have considerable significance in the development of advanced polymeric materials, offering great improvement in performance characteristics without a large increase in cost. Nanotechnology may therefore carve out a unique niche of its own in the area of vegetable oil-based polymer nanocomposites. 

Details of vegetable oil-based polymers conventional composites have been discussed in an earlier chapter. In this chapter, nanocomposites of vegetable oil-based polymers are discussed. Certain questions arise as to how much difference there is between these composites. The questions are significant when the same reinforcing agent is used in both cases. As an example, a vegetable oil-based polyurethane with alkali-treated chopped jute fibres in a conventional composite and cellulose nanofibres (obtained from jute fibres) in a vegetable oil-based polymer nanocomposite are discussed. The... 

A large number of nanomaterials, from metal to polymer and including ceramics, are used in vegetable oil-based polymer nanocomposites. Nanomaterials have different sizes and shapes. They may be spherical or in the shape of platelets, rods, ribbons, cylinders, tubes, and so on. Nanomaterials exhibit different properties from bulk materials. As an example, crystals of nanometre size have a lower melting point and lower thermostability than the analogous bulk crystals. 

Three different types of nanomaterials, based on their dimensional characteristics, are generally used to prepare polymer nanocomposites. These include nanomaterials with only one dimension in the nanometre range (e.g. nano-clay), those with two dimensions in the nanometre scale (e.g. carbon nanotubes) and those that have all three dimensions in the nanometre scale (e.g. spherical silver nanoparticles), as stated earlier. Thus nanosize thin layered aluminosilicates or nanoclays, layer double hydroxide (LDH), a large number of nanoparticles of metals and their oxides, carbon nanotubes and cellulose nanofibres are used as nanomaterials in the preparation of vegetable oil-based polymer nanocomposites. 

CNTs are used to obtain high performance vegetable oil-based polymer nanocomposites. Oxidative, acid and amine functionalisations followed by grafting of CNTs are the most widely used methods for this purpose. 

To obtain a homogeneous and thermodynamically stable dispersion of nanomaterials in the polymer matrix, a variety of techniques are used in vegetable oil-based polymer nanocomposites. The state of dispersion of nanomaterials in the polymer matrix is the main governing factor in obtaining the required nanocomposites. However, depending on the suitability, end-use applications and cost, the three most widely used methods for the preparation of polymer nanocomposites are (i) the solution technique, (ii) in situ polymerisation and (hi) the melt mixing technique. ... 

The ultraviolet (UV) - visible spectrophotometer is another important tool in the characterisation of vegetable oil-based polymer nanocomposites and is particularly effective for metal nanocomposites. The formation of metal nanoparticles in the matrix can be easily detected by UV-visible spectroscopy. Every metal nanoparticle has its own characteristic surface plasmon resonance value. This band is attributed to the collective oscillation of electron gas in the nanoparticles, with a periodic change in the electronic density at the surface. Parameters such as particle size, shape and dielectric constant of the medium and surface adsorbed species determine the position and shape of the plasmon absorption. When the particles become significantly smaller than the mean free path of electrons in the bulk metal, the plasmon oscillation is dampened. The plasmon absorption peak shifts to a higher wavelength than expected with an increase in aggregation of the nanoparticles. The sharpness of the peak indicates the narrow size distribution. 

A large number of vegetable oil-based polymer nanocomposites have been reported in the literature. Among these, vegetable oil-based polyesters, polyurethanes and epoxies are very important and are discussed in the following sub-sections. 

Why are vegetable oil-based polymer nanocomposites attractive to different scientists ... 

List the advantages and disadvantages of the different techniques which are used for the preparation of vegetable oil-based polymer nanocomposites. 

Explain the improvement in the following properties, with suitable examples, for different vegetable oil-based polymer nanocomposites (i) tensile strength, (ii) gas permeability, (iii) thermostability and (iv) biodegradability. 

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