Nanoscale reinforcement

The intercalation of organic polymers into the interlayer space has also been widely studied since hybridization may not only produce unique materials with high dispersive ability, but may also enhance polymeric properties by nsing nanoscale reinforcements compared to the conventional particnlate-lilled... 

PMMA has been extensively employed because of their potential applications in light-emitting devices, batteries, optics, electromagnetic shielding, and corrosion-resistant coatings. However, their poor mechanical strength limits their range of applications. Nanoscale reinforcement is considered to improve the mechanical and electtical performance of PMMA effectively. 

Nanoscale reinforcements have inherent properties that lead to different properties than other reinforcements, such as high aspect ratios. Ftowever, for the potential of these nanomaterials as reinforcements to be realized, particular challenges must be met. For example, these nanomaterials must be homogeneously dispersed in the matrix and the adhesion at the interface must allow an efficient transfer of stress from the matrix to the reinforcement. If these and other drawbacks are not overcome, disappointing results can be observed, mainly when compared to advanced composites reinforced with high-performance continuous fibers (Dzenis, 2008). ... 

Nanocomposite describes a two-phase material where one of the phases has at least one dimension in the nanometer range (1-100 nm). They differ from conventional composites by the exceptionally high surface-to-volume ratio of the reinforcing phase and/ or its exceptionally high aspect ratio. The reinforcing material can be made up of particles (e.g., minerals), sheets (e.g., exfoliated clay stacks) or fibers (e.g., carbon nanotubes, electrospun fibers or cellulose nanofibers). Large reinforcement surface area means that a relatively small amount of nanoscale reinforcement can have an observable effect on the macroscale properties of the composite. There has been enormous interest in the commercialization of nanocomposites for a variety of applications, and a number of... 

Polymer nanocomposite development has been a sensitive area of research and has evolved significantly over the last two decades because of the ability of nanoscale reinforcements to create remarkable... 

To date much of the development of polymer nanocomposites has been for structural applications with current commercial applications such as the step assist for the Chevrolet Astro van introduced by General Motors in 2002. However, there are other composite functions, such as tribological resistance, low friction or fire retardancy which are important in other applications and with nanoscale reinforcements it is possible to mix several different types of reinforcement to generate improvements in a range of properties. The following sections discuss how such properties are improved in nanocomposites. 

A range of structural composite materials were produced with different reinforcements for performance assessment. The systems were based on a conventional woven roving/thermosetting resin design but with added nanoscale reinforcement which was mixed with the resin prior to lamination. The systems... 

The results were compared with a standard steel sample which was tested either in the as-received condition or coated with a layer of lubricating grease. In addition to the modification of stmctural composites a number of polymer nanocomposites were made by mixing nanoscale reinforcements with a polyurethane resin. In this case the resin was again cast against a glass... 

The results presented so far indicate that no single nanoscale reinforcement generates ideal results, either alone or when used in conjunction with more conventional reinforcement materials. To control wear, a hard reinforcement such as silica is preferred whereas to reduce friction a low shear stress reinforcement such as M0S2 is more effective. Thus a combination of nanoscale reinforcements in vinyl ester resin has been investigated in further tests and the benefits of the mixed compositions on friction (Fig. 9.7) and speed at seizure (Fig. 9.8) have been demonstrated without compromising wear performance. 

The results presented here demonstrate the benefit of nanoscale reinforcement to improve wear resistance of the composite material but to improve the overall performance of the materials for a sliding seal application no single reinforcement material is suitable. However, a combination of reinforcements can be developed which impart multiple functionality to the composite. For instance, both silica and M0S2 nanoparticles added to a polyurethane resin matrix can generate improvements in both friction and wear behaviour. 

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