Polymer/filler composition, optical

Table VII Optical Clarity of Polymer/Filler Composition Silica...

Fillers may be broadly defined as solid particulates or fibrous materials, substantially inert chemically, incorporated in polymer compositions to modify the properties and/or to reduce cost. Cost reduction is not the primary reason to incorporate fillers in adhesives but they are used to impart specific properties such as flow, improved adhesion, mechanical, thermal, electrical and optical properties, chemical and weather resistance, and rheological behaviour. 

The study of filler distribution by the methods of optical and electronic microscopy has shown that in all compositions obtained by method 4 the filler is distributed rather uniformly as in an individual polymer. In the mixtures of incompatible polymers, obtained by methods 1 and 2, the filler is distributed nonuniformly and there are zones of high concentration of the filler and almost empty ones. The size of such zones is close to the size of polymer regions known for mixtures of thermodynamically incompatible polymers — 1 to 10 p. 

The refractive index is the most important optical property and its effect in determining the appearance of the polymer composite has already been referred to above. Amorphous fillers such as glass fibres and beads have only one refractive index, but most mineral fillers are crystalline and have anisotropic crystal structures resulting in a number of different indices, and this can cause complex and undesirable interference effects [27]. 

As discussed earlier, while the scale of the fillers is substantially different, nanocomposite materials concepts and technology are very similar to those of conventional composite materials. This is clearly demonstrated in the case of new thermosets for nonlinear optical (NLO) applications, " " where nanocomposite of liquid crystalline thermosets, IPNs, and simple filled thermosets are evaluated. Tripathy et al. discussed four different ways to prepare nonlinear optical polymers. (1) The polymer matrix is doped with NLO moieties in a guest/host system (2) In side-chain polymer systems, NLO polymers with active moieties are covalently bonded as pendant groups (3) In the main chain polymer, the chromo-phores are incorporated as parts of the main polymer backbone to enhance the temporal stability of the NLO properties and (4) Stability of the optical noninearity in sol-gel-based thermosets is related to... 

MAJOR PRODUCT APPLICATIONS thermistors, capacitors, optics, ferroelectric ceramics, filler for ferroelectric polymers, pyro and piezoelectric composites... 

The methanol wet, hydrophobic silica filler Is ready for formulating with polymer. Mentioned above Is the fact that the new silica possesses unusual characteristics relative to its ability to provide optically clear silicone compositions. A little background is in order to put this in perspective. 

However, in addition to their thermoplasticity, representatives of PHAs have optical activity, increase induction period of oxidation, exhibit the piezoelectric effect and, what is most important, they are characterized as being biodegradable and biocompatible. At the same time, the PHAs have disadvantages (high cost, brittleness), which can be partially or completely compensated by using composite materials based on blends with other polymers, with dispersed fillers or plasticizers. Taking into account all the above, we have suggested to create a mixed polymer composite based on poly-3-hydroxybutyrate (PHB) and polyisobutylene (PIB). 

In recent years, the limits of optimizing composite properties of traditional micrometer-scale composite fillers have been reached due to the compromises of the obtained properties. Stiffness is traded for toughness, or toughness is obtained at the cost of optical clarity. In addition, regions of high or low volume fraction of filler often results in macroscopic defects which lead to breakdown or failure of the material. Recently, a new research area has provided the opportimity to overcome the limitations of traditional micrometer-scale polymer composites. This new investigation area is the nanoscale filled pwlymer composites where the filler is <100 nm in at least one dimension. 

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