Fillers barrier properties

Pol Tner Nanocomposites are novel plastic compounds with a filler having dimensions between 1 and 100 nm. They have attracted much attention in the past because nanocomposites exhibit markedly improved properties like stiffness, thermal flammability, improved barrier properties and others compared to the unfilled matrices [3], Among all potential fillers, those based on easily available clay and layered silicates have been more widely investigated for some time now. 

Polymer-clay nanocomposites (PCN) are a class of hybrid materials composed of organic polymer matrices and organophilic clay fillers, introduced in late 1980s by the researchers of Toyota (Kawasumi, 2004). They observed an increase in mechanical and thermal properties of nylons with the addition of a small amount of nano-sized clays. This new and emerging class of pol miers has found several applications in the food and non-food sectors, such as in constmction, automobiles, aerospace, military, electronics, food packaging and coatings, because of its superior mechanical strength, heat and flame resistance and improved barrier properties (Ray et al., 2006). 

EVA-copolymers are used as sealants. With vinyl acetate contents ranging from 15-40 % these copolymers are particularly applicable for the production of hot melts because of their good compatibility with fillers and other plastics. Ethylene vinyl alcohol copolymer (EVOH) is a plastic with exceptional barrier properties. It is manufactured by saponification of EVA. 

Besides the coextruded laminate structure in Fig. 4b, cases c-f are also viable structures for some applications. Chapter 11(47) discusses the addition of inorganic fillers to EVOH copolymer to achieve large increases in barrier properties in some applications. The effects of different loadings of mica flake in several polymers other than EVOH was also recently reported to be effective (80). 

There are very few reports in the literature documenting the improvement in gas barrier properties that can be achieved using commercially available platelet-type fillers in melt processed polymer films and none showing the improvement in that class of polymers previously identified as high barrier polymers. 

Fillers significantly increase the tensile properties of polysulfides. This is related to the type of filler, its particle size and the type of cure. A balance of filler particle size and type is required to achieve the optimum wetting and rheology to produce the most cost effective compounds. Consideration must be given to the pH of the filler, since this affects shelf stability or well as cure properties of the compound. Fillers must be inert and insoluble in the sealants s environment. Care must be taken that the filler is adequately dispersed to ensure optimum thixotropy and barrier properties. 

In order to obtain a competitive product, the PHB performance can be greatly enhanced with the addition of nanometer-size inorganic fillers. This kind of materials are called nanocomposites and have an interesting characteristic The mechanical properties [42], the barrier properties [43], the thermal properties [44], and some others such as the flammability [45], water adsorption [46], and creep resistance [47] can be greatly enhanced with the addition of a small amount of filler (usually less than 10 wt%) [6,42-48]. 

Calcium carbonates (CaCOs), with a density of 2.7 g/cm, are commonly used filler materials for packing applications [57, 58]. CaCO filler improves flex modulus, impact strength, stiffness, tear strength, gas and water barrier properties, and printability. PE/carbonates are commonly used in the food packaging industry. 

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