Barrier nanocomposites

Nanocomposite based on polyurethane (PU) is prepared using silica, clay, and Polyhedral Oligomeric Silsesquioxane (POSS). Preparation, characterization, mechanical and barrier properties, morphology, and effect of processing conditions have been reported on polyurethane-based nanocomposites [72,73]. 

Nanocomposites have been prepared with this polymer and mechanical and barrier properties and ffacmre behavior have been studied [74—76]. The latex of this mbber has also been used for the same [77]. Sadhu and Bhowmick [78-81] have studied the preparation, stmcmre, and various... 

This is a highly polar polymer and crystalline due to the presence of amide linkages. To achieve effective intercalation and exfoliation, the nanoclay has to be modified with some functional polar group. Most commonly, amino acid treatment is done for the nanoclays. Nanocomposites have been prepared using in situ polymerization [85] and melt-intercalation methods [113-117]. Crystallization behavior [118-122], mechanical [123,124], thermal, and barrier properties, and kinetic study [125,126] have been carried out. Nylon-based nanocomposites are now being produced commercially. 

PP is probably the most thoroughly investigated system in the nanocomposite field next to nylon [127-132]. In most of the cases isotactic/syndiotactic-PP-based nanocomposites have been prepared with various clays using maleic anhydride as the compatibilizer. Sometimes maleic anhydride-grafted PP has also been used [127]. Nanocomposites have shown dramatic improvement over the pristine polymer in mechanical, rheological, thermal, and barrier properties [132-138]. Crystallization [139,140], thermodynamic behavior, and kinetic study [141] have also been done. 

PI nanocomposites have been prepared by various methods with different fillers. The nanocomposites might have many applications starting from barrier and thermal resistance to a compound with low coefficient of thermal expansion (CTE) [154-167]. These hybrid materials show very high thermal and flame retardation as well as barrier resistance and adhesion. Tyan et al. [158] have shown that depending on the structure of the polyimide the properties vary. Chang et al. [159] have also investigated the dependency of the properties on the clay modifiers. 

Owing to the good barrier property, the EVA-based clay nanocomposites are used for packaging, bottle-making, etc. [168]. 

It is likely that excellent gas barrier properties exhibited by nanocomposite polymer systems will result in their substantial use as packaging materials in fumre years. 

Rubber-clay nanocomposites are particularly attractive for potential applications where enhanced barrier properties are desired. Organoclays for rubber intercalation were prepared... 

Polyimide-clay nanocomposites constitute another example of the synthesis of nanocomposite from polymer solution [70-76]. Polyimide-clay nanocomposite films were produced via polymerization of 4,4 -diaminodiphenyl ether and pyromellitic dianhydride in dimethylacetamide (DMAC) solvent, followed by mixing of the poly(amic acid) solution with organoclay dispersed in DMAC. Synthetic mica and MMT produced primarily exfoliated nanocomposites, while saponite and hectorite led to only monolayer intercalation in the clay galleries [71]. Dramatic improvements in barrier properties, thermal stability, and modulus were observed for these nanocomposites. Polyimide-clay nanocomposites containing only a small fraction of clay exhibited a several-fold reduction in the... 

Above we have shown the attractiveness of the so-called green nanocomposites, although the research on these materials can still be considered to be in an embryonic phase. It can be expected that diverse nano- or micro-particles of silica, silicates, LDHs and carbonates could be used as ecological and low cost nanofillers that can be assembled with polysaccharides and other biopolymers. The controlled modification of natural polymers can alter the nature of the interactions between components, affording new formulations that could lead to bioplastics with improved mechanical and barrier properties. 

Most nanocomposite researchers obdurately believe that the preparation of a completely exfoliated structure is the ultimate target for better overall properties. However, these significant improvements are not observed in every nanocomposite system, including systems where the silicate layers are near to exfoliated [29]. While, from the barrier property standpoint, the development of exfoliated nanocomposites is always preferred, Nylon 6-based nanocomposite systems are completely different from other nanocomposite systems, as discussed [3,8]. 

In 2002, Lee et al. [51] reported the biodegradation of aliphatic polyester-based nanocomposites under compost. Figure 9.13(A, B) represent the clay content dependence of biodegradation of APES-based nanocomposites prepared with two different types of MMT clays. They assumed that the retardation of biodegradation was due to the improvement of the barrier properties of the aliphatic APSE after nanocomposite preparation with clay. However, there are no data about permeability. 

I, H. Tseng, Y. F. Liao, J. C. Chiang, M. H. Tsai, Transparent polyimide/graphene oxide nanocomposite with improved moisture barrier property., Materials Chemistry and Physics, vol. 136, pp. 247-253, 2012. 

Fiat projects new applications for nanocomposites in the form of PA fuel lines incorporating PA nanocomposite barrier layers from Ube. 

Ube developed the PA nanocomposite named Ecobesta to replace PVDF or other traditional barrier materials. The all-polyamide structure offers recycling advantages compared to traditional multi-materi designs. It incorporates ... 

Clay-polymer nanocomposites have proven to be interesting candidates as gas barrier materials preventing permeation of volatile gases by creating a long path for diffusion and as flame-retardant materials. Previous work mainly involves the utihzation of cationic clays, although LDH materials... 

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. 

Nevertheless the euphoric optimism where these materials were allowed a huge potential in material applications has given way to a more realistic view. Nanocomposites are not a universal solution for reinforced materials. Their full potential can only be realised if every step in the added value chain is taken into account during the whole development process. From todays perspective nanocomposite materials with an improved thermal flammability resistance or improved barrier properties have the best chances to fulfil these requirements. 

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). 

Park, H.W., Lee, W. K.,Park, C. Y.,Cho, W. J., Ha, C. S. (2003). Environmentally friendly polymer hybrids Parti. Meehanical, thermal, and barrier properties of thermoplastie stareh/elay nanocomposites. Journal of Materials Science, 38, 909-915. 

The most important materials developed are nanocomposites and nanotubes. Fabrication of the first nanocomposites was inspired by nature (biomineralisation). Nanocomposites based on nanoclays and plastics are seen as ideal materials for improved barrier properties against oxygen, water, carbon dioxide and volatiles [37]. This makes them in particular suitable for retaining flavours in foods. The technology is rather straightforward using commercially available nanoclays and extrusion processing. 

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