Permeability biodegradable polymer nanocomposite

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. 

Nanocomposites materials can be defined as composite materials, that combine one or more separate components in order to improve performance properties, for which at least one dimension of the dispersed particles is in the nanometer range [23]. In polymer clay nanocomposites, nanoscale particles have typically 10-100 nm in size [24]. Depending on the reinforcement, remarkable improvement in material properties when compared with neat polymer or conventional micro and macro-composites can be obtained. These improvements can include high moduli, increased strength and heat resistance, decreased gas permeability and flammability, and increased biodegradability of biodegradable polymers [25]. 

Biodegradable polymers can be mainly classified as agro-polymers (starch, protein, etc.) and biodegradable polyesters (polyhydroxyalkanoates, poly(lactic acid), etc.). These latter, also called biopolyesters, can be synthesized from fossil resources but main productions can be obtained from renewable resources (Bordes et al. 2009). However for certain applications, biopolyesters cannot be fully competitive with conventional thermoplastics since some of their properties are too weak. Therefore, to extend their applications, these biopolymers have been formulated and associated with nano-sized fillers, which could bring a large range of improved properties (stiffness, permeability, crystallinity, thermal stability). The resulting nano-biocomposites have been the subject of many recent publications. Bordes etal. (2009) analyzed this novel class of materials based on clays, which are nowadays the main nanoflllers used in nanocomposite systems. 

Fama LM, Pettarin V, Goyanes S, Bernal CR (2011) Starch based nanocomposites with improved mechanical properties. Carbohydr Polym 83 1226-1231 Fama LM, Ganan P, Bernal CR, Goyanes S (2012) Biodegradable starch nanocomposites with low water vapor permeability and high storage modulus. Carbohydr Polym 87 1989-1993 Fama L, Kumar R (2014) Nanocomposites based on polylactic acid (PLA) reinforced by functionalized carbon nanotubes (CNT). In Kumar R (ed) Polymer-matrix composites t3fpes, applications and performance. Nova Science Publishers, Inc. USA (in press)... 

The principal used in polymer-clay nanocomposites leads the individual clay layers as well as the polymer chains to function more effectively with numerous improved properties such as high moduli, increased strength and heat resistance, decreased gas permeability and flammability, increased biodegradability of biodegradable polymers, and attractive electrical properties when compared to virgin polymers or conventional micro- and macrocomposites [37]. These properties make them ideal materials for applications in food packaging, structural automotive components, and electronics among others. 

Ray S S, Yamada K, Okamoto M, Ueda K, Polylactide-layered silicate nanocomposite a novel biodegradable material . Nano Letters, 2002 2(10) 1093-6. Chang J-H, An Y U, Sur G S, Poly(lactic acid) nanocomposites with various organoclays. I. Thermomechanical properties, morphology, and gas permeability , J. Polym. Sci Polymer Physics, 2003 41 94-103. 

Famd, Lucfa., Ganan Rojo, Piedad., Bemal, Celina., Goyanes, Silvia. Biodegradable starch based nanocomposites with low water vapor permeability and high storage modulus. Carbohydr. Polym. 87(3), 1989-1993 (2012)... 

Shih YF, Wang TY, Jeng RJ, Wu JY, Wuu DS (2008) Cross-linked and uncross-linked biodegradable nanocomposites. I. Nonisothermal crystallization kinetics and gas permeability. J Appl Polym Sci 110(2) 1068-1079... 

Reeently, Lee et al reported the biodegradation of aliphatic polyester-based nanocomposites under compost. Results clearly showed that the biodegradability of polymer was depressed after nanocomposites preparation. They assumed that the retardation of biodegradation was due to the improvement of the barrier properties of the matrix after nanocomposites preparation with OMLS. However, like Maiti et they did not report any permeability data. 

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