Thermal stability biodegradable polymer nanocomposite

Ray, S.S. Thermal stability and flammability of environmentally friendly polymer nanocomposites using biodegradable polymer matrices and clay/carbon nanotube (CNT) reinforcements. Environmentally Friendly Polymer Nanocomposites, pp. 295-327. Woodhead Publishing, Cambridge (2013)... 

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. 

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The advantages of nanocomposite materials when compared with conventional composites are their superior thermal, mechanical and barrier properties at low reinforcement levels (e.g., < 5 wt%), as well as their better recyclability, transparency and low weight [31, 32]. Biodegradable polymers, in particular, may require improvement in terms of brittleness, low thermal stability and poor barrier properties [32]. A number of researchers have therefore explored the concept of fully bioderived nanocomposites as a route to development of bioplastics or bioresins with better properties [33, 34]. 

As the plastics produced from fossil fuels, when discarded into the environment, end up as waste that cannot degrade spontaneously, there is an urgent need for the development of biodegradable polymers. However, their low thermal stability and mechanical properties usually limit their application. Therefore, nanocomposite preparation is an option to overcome these problems. 

PBA-SS nanocomposites were synthesized by a novel, cost-effective, unconventional emulsifier-free emulsion technique. The XRD results showed a disordered layer structure due to intercalation of polymer into the layered silicate. These composites were further characterized by TGA, TEM and their burning rates and exhibited improved properties of thermal stability with good fire retardant properties. It is found that the fire retardant nanocomposites have average biodegradability and have promising future prospects. 

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