Degradation of Polymer Nanocomposites

A well-accepted definition of nanocomposite material is that one of the phases has dimensions in the order of nanometers [51]. Roy et al. [52] present in their paper on alternative perspectives on nanocomposites a summary of features of particle properties when particle size decreases beyond a critical size. As dimensions reach nanoranges, interactions improve dramatically at the interfaces of phases, as do the effect of surface area/volume on the structure-property relationship of the material [53]. There is definite increase in the modulus of the material reinforced with composites, higher dimensional stability to thermal treatment, as well as enhanced barrier, membrane (conductive properties) and flame resistance. Thus, as Paul and Robeson [54] rightly put it, the synergistic advantage of nanoscale dimensions ( nano effect ) relative to larger-scale modifications is an important consideration  

Powder Process Simple Low formation rate, high temperature, agglomeration, poor phase dispersion, formation of secondary phases in the product. 

Polymer Precursor Process Possibility of preparing finer particles better reinforcement dispersion Inhomogeneous and phase-segregated materials due to agglomeration and dispersion of ultra-fine particles 

Paul and Robeson discuss exfoliated clay nanocomposites in rigorous depth. They provide data on the various techniques used to characterize the structure and properties of synthesized nanocomposite materials. One such example is provided in the following an illustration of the different states of dispersion of organoclays in polymers with corresponding WAXS and TEM results. 

The purpose of providing a brief overview on recent reviews of nanocomposite materials that discuss synthesis, structure properties, and applications is to bring to the reader s attention the nascence of this field and justify the rare availability of degradation studies of these materials when we have only recently embarked on our journey to understanding the fundamentals about them. Nevertheless, a few examples of degradation studies of nanocomposite materials are provided with the hope of advances towards mechanistic aspects of degradation with nanomaterials components. Chrisaffis et al [56, 57] report studies on the decomposition mechanisms of syndiotactic polystyrene (sPS) nanocomposites with two different types of nano fillers multi-walled carbon nanotubes (MWCNTs) and carbon nanodiamonds (NDs). sPS is a semicrystalline polymer considered to be a 

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Pandey JK, Reddy KR, Kumar AP, Singh RP (2005) An overview on the degradability of polymer nanocomposites. Polym Degrad Stab 898 234—250... 

It is generally accepted that thermal stability of polymer nanocomposites is higher than that of pristine polymers, and that this gain is explained by the presence of anisotropic clay layers hindering diffusion of volatile products through the nanocomposite material. It is important to note that the exfoliated nanocomposites, prepared and investigated in this work, had much lower gas permeability in comparison with that of pristine unfilled PE [12], Thus, the study of purely thermal degradation process of PE nanocomposite seemed to be of interest in terms of estimation of the nanoclay barrier effects on thermal stability of polyolefin/clay nanocomposites. 

This volume is including information about thermal and thermooxidative degradation of polyolefine nanocomposites, modeling of catalytic complexes in the oxidation reactions, modeling the kinetics of moisture adsorption by natural and synthetic polymers, new trends, achievements and developments on the effects of beam radiation, structural behaviour of composite materials, comparative evaluation of antioxidants properties, synthesis, properties and application of polymeric composites and nanocomposites, photodegradation and light stabilization of polymers, wear resistant composite polymeric materials, some macrokinetic phenomena, transport phenomena in polymer matrix, liquid crystals, flammability of polymeric materials and new flame retardants. 

A description of various characterization techniques for studying the dispersion of nanoparticles, curing kinetics and thermal degradation will facihtate the readers better understanding of these techniques. Information on the applications of polymer nanocomposites in various fields has also been incorporated. 

Thermal Degradation of Polymer Blends, Composites and Nanocomposites... 

Abstract This chapter deals with a brief account of thermal degradation of polymer-based blends, composites and nanocomposites. Different synthesising, preparation and characterisation methods of thermal degradation of polymer-based blends, composites and nanocomposites are discussed. Finally the applications, new challenges and opportunities for these thermal degradation of polymer-based blends, composites and nanocomposites are discussed. 

Except montmorillonite, other clays like layered double hydroxide (LDH) can enhance thermal degradation of polymers. In such nanocomposites there are no reported for accelerating effect of LDH on polymer thermal degradation. This is because LDH can be more easily dispersed in intercalated or exfoliated structures, compared with MMT, into a polymer matrix and thus the stabilization effect is higher [22]. 

The mechanical properties of polymer nanocomposites are also influenced by the chemical treatment of nanoparticles due to the different neighborhood in the material. The free volume that characterizes the density of material is modified and, consequently, the penetration of fluids (solvents, oxygen) is rather favorable to degradation. The diffusion of xylene in ethylene-propylene diene terpolymer is unlike, if material presents different consistency (Fig. 14, [191]). The competitive radiochemical processes, crosslinking of polymer and degradation of covering layer are the most important reasons responsible for the different shapes of swelling curves. 

Pandey, J.K., Raghunatha Reddy, K., Pratheep Kumar, A., Singh, R.P. An overview on the degradability of pol3nner nanocomposites. Polym. Degrad. Stab. 88, 234—250 (2005)... 

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