Degradation thermoplastic nanocomposites

Ale Alessi, S., Conduruta, D., Pitarresi, G., Dispenza, C., Spadaro, G. Accelerated ageing due to moisture absorption of thermally cured epoxy resin/polyethersulphone blends Thermal, mechanical and morphological behaviour. Polym. Degradation Stability 96 (2011) 642-648. llAsi Asif, A., Rao, V. L., Ninan, K. N. Preparation, characterization, thermo-mechanical, and barrier properties of exfoliated thermoplastic toughened epoxy clay ternary nanocomposites. Polym. Adv. Technol. 22 (2011) 437 47. 

This chapter reviews the general context of starch as a material. After a survey of the major sources of starch and their characteristic compositions in terms of amylase and amylopectin, the morphology of the granules and the techniques applied to disrupt them are critically examined. The use of starch for the production of polymeric materials covers the bulk of the chapter, including the major aspect of starch plasticization, the preparation and assessment of blends, the processing of thermoplastic starch (TPS), the problems associated with its degradation and the preparation of TPS composites and nanocomposites. The present and perspective applications of these biodegradable materials and the problems associated with their moisture sensitivity conclude this manuscript. 

Thompson, M. R. and Yeung, K. K. 2006. Recyclability of a layered silicate-thermoplastic olefin elastomer nanocomposite. Polymer Degradation and Stability 91 2396-2407. 

Abstract Biodegradable thermoplastic materials offer great potential to be used in food packaging or biomedical industry. In this chapter we will present a review of the research done on starch and starch nanocomposites. In the case of nanocomposites based on starch, special attention will be given to the influence of starch nanoparticles, cellulose whiskers, zinc oxide nanorods, antioxidants, and antimicrobial inclusion on the physicochemical properties of the materials. The discussion will be focused on structural, mechanical, and barrel properties as well as on degradation, antibacterial and antioxidant activities. Finally, we will discuss our perspectives on how future research should be oriented to contribute in the substitution of synthetic materials with new econanocomposites. 

The combustion of the LDH nanocomposites leads to the formation of an intercalated nanostructure of mixed metal oxides (produced by thermal degradation of LDH) and char. This hypothesis is supported by XRD, due to the presence of a peak at 1.28 nm in the epoxy-LDHl and epoxy-LDH2 after the UL-94 test. It is interesting to note that Gilman et al. reported an intercalated structure of char from montmorillonite nanocomposites, with the same interlayer spacing of the chars, 1.3 nm, independent of the chemical structure of the polymer (thermoplastic or thermosetting) or nanostructure (delaminated or intercalated). The same value observed in an LDH-based nanocomposite (1.28 nm) shows that the interlayer spacing in the char may be independent of the nature of the layered crystal. 

Despite expectations that the addition of nanoparticulate layered silicates would improve the photooxidative stability of thermoplastics given their inertness toward UV radiation [109], it was concluded, as resulted from numerous studies, that PE-clays nanocomposites undergo accelerated photochemical degradation as compared to neat PE due to the presence of clay, either raw [110-115] or organically modified [111, 116-119], or in the presence of an oligomeric compatibilizer such as PE-g-MA or PP-g-MA [114]. 

Given the practical relevance of materials used in outdoor applications, different synthetic thermoplastic polymers were employed in nanocomposite formulations and submitted to UV irradiation. Thus, PC-clay nanocomposites seemed to display an increased rate of decomposition [110, 140], during which the carbonate scission reactions entailed a yellowing of the material. However, the degradation was less intense than in neat PC [141]. The presence of alumina (AI2O3) in PC nanocomposites reduced the overall light transmittance [10, 142]. 

Studies of the photochemical behavior of polyamides based nanocomposites were run using MMT [116] or silica [10, 144]. As in other thermoplastics, MMT enhanced the photooxidative processes and accelerated the nanocomposite degradation [116]. In poly(trimethylhexamethylene terephthalamide)-silica nanocomposites, the silica enhanced the light transmittance and the effect decreased gradually when its amount increased over 5 wt% [144]. 

Quan H, Zhang B, Zhao Q, Yuen RKK, Li RKY. Facile preparation and thermal degradation studies of graphite nanoplatelets (GNPs) filled thermoplastic polyurethane (TPU) nanocomposites. Compos Part A 2009 40 1506-13. 

Most thermoplastics degrade rapidly when used outdoors because of photooxidation promoted by ultraviolet (UV) irradiation. A recent study on natural weathering of micro-CaCOs filled PP showed that the composites filled with surface treated CaC03 provided better retention of mechanical properties than those filled with untreated fillers, which demonstrated the importance of interfacial properties.Weathering behaviors of nano-CaC03 filled polymers have not been reported, and a study on this topic would be useful for exploring applications of the nanocomposites. 

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