Thermal stability epoxy nanocomposites

Different results are obtained for high-thermal-stability epoxies. In this case the nanocomposite shows a decrease in the onset of decomposition temperature compared to the neat polymer. Hussain et al. showed that the onset of decomposition of an amino-cured epoxy is 420°C, whereas a nanocomposite containing 5 wt% octadecylammonium montmorillonite exhibits, at the same temperature, 420°C, a weight loss of 10%. It is obvious that in this case the weight loss in the nanocomposite is not only a direct effect of volatilization of the surfactant but is attributed to the catalytic effect of onium decomposition. Camino et al. compared the effect of different organo-modified montmorillonites on the thermal stability of a DGEBA cured with methyl tetrahydrophthalic anhydride. They observed that the octadecylammonium montmorillonite nanocomposite has the lowest onset at 5 wt% loss (288°C), compared to bis(2-hydroxyethyl)ammonium montmorillonite... 

Multicomponent hybrids containing zirconium propoxide, tetraethoxysilane and dimethyl-diethoxysilane, intended for dental restorative or adhesive materials, were successfully obtained by the dual-cure [272]. Zirconium-containing species proved to be highly effective in catalyzing the epoxy polymerization/crosslinking reactions, as compared to those containing Ti, and enhanced mechanical properties, as well as thermal stability of nanocomposites. 

J. Kim, K. Lee, K. Lee, J. Bae, J. Yang, and S. Hong, Studies on the thermal stabilization enhancement of ABS synergistic effect of triphenyl phosphate nanocomposite, epoxy resin, and silane coupling agent mixtures, Polym. Degrad. Stab., 79(2) 201-207, 2003. 

Thermal Stability and Conductivity. Thermal degradation temperature of PMMA, PS, and PVA (poly(vinyl alcohol)) nanocomposites shifts up by 10-100°C. During combustion [179], nanoparticles form a network of char layers that retards the transport of decomposition products. The thermal conductivity of epoxy composites is four times higher than that of the neat epoxy resin with 5 wt% loads. 

Suguna Lakshmi, M., Narmadha, B. Reddy, B. S. R. (2008). Enhanced thermal stability and structural characteristics of different MMT-Clay/epoxy-nanocomposite materials. Polymer Degradation and Stability, Vol. 93, No. 1, pp 201-213... 

At this concentration the strength growth is 26.8%. From the concentration range studied, the concentration 0.05% from ER weight is optimal to reach a high thermal stability. At this concentration the temperature of thermal destruction beginning increases up to 195°C. Thus, in this work the stable FS of Cu/C nanocomposite were obtained. The modified polymers with increased adhesive strength (by 26.8%) and thermal stability (by 110°C) were produced based on epoxy resins and FS. 

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. 

Carrasco, F., Pages, P. Thermal degradation and stability of epoxy nanocomposites influence of montmorillonite content and cure temperature. Polym. Degrad. Stab. 93, 1000 (2008)... 

The effects of Cloisite loading on the thermal decomposition behavior of an epoxy resin were reported by Ingram et al. [65]. It was shown that the addition of Cloisite in the systems improved the thermal stability of the epoxy resins which underwent an initial cure at 180 °C. However, when the nanocomposites were post cured at 220 °C, the nanoclay incorporation induced a decrease in the thermal stability of the systems. This behavior may be attributed to the dissociated alkyl chains, which destabilize the thermal properties after being subjected to high temperatures [66]. Therefore, a carefid selection of cure and post cure temperatures must be made in order to obtain nancomposites with improved physical properties and with enhanced thermal stability. 

The incorporation of 5 % organically modified sepiolite, which is a microcrystalline-hydrated magnesium silicate, in a bisphenol A-based epoxy resin has no significant effect over the thermal stability of the epoxy resin, due to the poor dispersion of the clay and poor diffusion of the resin between fibres [69]. The effect of attapulgite (magnesium aluminium phyllosilicate) over the thermal properties of hyperbranched polyimides was studied. The presence of this silicate in the nanocomposites significantly improved the thermal stability of the neat polyimide [70]. 

The incorporation of other type of nanoparticles, such as CuO, Ti02, silsequioxanes was found to affect the thermal degradation of the thermosetting materials. The thermal stability of the epoxy resin/cupric oxide (CuO) nanocomposites in air atmosphere was improved by the presence of CuO nanoparticles. Furthermore, the presence of these nanoparticles affected the degradation mechanism of the epoxy resin [72]. 

In the case of Ni-La-Fe-O/epoxy nanocomposites, the thermal degradation showed a more complicated behavior than the neat epoxy resin, with two peaks in the 300-475 °C temperature range. Moreover, the thermal stability of the resin decreased in the presence of Ni-La-Fe-0 nanoparticles, due to the fact that these nanoparticles may act as catalysts to degrade the epoxy matrix [76]. 

The incorporation of the hybrid Ti02-Si02 nanofillers into an epoxy resin increased the thermal stability of the neat resin [78]. Also the char yield increased from 0 % for the neat resin to 25 % for the nanocomposites. These phenomena are a consequence of the hybrid nanoparticles which acted as thermal stabilizers for the epoxy resin. 

Nanocomposites containing functionalized CNTs exhibited increased thermal stability, compared to the neat epoxy resin. In this case the functionalized CNTs had a better affinity for the pol3meric matrix than the un-functionalized CNTs [91]. Kuan et al. reported that the incorporation of the MWCNTs functionalized with vinyltriethoxysylane into an epoxy resin increased its thermal stability [92]. The same effects were obtained in the case of MWCNTs grafted with triethylenetetra-mine [91] and MWCNTs functionalized with silane [88]. 

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