Thermal stability/stabilization polymer nanocomposites

Tidjani, A., Wald, O., Pohl, M. M., Hentschel, M. P., and Schartel, B. 2003. Polypropylene-graft-maleic anhydride-nanocomposites. I. Characterization and thermal stability of nanocomposites produced under nitrogen and in air. Polymer Degradation and Stability 82 133M0. 

The thermal properties of polymer nanocomposites are significantly better than those of the pristine polymer. This may be due to the clay acting as a heat barrier, which enhances the overall thermal stability of the system as... 

At the same time inorganic nanoparticles are important component in synthetic rubber nanocomposites, this type of nanoparticles are less reactive than organic nanoparticles, because they are not involved in thermal degradation reactions. Inorganic nanoparticles can be subjected to high temperature, due of natural chemical, are considered an excellent choice as reinforcement in polymer matrix, has been reported that using this type of nanoparticles improve the thermal stability of nanocomposite. 

Thermal properties Thermal properties are the properties of materials that change with temperature. They are studied by thermal analysis techniques, which include DSC, thermogravimetric analysis (TGA), differential thermal analysis (DTA), thermomechanical analysis (TMA), dynamic mechanical analysis (DMA)/dynamic mechanical thermal analysis (DMTA), dielectric thermal analysis, etc. As is well known, TGA/DTA and DSC are the two most widely used methods to determine the thermal properties of polymer nanocomposites. TGA can demonstrate the thermal stability, the onset of degradation, and the percentage of silica incorporated in the polymer matrix. DSC can be... 

Wang H, Xu P, Zhong W, Shen L, Du Q (2005) Transparoit poly(methyl methacrylate)/ silica/zirconia nanocomposites with excellent thermal stabilities. Polymer Degrad Stabil 87 (2) 319-327... 

Hong et al. [231] have used this simple technique for the synthesis of ZnO-low-density polyethylene composites. ZnO nanoparticles and branched low-density polyethylene was melt-compounded in a high-shear mixer to prepare polymer nanocomposites with an improved resistance to thermal degradation. They also mixed submicron-sized ZnO particles with low-density polyethylene for a comparison and reported that the surface properties of nanoparticles (<100 nm) resulted in an increased thermal stability of nanocomposites. Ma et al. [232] also used melt blending for the synthesis of silane-modified ZnO-polystyrene resin nanocomposites. Incorporation of ZnO nanoparticles results in an increased flexural... 

J. Liu, G. M. Chen, and J. P. Yang, Preparation and characterization of poly(vinyl chloride)/layered double hydroxide nanocomposites with enhanced thermal stability. Polymer, 49 (2008), 3923-7. 

Uhl, F.W. WUde, C.A. Polystyrene/graphite nanocomposites effect on thermal stability. Polym. Degrad. Stab. 2002, 76, 111-122. 

Filho F.G.R., Melo T.J.A., Rabello M.S., Silva S.M.L., Thermal stability of nanocomposites based on polypropylene and bentonite . Polymer Degradation and Stability, 2005 89 383-392. 

A major aim to prepare the polymer-nanofiller composites is to enhance the thermal stability of the materials. The thermal properties of polymer nanocomposites are usually evaluated by differential scanning calorimetry (DSQ and thermogravimetric (TG) analyses. From DSC and TG testing, the glass transition temperature (Tg) and decomposition temperature can be determined, from which the thermal properties of polymer nanocomposites can be evaluated. 

Uhl F M, Wilkie C A (2002), Polystyrene/graphite nanocomposites Effect on thermal stability , Polym Degrad Stab, 76, 111. 

Polyimide-clay nanocomposites constitute another example of the synthesis of nanocomposite from polymer solution [70-76]. Polyimide-clay nanocomposite films were produced via polymerization of 4,4 -diaminodiphenyl ether and pyromellitic dianhydride in dimethylacetamide (DMAC) solvent, followed by mixing of the poly(amic acid) solution with organoclay dispersed in DMAC. Synthetic mica and MMT produced primarily exfoliated nanocomposites, while saponite and hectorite led to only monolayer intercalation in the clay galleries [71]. Dramatic improvements in barrier properties, thermal stability, and modulus were observed for these nanocomposites. Polyimide-clay nanocomposites containing only a small fraction of clay exhibited a several-fold reduction in the... 

CNTs can enhance the thermal properties of CNT-polymer nanocomposites. The reinforcing function is closely associated with the amount and alignment of CNTs in the composites. Well-dispersed and long-term stable carbon nanotubes/ polymer composites own higher modulus and better thermal property as well as better electronic conductivity (Valter et al., 2002 Biercuk et al., 2002). Both SWNT and MWNT can improve the thermal stability and thermal conductivity of polymer, the polymer-CNT composites can be used for fabricating resistant-heat materials. 

In the case of 34NBR, the polymer chains have H-bonding interactions with the clay along with van der Waals interactions. These in turn improve the thermal stability of the nanocomposite. 

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. 

By analogy with the works which dealt with cellulose micro crystal-reinforced nanocomposite materials, microcrystals of starch [95] or chitin [96, 97] were used as a reinforcing phase in a polymer matrix. Poly(styrene-co-butyl acrylate) [95,96], poly(e-caprolactone) [96], and natural rubber [97] were reinforced, and again the formation of aggregates or clustering of the fillers within the matrices was considered to account for the improvement in the mechanical properties and thermal stability of the respective composites processed from suspensions in water or suitable organic solvents. 

The impact of the nanocomposite technology on polymers is huge, reflected in enhanced properties of the resulting PNs, such as enhanced mechanical, barrier, solvent-resistant, and ablation properties.12 The effect of nanocomposite technology on the thermal and fire performance of the polymers is primarily observed in two important parameters of the polymers (1) the onset temperature (7( ,nsct) in the thermogravimetric analysis (TGA) curve—representative of the thermal stability of the polymer, and (2) the peak heat release rate (peak HRR) in cone calorimetric analysis (CCA)—a reflection of the combustion behavior (the flammability) of the polymer. The Tonset will be increased and the peak HRR will be reduced for a variety of polymers when nanoscale dispersion of the nanoadditive is achieved in the polymer matrix. 

The impact of nanocomposite technology on flame retardance (the thermal and fire resistance) of the polymers, as mentioned in Section 11.1, is primarily reflected in two important parameters (1) the ronset in the TGA curve—representative of the thermal stability of the polymer and (2) the peak HRR in the curve of CCA—reflection of the combustion behavior (the flammability) of the... 

Although the nanoadditive can enhance both the thermal stability and the fire performance of the matrix polymer, it has been noted that the enhancement on the fire performance is not parallel to that on the thermal stability, i.e an observation about the reduction of the peak HRR of the resulting PN does not necessarily mean that an enhancement of the thermal stability of the PN can be observed. A typical example is PA-6. It has been seen that the PA-6/clay nanocomposite shows a significantly reduced peak HRR,98 but it does not show enhanced thermal stability. 

FIGURE 11.36 (See color insert following page 530.) Mechanism of how crack-free and networked char barrier affects the thermal stability of polymer matrix. (From Gilman, J.F., Flame retardant polymer nanocomposite, http //www.epa.gov/oppt/nano/p2docs/casestudy2 gilman.pdf)... 

Leszczynska, A., Njuguna, J., Pielichowski, K., and Banerjee, J. R. (a) Polymer/montmorillonite nanocomposites with improved thermal properties, Part I Factors influencing thermal stability and mechanisms of thermal stability improvement, Thermochim. Acta (2007), 453, 75-96. (b) Polymer/montmorillonite nanocomposites with improved thermal properties. Part II Thermal stability of montmorillonite nanocomposites based on different polymeric matrixes, Thermochim. Acta (2007), 454, 1-22. 

Yang, F., Bogdanova, I., and Nelson, G. L. Mechanism study on the flammability and thermal stability of polymer/alumina nanocomposites via extrusion, PMSE Preprints (2008), 98, 319-320. 

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