Nanofillers polymer crystallization, effects

However, when compared with pure copolymer, the highly stretched nanocomposite exhibited a higher amount of unoriented crystals, a lower degree of crystal orientation, and a higher amount of 7-crystals. This behavior indicated that polymer crystals in the filled nanocomposite experienced a reduced load, suggesting an effective load transfer from the matrix to MCNF. At elevated temperatures, the presence of MCNF resulted in a thermally stable physically cross-linked network, which facilitated strain-induced crystallization and led to a remarkable improvement in the mechanical properties. For example, the toughness of the 10 wt% nanocomposite was found to increase by a factor of 150 times at 55°C. Although nanofillers... 

Effects of One-Dimensional Nanofillers Like layered-inorganic fillers, carbon nanotubes influence polymer crystallization when incorporated as filler in the polymer matrix however, these effects do not have as wide a variety as the layered silicates discussed above. In the vast majority of reports, carbon nanotubes act simply as heterogeneous nucleating agents in crystallizable polymer... 

Bhattacharyya, A Sreekumar, T. liu, T. Kumar, S. Ericson, L. Hauge, H. Smalley, R. (2003) Crystallization and Orientation Studies in Polypropylene/Single Wall Carbon Nanotube Composite. Polym. Vol.44, N0.8, pp.2373-2377, ISSN 0032-3861 Bilotti, E. Fischer, H. Peijs, T. (2008) Polymer nanocomposites based on needle-like sepiolite clays Effect of functionalized polymers on the dispersion of nanofiller, crystallinity, and mechanical properties, f. Appl. Polym. Sci. Vol.107, No.2 pp.lll6-1123, ISSN 0021-8995... 

For the comprehension of mechanisms involved in the appearance of novel properties in polymer-embedded metal nanostructures, their characterization represents the fundamental starting point. The microstructural characterization of nanofillers and nanocomposite materials is performed mainly by transmission electron microscopy (TEM), large-angle X-ray diffraction (XRD), and optical spectroscopy (UV-vis). These three techniques are very effective to determine particle morphology, crystal structure, composition, and grain size (48). 

Lee S, Hong J-Y, Jang J (2003) The effect of graphene nanofiller on the crystallization behavior and mechanical properties of poly(vinyl alcohol). Polym Int 62 901-908 Lele A, Mackley M, Galgali G, Ramesh C (2002) In situ rheo-x-ray investigation of flow-induced orientation in layered silicate-syndiotactic polypropylene nanocomposite melt. J Rheol 46 1091-1110... 

We will consider these groups one after the other and systematically try to understand the processes of crystallization as it concerns each group. To simplify these processes, we will consider first, the system of neat blends (i.e., without the deliberate addition of nanoparticles). The nanoparticles will be considered as one of the heterogeneities inside the blend. However, we should remember that the effect of the nanoparticles will depend greatly on the localization of the nanoparticles. In such ternary blends, preferential localization of the third component could be in either of the two polymers [21,22], which eventually affects the crystallization behavior. The preferential localization is driven by factors such as (i) thermodynamic (enthalpic interaction between each polymer and the third material) and/or (ii) kinetic factors (e.g., viscosity ratios of the two polymers) [36]. Wu et al. [22] reported the effect of localization of nanofillers, clay, and CNTs, on the morphology and crystallization of PLA/polycapro-lactone (PCL) blends. 

The presence of nanomaterial influences the crystaltization process as it acts as additional heterogeneity creating more interfaces [29]. In some cases, the presence of a nanofiller alters the crystaltization temperature and thus the thermal properties. In the dispersed phase, the presence of nanoparticles increases the occurrence of fractionated crystaltization [17,23,27,29,53-55,61-63,93-95]. Also, the extent of compatibilization effect from the nanomaterial can alter the whole process of crystaltization in the polymer blend. When a nanofiller is organically modified, using compounds with a similar chemical structure to one or both polymers present in the blend, the influence of the nanofillers here on the crystallization behavior is complex. This is because several factors have to be taken in consideration, such as the nucleating effect of the matrix on the dispersed phase or vice-versa, the nucleating effect of the nanofiller compatibitizer on both phases. There are reported cases where modified nanofillers have impeded the crystaltization process and thus retarded crystaltization in the overall material. 

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