Nanocomposite melt compounding

The morphology of rubber-based nanocomposites also seems to change in the presence of compounding ingredients [89, 90]. HNBR, when melt-compounded with organo-modified sodium montmorillonite clays (o-MMTs) prior to sulfur curing, resulted in the formation of nanocomposites with exfoliated or intercalated structures. In stark contrast, under similar conditions HNBR compounded with unmodified sodium montmorillonite clays (NA) formed microcomposites [90]. This was traced to its reactivity with the sulfur in the presence of amine-type organomodifiers. 

Melt processing is a common alternative that is particularly useful for dealing with thermoplastic polymers and holds great interest because of the ease with which the process could be scaled up to industrial standards. Thermoplastic polyurethane nanocomposites can be fabricated by melt compounding of CNTs with polymer resin. Melt processing makes use of the fact that thermoplastic polymers soften when heated. Amorphous polymers like elastomer... 

MWCNT > pure MWCNTs. Wu et al. (74) have molded PCL/ PLA-MWCNT ternary composites using melt-compounding and injection-moldingwith both carboxylic-acid-functionalized and non-function-alized MWCNTs. Although no discussion was presented related to dispersion of MWCNTs, it was observed that the carboxylic-acid-functionalized MWCNTs-filled nanocomposites showed better properties compared with non-functionalized ones. 

Wu and Liao (75) also used melt-compounding to process PLA-MWCNT nanocomposites similar to other studies listed above ... 

Intercalated and partially exfoliated PVC-clay nanocomposites were produced by melt blending in the presence and absence of DOP and characterised by X-ray diffraction and transmission electron microscopy. The effects of various factors, including volume fraction of clay, plasticiser content, melt compounding time and annealing, on nanocomposite structure and the thermal and mechanical properties of the nanocomposites were also examined. It was found that the best mechanical properties were achieved at 2% clay loading and 5 to 10% DOP loading. 18 refs. 

Polymer clay nanocomposites have, for some time now, been the subject of extensive research into improving the properties of various matrices and clay types. It has been shown repeatedly that with the addition of organically modified clay to a polymer matrix, either in-situ (1) or by melt compounding (2), exfoliation of the clay platelets leads to vast improvements in fire retardation (2), gas barrier (4) and mechanical properties (5, 6) of nanocomposite materials, without significant increases in density or brittleness (7). There have been some studies on the effect of clay modification and melt processing conditions on the exfoliation in these nanocomposites as well as various studies focusing on their crystallisation behaviour (7-10). Polyamide-6 (PA-6)/montmorillonite (MMT) nanocomposites are the most widely studied polymer/clay system, however a systematic study relating the structure of the clay modification cation to the properties of the composite has yet to be reported. 

L. Incamato, P. Scarfato, G. M. Russo, L. Di Maio, P. lannelli, and D. Aciemo. Preparation and characterization of new melt compounded copolyamide nanocomposites. Polymer, 44(16) 4625-4634, July 2003. 

Mohanty, S., and Nayak, S. K., Effect of clay exfoliation and organic modification on morphological, dynamic mechanical, and thermal behaviour of melt-compounded polyamide-6 nanocomposites, Polym. Compos., 28, 153-162 (2007). 

EPDM-based nanocomposites were melt-compounded with MMT preintercalated with MA that compatibilized the system and accelerated curing [Liu et al., 2006]. The CPNC comprising < 10 wt% MMT was exfoliated. The mechanical properties were measured under steady state and dynamic conditions (at 3°C/min and 10 Hz). Figure 16.27 displays the relative moduli versus clay content. Manifestly, there is a significant difference between Er and. The absolute values of E range from 1.9 to 2.4 MPa, while those of E from 1 to 3.9 MPa reversed difference was reported by Mishra et al. [2005] for TPO-based PNC. There E ranged from 13.2 to 22.6 MPa, in comparison to E which varied from 47 to 137 MPa. 

Incamato, L., Scarfato, R, Scatteia, L., and Aciemo, D., Rheological behavior of new melt compounded copolyamide nanocomposites. Polymer, 45, 3487-3496 (2004). 

Lee, S. H., Cho, E., and Youn, J. R., Rheological behavior of polypropylene/layered silicate nanocomposites prepared by melt compounding in shear and elongational flows, J. Appl. Polym. Sci, 103, 3506-3515 (2006). 

Wang, Y., Chen, F. -B., Wu, K. -C., and Wang, J. -C., Shear rheology and melt compounding of compatibilized-polypropylene nanocomposites effect of compatibilizer molecular weight, Polym. Eng. ScL, 46, 289-302 (2006a). 

Najafl, N., Heuzey, M.C., Carreau, P.J. Polylactide (PLA)-clay nanocomposites prepared by melt compounding in the presence of a chain extender. Compos. Sci. Technol 72(5), 608-615 (2012)... 

Pluta [49] studied the structure and properties of PLA/MMT nanocomposites and showed an effective enhancement of MMT dispersion with prolongation of the blending time (from 6 to 30 min). They stressed that this was possible due to strong interaction between PLA-MMT and shearing forces during melt compounding. The nanostructure was induced by the intercalation followed by tactoids formation and exfoliation of MMT, as confirmed by TEM analysis and XRD. The studies performed also clearly revealed the influence of MMT s dispersion in the PLA matrix on the physical properties of the nanocomposites formed as the improved MMT s dispersion (at their constant concentration) had increased the thermal stability of the nanocomposites under oxidative and nonoxidative conditions was improved with MMT s dispersion. Besides that, the crystallization ability of PLA also improved with incorporation of MMT. 

Pluta, M. Melt compounding of polylactide/organoclay Structure and properties of nanocomposites. J. Polym. Sci., Part B Polym. Phys. 44, 3392-3405 (2006)... 

As the hydrophilic clay is incompatible with polypropylene, compatibilization between the clay and PP is necessary to form stable PP nanocomposites. There are two ways to compatibilize the clay and PP. In the first approach, the enthalpy of the interaction between the surfactant and the clay is reduced. In the second approach, a compatibilizer, such as maleic anhydride grafted PP (PPgMA) can be used( Manias et al.,2001). The clay is melt compounded with the more polar compatibilizer to form an intercalated master batch. The master batch is then compounded with the neat PP to form the PP nanocomposite. 

Polymer nanocomposites are generally prepared by three methods solution intercalation, in-situ polymerisation or melt compounding. 

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