Montmorillonite Cloisite

The addition of plasticizer used for the improvement of mechanical properties leads generally to an increase in the oxygen permeability coefficient due to the higher mobility of the polymer chain and higher free volume [102]. On the contrary, the dispersion of nanoclays in PLA makes it possible to divide the permeability coefficient by 2 or 3 depending upon the type of the nanoclays (e.g. organomodified montmorillonite, cloisite 25A or 30B, organomodified synthetic fluorine mica) and exfoliation [129-131]. 

Reddy and Das made a silica-supported zirconocene catalyst in situ, by subliming ZrCl4 onto a high surface area silica, then adding NaCp. This catalyst was combined with an organically modified montmorillonite (Cloisite 20A), mixed with additional MAO (Al/Zr = 500). Propylene polymerization was conducted in the gas phase, at 8 bar and 70°C. Despite the absence of an obvious mechanism for interaction between the catalyst with the clay, or the presence of a solvent to swell the clay, the composite material was claimed to contain delaminated clay on the basis of decreased basal peak intensity in the XRD. The polypropylenes showed low melting points (132°C-134°C) consistent with large amorphous fractions. 

Two types of MMT-sodium montmorillonite (Cloisite Na, Southern Clay) and an organomodified montmorillonite (Cloisite 30B) -were used to prepare MMT-PFA nanocomposites, denoted as NaMMT-PFA and 30BMMT-PFA, respectively. 

Epoxy + MMTl Bis(2-hydroxyethyl)ammonium montmorillonite (Cloisite 30B) 4.0... 

Figure 15.3 PLA and nanocomposites based on montmorillonites (CLOISITE 30B and NANOFIL 804) before degradation (0 weeks) and after 3 and 4 weeks of degradation in compost at 40°C.

The XRD analysis of sodium montmorillonite (Cloisite Na shows that the interlayer spacing remains unchanged, that is to say that a microcomposite is formed rather than a nanocomposite. This structure has been confirmed by TEM where a clear microphase separation is observed. The properties of such a composite (filled with 3 wt% inorganics) remain in the same range as traditional microcomposites and very similar to the properties of the PCL matrix alone, as it will be shown further on. 

Similarly to PCL layered silicate nanocomposites, melt intercalation of plasticized PLA with a constant amount of nanoclays (3 wt%) leads to an intercalated nanostructure , even for the unmodified natural montmorillonite (Cloisite Na. This particularity can be explained by the sole intercalation of the plasticizer (PEG chains) into the interlayer spacing of the filler, leading to an increase of the interlayer distance from 1.21 to 1.77 nm, as already observed for simple blends of natural montmorillonite with PEG alone. Selective PEG intercalation was further confirmed by the impossibility to form a nanocomposite by melt blending (non plasticized) PLA with Cloisite Na, only microcomposites could be recovered. XRD analysis performed on organoclay based blends (Figure 8) does not allow... 

The role of the hydrophobic surface on the organomontmorillonite was evaluated by utilizing different quats that were ion exchanged onto the surface of the montmorillonite. Bis(2-hydroxy-ethyl)methyl tallow quaternary ammonium-exchanged montmorillonite (Cloisite 30B) would probably be considered to be the most hydrophilic organomontmorillonite. 

A superior strategy to the above approach is provided by Cui and Paul [18]. The quality of this work is enhanced by the full description of the polymers that were utilized and the complete characterization of the composites that were prepared. The PP that was employed in this study was Pro-Fax PH020 manufactured by Basell. MAPP (PP-g-MA) was PB3200 provided by Cromption with a MA content of 1.0 wt.%. The diamine and montmorillonite (Cloisite Na) were identical to the ones utilized in the above study. Cloisite 20A was utilized as a control organomontmorillonite. This is a superior choice to the organomontmorillonite employed in the studies above. The composites were prepared with a DSM Micro 5 compounder. The test samples were prepared with a DSM microinjection molder. This is a superior protocol in relation to the compression-molded test samples prepared above. PP-g-MA was reacted directly with the diamine in a Brabender at 195°C and 50 r/min for 5.5 min. The amine... 

Table 17.1 Thermal transitions determined by DSC of montmorillonite (Cloisite 20A, Cloisite 30B), silica (Aerosil R972) and hydroxyapatite /PDMS nanocomposites.

The color stability of silicone elastomer as well as of those loaded with montmorillonite (Cloisite SOB) and silica (Aerosil R972) nanoparticles can be seen in Table 17.9, in terms of the parameters determined by Lab chromato-metry. A total color change (AE) value of two units was assumed as the minimum significant color change that... 

PVC (K value 66.4) used in this study was donated by Shintech Inc. Other additives used in the manufacture of the nanocomposites are listed in Table 1. Montmorillonite clay supplied by Southern Clay Products (Texas, USA) was used as nanoparticles. The cation-exchange capacity of the non-modified sodium montmorillonite (Cloisite Na ) was 92.6 meq/lOOg clay. 

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