Mechanical properties montmorillonite organically modified clay

The incorporation of unmodified and organically modified montmorillonite nanoclays (namely 15A and 30B) in chlorinated polyethylene (CPE) by the solution intercalation method and their influence on mechanical properties of the nanocomposites have been studied by Kar et al. [137]. The o-MMT-embedded nanocomposites show enhanced tensile strength and Young s modulus in comparison to the nanocomposites containing the unmodified nanoclay. They have shown from and XRD analyses that organically modified clay shows better dispersion in the CPE matrix. This has been further substantiated from FTIR analysis, which proves an interaction between the CPE matrix and the clay intercalates. 

The results are reported of an in depth study of the structure, thermal properties, dynamic mechanical properties, flammability and smoke properties of melt blended PVC-sodium montmorillonite nanocomposites. Investigative properties employed included X-ray diffraction, TEM, TGA, DMA and cone calorimetry. The effects of clay loading, DOP concentration, annealing, blending time and molec.wt. on the formation of the composites are discussed and fire properties of PVC-organically modified clay and PVC-sodium clay nanocomposites are presented and discussed. 15 refs. USA... 

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. 

Various workers have investigated the mechanical and thermal properties of polymers in which organically modified clays and montmorillonites had been incorporated (Table 3.10). In general, it was found that increasing the clay contents of a polymer increased the storage and loss modulus as well as Young s modulus and reduced... 

On the other hand, Bhattacharya et al. have reported the plasticization effect of organically modified layered silicates on dynamic mechanical properties [13]. In this work, nanocomposites of SBR have been prepared using various nanofillers like modified and unmodified montmorillonite, SP, hectorite etc. It has been observed that the Tg shifts to lower temperature in all the nanocomposites, except for systems from hectorite and NA. This is due to the fact that clay layers form capillaries parallel to each other as they become oriented in a particular direction. Due to wall slippage of the unattached polymer through these capillaries, the Tg is lowered, which could be even more in the absence of organo-modifiers [13]. A similar type of plasticization effect is also noted in the case of the low... 

Single clay layers or 100% dispersion of the clay in polymer matrices is also the ideal situation in which to obtain nanocomposite materials with enhanced mechanical properties. This was achieved by researchers at the Pennsylvania State University ° with a semifluorinated organic surfactant to modify the montmorillonite, which is subsequently compounded with polypropylene (functionalized with, e.g., maleic anhydride). In The Netherlands the clay is intercalated with polyethyl-... 

Montmorillonite (MMT), a smectite clay, is probably the most extensively studied nanomaterial in terms of mechanical, thermal, fire retardant or crystallization behavior of polylactide, especially when these nanoparticles are organically modified allowing the achievement of intercalated and exfoliated nanocomposites.These nanocomposites show enhanced properties as compared to microcomposites and pristine polymer. However, biodegradation and hydrolytic degradation of PLA in the presence of nanoclays has been investigated to a small extent. 

The beneficial effects of organically modified montmorillonite clay on the mechanical properties of various polymers are now discussed in further detail. 

In this work, the effect of four types of clay (untreated montmorillonite Na-MMT, Modified MMT Cloisite lOA and Cloisite 30B, and synthetic Laponite-RD) on properties of starch/PVOH nanocomposite films was evaluated. The results show that compatibility and optimum interactions between polymer matrix, organic modifiers (if any) and the sihcate laj er surface are cracial to the formation of intercalated or exfoh-ated nanocomposite structure. Starch and PVOH are more compatible with Na-MMT and LRD than C30B and CIO A. With the increase of clay content, the clay layers are harder to be dispersed using the solution method. In such case, more mechanical... 

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