Characterization by Dynamic Mechanical Thermal Analysis

It has been found that the interaction of intercalated and/or exfoliated nanoparticles may restrict the mobility of the matrix polymer chains, which lead to an increase of Tg values, as observed in nanocomposites of polyamide-12-layered silicates [102], nitrile rubber-organophilic montmorillonite [103], natural rubber-montmorillonite [104], and EVA-day [105]. A slight increase with the organosurface treatment in Tg values was noticed in poly(vinyl chloride)-clay [106,107], poly(vinyl chloride)-CNTs [108], polyurethane-montmorillonite [109-111], LLDPE-layered tetrasilisic fluoromica [112], PP-montmorillonite [113-115], PP-sUica [116], and styrene-butadiene rubber [117]. 

The increased interaction between polymer and nanopartides can also be extracted from the enhanced values of the storage modulus, as observed in PP-carbon nanofibers (Table 5.3) [118], PS-montmorillonite [119], PLA-montmorillon-ite [120,121], PA6-montmorillonite [122], LDPE-ethylene-octene-montmorillonite [123], HDPE-montmorillonite [124], PP-montmorillonite [125], and PBT-montmo-rillonite [126]. 

Nevertheless, in other cases, a plastidzing effect of the nanopartides has been reported, which leads to a decrease in both the values of Tg and the storage modulus. Artzi et al. [127] reported in EVOH-montmorillonite nanocomposites a decrease of Tg values from 5 wt% of day. The same authors predict two opposing effects on the transition the confined chain mobility owing to interaction buildup, and an increased mobility due to reduction in the crystallinity degree as a consequence of polymer-clay interaction [128]. The addition of a compatibilizer, either maleic anhydride-grafted ethylene-vinyl acetate (EVA-g-MA) or maleic anhydride-grafted linear low-density polyethylene (LLDPE-g-MA), led to a decrease in the Tg values [129]. This 5wt% day content maximum is also described by McAdam et cd. in PA6-day nanocomposites [130]. 

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