Polyamide-12 , surface energies

While polymeric surfaces with relatively high surface energies (e.g. polyimides, ABS, polycarbonate, polyamides) can be adhered to readily without surface treatment, low surface energy polymers such as olefins, silicones, and fluoropolymers require surface treatments to increase the surface energy. Various oxidation techniques (such as flame, corona, plasma treatment, or chromic acid etching) allow strong bonds to be obtained to such polymers. 

In the case of polymer/clay nanocomposites, alkylammonium exchange species influence the affinity between the polymer and the clay surface. For example, it was reported that clays treated with dialkyl dimethylammonium halides, in particular with two chains of about 18 carbon atoms, have a surface energy similar to poly(olefins) such as polypropylene (PP) and polyethylene (PE) [27]. Polar polymers as polyamides (PA) have been recommended to get better interactions as reported by Toyota [8]. The alkyl chain length is related with increase in interlayer space required for the intercalation of polymer chains. Because of the nonpolar nature of their chains, they reduce the electrostatic interactions between the silicate layers and lower the surface energy of the layered silicates. As a consequence, an optimal diffusion of the polymer to dissociate the stacked clay layers, that is, an exfoliation process, can be obtained. Despite the compatibility of MMT modified by long alkyl chain quaternary ammonium with hydrophobic polymers (PE and PP), conventional alkylammonium ions show low thermal stability, that is, an onset decomposition temperature is close to 180°C.This poor thermal stability could limit their use in the preparation of PLS with matrices processed at high temperatures such as PA, poly(ethylene terephthalate) (PET), and poly(ether ether ketone) (PEEK) [30]. 

Ansari, D.M. and Price, G.J. (2004) Correlation of mechanical properties of clay filled polyamide mouldings with chromatographically measured surface energies. Polymer, 45 (11), 3663-3670. 

In a similar system, we simulated the effect of the chemical structure of the polymer and the polymer chain density on the liquid crystal orientation [87]. To see the effect on the orientation of the polymer structure, we compared the liquid crystal orientation (out-of-plane tilting and in-plane orientation) on a polyamide surface that had the same surface density as the above-described PMDA-PPD. Even though the polyamide is similar to PMDA-PPD, the adsorption energy of the 8CB molecules is only about 2/3 as high. 

Aqueous solution of acrylamide has been chosen as the grafting system for polyamidic filaments that had been preheated under gamma-rays, in air (35,48). If the filaments were irradiated under nitrogen, grafting occurs on the surface, but if the high energy treatment is carried on in air, the side chains are formed also inside the fiber (61). 

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