Effect of sodium dodecyl sulfate on the physical properties of gelatin/multi-walled carbon nanotubes solutions and films

The effect of sodium dodecyl sulfate (SDS) on multi-walled carbon nanotubes (MWCNT) dispersion, was studied. Four gelatin film forming solutions (GFFS) with SDS concentrations of 0, 0.1, 0.6 and 1.1g/100g gelatin, containing 0.1g of MWCNT/100g gelatin, were subjected to dynamic rheology. These GFFS were used for film obtainment, to which mechanical, optical, structural (diffractometry) and thermal (thermogravimetry) analysis were determined. The surfactant effect of SDS, was better at the critical micelle concentration of 1.1g/100g gelatin, causing the best MWCNT dispersion and highest elastic modulus (G’) in GFFS. Both the control and sample 0.1GFFS, at frequencies lower than 5 rad/s, behaved as mainly dilute solutions (G” > G’) at 25°C, while samples 0.6GFFS and 1.1GFFS, displayed physical gel properties (G’ > G”) at the same temperature. At 10°C, all GFFS showed typical viscoelastic gel-like behavior. Thermogravimetry and diffractometry showed re-ordering on gelatin triple helix, when the MWCNT dispersion increased. The SDS critical micellar concentration increased 60.66% the elongation at break of films. The optical photomicrographs showed an improved homogeneous distribution of the MWCNT, as the SDS concentration increased.