2. Experimental section
2.1. Materials
A commercial grade of polystyrene supplied by Tabriz Petrochemical Co. (GPPS grade 1460), and poly(vinyl methyl ether), Lutonal M40, supplied by BASF Co., were used in this study. The basic characteristics of the used polymers are listed shown in Table 1. The CetylTrimethyl Ammonium Bromide (CTAB) supplied by Merck, was employed as a coupling agent[34] to confer a hydrophobic nature to nanowhiskers. CATB was used as received.
2.2. Nanowhisker extraction
To prepare cellulose nanowhiskers (CNWs) suspensions in water, we used the method described by Revol et al.[36]. Cotton linters were hydrolyzed with 64 wt% sulfuric acid during 45 min at 45 °C. The suspensions were washed by repeated centrifugations and…show more content… Surface treatment functionalization of CNWs
The CTAB coupling agent was used to change the characteristic of CNWs from hydrophilic to hydrophobic. In order to change the surface character of CNWs from hydrophilic to hydrophobic, the CTAB coupling agent was employed. Hydrophobization treatment occurs by electrostatic adsorption of ammonium groups of CTAB to sulfonate functional groups on the surface of nanowhiskers. The reaction between a CTAB molecule and a CNW is shown schematically in Figure 1. The equivalent amount of CTAB with respect to the sulfonate groups on the surface of nanowhiskers was added dropwise over a period of 90 min to the CNWs suspensionwhile stirring at room temperature. After hydrophobization, the nanoparticles were sedimented in water media. Modified (hydrophobic) nanowhiskers (M-CNWs) were washed several times with acetone and then finally dispersed in acetone.
Fig. 1.Schematic of nanowhisker’s illustration for surface functionalization of nanowhiskers. Electrostatic adsorption of cetyl tri methyl ammoniumbromide (CTAB) to (sulfonated) cellulose nanoparticle.
2.4.Sample. Sample preparation
PS/PVME 15/85 blends with and without…show more content… Optical Microscopy (OM): The phase contrast optical microscopy (Leica DMRX) was used to investigate the morphological changes at different quench depths. Samples were placed in a hot stage sample holder (Linkam LTS350) which was controlled by the hot stage controller (Linkam CI94). Fresh nitrogen gas was circulated in the heating chamber of OM to avoid any possible thermal degradation. A CCD camera mounted directly on the microscope was used to record the evolution of the blends structure in real time.
2.5.4. Surface tension measurement: The surface free energy of nanowhiskers was determined using a Kruss G10 contact angle meter in a thermo stated cell (25 °C) interfaced to image capturing software. Double distilled water (H2O) and n-hexane (C6H14) were used to form a sessile drop at the end of a blunt ended needle to place it on the polymer surface. The Owens-Wendt method was applied to calculate the total surface free energy (γ), as well as its dispersive (γd) and polar (γp) components [40, 41].
2.5.5. Transmission Electron Microscopy