Surface energy determination Inverse gas chromatography

1 surface energy determination

1.1 applications
1.2 polymers , coatings
1.3 pharmaceuticals
1.4 fibers
1.5 nanomaterials
1.6 metakaolins
1.7 other

surface energy determination

the main application of igc measure surface energy of solids (fibers, particulates, , films). surface energy defined amount of energy required create unit area of solid surface; analogous surface tension of liquid. also, surface energy can defined excess energy @ surface of material compared bulk. surface energy (γ) directly related thermodynamic work of adhesion (wadh) between 2 materials given following equation:

w


a
d
h



=
2
(

γ

1



γ

2



)

1

/

2




{\displaystyle w_{\mathrm {adh} }=2(\gamma _{1}\gamma _{2})^{1/2}}

where 1 , 2 represent 2 components in composite or blend. when determining if 2 materials adhere common compare work of adhesion work of cohesion, wcoh = 2γ. if work of adhesion greater work of cohesion, 2 materials thermodynamically favored adhere.

surface energies commonly measured contact angle methods. however, these methods ideally designed flat, uniform surfaces. contact angle measurements on powders, typically compressed or adhered substrate can change surface characteristics of powder. alternatively, washburn method can used, has been shown affected column packing, particle size, , pore geometry. igc gas phase technique, not subject above limitations of liquid phase techniques.

to measure solid surface energy igc series of injections using different probe molecules performed @ defined column conditions. possible ascertain both dispersive component of surface energy , acid-base properties via igc. dispersive surface energy, retention volumes series of n-alkane vapors (i.e. decane, nonane, octane, heptanes, etc.) measured. dorris , gray. or schultz methods can used calculate dispersive surface energy. retention volumes polar probes (i.e. toluene, ethyl acetate, acetone, ethanol, acetonitrile, chloroform, dichloromethane, etc.) can used determine acid-base characteristics of solid using either gutmann, or good-van oss theory.

other parameters accessible igc include: heats of sorption [1], adsorption isotherms, energetic heterogeneity profiles, diffusion coefficients, glass transition temperatures [1], hildebrand , hansen solubility parameters, , crosslink densities.

applications

igc experiments have applications on wide range of industries. both surface , bulk properties obtained igc can yield vital information materials ranging pharmaceuticals carbon nanotubes. although surface energy experiments common, there wide range of experimental parameters can controlled in igc, allowing determination of variety of sample parameters. below sections highlight how igc experiments utilized in several industries.

polymers , coatings

igc has been used extensively characterization of polymer films, beads, , powders. instance, igc used study surface properties , interactions amongst components in paint formulations. also, igc has been used investigate degree of crosslinking ethylene propylene rubber using flory–rehner equation [17]. additionally, igc sensitive technique detection , determination of first , second order phase transitions melting , glass transition temperatures of polymers. although other techniques dynamic scanning calorimetry capable of measuring these transition temperatures, igc has capability of glass transition temperatures function of relative humidity.

pharmaceuticals

the increasing sophistication of pharmaceutical materials has necessitated use more sensitive, thermodynamic based techniques materials characterization. these reasons, igc, has seen increased use throughout pharmaceutical industry. applications include polymorph characterization, effect of processing steps milling, , drug-carrier interactions dry powder formulations. in other studies, igc used relate surface energy , acid-base values triboelectric charging , differentiate crystalline , amorphous phases [23].

fibers

surface energy values obtained igc have been used extensively on fibrous materials including textiles, natural fibers, glass fibers, , carbon fibers. of these , other related studies investigating surface energy of fibers focusing on use of these fibers in composites. ultimately, changes in surface energy can related composite performance via works of adhesion , cohesion discussed previously.

nanomaterials

similar fibers, nanomaterials carbon nanotubes, nanoclays, , nanosilicas being used composite reinforcement agents. therefore, surface energy , surface treatment of these materials has been actively studied igc. instance, igc has been used study surface activity of nanosilica, nanohematite, , nanogeoethite. further, igc used characterize surface of received , modified carbon nanotubes.

metakaolins

igc used characterize adsorption surface properties of calcined kaolin (metakaolin) , grinding effect on material.

other

other applications igc include paper-toner adhesion, wood composites, porous materials [3], , food materials.