Hydrophobic surface energy

In this relationship. S is alkane solubility, A is the cavity surface area and a is the hydrophobic free energy per unit area. Extensive fitting of this equation [24] yields a value of 88 kJ mol A for the proportionality constant a. This value corresponds to an unfavourable free energy of about 3.6 kJ mol for the transfer of a CH2 group to aqueous solution. 

The surface energy of fibers is closely related to the hydrophilicity of the fiber [38]. Some investigations are concerned with methods to decrease hydrophilicity. The modification, of wood cellulose fibers with stearic acid [43] hydrophobizes those fibers and improves their dispersion in polypropylene. As can be observed in jute-reinforced unsaturated polyester resin composites, treatment with polyvinylacetate increases the mechanical properties [24] and moisture repellency. 

With increasing alcohol concentration non-bulk electrostatic contributions become relevant. Because these non-bulk electrostatic contributions depend on the concentration of the cosolvent as well on the size of the alkyl-group, one can conclude that there is a relation to the smaller free energy necessary for exposing hydrophobic surfaces to the medium. It yields ... 

Extremely low Glass Transition Temperatures —123 °C) Very low Surface Energies (20-21 dynes/cm) Hydrophobicity... 

The surface of silica is covered by a layer of acidic silanol and siloxane groups. This highly polar and hydrophilic character of the filler surface results in a low compatibihty with the rather apolar polymer. Besides, highly attractive forces between silica particles result in strong agglomeration forces. The formation of a hydrophobic shell around the silica particle by the sUica-sUane reaction prevents the formation of a filler-filler network by reduction of the specific surface energy [3]. 

Hydrophobic or Hydrophilic Polymers with Excellent Mechanical Properties and Flexibility, Tunable Surface Energy for Cardiovascular Applications. Blood Compatibility ... 

It is generally believed that energy-independent chaperones are unable to allow refolding of non-native proteins. They bind to hydrophobic surfaces of denatured proteins to prevent aggregation and pass them to energy-dependent chaperones such as the DnaK or the GroE chaperone machines. 

Butylate probably exhibits a negative heat of solution (and hence a postive heat of adsorption) due to the hydroponic effect described by Tanford ( 4). This effect is caused by the disrupted water molecules rearranging themselves into a lower energy state at the hydrophobic surface of the butylate molecule. In addition, there is probably a negative entropy of solution as the water molecules find themselves in a more ordered state at the hydrophobic surface of the butylate molecule (15). The butylate molecule presents a hydrophobic surface from all directions but metolachlor and alachlor do not (Figure 5). 

In contrast, vehicle that are immiscible with water and those with a high proportion of oils have occlusive effects. They reduce both insensible perspiration and the release of sweat. The sweat collects as droplets at the opening of the glands, but does not spread as a film between the hydrophobic skin surface and the hpophific base because the free surface energy of the vehicle-skin interface is smaller than that between water and skin. If a lipophilic layer of vehicle is present, this is not spontaneously replaced by the water-skin layer if sweat is secreted. 

Retardation of the rate of penetration is necessary for many products and this can be brought about by the creation of a low energy, hydrophobic surface at the fibre-water interface which increases the contact angle formed between the drop of liquid and the surface. This important change can be achieved chemically in the process known as sizing which is discussed more fully in Chapter 7. 

The adsorption of fatty acids on the non-polar hydrophobic surface (Hg) is dominated by their hydrophobic properties. The extent of adsorption increases with increasing chain length. The following relationship of the free energy of adsorption, AGacis. and the number of C atoms, nc, of the fatty acids can be established ... 

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