Gelatin effect

Nathan et al(Ref 1) examined a number of carbamic acid esters and concluded that the best stabilizing action on NC is obtd with compds in which at least one H atom is replaced by an aryl radical. Davis(Refs 2 5) examined several comps for their gelatinizing effect on NC Refs 1)F.L.Nathan et ai, BritP 12743(1912) CA 7, 3842(1913) 2)T.L.Davis, IEC 14, 1140 (1922) 3)Franklin(1935), lllff 4)Sidgewick, OrgChem of N(1937), 272 5)Davis(1943), 322... 

Pure tetranitrodiglycerol is a very viscous oil, which is non-hygro-scopic, insoluble in water, and readily soluble in alcohol and ether. It has a lower explosive power than nitroglycerine, is less sensitive to impact, and its gelatinizing effect on nitrocellulose is not as satisfactory. 

Figure 8. DSC signal of starch gelatinization effect of the moisture (modified from [9])...

The swelling of gels is markedly affected by the presence of electrolytes, this effect being a minimum at the isoelectric point of the material. In general, sulphates, tartrates, etc. inhibit swelling, while iodides and thiocyanates promote the swelling. Thus gelatine disperses completely in iodide solution even at low temperatures. 

Thixotropy and Other Time Effects. In addition to the nonideal behavior described, many fluids exhibit time-dependent effects. Some fluids increase in viscosity (rheopexy) or decrease in viscosity (thixotropy) with time when sheared at a constant shear rate. These effects can occur in fluids with or without yield values. Rheopexy is a rare phenomenon, but thixotropic fluids are common. Examples of thixotropic materials are starch pastes, gelatin, mayoimaise, drilling muds, and latex paints. The thixotropic effect is shown in Figure 5, where the curves are for a specimen exposed first to increasing and then to decreasing shear rates. Because of the decrease in viscosity with time as weU as shear rate, the up-and-down flow curves do not superimpose. Instead, they form a hysteresis loop, often called a thixotropic loop. Because flow curves for thixotropic or rheopectic Hquids depend on the shear history of the sample, different curves for the same material can be obtained, depending on the experimental procedure. 

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