Antithixotropic behavior

Figure 1-5 Time-Dependent Shear-Thickening (antithixotropic) Behavior of a Cross-linked Waxy Maize Starch Dispersion Heated at 120°C for 30 min. Data of Chamberlain (1996). Note that the decreasing shear curves of the samples had higher stress values than the increasing shear curves.

The Weltman (1943) model has been used to characterize thixotropic (Paredes et al., 1988) behavior and of antithixotropic behavior (da Silva et al., 1997) of foods ... 

Antithixotropic Behavior of Cross-Linked Starch Dispersions... 

The antithixotropic nature of the thermally processed for 8, 15, and 30 min at 120°C cross-linked waxy maize (CWM) starch dispersions was observed clearly in shear cycles 5-min ascending and 5-min descending. The response curves of each sample (Figure 4-22) indicate that each sample became more viscous with shearing, that is, it exhibited time-dependent shear-thickening (antithixotropic) behavior. Further, the antithixotropic behavior was irreversible in that after the shearing was stopped the structure did not return to the structure prior to shearing. 

Tattiyakul and Rao (2000) carefully examined the shearing conditions in studies on starches that reported antithixotropic behavior (Table 4-6). From the data in the table, she suggested that antithixotropic behavior resulted from shear-induced structure formation, that occurred predominantly when the level of shear stress imposed on the sample was less than 120-150 Pa. 

Table 4-7 Shear Stress Range at Which Antithixotropic Behavior of Starch Dispersions was Reported (Tattiyakul, 2000)...

Chamberlain, E. K., Rao, M. A., and Cohen, C. 1998. Shear thinning and antithixotropic behavior of a heated cross-linked waxy maize starch dispersion. Int. J. Food Properties 2 63-77 errata, 2 195-196. 

Cheng, D. C. H., and Evans, F. (1965). Phenomenological characterization of the rheological behavior of inelastic reversible thixotropic and antithixotropic fluid. Br. J. Appl. Phys. 16, 1599-1617. 

The opposite situation is encountered when the viseosity increases as a function of time and shear rate. This behavior, albeit less common, is termed antithixotropic or rheopectic behavior. 

There are several terms that apply to time-dependent behavior. Thixotropic fluids possess a structure that breaks down as a function of time and shear rate. Tlius the viscosity is lowered. A famous example of this reversible phenomenon is the ubiquitous catsup bottle, yielding its contents only after sharp blows. The opposite effect, although rarely observed, is called antithixotropic, or rheopectic behavior, where materials set up as a function of time and shear rate that is, the viscosity increases or the material gels. 

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