Viscosity temperature behaviour

Figure 2.6. The viscosity/temperature behaviour of two polysaccharides showing the order-disorder transition at T. This transition is much clearer for the heteropolysaccharide (from Ash et al, 1983).

Fig. 4.8 Temperature dependence of the dielectric characteristic times obtained for PB for the a-relaxation (empty triangle) for the r -relaxation (empty diamond), and for the contribution of the -relaxation modified by the presence of the a-relaxation (filled diamond). They have been obtained assuming the a- and -processes as statistically independent. The Arrhenius law shows the extrapolation of the temperature behaviour of the -relaxation. The solid line through points shows the temperature behaviour of the time-scale associated to the viscosity. The dotted line corresponds to the temperature dependence of the characteristic timescale for the main peak. (Reprinted with permission from [133]. Copyright 1996 The American Physical Society)...

Analysis of the results threw into relief a number of feedback loops governing the behaviour of these bearings. The viscosity-temperature relationship was found to be the most powerful transfer function. The value of friction was found to be in accord with narrow-bearing theory and good correlations were found between friction and effective viscosity based on either the mean outlet temperature or the load-line bush temperature. 

There has been a great interest in this area of application for PUR adhesives. They are currently been used for textile coating and some products have been developed for bonding very soft low-surface-energy materials such as Teflon, and PUR films for active-wear applications. The main characteristics that make PUR suitable for textile coating are its low viscosity Newtonian behaviour that allows rapid machining at low temperature, great hydrolysis resistance for fabrics to be washed several times and contain reactive flame retardants. 

Reprinted with permission from C Alonso and J A. Zasadzinski, A brief review of the relationships between monolayer viscosity, phase behaviour, surface pressure and temperature using a simple monolayer viscometer, 7- Phys. Chem. B, 110, 22185-22191. Copyright 2006 American Chemical Society. 

Figure 10.23 Thermomechanical analysis (TMA) parallel-plate viscometry is used to investigate the behaviour of the oxyfluoride glass 32Si02-9AIOi.5-31.5CdF2-18.5PbF2-5.5ZnF2-3.5ErF3 (mol %) in which nanocrystals are homogeneously nucleated above Tg [39]. Description of the viscosity-temperature curves may be found in Section 10.5.6.

All gases and most liquids of simple molecular structure exhibit what is termed Newtonian behaviour, and their viscosities are independent of the way in which they are flowing. Temperature may, however, exert a strong influence on viscosity which, for highly viscous liquids, will show a rapid decrease as the temperature is increased. Gases, show the reverse tendency, however, with viscosity rising with increasing temperature, and also with increase of pressure. 

H. U. Khan, J. Handoo, K. M. Agrawal, and G. C. Joshi. Determination of wax separation temperature of crude oils from their viscosity behaviour. Erdol Erdgas Kohle, 107(l) 21-22, January 1991. 

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