Temperature Effects on Rheological Properties

Polymer Processing Principles and Design, Second Edition. Donald G. Baird and Dimitris I. Collias. 2014 Jdm WQey Sons, Inc. Published 2014 by John Wiley Sons, Inc. 

FIGURE 5.1 Schematic of a film casting process showing the polymer film being cast onto a rotating drum. 

The value of the reduced variables approach is that given the flow curve at one temperature, we can And the complete flow curve at any other temperature, if we know the ratio of the zero shear viscosities at the two temperatures. 

because Topo/Tp is about unity, this implies that Xy is insensitive to temperature. The horizontal shifting of different Tr(y,ro) curves gives a master curve of Tr(yr,Tb) with the amount of shifting along the shear rate axis at each temperature being ar- 

Another way to estimate ar is through the WLF equation, which has been found to hold for a wide variety of polymers for temperatures between the glasstransition temperature. 

Returning to our definitions in Chapter 3, temperature is a measure of the average kinetic energy of the molecules in a system. This means that the higher the temperature, the more movement in the polymer chains. Taking this one step further, the greater movement reduces 

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A wide range of temperatures are encountered during processing and storage of fluid foods, so that the effect of temperature on rheological properties needs to be documented. The effect of temperature on either apparent viscosity at a specified shear rate (Equation 2.42) or the consistency index, K, of the power law model (Equation 2.43) of a fluid can be described often by the Arrhenius relationship. The effect of temperature on apparent viscosity can be described by the Arrhenius relationship ... 

Varshney, N. N. and Kumbhar, B. K. 1978. Effect of temperature and concentration on rheological properties of pineapple and orange juice. J. Food Sci. Technol. India 15(2) 53-55. 

Table 5-M Effect of Temperature on Rheological Properties of Oils and Fats (Lang et al., 1992)... 

The effect of overall molecular weight or the number of blocks on rheological properties for the samples from the second fractionation can be illustrated as a plot of reduced viscosity vs. a function proportional to the principal molecular relaxation time (Figure 2). This function includes the variables of zero shear viscosity, shear rate, y, and absolute temperature, T, in addition to molecular weight, and allows the data to be expressed as a single master curve (10). All but one of the fractions from the copolymer containing 50% polystyrene fall on this... 

The selection of a heat stabiliser requires consideration of the precise processing operation and its temperature range, the effect of the stabiliser on melt rheology, its compatibility with the polymer formulation as a whole, possible plate-out, and its effects on ultimate properties, cost, and health and safety issues. Several heat stabilisers have been criticised on environmental grounds. 

Kalyan et al. [56] have also studied the effect of alpha-olefin comonomers on the rheological properties and processing of LLDPE. The characteristics of the resins are shown in Table 2. It is found that 1-octene-based LLDPE has the lowest shear viscosity as compared to 1-butene- and 1-hexene-based polymers (Fig. 9). Decrease in power consumption, pressure before the die, temperature in the die, and increase in output has also been found according to shear viscosities of the polymers during tubular film extrusion. 

Optical and electro-optical behavior of side-chain liquid crystalline polymers are described 350-351>. The effect of flexible siloxane spacers on the phase properties and electric field effects were determined. Rheological properties of siloxane containing liquid crystalline side-chain polymers were studied as a function of shear rate and temperature 352). The effect of cooling rate on the alignment of a siloxane based side-chain liquid crystalline copolymer was investigated 353). It was shown that the dielectric relaxation behavior of the polymers varied in a systematic manner with the rate at which the material was cooled from its isotropic phase. 

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