Rheological behaviour investigations

In a later study [56], the effect of gas volume fraction (foam rheology was investigated. Two models were considered one in which the liquid was confined to the Plateau borders, with thin films of negligible thickness and the second, which involves a finite (strain-dependent) film thickness. For small deformations, no differences were observed in the stress/strain results for the two cases. This was attributed to the film thickness being very much smaller than the cell size. Thus, it was possible to neglect the effect of finite film thickness on stress/strain behaviour, for small strains. 

Figure 3a-b illustrate the LCB effect on the melt rheological properties. The response of the rheological behaviour to the copolymerisation ability and vinyl end group selectivity of the siloxy-substituted metallocenes has been investigated from their dynamic modulus curves. The frequency dependency of the dynamic modulus of the polyethenes produced with catalysts 2 is demonstrated in Fig. 3a. For comparison dynamic modulus for a linear polyethene, prepared by the catalyst -BuCp2ZrCl2, is shown in Fig. 3b. 

Coalescence of mesophase is often said to be determined by the mesophase viscosity. This aspect requires much further investigation. However, it is clear that, amongst other factors, the rheological behaviour (including viscoelastic effects) of each phase is important in mesophase growth and coalescence. Diffusion of molecular species through the isotropic pitch to the mesophase spheres is likely to be related to the viscosity of the isotropic med i urn. 

The influence of addition of sodium bentonite (a commonly used antisettling system) on the rheological behaviour of a pesticide suspension concentrate (250 g dm ) has been investigated. Steady state shear stress-shear rate curves were carried out to obtain the yield value and viscosity as a function of shear rate. The shear modulus was also measured using a pulse shearometer, and the residual viscosity was obtained in afew cases from creep measurements. The rheological parameters Tg (Bingham yield value),... 

The possibility of cofeeding plastic wastes with petroleum cuts such as vacuum gas oil (VGO) [110], Arabian fight petroleum residues [111], light cycle oil [84], lube oils [88] or even raw chemicals such as benzene [85] has been widely investigated in the literature. The underlying aim is to reduce the high viscosity of the molten plastics. However, there is a limit since the maximum amount of plastics in the mixture to achieve a convenient rheological behaviour must be at most within 5-10 wt%. 

In the present investigation it has not been possible to undertake a systematic investigation of all the variables that might affect the viscosity of a glass fibre slurry, but an attempt has been made to identify the more important parameters. Polyol blends as described in a preceding paper in this volume (1) were used. Three specific aspects of rheological behaviour have been investigated. 

Short siloxanediols are important precursors in a wide variety of industrial products. They can be considered also as the monomeric representatives of a series of polymeric compounds which exhibit unique and highly desirable features such as specific rheological behaviour or thermal and chemical resistance. However, despite the broad knowledge about their physical and material properties, only limited information is available on the photoluminescence behaviour of these classes of compounds [1-6], In order to obtain a basic understanding of the influence of methyl and phenyl substituents on the photoluminescence of siloxanes, several siloxanediols have been prepared and investigated. 

The investigation of the rheological behaviour of chitosan solutions has been carried out by studying the influence of different parameters such as chemical con5)osition, concentration, ionic strength, pH and the effect of the type of acid [54, 80-85]. Furthermore, the role of hydrophobic association phenomena on the viscoelastic behaviour of chitosan solutions is an interesting feature [86] which requires further understanding. 

The processability of the homopolymer blends depends, of course, on the rheological behaviour of the two components and their compatibility. The torque recorded at the end of mixing, when steady-state conditions are attained, is a good parameter to evaluate processability, see Fig. 11, [4]. In the investigated case, the processability of the pipe grade PVC decreases by adding recycled PVC. Both the recycled PVC... 

Cowman et al. [43] investigated the effect of temperature in the range of 25-65 °C on the dynamic rheological behaviour of salt-containing aqueous solution of hyaluronan, Hylan A (cross-linked HA) and a mixture of hylans (known under the trade name Synvisc ). The increase in temperature substantially reduces the modulus and complex viscosity for all three samples. 

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