Dynamic melt rheology

Dynamic Melt Rheology of Polyethylene—lonomer Blends... 

Dynamic melt rheology studies were carried out on PE/EMA and PE/EMA-salt in order to better understand the role of EMA-salt as a compatibilizer in the PE/EMA/PA system. The tlme-ten jerature superposition principle was applicable in all cases for G. Also, G super master curves were constructed for blends of PE/EMA and PE/EMA-salt when the EHA and EMA-salt are derived from the same parent polymer. Superposition of G" was possible for all blends containing EMA in the free acid form, but not for those in the salt form, with the extent of deviation from superposability being a function of EMA-salt concentration. 

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. 

C. M. Ylitalo, J. A. Komfield, G. G. Fuller, and D. S. Pearson, Molecular weight dependence of component dynamics in bidisperse melt rheology, Macromolecules, 24, 749 (1991). 

Polymer silicate nanocomposites offer unique possibilities as model systems to study confined polymers or polymer brushes. The main advantages of these systems are (a) the structure and dynamics of nanoconfined polymer chains can be conveniently probed by conventional analytical techniques (such as scattering, DSC, NMR, dielectric spectroscopy, melt rheology) (b) a wide range of different polymers can be inserted in the interlayer or end-grafted to the silicate... 

FIGURE 1 Size-exclusion chromatography and rheology of various polymers made with the three common commercial catalysts. Above Molecular weight distribution. Below Dynamic melt viscosity versus shear (frequency) at 190 °C. 

ASTM D 4440-01, Standard Test Method for Plastics Dynamic Mechanical Properties Melt Rheology ... 

We conclude this section by drawing attention to various theories considering the dynamics of block copolymer melts rheology of these systems has been considered [340-342], single chain dynamics and selfdiffusion [343, 344], nu-cleation of the ordered phase [61], ordering kinetics [345,346], and dynamics of concentration fluctuations [347]. These topics are not under consideration here, just as other extensions of the theory random copolymer melts [348, 349], multiblock copolymer melts [350] etc. 

Dynamic mechanical properties are measured to evaluate melt rheology of thermoplastics with and without additives which may modify rheological characteristics of these compositions. " Dynamic oscillatory shear rheometers are used for these purposes. Two geometries of test fixtures are used including parallel plates and cone and plate. Instrument use for these measurements must be capable of measuring forces (stress or strain) and frequency. Temperature must be controlled in a broad range and various modes of temperature sweeps should be available. Sample geometry is not specified but it should be suitable for measurement in particular experimental setup. 

Dynamic mechanical and melt rheological properties of sulfonated poly(butylene succinate) ionomers. Polymer, 44, 7165. 

Melt rheology was examined in a Rheometrics dynamic anaiyzer with a 25 mm paraiiei piate attachment in an osciiiatory mode at 1 Hz from 90-150 °C. 

Samples of H-H and H-T PS were also subjected to the measurements of the dynamic shear complex viscosity and dynamic shear moduli at 160° and 190°C (53). At lower shear stress the behavior of the H-T is essentially Newtonian. The departure from the Newtonian behavior occurs above 10 dyn/cm. On the other hand, the behavior of the H-H PS is non-Newtonian even at 160°C. and at low shear stresses of 10 dyn/cm. The melt viscosity of H-H PS decreases more rapidly with stress as does the melt viscosity of the H-T polymer. As temperature and stress is increased, the rheological behavior of the two polymers are the same (as can be seen at 190°C.). The dynamic shear storage modulus reveals also a small but significant difference in the rheological behavior of H-T and H-H PS as the G with u for the H-H PS is smaller than for the H-T polymer. Results from the melt rheology studies also indicate as does solution behavior that the polymer chain in H-H PS is stiffer than is H-T PS (53). 

Rheology. Every process used to convert LLDPE into a finished product involves melting. Therefore, polymer viscosity is a very important resin parameter that must be considered when selecting a resin for use. LLDPE melts in the normal processing range of 150-300°C exhibit non-Newtonian (shear thinning) behavior as their apparent viscosity is reduced when melt-flow speed is increased (82-85). Figure 23 shows a plot of dynamic melt viscosity for LDPE, gas-phase... 

Oommen et al. had studied melt rheological behaviour of the blends between NR and poly(methyl methacrylate) based on the effect of blend ratio, processing conditions and graft copolymer concentration as a function of shear stress and temperature. It was clarified that the viscosity of the blends increased with the increase of the amount of NR. On the other hand, the flow behaviour of the blends was found to be influenced by dynamic vulcanization of the rubber phase. 

The melt-spinning dynamics and rheological properties of nylon 6 have been studied together with eifects of drawing and of swelling and additive incorporation,and the effects of crystallite dimensions on structure and modulus. Crystallinity and crystallite size measurement in both polyamides and polyesters has also been reviewed. ... 

Dealy J.M, Chapman Hall, 1981, 82.95 (The) Theory of Polymer Dynamics, Doi M, Clarendon Press, 1989 (reprint), 25 Thermoplastic melt Rheology and processing, Shenoy A.V Saini D.R, Marcel Dekker, 1996, 175 Viscoelastic properties of polymers (3rd Ed), Ferry J.D, John Whey Inc, 1980, 120... 

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