Molecular weight temperature

Molecular weight, temperature, and pressure have little effect on elasticity the main controlling factor is MWD. Practical elasticity phenomena often exhibit little concern for the actual values of the modulus and viscosity. Although MW and temperature influence the modulus only slightly, these parameters have a great effect on viscosity and thus can alter the balance of a process. 

In order to minimize confusion, only the curves representing the smoothed results are shown for squalene-benzene, polyisoprene-ben-zene, and rubber-benzene. Calorimetric methods were applied to those polymers of comparatively low molecular weight temperature coefficients of the activity were used for the rubber-benzene mixtures. The ratio of the heat of dilution to the square of the volume fraction t 2, which is plotted against in Fig. 112, should be independent of the concentration according to the treatment of interactions... 

Figure 1.3 Diagram representing the relation between molecular weight, temperature and...

Thus, one may conclude that, in the region of comparatively low frequencies, the schematic representation of the macromolecule by a subchain, taking into account intramolecular friction, the volume effects, and the hydrodynamic interaction, make it possible to explain the dependence of the viscoelastic behaviour of dilute polymer solutions on the molecular weight, temperature, and frequency. At low frequencies, the description becomes universal. In order to describe the frequency dependence of the dynamic modulus at higher frequencies, internal relaxation process has to be considered as was shown in Section 6.2.4. 

For a given polymer in a given solvent the sedimentation coefficient is dependent on polymer concentration, molecular weight, temperature and pressure. 

Extensional viscosity is obviously dependent on average molecular weight, temperature and rate of extension. Apparently, also the tensile strain (degree of extension) is important. 

Products Weight, lb Molecular weight Temperature correction Volume at 600° F, ft3... 

In conclusion, the deformation behavior of poly(hexamethylene sebacate), HMS, can be altered from ductile to brittle by variation of crystallization conditions without significant variation of percent crystallinity. Banded and nonbanded spherulitic morphology samples crystallized at 52°C and 60°C fail at a strain of 0.01 in./in. whereas ice-water-quenched HMS does not fail at a strain of 1.40 in./in. The change in deformation behavior is attributed primarily to an increased population of tie molecules and/or tie fibrils with decreasing crystallization temperature which is related to variation of lamellar and spherulitic dimensions. This ductile-brittle transformation is not caused by volume or enthalpy relaxation as reported for glassy amorphous polymers. Nor is a series of molecular weights, temperatures, strain rates, etc. required to observe this transition. Also, the quenched HMS is transformed from the normal creamy white opaque appearance of HMS to a translucent appearance after deformation. 

It was, however, observed that such systems under appropriate conditions of concentration, solvent, molecular weight, temperature, etc. form a liquid crystalline solution. Perhaps a little digression is in order here to say a few words about liquid crystals. A liquid crystal has a structure intermediate between a three-dimensionally ordered crystal and a disordered isotropic liquid. There are two main classes of liquid crystals lyotropic and thermotropic. Lyotropic liquid crystals are obtained from low viscosity polymer solutions in a critical concentration range while thermotropic liquid crystals are obtained from polymer melts where a low viscosity phase forms over a certain temperature range. Aromatic polyamides and aramid type fibers are lyotropic liquid crystal polymers. These polymers have a melting point that is high and close to their decomposition temperature. One must therefore spin these from a solution in an appropriate solvent such as sulfuric acid. Aromatic polyesters, on the other hand, are thermotropic liquid crystal polymers. These can be injection molded, extruded or melt spun. 

Using the expression DP = p/(fc,r[M] + kt) and molecular weight-temperature data, the authors derive activation energies (A.E.) for propagation and transfer ... 

Nakayasc, H., and T. G Fox Molecular weight-temperature-concentration relationship for the viscosity of poly(vinyl acetate) and its dieth5rl phthalate solutions. Abstr. 137 th ACS, p. ll-I, Cleveland, Ohio (Apr. 1960). 

Variables such as molecular weight, temperature and composition of the two component materials have been shown to be important in understanding the phase behavior present in these systems (1.). 

The adsorption of polymeric surfactants is more complex, since in this case the process is irreversible and produces a high-affinity isotherm with a steep rise in the adsorption value at low polymer concentrations (in this region most of the molecules are completely adsorbed). Subsequently, the adsorbed amount remains virtually constant, giving a plateau value that depends on the molecular weight, temperature and solvency of the medium for the chains (this topic was discussed in detail in Chapter 6). 

Molecular weight, temperature, and pressure have little effect on elastic-... 

Both equations (9-157) and (9-159) give the Staudinger index as a function of the molecular weight. It has been shown experimentally that equation (9-156) is valid over a wider range of molecular weights, temperature, and solvents than equation (9-159). Equation (9-159) is fulfilled satisfactorily, but at higher molecular weights it yields values of that... 

In general, a miscible blend of two polymers is likely to have properties somewhere between those of the two unblended polymers. The relative miscibility of polymers controls their phase behavior, which is of crucial importance for final properties. Polymer-polymer miscibility depends on a variety of independent variables, viz., composition, molecular weight, temperature, pressure, etc. 

The above described technique seems to be prospective for fabrication of polymer based optical devices. The method is simple, free of disadvantages of conventional techniques. It gives highly reproducible results and is suitable for production of high-quality pol)nner waveguides. However, it should be noted, that the response to external electric field is not the same for different pol)nners. Apparently the quality and the shape of the structures created by the effect of the external electric field depend on the polymer type, its molecular weight, temperature of flow, molecular structure ect. Therefore the conditions of pattern preparation must be optimalized for each particular case. 

Miscibility of polymer blends is relatively rare, and is usually limited to a narrow range of independent variables, such as composition of a copolymer, molecular weight, temperature, pressure, and so on [185]. The miscible blends are mainly of academic interest - the information obtained is useful for designing compatibilizers. Exceptions are blends of poly(vinylidene fluoride) (PVDF) with acrylic or polyimide (e.g., PMMA), which are characterized by outstanding UV stability and are used for... 

Solving all the expressions numerically for a specific bulk polymerization gives the profiles of conversion, molecular weight, temperature, and pressure characterizing the progress of the reaction in the extruder. 

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