Functional polymer composites, parameters

In conjunction with molecular weight sensitive detection systems, SEC can be used for determining various molecular weight parameters, such as molecular size, conformation and branching, as a function of MW. Furthermore, by interfacing SEC with spectrometry, polymer compositional heterogeneity can be determined. 

The use of a continuous GPC viscosity detector in conjunction with a DRI detector permits the quantitative determination of absolute molecular weight distribution in polymers. Furthermore, from this combination one can obtain Mark-Houwink parameters and the bulk intrinsic viscosity of a given polymer with a GPC calibration curve based only on polystyrene standards. Coupling these two detectors with ultraviolet and infrared detectors then will permit the concurrent determination of polymer composition as a function of molecular weight and... 

The conductivity of carbon black/polymer composites is a function of a number of parameters, including ... 

Figure 2.15. Unit cell parameters as function of composition for a polymer mixture (open squares) and for a random copolymer (filled circles) of hexyl- and octylthiophene [72]. (Reproduced from ref 72 by permission of Elsevier Science S.A. Switzerland.)...

Classical polymer solution thermodynamics often did not consider solvent activities or solvent activity coefficients but usually a dimensionless quantity, the so-called Flory-Huggins interaction parameter % is not only a function of temperature (and pressure), as was evident from its foundation, but it is also a function of composition and polymer molecular mass. As pointed out in many papers, it is more precise to call it %-function (what is in principle a residual solvent chemical potential function). Because of its widespread use and its possible sources of mistakes and misinterpretations, the necessary relations must be included here. Starting from Equation [4.4.1b], the difference between the chemical potentials of the solvent in the mixture and in the standard state belongs to the first... 

The effect of polymer-polymer interactions on the miscibility and macroscopic properties of PVC/PMMA, PVC/PS, and PMMA/PS blends were studied and the miscibility of the components was characterized by the Flory-Huggins interaction parameter or by quantities related to it by Fekete et al. (Fekete et al. 2005). The comparison of interaction parameters determined by different methods indicates that PVC and PMMA are nearly miscible, while PS is immiscible either with PMMA or with PVC at all compositions. Hory-Huggins interaction parameters calculated from equihbrium methanol uptake (y jj) are plotted as a function of composition in Fig. 10.24. The negative values obtained for the PVC/PMMA blends hint at complete miscibility, although x,2 depends on composition which indicates limited miscibility. The positive interaction parameters determined for the PVC/PS and PMMA/PS blends suggest immiscibility. 

Parameters affecting the performance of polymer composites containing functional fillers are related to... 

Part I, entitled Polymers and Fillers, contains a general introduction to polymer composites, a review of the parameters affecting mechanical and rheological properties of polymers containing functional fillers and an overview of mixing and compounding equipment along with methods of filler incorporation in molten and liquid polymers. 

The Flory-Huggins equation is one of the simpler models in polymer systems to accurately predict the phase behavior of a real system. In its original version with constant interaction parameters, it cannot even predict the LCST, a common phenomenon in polymer systems. However, its simple form and requirement for less number of parameters make it very suitable for more complex systems. Furthermore, parameters in the Flory-Huggins equation can be made a function of composition or even molecular weight to account for the deviation from experimental data. Thus, the Flory-Huggins model is still very useftil and one of the most frequently used methods for polymer systems. 

Most utility polymeric articles available today contain multiphase polymeric systems comprised of semi-crystalline polymers, copolymers, polymers in solution with low molar mass compounds, physical laminates or blends. The primary aim of using multicomponent systems is to mould the properties available from a single polymer to another set of desirable material properties. The property development process is complex and depends not only on the properties of the polymer(s) and other components but also on the formation process of the system which determines the developed microstmcture, and component interaction after formation. Moreover, the process of polymer composite formation and the stability of the composite is a function of environmental parameters, e.g., temperature, presence of other species etc. The chemical composition and some insight into the microscopic structure of constituents in a polymer composite can be directly obtained using Infrared (IR) spectroscopy. In addition, a variety of instrumental and sampling configurations for spectroscopic measurements combine to make irrfra-red spectroscopy a versatile characterization technique for the analysis of the formation processes of polymeric systems, their local structure and/or dynamics to relate to property development under different environmental conditions. In particular, Fourier transform infrared (FTIR) spectroscopy is a well-established technique to characterize polymers [1, 2]. 

Baltes, T., Garret-Flaudy, F., Freitag, R. (1999). Investigation of the LCST of polyacrylamides as a function of molecular parameters and the solvent composition. Journal of Polymer Science Part A-Polymer Chemistry, 37, 2977-2989. 

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