![]() The operator enters the samples identification data, selects the analytical method and starts the analysis that proceeds unattended until all the vials defined in the instrument run queue are analyzed. Samples are put in solid form into 20 mL vials and brought to an autosampler tray with capacity of 42 vials. The proposed method constitutes a precise and convenient approach to intrinsic viscosity measurement, due to the automation of all the analytical procedures, from filling of vials to the reporting of results. The relative viscosity is calculated as a function of time as the injected solution goes through the system, and any influence of flow-rate variations (such as high frequency pump pulsations) or thermal effects are cancelled out directly by the reference capillary, resulting in very high sensitivity and long-term stability.Īn automated technique for Intrinsic Viscosity Analysis It also accounts for differences in tubing dimensions, so in this design, it is not required that the capillaries stay accurately matched. The constant is automatically measured with every injection thus, compensating for small, long-term variations in capillaries (self-calibrating). An instrumental constant is easily measured by flowing pure solvent through the two capillaries. The pressure drop across each capillary is measured continuously as a function of time by high sensitivity differential pressure transducers.Īccording to Equations (1) and (2), the relative viscosity is proportional to the ratio of differential pressures, being independent of the flow rate. The proposed new method performs the polymer intrinsic viscosity measurement by means of a two-capillary relative viscosity detector, concept that was developed and patented by Yau in the 80s (US 4,793,174), as a robust method in contrast to temperature, pressure or solvent flow-rate variations.Ĭapillary viscometers rely on the principle that under a forced flow (Q), the pressure drop (ΔP) due to a fluid traveling along a capillary tubing of length L and radius r, is proportional to the absolute viscosity of the flowing fluid (η), according to Poiseuille’s law:Ī serial viscometer design has been implemented for the new method: two pieces of capillary tubing are connected in series in such a way that the first one experiments the flow of pure solvent while the second one simultaneously receives the flow of the dilute polymer solution. Dissolution temperature and analysis temperature can be set independently, from ambient to 200✬, so that a wide range of polymers, even the most crystalline ones, can be analyzed with convenience and safety with this alternative approach. It is compatible with typically used organic solvents such as decalin, tetralin, tri-chlorobenzene (TCB) and ortho-dichlorobenzene among many others. ![]() ![]() The recently developed technique is an automated process for viscosity measurements of polymeric materials in solution. It must be noted however, that intrinsic viscosity is not a property of the polymer itself, as molar mass is, but rather a property of the polymer solution, influenced by the solvent and temperature. The relative viscosity of a dilute polymer solution to that of the pure solvent itself is measured and, from it, the Intrinsic Viscosity ( IV or ) of the polymer is calculated.ĭue to the popularity of dilute solution viscosity measurements, and the availability of those methods in many manufacturing laboratories, the intrinsic viscosity of polymers has been traditionally used to specify and to control the production grades. The determination of the solution viscosity of polymeric materials is very important to the industry, both to research and manufacturing, since it can be used to estimate the molar mass, providing important information relating to the physical properties of polymers. This new process becomes a practical and convenient alternative to manual or semi-automated methods. The serial capillaries design is self-cleaning and self-calibrating, ensuring reliable and precise data. The technique uses a two-capillary serial viscometer that collects relative viscosity data from which intrinsic viscosity is derived. New research leads to the development of an automated and versatile technique for intrinsic viscosity (or solution viscosity) determination of a wide range of polymers in different solvents, from ambient temperature up to 200✬. Preparative Fractionation Analytical Servicesīy Alberto Ortín, Pilar del Hierro.Intrinsic Viscosity Analytical Services.Bivariate Distribution Analytical Services.Chemical Composition Analytical Services.
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