The new method performs the polymer intrinsic viscosity measurement by means of a two-capillary relative viscosity detector, which was developed and patented by Yau in the 1980s (1), 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 (âP) from 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:Ībsolute viscosity of fluids is important to many industries and can be measured using a variety of different viscometers. TCB was used for PE and PP samples, while a mixture of phenol and o-DCB was used for PET. Different conditions for other polymers or analysis are indicated in the text below.Ī number of industrial samples of polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) from different manufacturers were analyzed. Standard operating conditions for polyolefins were: dissolution temperature: 140–160 ☌, time: 60–90 min, with gentle shaking under nitrogen atmosphere measurement flow rate: 3 mL/min, solvent: TCB, concentration: 1 mg/mL. The intrinsic viscosity of different polymers was determined using an automated instrument model IVA, Intrinsic Viscosity Analyzer (Polymer Char). Dissolution temperature and analysis temperature were 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 approach. It is compatible with organic solvents typically used such as decalin, tetralin, tri-chlorobenzene (TCB), and ortho-dichlorobenzene (o-DCB) among many others. This article will discuss a recently developed method for viscosity measurements of polymeric materials in solution. It must be noted, however, that IV 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 popularity of dilute solution viscosity measurements and the availability of those methods in many manufacturing laboratories has meant that the IV of polymers has traditionally been used to specify and to control the production grades. The relative viscosity of a dilute polymer solution to that of the pure solvent itself is measured and from that the intrinsic viscosity (IV or ) of the polymer is calculated. Determining the solution viscosity of polymeric materials is very important for the research and manufacturing industries because it can be used to estimate the molar mass to provide important information related to the physical properties of polymers. The dissolution conditions were studied and optimized to reduce thermal and oxidative degradation, which are detrimental to the accuracy of the observed viscosity. This new approach automates sample preparation and injection to the viscometer detector, with benefits in efficiency and safety as well as in analysis precision. Sample preparation is a tedious and error-prone process in viscosity determinations of polymeric materials, especially when elevated temperature or when hazardous solvents are required. This article introduces the development of an automated and versatile technique for solution viscosity determination of a wide range of polymeric materials in different solvents. Alberto Ortín and Pilar del Hierro, Polymer Char, Valencia, Spain
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