IVA: Automated method for solution viscosity in polymeric materials

New research leads to the development of an automated and versatile instrument for solution viscosity determination of a wide range of polymeric materials in different solvents, from ambient temperature up to 200ºC. The Intrinsic Viscosity Analyzer, developed by Polymer Char, uses a two-capillary serial viscometer that collects relative viscosity data from which intrinsic viscosity is derived. The serial capillaries design is self-cleaning and self-calibrating, ensuring reliable and precise data. IVA is a practical and convenient alternative to the manual or semi-automated methods currently available.

The IVA is a precise and convenient approach to IV measurement as a result of the automation of all the analytical procedures, from filling of the vials to the reporting of the results. The only manual work required is putting the samples in solid form in the vials, which are then placed in the instrument’s autosampler. The operator enters the samples identification data, selects the analytical method and starts the analysis that proceeds unattended until all the vials in the queue are analyzed. The rest of the process is all performed under software control: adding the solvent to the vials, programming the dissolution time per vial, injecting each solution and rinsing of the capillary lines. No solvent needs to be handled by the analyst at any time and no vapours are released to the atmosphere because the system is airtight at all times.

The careful design of the heated compartment and transfer lines ensure that no cold spots are found, thus, a wide range of polymers, even the most crystalline ones, can be analyzed with convenience and safety with this instrument.

In order to maintain the polymeric sample integrity along the dissolution and measurement processes, Sample Care protocols have been implemented as part of the method. Those include purging the vial atmosphere with Nitrogen before dissolution starts, and accurately controlling the time they spend at high temperature. The vials remain in an external tray at room temperature until the scheduling software requests their transfer to the dissolution oven. Efficient heat transfer to the vial, together with preheating of the solvent prior to delivery to the vial, help in shortening the time required for dissolution. Oxidative and thermal degradation is thus minimized, ensuring that accurate intrinsic viscosity is measured even for the most challenging ultra-high molar mass materials, or oxidation-prone polymers, such as polypropylene.

As an option, the infrared detector IR4 can also be added to accurately quantify the injected polymer mass, ultimately upgrading the precision and accuracy of the viscosity results of polyolefins and other polymers with significant C-H content.