Центр знаний

The most common approach for measuring viscoelastic properties using a rotational rheometer is to perform small amplitude oscillatory shear (SAOS) testing within the samples linear viscoelastic region (LVER). An alternative approach for obtaining time dependent viscoelastic information is by means of a creep test in which a constant and unidirectional shear stress is applied to the sample and the resultant shear strain measured with time. While creep and oscillatory tests, and the results generated, are often considered independently they are in fact intrinsically linked. As with spectroscopic techniques such as NMR the time domain data can be transformed to the frequency domain using mathematical procedures such as the Fourier transform or equivalent algebraic procedures. One such algebraic procedure is based on an approach widely used in the field of microrheology for converting the mean square displacement to complex modulus which has also been adapted for converting creep compliance data also. In this technical note we demonstrate how such an approach can be used to generate comparable data to oscillatory testing but in a fraction of the time.

Оборудование:

Kinexus lab+

Дата:

August 7 2018

Язык:

English

Dynamic light scattering (DLS) is a technique that is widely used to measure dispersed particle size (specifically the hydrodynamic diameter) via direct measurement of the translational diffusion coefficient within the continuous phase. By utilizing the superior accuracy and resolution of multi-angle dynamic light scattering (MADLS®), it is now possible to determine the absolute particle concentration distribution using the Zetasizer Ultra. This provides the user with a fast assessment of the concentration of each population of particles present within their dispersion. Particle concentration measurements are achieved by recording the time averaged photon count-rate scattered by the sample to perform a transformation of the size distribution to derive the absolute number of particles present. In this technical note we describe the method and calculations used to determine particle concentration..

Оборудование:

Zetasizer Ultra

Дата:

July 20 2018

Язык:

English

Multi-angle dynamic light scattering (MADLS®) available on the Zetasizer Ultra delivers an angular-independent particle size distribution (PSD) with increased resolution by combining scattering information from multiple angles. The measurement provides improved insight into all particle size populations present in the sample, as populations that may be weakly scattering at one detection angle, are revealed in the other detection angles, and brought into the combined-angle PSD. In this technical note we explain the basic principles behind the MADLS measurement and demonstrate the benefits for a mixture of polystyrene spheres of different sizes..

Оборудование:

Zetasizer Ultra

Дата:

July 19 2018

Язык:

English

The Zetasizer Nano series of instruments, in conjunction with appropriate accessories, allows for the measurement of surface zeta potential (i.e. the zeta potential of planar surfaces) and characterization of rheological properties of molecular solutions (i.e. DLS microrheology). Both of the measurement types require the use of tracer particles and selection of the most appropriate tracer is important in determining the success of the measurements. This technical note discusses the requirements of the tracers for use with surface zeta potential and microrheology measurements..

This technical note investigates several common multi-detector GPC configurations and discusses the trade-offs of modular detectors versus integrated detectors.

Оборудование:

Система OMNISEC

Дата:

February 7 2017

Язык:

English