Contact us
Division of Polymer Science
Department of Chemistry
and Polymer Science
University of Stellenbosch
Private Bag X1
7602 MATIELAND
South Africa
Telephone: +27 (21) 808 3172
Student enquiries
+27(21) 808 3172
Where to find us
GPS Coordinates:
S 33° 55' 58" E 18° 51' 59"
Equipment available at Polymer Science
Last revision: 20 April, 2022
Physical characterisation
CRYSTAF SCALLS Equipment PALS Microhardness tester Brookfield viscometer Optimelt melting point apparatus Reactor system
Crystallisation analysis fractionation
Polymer Char CRYSTAF
Room: 1007
Responsible person: Dr Helen Pfukwa
Crystallization Analysis Fractionation (CRYSTAF) is a fully automated instrument for the fast measurement of the chemical composition distribution (CCD) in polyolefins. The aim of the fractionation is to separate the polymer by its comonomer content. The process occurs during a single controlled temperature ramp, where the polymer solution is cooled down and thus crystallizes out of solution. The concentration is monitored using an infrared (IR4) detector.
The instrument has five crystallization vessels and can thus analyse five polymer samples simultaneously, in an 8-hour period, under standard conditions. The results of the CCD are obtained directly from the software, and the cleaning of the vessels and lines at the end of the analysis occurs automatically.
Solution crystallisation by laser light scattering
Room:
Responsible person: Prof AJ van Reenen
This allows for the measurement of the solution crystallization of polyolefins by laser light scattering, and while it performs much the same type of measurement as Crystaf®, the technique is more sensitive, and much faster. In addition it allows for fundamental, basic research which in turn creates opportunities for post-graduate programs and papers to be published.
Positron annihilation lifetime spectrometer
Room: 1004
Responsible person: Prof PE Mallon
PALS provides direct measurement of the free volume properties of polymer materials. This is achieved by measuring the positron annihilation lifetime spectrum of positrons in the polymer. In the case of the PALS in polymers, the lifetime spectrum can typically be resolved in three or four components depending on the complexity of the morphology of the polymer. The third and fourth components (the longest lived components) correspond to the annihilation of the ortho-positronium (o-Ps) which is localised within the free volume of the polymer.
These lifetimes can be used to determine the size and number of the free volume “holes” in the polymer. The o-Ps atom is the ideal probe of the free volume in polymer materials since its very short lifetime (about 2 – 5 ns) in the polymer free volume holes means that it will spend its entire lifetime in a single hole despite the dynamic nature of the free volume in polymer materials and its size is in the same order of magnitude (although smaller) than the typical free volume hole.
Typical positron annihilation lifetime spectrum showing four components.
The Instrument capabilities: The current PALS system has a specially developed sample holder system which allows for measurements to be done from room temperature up to 200°C, without significantly reducing the count rate for the acquisition of the lifetime spectrum.
Walter UHL VMHT
Room: 1010
Responsible person: Dr Helen Pfukwa / Dr Divann Robertson
The hardness tester has the ability to indent polymer samples with loads as low as 50 mN, and at variable indentation rates and dwell times thus allows the user to do direct comparison of mechanical properties (like hardness values) with molecular composition variations. This is fundamental to the understanding of structure/property relationships.
Brookfield DV-II+Pro Viscometter
Room: 1010
Responsible person: Dr Helen Pfukwa
The Brookfield DV-II+Pro Viscometer measures fluid viscosity of dispersions, emulsions and latex samples at given shear rates. Viscosity is a measure of a fluid’s resistance to flow. The principal of operation of the DV-II+Pro is to drive a spindle immersed in the test fluid through a calibrated spring.
The viscous drag of the fluid against the spindle is measured by the spring deflection. Spring deflection is measured with a rotary transducer. The measurement range of a DV-II+Pro (in centipoise or milliPascal seconds) is determined by the rotational speed of the spindle, the size and shape of the spindle, the container the spindle is rotating in, and the full scale torque of the calibrated spring.
MPA100 Optimelt automated melting point system
Room: 1010
Responsible person: Michael-Phillip Smith, Dr Helen Pfukwa
The Optimelt MPA100 melting point apparatus is equipped with an automated operating system, PID-controlled temperature control with a Pt RTD sensor, fan-assisted cool-down, digital video data acquisition, stand-alone LCD display and operation as well as USB integration to a computer terminal and a printer output. The built-in algorithm uses digital image processing to determine the sample’s phase transitions which has shown improvement over optical absorption or reflection techniques. Temperature range: Ambient (+10°C for best reproducibility) – 400°C.
Room: 1007
Responsible person: Prof AJ van Reenen
Purchased from Autoclave Engineers, incorporating Sentinel®control system (Watchtower® software) and integrated mass flow controller. This allows for good control and monitoring during olefin polymerization reactions (pressure, gas flow, temperature).
