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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

Mrs E Cooper

+27(21) 808 3172

 

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GPS Coordinates:

S 33° 55' 58" E 18° 51' 59"

Equipment available at Polymer Science

Last revision: 13 November, 2020

 

Physical characterisation

 

CRYSTAF SCALLS Equipment
PALS Microhardness tester
Brookfield viscometer Optimelt melting point apparatus
Reactor system Impact tester
Abrasion tester MFI
Tensile tester

 

CRYSTAF

Crystallisation analysis fractionation

Crystallisation analysis fractionation

Room: 1007

Responsible person: Dr Anthony Ndiripo

CRYSTAF is a fully automated instrument intended for the fast measurement of the chemical composition distribution (CCD) in polyolefins.  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 by means of an infrared detector. 

The instrument has five crystallization vessels and can thus analyse five polymer samples simultaneously.  The user puts the dry polymer samples in the vessels after which the virtual instrumentation software controls the process.  At the end of the analysis, approximately 8 to 10 hours, the instrument automatically cleans the vessels and lines.  The results are obtained directly from the software.

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SCALLS equipment

Solution crystallisation by laser light scattering

Solution crystallisation by laser light scattering scheme

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.

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PALS

Positron annihilation lifetime spectrometer

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.

PALS spectrum

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.

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Microhardness tester

Microhardness tester

Room: 1003

Responsible person: Dr Helen Pfukwa / 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 teh 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.

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Brookfield viscometer

Boorkfield viscometer

Room: 1010

Responsible person: Lauren Ball

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.

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Optimelt melting point apparatus

Optimelt melting point apparatus

Room: 1010

Responsible person: Lauren Ball

Determining a sample’s melting point serves as a rapid, indicative analysis of its identity and purity. It is often encountered in many quality control regimes and in the pharmaceutical industry since the results are easily reproducible and no standards are required if the sample’s melting point is known. Our melting point apparatus is an Optimelt MPA100 automated melting point system.

This device 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.

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Reactor system

Reactor system

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).

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Impact tester

Room: 1007

Responsible person: Dr AHA Roediger

The instrument uses a weighted pendulum to measure the energy needed to break a rectangular sample. The impact strength is calculated as the energy needed to break the sample, divided by the cross-sectional area of the sample. Tests done on this instrument (Ceast) include tensile impact tests, where the impact force is directed parallel to the lengfth of the sample, and IZOD impact tests, where the impact force is directed perpendicular to the lenght of the sample. Notched impact strength can also be determined. We also have facilities for falling weight impact tests.

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Impact tester

Room: 1020

Responsible person: Dr AHA Roediger

MTS instrument capable of IZOD and Charpy impacts, notched as well as unnotched.

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Abrasion tester (Sutherland rub tester)

Room: 2024

Responsible person: Dr AHA Roediger

The PIRA abrasion tester (also known as scuff tester) is used in design and graphics packaging applications, in measuring the abrasion resistance of substrates such as paper, varnishes and foils. The scuff tester provides a comparative test for these measurements, and works on the principle of mechanically scuffing the test substrate with a specified abrasive substrate under a specified weight.

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MFI

Melt flow index plastometer

Room: 2024

Responsible person: Dr AHA Roediger

The Ceast MFI measures the flowability of thermoplastic polymers and is used often for polyolefins. The MFI gives an indication of the flow properties of the melt, thus indicating processing qualities of the polymer. The MFI can also give an indication of flow rate of polymers, application fields of polymers (injection moulding, extrusion blow moulding) as well as grade consistance of polymers.

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Tensile tester

Room: 2024

Responsible person: Dr AHA Roediger

The Instron tensile tester measures basic mechanical properties of polymer samples. The instrument uses a load cell to stretch a sample at a set strain rate, while recording the force as a function of strain. This enables the following calculations: tensile strength, yield point, tensile modulus and other mechanical property data, tenacity of fibers, etc.

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