Physical Chemistry of Polymers Laboratory

Head: Dr. Naser Mohammadi
Technicians: Mehdi Mohammadi, Fatemeh Ramezani
Address: second Floor, Department of polymer Engineering
Telephone: +98(21)64542479



Educational/Research:
Training Bachelor (BSc) Students/Working on research projects in BSc, MSc and PhD level as well as industrial projects

Principal tests:
Tensiometry, Turbidimetry, Gel permeation chromatography, Dilute solution viscometry, Vapor pressure osmometry, Membrane osmometry


Main Tests/ Instruments:
 
Tensiometry
The device can measure the surface tension of liquids and solids. Du Nouy ring is used to measure the surface tension of liquids by a thin metal (often platinum) wire ring. In this method, the surface tension is calculated using the force applied to the liquid from the ring and the relevant equations. First, the ring is immersed vertically in liquid. Then by pulling the ring out of the liquid, a layer of liquid is formed as a hollow cylinder. The surface tension force of the liquid film opposes the pulling force. This technique is based on measuring the maximum force. Wilhelm Plate is another method to measure the surface tension of liquids. In this method, a thin plate is immersed in the liquid and then is pulled out. The surface tension of the liquid is measured using the known equations. In order to measure the surface tension of solids, two immiscible liquids with different polarities is used.
 
Turbidimetry (the name being derived from turbidity) is the process of measuring the loss of intensity of transmitted light due to the scattering effect of particles suspended in it. Light is passed through a filter creating a light of known wavelength which is then passed through a cuvette containing a solution. Accordingly, the molecular weight and size of the scattering particles could be measured.
 
Gel permeation chromatography
Gel permeation chromatography (GPC) makes use of the size exclusion principle. The size of the molecule, defined by its hydrodynamic radius, can or cannot enter small pores in a bed of cross-linked polymer particles, the most common form of the stationary phase. The smaller molecules diffuse in and out of the pores via Brownian motion and are delayed. The larger molecules pass by and continue in the mobile phase. The stationary phase consists of small, porous particles. While the mobile phase flows at a specified rate controlled by the solvent delivery system, the sample is injected into the mobile phase and enters the columns. The refractive index detector is most popular concentration-sensitive detector, measuring the change in refractive index as the concentration of polymer in the solution changes. When the polymer chains arrive at the detector, then the refractive index of the solution changes, providing a measure of the polymer concentration. The calibration of GPC instrument utilized anionically polymerized polystyrene standards. It can measure number and weigh average molecular weight of polymer which are soluble in toluene in room temperature.
 
 
Dilute solution viscometry
This test can determine the intrinsic viscosity of a dilute polymer solution and viscosity-average molecular weight of a polymer. The most frequently used instrument is the Ubbelhode viscometer, which equalizes the pressure above and below the capillary. A dilute polymer solution (C  
Vapor pressure osmometry
This test is measures the number average molecular weight of short-chain polymers (Mn<10000 g/mol) and oligomers in dilute solutions. The device works on the basis of lower vapor pressure of the polymer solution than the pure solvent at a same temperature and pressure. It defines the vapor pressure indirectly by measuring the changes in voltage, which is proportional to the temperature changes. Molecular weight is calculated by voltage changes, polymer solution concentration and the calibration constant of the device.
 
Membrane osmometry
Membrane osmometry can directly measure the number average molecular weight of polymers in the range of 10,000-10,000,000 g/mol. The device has two chambers for polymer solution and pure solvent.  Molecular weight is calculated by measuring the osmotic pressure of the solvent through semi-permeable membrane

Brief description of laboratory/workshop activities:
Training BSc. Students/Working on research projects in BSc, MSc and PhD levels as well as industrial projects.

Average number of students trained annually:
70
Average number of industrial tests conducted annually:
More than 200
Average number of research tests conducted annually:
More than 2000


 



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