Especially for polymers: Size Matters!
Important properties of polymeric materials like tensile strength and viscosity critically depend on the size, or rather, the chain length of the macromolecules that they consist of. In other words, these properties are defined by the molecular weight distribution and the average molecular weight of the polymer.
Measuring the molecular weight of a polymer therefore provides crucial information for understanding many aspects related to the behaviour of polymeric materials.
Thus, chemically identical polymers can show different tensile properties as a result of differing molecular weight. Such differences frequently result from polymer degradation and are especially relevant in the context of recycling. Also in polymer production, the molecular weight is a key parameter in quality control. While often only the melt flow index (MFI) is measured, knowledge of the actual molecular weight (distribution) provides a more detailed picture. Finally, in the development of new polymer materials, assessment of the molecular weight is a key factor for optimizing synthesis conditions.
The molecular weight of many conventional polymers can conveniently be assessed by a technique called Size Exclusion Chromatography (SEC). This technique separates dissolved polymer molecules according to their size by passing them through a column packed with porous particles. While the larger molecules cannot enter the pores and therefore elute from the column relatively rapidly, the smaller ones do enter the pores of the column material and thus experience a net retardation. The final result is a chromatogram, showing the amount of material eluting from the column versus the elution time, with the elution time being inversely related to the molecular weight.
One key issue with SEC is the fact that polymeric materials need to be dissolved in a suitable solvent. However, not all polymers are the same and their solubility heavily depends on their chemical nature and molecular weight. While many common polymers (e.g. perspex or polystyrene) are easily dissolved in tetrahydrofuran (THF), more polar materials like polyamides or some polyesters, require hexafluoroisopropanol (HFIP) for complete dissolution. Even water (H2O) may be the only suitable solvent for certain polymers. On the other hand, the industrially important class of polyolefins (e.g. polyethylene, polypropylene) can only be dissolved in a chlorinated solvent and the complete SEC analysis is performed at 160 °C!
It is clear that every type of material needs specific measurement conditions to assess its molecular weight. At PTG/e, we have many years of experience with polymers of widely varying nature. Our state-of-the-art SEC equipment, running on different solvents, enables us to cover molecular weight determinations of almost any polymeric material, including those that are notoriously ‘difficult’ to dissolve.
Please contact us if you would like to find out whether molecular weight determination by SEC can provide a breakthrough insight into your material of interest!
PTG/e is sponsoring Brightlands Polymer Days 2021
Brightlands Polymer Days 2021 is a scientific conference in the field of polymer science and technology. It is organised by the Belgian Polymer Group, KNCV Macromolecular Division, PTN, the former Dutch Polymer Days and Brightlands Rolduc Polymer Conference. These partners have joined forces to start a new scientific conference where academia, from student to Nobel Prize winner, and industry can meet.
More information about this conference can be found on https://polymerdays.brightlands.com/about-the-conference/
Warm Season’s Greetings from PTG/e!
We would like to wish you all the best for 2022 and thank our customers for the cooperation and trust that has been given to us again over the past year.
Looking forward to strengthening our partnerships and developing our collaborations in the upcoming year, providing innovative and professional support.
Our laboratories will be closed December 25, 2021 till January 2, 2022.
With kind regards, Team PTG/e
Remeltable concrete, an industrial revolution!
PTG/e cooperated with Shell in the development of sulfur concrete which is now commercialized by the Belgian concrete manufacturer De Bonte for the production of ‘green’ railway sleepers.
Further details on this 100% circular concrete can be found on the website of De Bonte.
A look at the daily work of a Research fellow at PTG/e?
Fontys University of Applied Sciences has asked some alumni what their job looks like after graduation. Thijs Jansman gives a good impression of his activities and the infrastructure at PTG/e.
Making green hydrogen more cost-effective
PTG/e takes its role in enabling the energy transition from fossil to renewable energy. One of the promising energy carriers for this energy transition is hydrogen, produced by wind or solar power, the so called green hydrogen. One of the current barriers to success are the costs of the electrolyzers needed for the hydrogen production.
Together with our partners in the Ampere consortium funded by TKI Nieuw Gas, we aim at making green hydrogen more cost-effective. To this end, PTG/e contributes to the development of new, fluorine-free proton-exchange membranes (PEM) which are used in the electrolyzers. The primary goal is to lower costs, but an additional benefit of this chemistry is the absence of organofluorine compounds in PEM-electrolyzers, which would also reduce the ecological footprint of water electrolysis.
To give you a short impression of the project, see the movie (unfortunately only in Dutch), where our teamleader Chemistry, Timo Sciarone explains the role of PTG/e.