Publications

Since 2004, PTG/e has supported many companies with its knowledge and expertise in the field of polymers. Some of our projects have resulted in patents and scientific publications. Information on these can be found on the Patents and Scientific Publications sections of this website. PTG/e news and other relevant news can be found in the News section.

Examples of projects we have performed in the past are highlighted in the Cases section.

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!

Surface structure analysis by profilometry

The analysis of surface structures is of great importance in many industries, such as chip/sensor manufacturing, inkjet printing or membrane production. In these industries surface analyses are used for instance as quality control, checking surface roughness or finding the root cause of defects.

 

As an example, one of our customers had approached us to help solve an issue with a curable resin product. The application of this product requires a very flat surface. At first, the resin was cast on a Teflon film, in order to ‘copy’ the flat surface of these films onto the resin product. By the naked eye, such a film indeed appears very flat, but surface profiling revealed that the film has depth differences of 1-1,5 micrometers (see Figure 1). A silicon wafer, a known flat substrate material, shows depth differences of just 30 nanometers (see Figure 2). Using this silicon wafer as substrate for the curable resin did result in the desired smoothness of the final product. Therefore, surface profiling enabled our customer to choose the right substrate for their product.

PTG Eindhoven Surface structure analysis by profilometry
Surface profiling

Figure 1: Surface profile of Teflon foil.

Profilometry is a great way to analyse a surface of a product. There are two ways optical profilometry and stylus profilometry, For a soft surface optical profilometry will gif the best results.

Graph of surface profilometry. When a surface seems flat is doesn't mean it is. With this analysis technique we at PTG Eindhoven can analyse the surface of the material.

Figure 2: Surface profile of the silicon (Si) wafer with a line profile analysis, indicated by the pink raster. The line profile is represented in the graph.

Another example below shows a microchip, which can be found in everyday devices like laptops or smartphones. A detailed image of its complex surface profile can be used to inspect the chip for any damages or incorrect assembly. The surface images in Figure 3 were obtained by an optical surface profiling technique.

2D image of a surface structure analysis by profilometry.

3D structure analysis by profilometry, in this result it's easy to see the surface is not flat.

Figure 3: Surface profile in 2D and 3D of a microchip in common electronics.

Using this technique, surfaces can be analysed quickly and accurately. Surface profiling can be done optically (optical profilometry), in which case light is used to illuminate a surface. The reflected light is detected and translated into a 2D/3D profile image. However, profiling can also be performed physically (stylus profilometry), where a stylus is used to probe a surface. Both techniques are extremely sensitive, capable of measuring depth differences of less than 1 nanometer. The choice of which technique is preferred mostly depends on the sample surface. For a very soft surface, you want to choose optical profilometry, so the surface is not changed as a result of the measurement. If a surface is absorbing (almost) all light, stylus profilometry is preferred.

At PTG/e, we offer both optical and stylus profilometry, as each technique has its pros and cons (which can often be compensated by the other technique). As such, we will always decide together with our customers which technique is best suited for their samples.

Interested in optical and physical surface profiling? Please contact us, it’s our pleasure to discuss the possibilities.
Contact

 

Surface analysis

Bio-based aliphatic/aromatic poly(trimethylene furanoate/sebacate) random copolymers: Correlation between mechanical, gas barrier performances and compostability and copolymer

Agata Zubkiewicz, Anna Szymczyk, Rafaël J. Sablong, Michelina Soccio, Giulia Guidotti, Valentina Siracusa, Nadia Lotti
Polymer Degradation and Stability, 195,2022, 109800

Identifying complex and unknown materials with TGA-IR-GC-MS ‘Hyphenation setup’

By combining the analysis techniques TGA, FT-IR and GC-MS via coupling of the devices one obtains a powerful analysis technique. With this TGA-IR-GC-MS ‘Hyphenation setup’ it is possible to identify complex and unknown materials.

PTG/e makes use of a TGA-IR-GC-MS ‘Hyphenation setup’ from PerkinElmer.
Some applications for this technique are:

  • The identification of additives, like plasticizers, in plastics
  • Determination of the primary components of a material
  • Analysis of unknown contaminations in a material, like fragrances or solvents

To characterize a material, it is first placed in the oven of the TGA, where it is heated with a programmed heating rate. During heating, weight loss can occur due to thermal decomposition or solvent evaporation. The evolved gases from these events are transferred via a transfer line to a heated chamber of the FT-IR. There, the gas is exposed to an infrared beam. The functional groups in the measured gas each respond differently to infrared radiation, which helps to identify the molecules.

TGA spectrum

IR spectrum

Following the FT-IR, the gas is transferred via another transfer line to be injected onto the column of the GC. Depending of the affinity of the injected gas with the column, the temperature of the column and the speed of the carrier gas, the injected gas has a certain retention time. Different components have a different retention time, which enables the GC to separate the individual components of the injected gas.

GC spectrum

An mass spectrometer (MS) is located at the end of the column. In the MS, the separated components are ionized and brought into an electric field. This field will accelerate the ionized components to a certain speed, depending on their mass and charge. The MS uses this principle to create a spectrum, which, together with the retention time of the GC, is unique for each component. Combining the data from FT-IR and GC-MS, the individual components of the evolved gases from TGA can be characterized.

MS spectrum

Aside from the fully hyphenated setup, it is also possible to use the individual analysis techniques, or a partially hyphenated setup, for example TGA – IR or TGA – GC-MS. The specific required setup will depend on what needs to be analyzed exactly.

Hyphenation setup

PerkinElmer equipment:
TGA 4000
FT-IR Frontier
Clarus 690 GC & SQ8T MS
RedShift Transferline

For more information about our equipment and techniques

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/

Polymer days 2021

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

Season's greetings PTGe