Building a Better Plastic with FTIR

Polymer engineering focuses on ensuring specific, desirable properties are present in the final material. The goal may be to strengthen the polymer, make it less brittle, more heat tolerant, or facilitate processing and manufacturability. Mixing dissimilar polymers can result in materials with even more valuable properties than those of the individual component polymers, but the interplay between components in these blends is complex; multiple techniques are required for complete characterization.

There are several polymer analysis tools available to verify the correct co-polymer blend ratio or quantify the amount of release agent, UV stabilizer, or other additives in your materials. Component identification can be achieved with Raman microscopy because individual polymers exhibit unique spectra, which are then used for identification and quantification. The ability to identify individual components of polymer blends in combination with Raman imaging provides valuable information that explicitly establishes the chemical-morphology-property relationship in materials.

Fourier transform infrared (FTIR) spectroscopy is another tool that can analyze polymer materials. Thin films can be produced by heating thermoplastics to just below their melting point, then pressing them into films. These films can be used for rapid and accurate quantitative analysis of polymer constituents and additives and for determination of crystallinity and monomeric ratios in copolymers.  Attenuated Total Reflectance (ATR) simplifies the analysis of polymer surfaces even further through a simple contact-and-collect process.

A recent example of the use of FTIR to characterize a polymer blend was reported on the Department of Energy’s Oak Ridge National Laboratory website.  The article describes how researchers have made a better thermoplastic by replacing the styrene in ABS (acrylonitrile, butadiene, styrene) polymer with lignin, a brittle, rigid polymer that, with cellulose, forms the woody cell walls of plants. Their process interconnects equal parts of nanoscale lignin dispersed in a synthetic rubber matrix to produce a meltable, moldable, ductile material that’s much tougher than ABS. The resulting thermoplastic—called ABL for acrylonitrile, butadiene, lignin—can be recycled three times and still perform well. 

To produce an energy-efficient method of synthesizing and extruding high-performance thermoplastic elastomers based on lignin, the ORNL team analyzed the morphologies of the blends using scanning electron microscopy for surface analysis, transmission electron microscopy for soft matter phase analysis, and FTIR to identify chemical functional groups and their interactions.

FTIR spectroscopy can be applied across all phases of the product lifecycle including design, manufacture, and failure analysis to quickly and definitively identify compounds such as compounded plastics, blends, fillers, paints, rubbers, coatings, resins, and adhesives. This makes it a useful tool for scientists and engineers involved in product development, quality control, and problem solving. To learn more FTIR and the best sampling techniques available for polymer analysis, visit the FTIR Spectroscopy Academy.