Developing Polyurethanes Based on Vegetable Oils — Chromatography Helps Out

Polyurethanes are an essential element of the chemical industry and are a part of our everyday modern lives. Car seats, adhesives, insulation and shoes are just some of the uses for polyurethanes. But even though they are a plastic — similar in many respects to other plastics — they are also different. One of the major differences is in the method of manufacture of polyurethanes compared to other polymers.

A recent paper published in the European Journal of Chemistry — High thermal stability of aliphatic polyurethanes prepared from sesame and peanut oil and their kinetic parameters — looks at how polyurethanes could be made from renewable resources — a key element of green chemistry. Let’s delve deeper into the world of polyurethane and see how it could be getting greener.

Monourethane to polyurethane?

Polyurethanes are a polymeric family — a family of polymers that are different to other forms of plastics in that there is no urethane monomer. Polyurethanes are also different in that they are generally made during the manufacture of a particular object. This is different to other forms of plastic that are generally made from monomeric units — styrene to polystyrene for example — and then the polymer is then used as a raw material to make a product, perhaps a bag.

Polyurethanes are formed during exothermic reactions between alcohols having two (or more) reactive hydroxyl (-OH) groups on each molecule and isocyanates that have more than one reactive isocyanate (-N=C=O) group per molecule. The isocyanate and hydroxyl react to form a ‘urethane’ bond — with chains forming to create polyurethanes.

Going green — plant-based chemistry

As with many other industries, the chemical industry is keen to find ‘green alternatives’ to fossil fuel-based resources. In chemistry, this includes:

• finding renewable sources of raw materials and intermediates,
• by reducing the energy efficiency of chemical plants and processes,
• improving efficiency of chemical processes, and
• eliminating hazardous substances from chemical processes.

Many plastics, including polyurethanes have their beginnings in fossil fuels and materials extracted from the Earth. To reduce the impact on the Earth chemists are looking for green alternatives. Hence, the reason for the work reported above on the use of vegetable-oil based raw materials used to make polyurethanes.

A nutty polyurethane analysed by GPC

The study referenced above, looks at alternative methods of synthesizing polyurethanes using vegetable oils — sesame and peanut based oils to be precise. Following various processes, the researchers formulated polyurethanes based on the nut oils. The resulting polyurethanes were analysed by various methods including chromatography — that was used to give an indication of the molecular weight of the polymers formed. Of course, chromatography is used to analyse many different oils as discussed in the article, Blue Jacaranda Seed Oil Analysed Using Comprehensive Two Dimensional Liquid Chromatography with Quadruple Parallel Mass Spectrometry.

The team report success in developing polyurethanes from nut oils. In the paper they state: ‘The resultant polyurethanes which can be used as coating, adhesives, foams, biomedical, battery and sensor applications.’