High-Performance Polymers Under Hydrothermal Conditions
Executive search consultants have been monitoring developments in university research to find candidates for plastics industry recruitment and polymer chemistry recruitment. Progress in hydrothermal polymerisation in particular is expected to increase career opportunities for suitably qualified research chemists and chemical engineers and so expand the field of plastics industry recruitment.
High-performance polymers form a crucial part of many electronic and sensing devices found in car engines, smartphones and spacecraft. In contrast to the softer types of plastic used domestically, such as in toothbrushes or cutlery, these types of commodity plastic need very harsh and toxic conditions for their manufacture.
The reason is that their molecular structure is either aromatic or heterocyclic. This structure gives the polymers their high strength and high chemical resistance but also means that they have to be made using temperatures of more than 700 degrees Celsius and using toxic materials such as chlorobenzenes, xylenes and cresols.
Conscious of today’s higher environmental standards and stricter regulations, researchers at the Technical University in Vienna, Austria, have developed a more benign method of manufacturing these high-performance plastics called polyimides. These plastics can be used to replace metals in many applications, ranging from a car chassis to an oven hood lining.
Replicating Geological Processes
The idea is to use water as a medium at temperatures above its 100 degrees Celsius boiling point and in a closed vessel so that pressures exceed one bar – or atmospheric pressure. The process is called hydrothermal polymerization. This design effectively mimics hydrothermal processes in geology. Most mineral ores, including precious and semi-precious stones, in the Earth’s crust are formed by this process. They are salts dissolved in water that is heated to a high temperature by neighbouring magma and the solution is kept at a high pressure within crevices and cracks of a mass of rock. The solution crystallises as it cools and condenses and is visible as a vein running through the rock.
Range of Temperature Levels
The Vienna Technical University team led by Miriam M. Unterlass developed this type of condensation reaction to produce polymers. They found that the resulting crystallinity varied with temperature and pressure. A very high crystallinity was observed at temperatures greater than 180 degrees Celsius and at pressures greater than 14 bar. A semi-crystalline and amorphous type of polymer was formed at temperatures below 150 degrees Celsius. Working at the higher temperatures, the researchers were able to refine the crystal morphology of the polymer.
As a result of this research, crystalline polyimides may be manufactured in the future in cleaner, environmentally-friendly conditions. They can also be made small enough for use in sensors and other measuring devices in harsh-environment applications where their high temperature and chemical resistance will be vital.