Polyethylene is very sensitive to heating and it burns almost entirely. It's chemical nature has prevented its matrix from binding with mineral particles. Russian chemical physicists have developed a new composite material, which looks like polyethylene, but has improved properties. Scientists developed an elegant synthesis technique, which solves previously unmanageable problem – keeping mineral structure intact, while introducing it into a polymer with absolutely different chemical nature. After thoroughly studying the structure of the new material, Russian chemists have developed the technique of using a mineral as a filling agent, which consists of numerous layers, none of which are bonded. The new composite is much more rigid and better resists high temperatures.
These remarkable properties are due to the layer mineral “montmorillonite”, which originates in Montmorillon settlement in France. The new PE composite has only traces of montmorillonite. Scientists developed an elegant synthesis technique, keeping mineral structure intact, while introducing it into a polymer with absolutely different chemical nature. The researchers used unusual filling agent – a mineral, which consists of numerous layers like a large book – however, these layers are not bonded, using non-natural mineral, but slightly modified. This modified montmorillonite had expanded space between the layers, and layer surface contained organic (more hydrophobic) cations instead of part of original sodium. The scientists found out that the mineral should first be saturated with a catalytic agent (this can be done by adsorption into interlayer space), and only after that ethylene should be polymerized. Since the catalytic agent is located both inside and outside mineral layers, polyethylene forms inside and outside mineral layers as well – thus multilayer “filling” becomes tightly bonded with polyethylene matrix. The result is new composite material, with evenly distributed nanolayers of montmorillonite (which as any clay doesn't burn and doesn't stretch under heating) in the total volume of polyethylene.
Scientists thoroughly studied the structure of the new material and its properties. They used many techniques and, what is notable, were the first, who used the technique of very cold (very slow) neutron scattering. Researchers found out that they can synthesize the material with predetermined structure and properties by varying synthesis parameters and mineral modifications. Introduction of as little as 1-3% volume of montmorillonite in PE significantly reduces flammability and gas permeability of the new composite and its thermal stability in comparison to PE.
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