Nanomaterials and Poymers
John Whitehead

Nanomaterials seem likely candidates for 'historic subjects of the future', so worth having a look at now. Their potential for imparting a variety of benefits to polymer-based structures was looking increasingly attractive during the late 1990s and early years of the new millennium. Proponents talked enthusiastically of the improvements in a whole raft of properties which could be attained by combining these tiny particles with existing polymers such as polyamide or polypropylene.

Nanomaterials (from the Greek for 'very small' or 'dwarf') are in the range of 1-100 nanometres, where one nanometre is equal to one-billionth of a metre. A human hair is typically five times the diameter of a nanoscale particle. The introduction of such tiny particles has the effect of closing the gaps between those within the normal molecular structure, providing an obvious advantage in terms of gas permeability.

For use with polymers, most attention has focused on treated clay such as montmorillonite whose nanoparticles improve barrier properties, strength and stiffness: however, it needs to be chemically treated before it becomes miscible with such matrices as polyamide. Ion exchange is one method by which such particles can be made compatible with polymeric substances. The ability of such composites to be processed by traditional industry methods such as injection moulding or extrusion is a significant benefit. However, the price and R & D premium required for such materials place a big question mark over their viability leading to some scaling down of the more optimistic forecasts. From an estimated figure of 100 tonnes in 2000, none of it in Europe, some seers have predicted figures as high as 125 000 tonnes per annum by the middle of this first decade of the new century

A promising example of the materials' properties in use was provided by cablemaker Kabelwerk Eupen which makes ethylene-vinyl acetate copolymer-based nanocomposites, using five per cent nanoclay which brings about a dramatic improvement in fire resistance. This Belgian company found that the materials promoted char formation and delayed degradation, and extended its interest to the use of nanoclay in conjunction with other flame retardants. It has also claimed higher extrusion speeds and improved elasticity of the compounds as further benefits.

Meanwhile both Ford and Fiat have expressed confidence that nanotechnology has a role to play in automotive components in applications ranging from fuel lines to body panels. But enthusiasm for the nano concept is not universal. The trend has come under fire from Prince Charles who has added his voice to those complaining of 'grey goo'.

[It seems difficult, however, to relate these criticisms at least to the applications mentioned above - Ed.]