Innovations in plastics - the ANTEC conference
Anybody hunting for innovations in plastics technology should consider attending Antec, the annual technical conference organised by the Society of Plastics Engineers in the USA. Delegates at this year's event - held in Charlotte, South Carolina, in early May 2006 - were spoilt for choice with more than 700 technical papers on offer.
Several sessions dealt with nanomaterials. When added to a conventional polymer, they can have startling effects, such as improving the barrier properties of nylon film. Nanomaterials may also help to enhance the properties of shape memory polymers (SMPs).
A team at Akron University in the USA has used a nanosized clay filler to improve the recovery force of a polyurethane SMP. The nanoparticles bond chemically to the polyurethane matrix, helping to fix its shape. By adding one to three per cent of nanoclay by weight, the storage modulus of the PU, and therefore its recovery, was improved.
‘The materials will be used in shoes, as stents in biomedical applications and as structural and insulation foams,' said the paper's co-author, Sadhan Jana.
SMPs might also move into a range of orthodontic applications. New Ortho Polymer in the USA is studying how one SMP measures up against traditional orthodontic plastics such as thermoplastic polyurethanes. The material, developed by Patrick Mather of Case Western Reserve University, is a copolymer of butyl methacrylate and methyl methacrylate. Mather and New Ortho Polymer are looking to develop ‘intelligent orthodontic appliances', which, he says, ‘change shape, configuration, or mechanical properties as conditions change during orthodontic treatment'.
Case Western was involved in another emerging Antec theme - how polyolefins can be improved by modification. Researchers are studying how biaxially oriented polypropylene (BOPP) (the material used to make crisp packets) might improve the performance of body armour.
While crisp bags use BOPP film stretched in two directions to improve strength, this Case Western experiment compresses PP sheets between rollers. The researchers produced and tested two cross-rolled samples, each 4.5mm thick. One had been compressed from 9mm, while the second had originally been 18mm thick.
In a ballistic test, both samples showed improved resistance to higher velocity shots. They also absorbed the energy of the projectile by delaminating. The unoriented PP simply shattered under the test.
Meanwhile, chemical modification could lead to new polyolefin-based blends. Inhance Fluoro-Seal has used fluorination to add polarity to the surface of polyolefin molecules, allowing them to mix more effectively with polar resins.
Kelly Williams of Inhance told delegates that the modified substance could be used as a compatibiliser between polyolefins and polar resins. The company has produced improved blends of high density polyethylene (HDPE) with polyamide. Micrographs of the blends show large polyamide domains - proving incomplete mixing - when using the standard HDPE. The sample become more homogenous with the addition of modified HDPE.