Co-polymerising extends life of plastics

New resins extend the service limits of engineering plastics without incurring excessive cost. Tom Shelley reports New developments in polymer technology raise usable working temperatures and provide long term resistance to weathering and extreme temperature fluctuations without incurring any of the high costs associated with the likes of PEEK, Ormocers (Organic modified ceramics) or other very advanced materials. Golnar Motahari Pour, President for Europe for GE Advanced Materials - Plastics, speaking at a just held press conference, explained that many of the advances have come from combining properties by co-polymerising rather than trying to obtain them by compounding mixtures. As an example, 'Lexan EXL' polycarbonate resins are co-polymerised with siloxane. The effect of the siloxane soft blocks in the polycarbonate backbone extends low temperature impact strength and ductility and UV stability while retaining the properties of polycarbonate. As a result the polymer offers long term resistance to weathering and temperature fluctuations in the range -40 deg C to +100 deg C, without loss of dimensional stability or ductility. A number of grades have been developed, one of which, EXL 1414 has been specially formulated to meet the needs of the consumer electronics and telecommunications industries. It is, for example, used for the battery enclosure of the Motorola V300 mobile phone, because of its ability to maintain its strength down to -60 deg C. The EXL grades form part of what GE Advanced Materials has designated as its "X GEN" portofolio, the 'X' standing for eXtreme. Another 'X GEN' designated product is 'Ultem' EXSP0023 polyetherimide film, which has a glass transition temperature of 245 deg C, and is aimed at the middle of the flexible connector market as a lower cost alternative to polyimide. At the press conference, it was claimed to be "The highest heat amorphous polymer on the planet capable of being injection moulded." It also has a dielectric strength of 4,700 volts/mil and good tear resistance. It is heat sealable and offers good overall adhesion to most metals. It is said to additionally provide "Excellent" chemical resistance and a dielectric constant of only 2.9 when tested at 10GHz. For those interested in polymers with a strictly limited life, the same press conference was also used to unveil the Flexplay "EZ-D" 48 hour DVD. A Flexplay enabled DVD is similar to a conventional DVD, except that 48 hours after it is removed from its sealed packet, it discolours and can no longer be read by the DVD player. This feature depends on a specially developed and patented 'Lexan' co-polymer. GE Advanced Materials Pointers * Co-polymerised polycarbonate siloxane resins can endure temperature fluctuations within the range -40 to +100 deg C, without loss of dimensional stability or ductility and show extended low temperature strength and UV stability while retaining the properties of polycarbonate * 'Ultem' EXSP0023 polyetherimide film has a glass transition temperature of 245 deg C, and is aimed at the middle of the flexible connector market as a lower cost alternative to polyimide. * A newly developed and patented polycarbonate co-polymer is key to Flexplay DVDs, which discolour and cease to be readable by DVD players 48 hours after they are removed from their sealed packets.