New Impet 740 polyethylene terephthalate (PET) from Ticona reportedly provides greater strength, stiffness, and thermal stability than competitive polycyclohexylenedimethylene terephthalate (PCT), making the new PET a cost-effective alternative for automotive and electrical applications. The 45 percent glass/mineral-filled PET is suitable for electrical connectors, switches, and related parts not requiring a UL 94 V-0 flammability rating.

Impet 740?s tensile strength is 40 percent greater than that of comparable 27.5 percent glass/mineral-filled PCT; its flexural modulus is 1.45 times that of PCT; and its notched Izod impact strength is 16 percent higher than that of PCT. It also has a DTUL 70 deg C higher than that of competing PCT under ISO conditions. Impet 740?s mechanical properties make connectors tougher and less prone to damage during assembly and mating. According to the manufacturer, in trials with selected customers, Impet 740 reduced molding cycle time by as much as 15 percent compared to PCT resins.

The high melt stability means fewer reject parts due to process variations. The melt viscosity falls just 13 percent after 25 minutes in the injection barrel. By comparison, a 27.5 percent glass/mineral-filled PCT loses 60 percent of its melt viscosity in the same time. Lower thermal stability typically means lower performance in part impact strength, elongation, and other mechanical properties.

In hot-oil testing, connectors molded in Impet 740 have also demonstrated less warp than PCT parts. Warp on a 50-pitch SIMM connector after a 2-minute exposure to oil at 220C is .57 percent for the Impet 740 vs. .92 percent for the same part molded in PCT. Production quantities of Impet 740 are available in black or natural color formulations.

Also new from Ticona is the Impet Hi 430 PET resin, developed to be molded into highly impact-resistant structural parts for automobiles and appliances. It contains only 15 percent glass, is easy to mold with relatively low tool and machine wear, and flows easily without high injection pressures. At ?20C, the Impet Hi 430 PET exhibits 40 percent higher notched impact strength than conventional glass-reinforced PET resins. It also exhibits a notched Izod impact rating of 8.8 kJ/sq m, compared with 5.5 kJ/sq m for one conventional PET grade. At room temperature, it has 73 MPa tensile strength and 4200 MPa flexural modulus. The Impet grades cost about $1.50/lb for truckload quantities.