The particles, which are between 50 and 300 m, reduce melt viscosity by up to 50% while maintaining the non-Newtonian behavior of the plastic. Other mechanical, shrinkage, and heat-resistance properties are hardly affected by the modification.
The partly crystalline PBT, from BASF Corp., Florham Park, N.J., has exceptional flow properties and is a candidate for highly stressed parts including plug-in connectors for laptops, telephones, and other devices with ISDN and DSL connections. Ultradur High Speed B4300 G2, a variant containing 10% glass fibers, has high stiffness and strength, good dimensional stability at elevated temperatures, and low water absorption. It also resists many chemicals and boasts outstanding heat-aging performance.
In a small connector design, for example, excellent flow properties let the B4300 G2 PBT easily fill a complex tool with eight cavities. With conventional PBTs the intricate parts were harder to mold and there was a lot of scrap because of voids left by trapped air inside the thin connector walls. Switching to B4300 G2 PBT improved filling and de-aerating of the tool and let the OEM reduce cycle times by 20 to 25%.