SABIC Innovative Plastics has developed cross-linked polycarbonates with improved chemical resistance and flame retardance in an effort to boost sales for thin-walled applications.
One recent patent application states:
“Bisphenol-A based polycarbonate is inherently flame retardant, however the material drips when exposed to flame, and this behavior worsens as the thickness of the material decreases (e.g., 3 mm or less). This diminishes greatly its use in clear thin wall applications where UL 94 V0 ratings, as well as 5VA ratings are required.”
To overcome this problem, the cross-linked PC contains an additive formed from the UV reaction of a monohydroxybenzophenone, a dihydroxybenzophenone, a diol chain extender, and one or more linker chemicals. In a paper prepared for presentation in March at the Annual Technical Conference of the Society of Plastics Engineers (Antec), the additive is described as a UV-active ketone.
Key mechanical properties are maintained, while flame and chemical resistance are improved, according to the paper by Jean-Francois Morizur, Peter Johnson, James Hoover, and Amanda Flores of SABIC IP. Morizur, who is also listed as an inventor, is a senior manager in SABIC’s Technology and Innovation group in Evansville, Indiana. Test results indicate the new compound would pass UL V0 testing 98 percent of the time. The paper was not actually presented, but was posted online as part of the Antec proceedings. It was not clear why the paper was withdrawn.
Transparency is 70 percent or greater at a thickness of 3.2 mm, measured according to ASTM-D1003-00. The flame retardant used in the new compound is potassium perfluorobutane sulfonate (Rimar salt) and potassium diphenyl sulfone-3-sulfonate (KSS).
Potential applications include components for cell phone parts, X-ray machines, and auto interiors.