Weatherable polycarbonate sheet can be produced by coextruding a cap layer containing a UV absorber over a minimally-stabilized bulk layer. A new UV absorber based on hydroxyphenyltriazine chemistry has been developed that is especially suited to this application. The product provides superior long term weatherability due to its strong UV absorbance and its excellent photostability. It is also relatively nonvolatile, and has only a minimal effect on melt viscosity.
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