A new general approach for rapid performance-screening of polymer compositions is provided. Multiple compositions are generated as one-dimensional libraries in a microextruder with step- or gradient-composition changes in 2-10 g of polymer in < 1 min. To accelerate testing, environmental stress is applied to only local regions, followed by high-sensitivity spatially resolved characterization. We applied our methodology for weathering of arrays of polymeric compositions and provided ranking of polymer/ UV absorber compositions equivalent to traditional weathering data while achieved 20 times faster.