Abstract: The present invention provides a method for directly measuring the color of transparent polymer particles. A composite liquid, comprising a transparent liquid with nanoparticles and matching the refractive index of the polymer, can be used to mitigate the light scattering due to the roughness of the particles surface. The method can be applied to copolyester particles, such as copolyester pellets.

Abstract: Provided herein is an uncoated functional paper formed from a slurry comprising about 10 wt % to 90 wt % cellulosic fibers and about 1% to 25% sizing solution per total weight of the fibers. The sizing solution can be applied during papermaking and/or applied in a size press or coater. The paper can be calendered at a temperature greater than 50° C. Methods of making are also provided. Also provided are flexible electronics including a functional paper substrate printed with a conductive ink.