Cost-effective way to improve the optical properties of poly(methyl methacrylate)/poly(ethylene terephthalate) light scattering materials: drop coalescence.

Herein, the dependence of the dispersed phase diameter on the shear history during melt processing is verified experimentally. We fabricated different kinds of poly(methyl methacrylate) (PMMA)/poly(ethylene terephthalate) (PET) blends by modifying the shear rate and shear time in a torque rheometer. Light-scattering sheets (LSSs) were then prepared by compression molding with the above blends. The total transmittance of the LSS with a shear history of 8 min at 30 rpm and then 20 min at 5 rpm achieves 84.8% due to the drop coalescence and larger diameters of the PET scatterers in the PMMA matrix, while the total transmittance of a sheet with a shear history at only 30 rpm is just 70.8%. In addition to high total transmittance, the sheet also features high haze (beyond 92.5%) and tiny direct transmittance (less than 5%), which is vital for uniform illumination and glare protection from lasers and light-emitting diodes.