New UV absorbing microspheres of sizes ranging between 0.2 +/- 0.03 and 3.0 +/- 0.2 mu m were formed by dispersion polymerization of the monomer 2-(2'-hydroxy-5'-methacryl oxyethyl phenyl)-2H-benzotriazole (trade name: NORBLOC) in methyl ethyl ketone as a continuous phase. The effect of various polymerization parameters, such as monomer concentration, initiator type and concentration, stabilizer concentration and crosslinker monomer concentration, on the size and size distribution, and on the polymerization yield of the produced PNORBLOC microspheres has been elucidated. Polyethylene/ PNORBLOC resins and films of 150 +/- 25 mu m thickness were prepared by melt blending of low density polyethylene with 2% (w/w) PNORBLOC microspheres of 0.25 +/- 0.03 mu m diameters, followed by a tubular blown process at 170-190 degrees C. The UV irradiation (200-390 nm) cut-off efficiency of these films has been demonstrated. (C) 2009 Elsevier Ltd. All rights reserved.