ZnS:Mn is one of the brightest mechanoluminescent (ML) materials known, which makes it a prime candidate for use in Structural Health Monitoring (SHM) applications. For this work crystalline ZnS:Mn powder was embedded in a clear polyurethane (PU) matrix. The total emitted energy per unit solid angle per unit area, as well as the average radiance values of different samples are measured with a calibrated camera to determine the concentration and thickness of ZnS:Mn/PU for optimal emission. A trend is observed where emission from tensile loading appears stronger than that from compressive loading, and emission from fracture is stronger than that from plastic loading which itself is stronger than that from elastic loading. Also, the ML emissions by elastic and plastic loadings tend to increase with material thickness and ZnS:Mn concentration. Both tensile- and bending-induced fracture modes were tested. While for tensile fracture the emission is approximately independent of thickness and concentration, the emission accompanying an abrupt bending fracture increases with the ZnS:Mn concentration. This work presents a first quantitative absolute measurement of ML emission of ZnS:Mn, while also introducing the use of PU as potential host material, that can benefit many SHM and other applications.