Understanding of the mechanical behaviour of the polymeric interlayer plays a significant role in the design of laminated safety glass (LSG): In the intact state, the maximum glass stress and the maximum deformation are significantly influenced by the shear coupling through the interlayer. In the post-fractured state, the interlayer material behaviour influences the required residual load bearing capacity. However, polymers show a complex material behaviour, which is dependent, both on the ambient climate (e.g. temperature, humidity) and on the load (e.g. duration and height). Numerically, this can be illustrated by visco- and hyperelastic material models. Using the example of a polyvinyl butyral based interlayers, results from dynamic mechanical thermal analyses as well as from tensile and relaxation tests at different environmental conditions and strain rates or strains are presented and interpreted. In addition, the material parameters of viscoelastic and hyperelastic material models are given.