The structure-property relationships of one-component moisture-curing polyurethane (1C PUR) adhesives are highly responsible for their performance under thermal load. Therefore it is necessary to know the effects of individual influencing factors to fabricate adhesives that comply with the high demands of standards regarding thermal stability. In this study, the chemical composition of PUR prepolymers was systematically varied and different types of organic and inorganic filler materials were incorporated to investigate their effects. The properties of films and bonded wood joints were analyzed by several specific methods, including macroscopic tensile shear tests, micro-mechanical tests, such as nanoindentation, spectroscopic analyses, such as FTIR and EDX, and microscopic investigations on the micro and nano scale by means of ESEM and AFM. Through the presented results, it could be shown that by optimized combinations of prepolymer and formulation in addition to filler materials, reliable bonds can be realized.