The development of belt transmissions with wedge belts and new materials used to produce belts inspire designers and people who deal with the exploitation of belt drives to carry research on the possibilities of increasing the load and durability of the belts. It is necessary to know the actual mechanical and rheological characteristics of the belts in the range of their durability features and to comply with the conditions of proper transmission work. It is possible to find in literature many information referring to classic, single rubber belts. In case of polyurethane heat-sealed belts obtaining such information is not easy. It has been a starting point to carry out experimental research in order to determine the material characteristics of belt PU 75 A ( red colour). The article presents experimental research results on creeping, cyclical squeezing and stretching of the belt; also the subjection of a side-slip and transmission efficiency in the torque function for PU 75 A belt was determined. The research results will be used to create a transmission model in Abaqus Explicit programme.