Devolatilization is the controlled removal of volatile components from polymers. This unit operation has major commercial significance in the manufacturing process of plastics, since it is necessary to fulfill the high quality requirements of the final products and to comply the tight environmental regulations. Especially for the treatment of high-viscous polymer melts and very low residual concentrations of volatiles screw extruders are commonly used for degassing. In this case mass transfer is usually liquid-phase diffusion controlled and the flow is bubble-free. Common models propose that good mixing and a frequent surface renewal is crucial for an efficient degassing. Only few published literature on the topic is available, which often focuses on a theoretical treatment without experimental validation. In order to investigate this area, this contribution presents an experimental study of bubble-free polymer devolatilization in a simplified extruder model. To perform all measurements at ambient temperature a model substance system consisting of high-viscous polydimethylsiloxane as polymer and 1,1,2-trichloro-1,2,2-trifluoroethane as volatile is used. Inside the partially filled extruder model a blade stirrer generates contiguous free surfaces in the form of a recirculating melt pool and a wiped melt film. A stripping flow of nitrogen provides the driving force for devolatilization by lowering the partial pressure of volatiles in the gas phase. A systematic investigation of film degassing is performed under variation of rotational speed and degree of fill. The concentration of volatiles in the melt is measured by thermogravimetric analysis. Mass transfer coefficients are calculated. Video analysis is used to determine surface renewal times and areas. The results of both experimental methods are evaluated and compared with common devolatilization models. In addition, exemplary experiments are carried out on a twin-screw extruder for further validation.