Targeted surface modification of materials is becoming a commonly used process in the production and research environment. This process alters the functional properties of the polymer surface and, under laboratory and manufacturing conditions, can ideally be initiated by a diffuse coplanar surface barrier discharge plasma, also called a cold plasma. The efficiency of the surface modification process by this type of discharge is given mainly by the speed of the plasma‐chemical modification process. An interesting area of research in this area is the characterization of changes in the above plasma chemical modification. The nature of the changes can be observed ideally on the flat surfaces of selected materials, since the height of the visually homogeneous plasma layer is approximately 0.3 mm. During the process of plasma chemical modification, the investigated surface of the polymeric material is also exposed to temperature, electric micro‐discharges, heat flow and ultraviolet radiation. All these elements affect changes that need to be investigated and described. The effect of temperature and micro‐discharges during the cold plasma treatment can be evaluated from thermograms. Visually homogenous plasma respectively heat flow from its generation is first time monitored with Schlieren Imaging system. The effect of degradation (due to ultraviolet radiation) of polymers is monitored with static tensile test.