This part of ISO 6721 specifies the general principles of a method for determining the dynamic rheological properties of polymer melts at angular frequencies typically in the range 0,01 rad.s1 to 100 rad.s1 by means of an oscillatory rheometer with a parallel-plate geometry. Angular frequencies outside this range can also be used (see note 1). The method is used to determine values of the following dynamic rheological properties: complex shear viscosity *, dynamic shear viscosity ', the out-of-phase component of the complex shear viscosity '', complex shear modulus G*, shear loss modulus G'' and shear storage modulus G'. It is suitable for measuring complex shear viscosity values typically up to approximately 10 MPa.s (see note 2). NOTE 1 The angular-frequency measurement range is limited by the specification of the measuring instrument and also by the response of the specimen. When testing using angular frequencies lower than 0,1 rad.s–1 the test time can increase significantly as the time taken to obtain a single measurement is proportional to the reciprocal of the angular frequency. Consequently, when testing at low angular frequencies degradation or polymerization of the specimen is more likely to occur and have an effect on the results. At high angular frequencies the specimen may distort or fracture at the edge, consequently invalidating the test results. NOTE 2 The range of complex shear viscosity values that can be measured is dependent on the specimen dimensions and also the specification of the measuring instrument. For a specimen of given dimensions, the upper limit of the range is limited by the machine's torque capacity, angular-displacement resolution and compliance. However, correction can be made for compliance effects.