Relative flowability within a molding compound range is the fluidity graded by rheological test values (e.g. MFR; MVR). Thermoplastic melts are structurally viscous and viscoelastic media whose viscosity (or fluidity) depends not only on the temperature but also on the amount of mechanical stress exerted on the melt by shear and strain. A comprehensive description of the flow behavior is only possible using elaborate flow curves or viscosity functions. For a simplified characterization of the flow behavior, rheological single-point data of the melt are generated, which are currently mostly measured as volume flow rate (MVR) or mass flow rate (MFR) according to ISO 1133. Different test conditions are prescribed for each polymer type, so that a general comparison between different polymers is not possible. However, the molding compound manufacturers give an evaluation of the flow behavior within the respective type range (e.g. easy-flowing, normal-flowing, heavy-flowing), so that the program user is sufficiently informed.
Stiffness and hardness are quantified by the original E-modulus from the rapid standard tests (tension, bending, compression) as well as by the shore hardness according to DIN EN ISO 868 (method A and D) or by the sphere indentation hardness according to DIN ISO 48 (International Rubber Hardness Degree IRHD).