Practical Method of Impact Resistance Evaluation of Talc-Reinforced Polypropylene
Hidetoshi TAKEDA, Mikiko NAKAJIMA and Tetsuo SHOJI
Abstract:As an alternative to the conventional Izod method, we investigated a new impact-resistance test method employing a high speed tensile tester and stress-concentrated specimens. We proposed a more practical method of impact resistance evaluation based on the combined use of a high speed tensile tester and stress-concentrated specimens. We clarified that this method has the following excellent features: 1) The method allows a tensile rate and notch radius to be selected for the specimen in accordance with the product's usage conditions. In addition, quantitative evaluation of the effects of these specimen-related factors on the impact-resistance performance of the final products can be conducted. 2) The method enables the creation of injection-molded specimen surfaces more like those of actual final products than previous methods. 3) This makes it possible to obtain not just energy values, but trends of stress and displacement behavior, enabling identification of the contribution of each behavior to effective energy development. 4) The low variation in measured values enables evaluations to be conducted using a small amount of specimen material and assures the high reliability of the resulting data. When this evaluation method was used to assess the impact-resistance performance of talc-reinforced polypropylene copolymer, the following facts were elucidated: 1) The material's impact resistance is less dependent on the specimen's notch radius, as reflected in the relatively small loss of impact resistance even with a significantly reduced notch radius. This gives the developed copolymer great utility for use in automotive components, which have many areas of stress concentration. 2) The developed material features greater impact resistance and rigidity than conventional materials, indicating the possibility of a superior balance between impact resistance and rigidity in future formulations. Key Words:Talc-reinforced polypropylene copolymer, Injection process, Impact, Stress concentration, Notch, High-speed Tension test