Tensile and flexural properties of β-nucleated polypropylenes

Resuming our previous work on beta-nucleated polypropylenes, namely on their impact strength, our present work directs attention towards a flexural and tensile behavior of beta-nucleated polypropylenes (beta-iPP). For the purposes of this work, commercially available isotactic polypropylene was modifled using various amounts of a specific nucleating agent based on N, N'-dicyclohexylnaphtalene-2,6-dicarboxamide (NU100). From the prepared blends test specimens were prepared by injection molding. Structural characterization (crystallinity and the content of beta-phase) was carried out by X-ray diffractometry. A multipurpose mechanical property tester was used for determination of tensile and flexural properties. It was found that beta-phase content decreased both tensile and flexural strength; on the other hand, the presence of beta-phase dramatically raised cold drawability of the injection-molded specimens; addition of 0.03 wt.% of NU100 in the injection-molded parts led to a more than 800% increase of the draw ratio of specimens tested at the testing speed of 100 mm/min. Furthermore, tensile testing carried out using various strain speeds (10 and 100 mm/min) revealed that higher ductility of the material containing beta-phase is particularly pronounced by faster deformation processes, such as fast drawing or impact load.