Having outstanding functional properties make isotactic polypropylene (i-PP) foams quite attractive to be applied in broad fields in polymer industry (e.g., acoustic and thermal insulators, automotive components) [1]. Nevertheless, obtaining foams with a fine cell structure is restricted due to the weak melt strength and melt elasticity of i-PP [2]. To address this, new generation benzene-trisamide based nucleating agents (NAs), which can be dissolved completely in i-PP melt at the operated processing temperature, have been used. The dissolved NAs have a tendency to crystallize upon cooling in very finely dispersed, one-dimensional, highly ordered nano-fibrillar objects which are formed by intermolecular hydrogen bonds between the stacks composed of trisamide based molecules. Self-assembly of these nanofibrils into three-dimensional objects, which act as nucleating sites for the foam cells, takes place [3]. In this study it was aimed to investigate the influence of 1,3,5-benzenetrisamide NAs with different molecular structures and concentrations on the nucleation behavior and foamability of extruded i-PP foams. Several testing methods were employed to characterize the morphological and mechanical properties of the foams. In the presence of NAs, i-PP exhibited excellent foaming performance, yielding smaller mean cell sizes and narrower cell size distributions than those of neat iPP. Depending on the molecular structure and the concentration of the NAs, significant enhancement in the compression modulus of the foams in comparison with a reference foam including talc was achieved. References: [1] R. Liao, W. Yu, and C. Zhou, Polymer, vol. 51, pp. 6334–6345, 2010. [2] K. Wang, F. Wu, W. Zhai, and W. Zheng, J Appl Polym Sci, vol. 129, pp. 2253–226, 2013. [3] N. Mohmeyer, B. Müller, N. Behrendt, J. Hillenbrand, M. Klaiber, X. Zhang, P. Smith, V. Altstädt, G. M. Sessler, and H.-W. Schmidt, Polymer, vol. 45, no. 19, pp. 6655–6663, Sep. 2004.