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Crystal nucleating agent Bis (3, 4- dimethylbenzylidene) sorbitol (DMDBS) was used to tune the melt strength and microcellular foaming properties of isotactic polypropylene (iPP) in this study. Rheological testing results reveal that the introduction of DMDBS could enhance the storage modulus and complex viscosity of iPP, obviously increase its crystallization onset temperature, compared to its counterparts without DMDBS. The addition of DMDBS could also significantly increase the cell nucleating ability of iPP, due to its large surface, cooperating with a thermal history control treatment. Quite fine microcellular iPP/DMDBS foams were fabricated with relatively small average cell sizes of nano to several micrometers, and cell densities up to 1011∼1012 cells/cm3, using the synergy effect of DMDBS and iPP's melt self-enhancement. Under a comparatively low re-saturation pressure of 8 to 12 MPa, ideal microcellular foams could be generated, at a temperature zone of 158 to 162°C, which is slightly below to iPP's original pellets nominal melting point. [ABSTRACT FROM AUTHOR]

This study is aimed at using thermal history control and nucleating agent to adjust the foaming behavior of isotactic polypropylene (iPP). Through the introduction of an annealing stage and α nucleating agent, the crystallization and rheological properties of iPP were changed, and its microcellular foaming behavior was tuned correspondingly. Rheological testing results verified the enhancement of melt strength through the presentation of the crystallization stage and α nucleating agent. After an annealing at 110 °C, 10 MPa, for 40 min, iPP was further saturated at 165 °C, 12 MPa for 30 min and then foamed, the cell density is 7.95 × 10 9 cells/cm 3 , while the average cell size is 11.66 μm. Furthermore, the synergy between the annealing treatment and an addition of 0.2 wt.% α nucleating agent could positively affect the heterogenous cell nucleating ability and melt strength of iPP, much smaller sized cells with relatively quite high cell density up to 10 13 –10 14 cells/cm 3 were induced. [ABSTRACT FROM AUTHOR]