**7. Conclusions**

Nowadays α/β compounded NAs for polypropylene have attracted more and more attention. This short review summarized the research on α/β compounded NAs in recent years. Three kinds of well studied α/β compounded nucleating agents (NAs), Phosphate/Amide, Sorbitol/Amide, and Phosphate/Carboxylate were selected to review their influence on the crystallization kinetics, crystallization morphologies, and mechanical proprieties of isotactic polypropylene (iPP). The results showed that α/β compounded NAs could not only increase the crystallization temperature of iPP but also shorten the crystallization half-time, consequently reduce molding cycle time of iPP more obviously. The obtained Avrami exponent indicated that the type of nucleation of iPP could be changed while the geometry of crystal growth of iPP remains. The size of spherulites in nucleated iPP appeared much smaller than that in pure iPP. However, iPP nucleated by different α/β compounded NAs showed different morphologies. The same result was obtained by the investigation of the mechanical properties of iPP. Some α/β compounded NAs were able to enhance stiffness and toughness of iPP simultaneously while the other α/β compounded NAs could only devote to one aspect. It was summarized that the key factor of affecting the α/β compounded NAs is the crystallization temperature of iPP nucleated with NA individually (TC). The NA with higher Tc plays a leading role in the crystallization process. Consequently the mechanical properties, crystallization properties and crystalline microstructure of iPP appear close to it. Competitive nucleation will occur when the difference of Tc between two NAs is not pronounced. According to this rule, the optimization method for compounding α and β NAs was developed. That is to find out the ratio of α and β NAs with TC <sup>α</sup> = TC <sup>β</sup> so as to let competitive nucleation occur during crystallization. Then the method was applied to an example of adjusting the stiffness and toughness of iPP based on different of α/β compound NAs. Rely on it the optimal ratios of α/β compounded NAs can be easily determined by calculation TC at different ratios instead of testing them on mechanical properties. Sequentially it makes more effective to enhance stiffness and toughness of iPP based on α/β compounded NAs.
