**9. References**

138 Polycrystalline Materials – Theoretical and Practical Aspects

iPP - 29.9 1171 31.7 NA40 - 32.9 1616 27.1 NABW - 25.4 1031 98.2 NA40/NABW 1:3 31.1 1443 58.0 H-Ba - 26.9 1018 93.6 NA40/H-Ba 1:9 30.8 1309 79.0 PA-03 - 27.1 1022 103.7 NA40/PA-03 3:7 31.0 1344 64.0

Table 5. Mechanical Properties of iPP Nucleated with different NAs (addition amount 0.2 wt

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.

Flexural modulus (MPa)

Impact strength (J/m)

Tensile strength (MPa)

Nucleating agents

%) (Shi & Xin, 2011)

**7. Conclusions** 

Compound ratio


**7** 

*Russia* 

**Influence of Irradiation on** 

V.V. Krasil'nikov1 and S.E. Savotchenko2

*and Professional Retraining of Specialists* 

*2Belgorod Regional Institute of Postgraduate Education* 

*1Belgorod State University* 

**Mechanical Properties of Materials** 

The one of actual problems of radiation material science is to reveal plastic deformation laws, hardening and fracture ones of materials under intense external action, particularly irradiation. Herein we imply different kinds of irradiation, for instance, such a (*e*, ) beam irradiation, ion or neutron irradiation and so on. Evolution of a construction material microstructure at a high temperature trial operation is substantially conditioned by free migrating defects [1]. The processes of interaction of point defects with each other, with dislocations and interface underlie all of metal radiation hardening mechanisms [2]. In the section 1, the nonlinear model of dose dependence saturation of the yield strength is proposed on the base of the vacancy and interstitial barrier interaction. Processes of mutual recombination of vacancy and interstitial barriers and formation of vacancy and interstitial

A series of different radiation defects (retardation barriers of dislocations), and their sizes, and a form of their volume distribution contribute into a yield strength increment for all of sorts of irradiation. The contribution of a barrier type is determined by conditions of irradiation and tests. At the low temperature irradiation (at the test temperatures up to 0.3 Tm, Tm is melting temperature), interstitial atoms, and vacancies, and their clusters contribute mainly into the hardening. In the section 2, evolution of radiation barrier (vacancies and interstitials) clusters is analyzed under low temperature radiation in the presence of the most important secondary effectes: recombination and formation of divacancy complexes. It is proposed a barrier hardening model in that mechanisms of mutual annihilation of the vacancy

In the section 3 unlike two preceding sections where the dose dependences are considered, the phenomenological model is formulated to describe a yield strength temperature dependence of polycrystalline materials that have undergone irradiation and mechanical experiences in a wide temperature interval including structure levels of plastic deformation. In this section, a new phenomenological model is proposed to give a suitable description of yield strength temperature dependence of some of irradiated materials in a temperature

**1. Introduction** 

clusters are taken into consideration.

and interstitial barriers and their clusterization play a main role.

interval including plastic deformation structure levels.

