Optimization Techniques with FORTRAN

Effect of in situ prepared silica nano-particles on non-isothermal crystallization of polypropylene

The present short review aims to summarize advanced nucleating agents for polypropylene (PP). Reviewing the relevant literature, we focused on powerful nucleators that are capable of significantly increasing the crystallization temperature of the polymer at very low working concentrations and also serving as clarifying agents. The nucleation mechanism and efficiency of these compounds are discussed in detail. The nucleating agents were divided into groups according to their tendency to induce monoclinic (α), hexagonal (β), or orthorhombic (γ) PP cell geometries. The major α-nucleators and clarifiers are sorbitol-based compounds that speed-up the polymer crystallization due to gelation phenomena and induction of epitaxial crystallization by the metal salts of substituted aromatic heterocyclic phosphate. Among β-nucleators, N,N′-dicyclohexyl-2,6-naphthalene dicarboxamide was found to be very efficient and its nucleation ability was highly concentration dependent. In addition, it was shown that nucleation efficiency of a nucleator can be significantly increased by a new dispersion method comprising its solubilization in a microemulsion. Moreover, the nucleator (HPN-68) increased the γ-modification present in the polymer. Copyright © 2007 John Wiley & Sons, Ltd.

Advanced nucleating agents for polypropylene

A highly active novel β-nucleating agent for isotactic polypropylene

The combination of moderately slow crystal growth at large undercoolings together with the practical absence of sporadic nucleation makes isotactic polypropylene (iPP) an ideal material for controlled nucleation. In this review the different types of nucleating agents – inorganic and organic, particulate and soluble – for the different crystal modifications of iPP (α, β and γ) are presented together with their working mechanism and criteria for activity. The interaction between polymer type, nucleating agent and processing conditions in determining mechanical and optical properties conclude the survey.

Nucleation of Polypropylene Homo- and Copolymers

The effects of an organic phosphorus nucleating agent on the crystallization behavior and mechanical properties of poly(propylene) were investigated. As the concentration of nucleating agent increased from 0 to 0.8%, the tensile and flexural strengths of the nucleated poly(propylene) resin increased by 15%, the flexural modulus increased by 35%, the crystallization peak temperature increased by 10°C, and the nucleation density (calculated with the nonlinear Voltrra integral equation) increased by 106 times. Mechanical properties increased with nucleation density. Linear equations between the mechanical properties and the logarithmic nucleation density were revealed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 297–301, 2003

Effects of an organic phosphorus nucleating agent on crystallization behaviors and mechanical properties of poly(propylene)

Nucleation effects of 2,2′-methylene-bis (4,6-di-tert-butylphenyl) phosphate metal salts as a nucleating agent for isotactic polypropylene (iPP) were investigated with differential scanning calorimeter and polarized optical microscope, and their effects on mechanical, optical, and heat resistance properties of iPP were also studied. The results showed that monovalent metal salts of substituted aromatic heterocyclic phosphate such as sodium salt, lithium salt, and potassium salt had a good performance. With 0.2 wt % of sodium salt, lithium salt, or potassium salt incorporated into iPP, the crystallization peak temperature of iPP could be increased by 13.5, 13.6, and 15.0°C, respectively; the mass fraction of crystallinity of iPP could be increased by about 5%; and crystallization rate was enhanced increasingly. Meanwhile the tensile strength and flexural modulus of iPP could be increased by about 10 and 30%, respectively, and the clarity and heat distortion temperature of iPP could also be improved significantly. But bivalent and trivalent metal salts of substituted aromatic heterocyclic phosphate had little effect on properties of iPP. Meanwhile the morphology study showed that the addition of monovalent sodium salt could decrease the spherulite size of iPP significantly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4868–4874, 2006

Effects of substituted aromatic heterocyclic phosphate salts on properties, crystallization, and melting behaviors of isotactic polypropylene

The crystallization kinetics of isotactic polypropylene (iPP) and nucleated iPP with substituted aromatic heterocyclic phosphate salts were investigated by means of a differential scanning calorimeter under isothermal and nonisothermal conditions. During isothermal crystallization, Avrami equation was used to describe the crystallization kinetics. Moreover, kinetics parameters such as the Avrami exponent n, crystallization rate constant Zt, and crystallization half-time t1/2 were compared. The results showed that a remarkable decrease in t1/2 as well as a significant increase in overall crystallization rate was observed in the presence of monovalent salts of substituted aromatic heterocyclic phosphate, while bivalent and trivalent salts have little effect on crystallization rate of iPP. The addition of monovalent metal salts could decrease the interfacial free energy per unit area perpendicular to PP chains σe value of iPP so that the nucleation rate of iPP was increased. During nonisothermal crystallization, Caze method was used to analyze the crystallization kinetics. It also showed that monovalent metal salts had better nucleation effects than bivalent and trivalent metal salts. From the obtained Avrami exponents of iPP and nucleated iPP it could be concluded that the addition of different nucleating agents changed the crystal growth pattern of iPP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3307–3316, 2006

Zhong Xin

Papers

Effects of an organic phosphorus nucleating agent on crystallization behaviors and mechanical properties of poly(propylene)

Effects of substituted aromatic heterocyclic phosphate salts on properties, crystallization, and melting behaviors of isotactic polypropylene

Isothermal and nonisothermal crystallization kinetics of isotactic polypropylene nucleated with substituted aromatic heterocyclic phosphate salts