Cold‐crystallization kinetics of syndiotactic polystyrene

Abstract

ABSTRACT:The kinetics of the isothermal and nonisothermal cold crystallization of syndiotactic polystyrene (s-PS) were characterized with differential scanning calorimetry. A Johnson-Mehl-Avrami analysis of the isothermal experiments indicated that the cold crystallization of s-PS at a constant temperature followed a diffusion-controlled growth mode with a decreasing nucleation rate. Furthermore, the slow nucleation rate was the controlling step of the entire kinetic process. For nonisothermal cold-crystallization kinetics, we used a simple model based on a combination of the well-known Avrami and Ozawa models. The analysis revealed that, unlike for melt crystallization, the Avrami and Ozawa exponents were not equal. The activation energies for the isothermal and nonisothermal cold crystallizations of s-PS were 792.0 and 148.62 kJ mol Ϫ1 , respectively, indicating that the smaller motion units in cold crystallization had a weaker temperature dependence than those in melt crystallization.

Morphology, structure, and kinetic analysis of nonisothermal cold‐ and melt‐crystallization of syndiotactic polystyrene

“…Comparing the Δ E s obtained from Kissinger and Friedman equations, respectively, good agreement was observed, indicating Kissinger and Friedman equations could be successfully utilized for calculation of effective energy barrier of nonisothermal cold‐crystallization process of sPS. The effective energy barrier values for A in Table VIII are very close to that (148.6 kJ/mol) of a sPS sample with syndiotactity of 90%, obtained by Lu and Nutt38 using Kissinger equation.…”

“…As such, the effective energy barrier of nonisothermal melt‐crystallization of sPS could be obtained using Friedman equation, the results were listed in Table VII, together with the nonisothermal cold‐crystallization. The effective energy barrier of nonisothermal melt‐crystallization process of sPS ranged from −123.8 to 129.9 kJ/mol, which is smaller than the literature value (−315.9 kJ/mol) obtained by using Kissinger equation38 (possibly their value is invalid, as suggested by Vyazovkin35).…”

Syndiospecific styrene polymerization with CpTiCl3/MAO: Effects of the order of reactant addition on polymerization and polymer properties

“…sPS exhibits extended polymorphism. Its morphology is influenced by thermal, solvent, and/or mechanical treatment 29–41. Our sPS samples, after extracting atactic PS with MEK, showed several small endotherms in the temperature range 100–190°C during the first heating cycle.…”

Polymer‐based metal adsorbents via graft copolymerization of polyvinyl alcohol with diaminomaleonitrile: A green chemistry approach

“…For example, crosslinked amphoteric starch with quaternary ammonium groups can effectively remove Cr (VI), Cu (II), and Pb (II) ions in aqueous solution. [7][8][9] The ceric ion method is one of the most interesting methods to graft olefins on polymers presenting oxidizable functional groups. [10][11][12] Kinetics and mechanism of heterogeneous graft polymerization of acrylonitrile onto polyvinyl alcohol (PVA) initiated with ceric ammonium nitrate were investigated.…”