DSC study on the effect of isocyanates and catalysts on the HTPB cure reaction

The urethane forming cure reactions of hydroxyl terminated polybutadiene (HTPB) binder with three different isocyanate curatives, viz., toluene diisocyanate (TDI), isophorone diisocyanate (IPDI) and 4,4-methylene bis(cyclohexyl isocyanate) (MCHI), were investigated by differential scanning calorimetry (DSC). The effect of two cure catalysts, viz., dibutyl tin dilaurate (DBTDL) and ferrric tris-acetylacetonate (FeAA) on the cure reactions was also studied. Cure kinetics was evaluated using the multiple heating rate Ozawa method. The reactivities of the three isocyanates and catalytic efficiencies were compared based on the DSC reaction temperatures, activation energies and rate constants. Viscosity build-up in these systems at isothermal temperature was also studied and compared with the results from DSC.     

Thermogravimetric characterization of styrene–divinylbenzene copolymers containing alpha-isopropylaminophosphonic acid groups

A commercial styrene–divinylbenzene copolymer was functionalized by multistep reactions with alpha-isopropylaminophosphonic acid groups. Three different functionalized copolymers were obtained in which the phosphonic groups are in meta (1E), para (2E), and ortho (3E) positions. The thermal behavior was studied using the TG/IR hyphenated technique and kinetic analysis of thermo-oxidation under nonisothermal conditions. The evolved gas analysis confirms the partial thermo-oxidative degradation of polymeric materials, with significant preservation of the aromatic ring. The kinetic analysis was performed by three methods: Friedman, Flynn–Wall–Ozawa, and nonparametric kinetic.     

一种研究聚合物非等温结晶动力学的方法

作者基于多年对聚合物结晶动力学方面研究的工作积累,联合Avrami方程和Ozawa方程,提出了一种研究聚合物非等温结晶动力学的新方法.该方法既克服了使用Ozawa方程所获得的数据点过少,常常出现非线性,不能获得可靠的动力学参数的缺点,又克服了使用经Jeziorny修正的Avrami方程所获得的表观Avrami指数无法准确预测非等温过程成核生长机理的缺点.该方法已成功用于多种聚合物体系,被国内外学者引用数百次,已成为研究聚合物非等温结晶动力学一种有效方法.     

Kinetic study of dipivaloylmethane by ozawa method

The lanthanidic complexes of general formula Ln(C₁₁H₁₉O₂)₃ were synthesized and characterized by elementary analysis, infrared absorption espectroscopy, thermogravimetry (TG) and differential scanning calorimetry (DSC). The reaction of thermal decomposition of complexes has been studied by non-isothermal and isothermal TG. The thermal decomposition reaction of complexes began in the solid phase for Tb(thd)₃, Tm(thd)₃ and Yb(thd)₃ and in the liquid phase for Er(thd)₃ and Lu(thd)₃, as it was observed by TG/DTG/DSC superimposed curves. The kinetic model that best adjusted the experimental isothermal thermogravimetric data was the R1 model. Through the Ozawa method it was possible to find coherent results in the kinetic parameters and according to the activation energy the following stability order was obtained: Tb(thd)₃>Lu(thd)₃>Yb(thd)₃>Tm(thd)₃>Er(thd)₃ This revised version was published online in August 2006 with corrections to the Cover Date.     

Nonisothermal crystallization and melting behavior of the copolymer derived from p-dioxanone and poly(ethylene glycol)

Nonisothermal crystallization and melting behaviors of poly(p-dioxanone)(PPDO)-b-poly(ethylene glycol)(PEG) with mole ratios of 80:20 and 30:70, has been studied by differential scanning calorimeter using various cooling rates. Crystallization behavior of each crystallizable segments of the copolymer was compared with the corresponding segment of homopolymer. For a given composition, the crystallization process began at higher temperature when the slower scanning rates were used. The kinetics of the PPDO segments and the PEG segments in the copolymers under nonisothermal crystallization conditions were analyzed by Ozawa equation and also the crystallization results of the copolymer segments were compared with the corresponding homopolymers. The results showed that the Ozawa equation fails to describe the whole crystallization process of the copolymer segments along with PPDO homopolymer, but describes the crystallization behavior of the PEG homopolymer. Crystallization activation energy and absolute crystallinity values were estimated from the cooling scans (using Kissinger’s method) and fusion endotherms of the subsequent heating scans, respectively.     

Synthesis and Characterization of Novel Methacrylates Derived from Morpholine and Pyrrolidine: The Determination of Kinetic Parameters with Thermogravimetric Analysis

Abstract

The synthesis of two new methacrylate esters containing morpholine and pyrrolidine group are described. The monomers produced from the reaction of corresponding morpholino chloroacetamide and pyrrolidino chloroacetamide with sodium methacrylate were polymerized in DMSO solution at 65°C using AIBN as an initiator. The monomers and their polymers were characterized by Fourier transform infrared (FTIR), ¹H‐ and ¹³C‐NMR spectroscopy. The glass transition temperature of the polymers were investigated by DSC and thermal decomposition activation energies were calculated by the Ozawa method using the SETARAM Labsys thermogravimetric analysis (TGA) thermobalance, respectively. By using gel permeation chromatography, weight average (M¯_w) and number average (M¯_n) molecular weights and polidispersity indices of the polymers were determined.     

Effect of Electron Beam Irradiation on the Kinetics of Non-isothermal Crystallization of Nylon 66

The non-isothermal crystallization kinetics was studied by differential scanning calorimetric analysis on nylon 66 and e-beam irradiated nylon 66 at different cooling rates. The Modified Avrami equation, the Ozawa equation and the Combined Avrami-Ozawa equation were applied to study the kinetics of non-isothermal crystallization of nylon 66. The crystallization behavior of pristine nylon 66 polymer was compared with that of e-beam irradiated nylon 66 and observed that the kinetics of non-isothermal crystallization of nylon66 was affected largely upon e-beam irradiation. E-beam irradiation not only decreased the crystallization temperature of nylon 66, but influenced the mechanism of nucleation and crystal growth and reduced the overall crystallization rate of nylon 66 also. The crystallization activation energy calculated by the Kissinger method for irradiated nylon 66 was lower than that of pristine nylon 66.     

Study of the Thermal Stability Properties of Pyridoxine Using Thermogravimetric Analysis

The thermal decomposition behavior and kinetics of pyridoxine in nitrogen-only and air atmospheres were studied using thermogravimetry analysis (TGA). Kinetic interpretation of thermal analysis data for pyridoxine decomposition was carried out using Ozawa and ASTM E698 isoconversional methods. The activation energy of the decomposition process varied with the degree of decomposition and was different in the nitrogen and air atmospheres. At a 5% decomposition level, the activation energy and the pre-exponential factor were found to be 28.3 kcal mol^?1 and 1.2 × 10¹⁴ min^?1, respectively, in the nitrogen-only atmosphere. Thermal stability was determined by calculating the time for 5% of the pyridoxine vitamer to decompose at 25°C. The calculated shelf life for the pyridoxine vitamer obtained via TGA was surprisingly smaller in nitrogen (0.9 years) than in air (1.5 years). This is speculated to be the result of a more complex decomposition mechanism in air, involving thermo-oxidative decomposition in the presence of oxygen.     

Isothermal and non-isothermal crystallisation kinetics of pCBT and PBT

The crystallisation behaviour of in situ polymerised cyclic butylene terephthalates (pCBT) and poly(butylene terephthalate)s (PBT) were studied by differential scanning calorimetry (DSC) both under isothermal and non-isothermal conditions. The crystallisation was analysed by adopting the Avrami, Ozawa and Kissinger methods for the isothermal and non-isothermal crystallisations, respectively. An Avrami exponent n between 2 and 3 was found for the pCBTs whereas the exponent ranged between 3 and 4 for the PBTs. The Ozawa exponent m varied for all materials between 2 and 3. Differences in the crystallisation kinetics were also reflected in the related activation energy data.