Effect of DFA Modification on Thermal Properties of Multifunctional Epoxy/Anhydride Systems

The thermal stabilities of two amine based multifunctional epoxy resins (TGDDE/MNA & TGBAPP/MNA) and two dimer carboxylic acid (DFA) toughened resins (DFA-TGDDE/MNA & DFA-TGBAPP/MNA) were comparatively investigated with the thermo-gravimetric analysis (TG). The TG parameters of the resins indicated that the thermal stability of the resins was increased after the modification. Furthermore, the thermal degradation kinetics was studied with a dynamic method according to Ozawa model, which explained this phenomenon.

From confrontation to cooperation – institutional support in building cooperation of Polish enterprises

The article presents results of critical theoretical and empirical analysis of cooperation between Polish enterprises based on two models: made by T. Ozawa and M.E. Porter, and followed by market research concerning opportunities to support cooperation of Polish enterprises. Polish companies seem to opt for confrontation as the main market strategy, basing on the development of one company while worsening the position of rivals at the same time. The aim of this paper is to show possibilities in supporting Polish companies to build their capabilities, as well as identifying barriers, in transition from confrontation to cooperation. The article is divided into four parts. In the first part, the stages of development of economy and enterprises in Europe are defined with reference to T. Ozawa model. The analysis covers the internationally recognised innovation indicators with regard to cooperation aspects. In the second part, the authors analyse the essence and forms of cooperation between companies. The third part of the paper concentrates on the market research of the support means available for Polish enterprises. In conclusion, a brief summary of the main findings was given, concerning the opportunities and barriers of institutional approach towards cooperation between Polish enterprises. In the paper, two types of research methods were used: methods of data collection and methods of organizing and processing information, especially methods of systems, cause and logical analysis of institutional support.

Parameters characterizing the kinetics of the non-isothermal crystallization of polyamide 5,6 determined by differential scanning calorimetry

The non-isothermal crystallization behavior of polyamide 5,6 (PA56) was investigated by differential scanning calorimeter (DSC), and the non-isothermal crystallization kinetics were analyzed using the modified Avrami equation, the Ozawa model, and the method combining the Avrami and Ozawa equations. It was found that the Avrami method modified by Jeziorny could only describe the primary stage of non-isothermal crystallization kinetics of PA56, the Ozawa model failed to describe the non-isothermal crystallization of PA56, while the combined approach could successfully describe the non-isothermal crystallization process much more effectively. Kinetic parameters, such as the Avrami exponent, kinetic crystallization rate constant, relative degree of crystallinity, the crystallization enthalpy, and activation energy, were also determined for PA56.

Kinetics of crystallization of Ge30-xSe70Sbx (x=15, 20, 25) chalcogenide glasses

The kinetics of crystallization of Ge30-xSe70Sbx (x=15, 20, 25) chalcogenide glasses has been investigated using differential scanning calorimetery at different heating rates under non-isothermal conditions. The kinetic analysis of crystallization has been discussed using different theoretical approaches such as Ozawa model, Augis and Bennet model, Matusita model and Gao-Wang model. It is evident from this study that the activation energy of crystallization Ec is composition dependent. The activation energy decreases with increasing Sb content due to the increasing of rate of crystallization. The minimum value of the frequency factor Ko, which is defined as the number of attempts made by the nuclei per second to overcome the energy barrier, confirms the fact that glass is more stable. It has been found that Ge15Se70Sb15 glass is more stable compared to the other compositions.

Thermal Degradation Kinetics of Polyurethane/polybenzoxazine Alloys

Recently, the alloys of polyurethane (PU)/polybenzoxazine (PBA-a) have been studied due to many interesting properties; however, the thermal degradation kinetics of the system has not been mentioned before. In this study, the degradation temperatures of the obtained alloys were determined using Thermogravimetric Analyzer (TGA) with various heating rate of 10, 20, 25oC/min. The polyurethane /polybenzoxazine alloys at the weight ratios of 30/70 were prepared for determination due to its highest degradation temperature. The first derivative curves of the thermograms (DTG) were deconvoluted with Peak-fit program. The results reveal three main sub-stages of degradation. According to Arrhenius Eq., the activation energies (Ea) of each degradation sub-stage were determined using Kissinger model and Fynn-Wall Ozawa model.