Fernando Barbadillo

Simultaneous thermal analysis of hexahydrophtalic anhydride

Hexahydrophtalic anhydride is studied by means of a simultaneous thermal analyzer (STA) over a temperature range of 20–400 8C, at the heating rates of 5, 10, 20, and 40 8C/min. All the experiments have been conducted under argon gas environment and then repeated with dried air as the purge gas. All samples show the melting transition followed by the vaporization indicated by the weight loss. The activation energy calculated from the weight loss data has been compared with the enthalpy of vaporization. Although a zero order transition fits well with a reaction order model, the kinetics of vaporization does not follow this model. # 2002 Elsevier Science B.V. All rights reserved.

Study of the Degradation of a Polyesther-Polyurethane by TGA and the Logistic Mixture Model

The logistic mixture model was successfully studied previously in the separation of overlapping steps in some polymeric systems by the authors. In the present work, this method is applied to a polyesther-polyurethane degradation under air and inert atmospheres at several heat rates (5, 10, 15, 20 and 25 °C/min) in dynamic TGA. Every logistic component is fitted by reaction order, Johnson-Mehl-Avrami and Sestak-Berggren kinetics equations in order to calculate its kinetic parameters (activation energy, frequency factor and exponents). The reaction order model gives a good fitting and reproduces accurtelly the experimental curves. Johnson-Mehl-Avrami and Sestak- Berggren equations resulted to be not suitables because of the activation energy values obtained.

Tribological Behaviour of an A355 Steel Pipe Welding

This work studies the behaviour of welding joints under abrasive wear in A355 Gr. P11 steel pipes carrying liquids at high temperatures. Various welding processes were tested on different joints in an effort to choose the one that gave the best wear response. For this purpose, a pin-on-disk tribometer was used at 200°C to simulate the service conditions of the pipes. The tests were carried out by pressing a hard chromium-plated steel pin, with a diameter of 4 mm and hardness of about 775 HV, on steel specimens in order to measure their mass loss and friction coefficient in the three welding zones: base metal (BM), heat affected zone (HAZ) and weld bead (WB). The tests conditions were 10 N of load, 200 rpm of rotation velocity and a radius of 3 mm. In addition, metallographic studies and hardness measurements of the three welding zones were done to complete this work.

Study of the Cure of a Diglycidyl-Ether of Bisphenol-a (DGEBA) / Triethylenetetramine (TETA) Epoxy System by Non-Isothermal Differential Scanning Calorimetry (DSC)

A diglycidyl-ether of bisphenol-A (DGEBA)/Triethylenetetramine (TETA) system was studied by non-isothermal differential scanning calorimetry (DSC) to establish its kinetics of cure. The DGEBA resin was Araldite GZ 601 X75 used in the marine coatings formulations. Previously, the optimum resin/hardener ratio was determined by the reaction heat measuring (.Hc) calculated from the curing exothermic peak. Tests at different heating rates (10, 15, 20, 25 and 30°C/min) under inert atmosphere were carried out in order to study the reaction kinetics. The activation energy of the cure (Ea) was obtained from these tests data by Borchardt-Daniels, autocatalytic, Duswalt and isoconversional Ozawa methods. Once the activation energy was determined, the master curves method was applied to find the kinetic model which best describes the measured DSC data. The Sestak-Berggren model SB (m,n) was found to be the most adequate for the system studied.

Comparative Study by Thermal Analysis of Four Different Kinds of Wood

Abstract. Knowledge of thermal behavior is needed when structural applications are concerned, and quick method of identifying species of wood is desirable in order to track the materials in industrial processes and in the life service. Samples of wood from four different species of trees (Castanea sativa, Quercus robur, Eucalyptus globulus, and Pinus sylvestris) have been studied by means of Simultaneous Thermal Analysis (STA). Dynamic scanning runs have been conducted under argon and air atmospheres. The simultaneous information of both weight and heat has been used in order to distinguish between species. Kinetic studies have been performed on the devolatilization processes. Similarities and differences have been pointed out and a quick and reliable procedure is suggested to distinguish among these four kinds of wood.