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Abstract  

The activation energy associated with the glass transition relaxation of an epoxy system has been determined by using the three-point bending clamp provided in the recently introduced TA Instruments DMA 2980 dynamic mechanical analyzer. A mathematical expression showing the dependency of modulus measurements on the sample properties and test conditions has also been derived. The experimental results showed that the evaluation of activation energy is affected by the heating rate and test frequency, as well as the criterion by which the glass transition temperature (T g) is established. It has been found that the activation energy based on the loss tangent (tanδ) peak is more reliable than on the loss modulus (E 2) peak, as long as the dynamic test conditions do not cause excessive thermal lags.

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The glass transition temperatures,T g, and thermal effects of polymerization,ΔH, have been determined for five epoxy adhesives of unknown composition. From the trendsΔH vs./t cure it has been possible to attain a phenomenological kinetic order of the polymerization rate at 100° through an iterative calculation procedure. For most of the investigated adhesives there are reasons (double peak of polymerization and doubleT g signal) to assume that they are graft copolymers.

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Abstract  

One-component silver-filled epoxy adhesives electrically conductive with low extractable ionic content have been used in microelectronics for attach applications. For the specific application described here there was evidence showing that adhesive polymerisation was not complete with negative consequences for the electronic devices. The present study aimed at understanding the causes of such disadvantages and setting up the best conditions to make the epoxy adhesive perfectly suitable for the required applications. The work was carried out mainly by means of differential scanning calorimetry (DSC) and with the help the dynamic mechanical thermal analysis (DMTA) technique. The study succeeded in determining that the technological problems were due to incomplete polymerisation that caused solvent and monomer retention. These residues produced a leakage of the insulating properties of some capacitors present in the devices jeopardising the sensor working. Moreover, the study also showed that it was possible to avoid these difficulties adjusting the polymerisation temperature to 130C and respecting curing time of 3 h: with these new curing conditions excellent results were achieved.

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A study was made of the thermal stability of epoxy compounds which were unfilled or contained metallic fillers such as aluminium dust, aluminium flakes, powdered bronze, powdered brass and silver flakes. The properties of the compounds were modified by the use of various hardeners.

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for each experiment conducted for the epoxy adhesive and reformed graphite material mixed in a certain mass percentage, and for HDF made by increasing the mass percentage between the adhesive and reformed graphite. HFM materials

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Measurements of Conductive Epoxy Adhesives by MDSC . In: Thermal Library Application Brief TA312 , TA Instruments New Castle , Delaware . [14]. D. Schrader

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Journal of Thermal Analysis and Calorimetry
Authors: C. Gracia-Fernández, J. Tarrío-Saavedra, J. López-Beceiro, S. Gómez-Barreiro, S. Naya, and R. Artiaga

1. Petrie , EM . Epoxy adhesive formulations . New York : McGraw-Hill ; 2006 . 2. Paz-Abuín , S . Epoxy adhesives: a view of the present and the future

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characterization and two-step cure kinetics of a high performance epoxy adhesive system . MS Thesis. Wichita State University, Wichita; 2006 . 17. Ruiz , E , Trochu , F . Thermomechanical

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. Li , G , Lee-Sullivan , P , Thring , RW . Determination of activation energy for glass transition of an epoxy adhesive using dynamic mechanical analysis . J Therm Anal Cal . 2000 ; 60 : 377 – 390 . 10.1023/A:1010120921582 .

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behaviour of nanoreinforced epoxy adhesives of low electrical resistivity for joining carbon fiber/epoxy laminates . J Adhes Sci Technol . 2010 ; 24 : 1097 – 1112 . 10.1163/016942409X12584625925060 . 13

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