Determination of cure schedules of epoxies by differential scanning calorimetry

Abstract

The dynamic DSC method, which utilizes the variation in peak exotherm temperature with heating rate, is used to measure the energy of activation for anhydride cured bisphenol-A epoxy and epoxidized novolak systems. Kinetic parameters are also determined for Bstage glass fabric reinforced epoxy novolak hardened with precursor novolak. Using the expression developed for life estimation of wire enamels by Toop, probable cure schedules are evaluated. The results are compared with glass transition temperature measured under isothermal conditions. It is inferred that the "loop's equation of thermal index can be used to derive reliable cure schedules of epoxies with relative improvement in speed and ease.Differential Scanning Calorimeter (DSC) which measures the heat flow to the sample as a function of temperature directly, rapidly and accurately has been extensively used to study the cure kinetics of various thermosets. This method requires small quantity of sample and the measured value of heat of polymerzation is uncomplicated by complex changes in physical state (liquid-solid) which accompany curing and therefore correlates directly with progress of chemical reaction [1][2][3][4][5][6][7][8][9].Ozawa's method [10] based on the variable programme rate has been commonly used to derive kinetic parameters for many industrial materials and forms the basis of the ASTM method on Arrhenius Kinetic Constants for Thermally Unstable Materials [11]. The present paper examines the possibilities of extracting data on cure schedule of epoxies by fitting the kinetic data into the mathematical expression developed by Toop [12] that relates activation energy to time by temperature.John Wiley & Sons, Limited, Chichester Akad~miai Kiad6, Budapest

Method for time–temperature–transformation diagrams using DSC data: Linseed aliphatic epoxy resin

“…Differential Scanning Calorimetry (DSC) technique measures the instantaneous heat, , from a reactive sample as a function of temperature; it can be used directly, accurately and fast to study the rate of cure from the reaction heat. Assuming that the exothermic heat during cure is proportional to the extent of monomer conversion, cure kinetics and physical information can be estimated from dynamic and isothermal DSC tests . Therefore, the reaction can be monitored using a relationship between heat and curing degree, (where is the total heat released during a reaction).…”

Cure kinetics of ternary blends of epoxy resins studied by nonisothermal DSC data

“…Differential scanning calorimetry (DSC), which measures the heat flow of the sample as function of temperature, has extensively used to study the cure kinetics of various thermosetting polymers 10–13. An optimal curing process depends on understanding the curing kinetics, the curing mechanism (as shown in Schemes and ), and accurate modeling of the curing process.…”

Benzimidazole derivatives and their complexes as accelerators for curing of epoxy resin

“…Also, several reports are available based on thermal analytical techniques. This concept has been used for the purpose of finding out the cure schedules30 using the cure kinetics, which is based on the data obtained from DSC. The data obtained for benzimidazoles and their complexes are recorded in Table II.…”