New thermosets obtained by cationic copolymerization of DGEBA with γ‐caprolactone with improvement in the shrinkage. II. Time–temperature–transformation (TTT) cure diagram

Abstract

Mixtures of diglycidylether of bisphenol A (DGEBA) with different proportions of g-caprolactone (g-CL) were cured with ytterbium triflate as initiator. The curing was studied with differential scanning calorimetry (DSC) and thermo mechanical analysis (TMA). The results are presented in the form of a time-temperature-transformation diagram. The kinetic analysis was performed by means of the isoconversional integral procedure and the kinetic model was also determined using the Coats-Redfern method. Gelation was determined by means of combined experiences of DSC and TMA. The relationship between the glass transition temperature (T g ) and the degree of conversion a was determined by DSC. Using the isoconversional lines and the T g -a relationship, the vitrificacion curve was obtained. The methodology developed makes it possible to obtain the TTT diagram using only no-isothermal experiments with equivalent results to those using classical isothermal procedures. The addition of g-CL accelerates the curing and reduces the shrinkage after gelation and consequently the internal stresses in the material.

Unexpected differences between thermal and photoinitiated cationic curing of a diglycidyl ether of bisphenol A modified with a multiarm star poly(styrene)-b-poly(ε-caprolactone) polymer

“…Equation (4) may be integrated employing Doyle's approach [28] and rewritten in logarithm form as shown by Equation (5) . This model has been previously determined for the resin/initiator system used in this work [30]. In this work it has been confirmed that the curing of PS-10/DGEBA formulations is also described by R 3 model.…”

New Epoxy-Anhydride Thermosets Modified with Multiarm Stars with Hyperbranched Polyester Cores and Poly(ϵ-caprolactone) Arms

“…The linear integral isoconversional, model-free method of Kissinger-Akahira-Sunose (KAS) was used for the determination of the activation energy based on the nonisothermal curing curves [22,23] :…”

Epoxy/anhydride thermosets modified with end-capped star polymers with poly(ethyleneimine) cores of different molecular weight and poly(ε–caprolactone) arms

“…In addition, isothermal curing times determined by simulation of non-isothermal kinetic data (Equations (3) and (4)) were compared with experimental isothermal curing times obtained by means of FTIR experiments. Details of the kinetic methodology used can be found in previous works [21,22].…”