The Use of the ATD Technique to Measure the Gelation Time of Epoxy Resins

Abstract

In this paper, we investigated the thermodynamics of the resin curing process, when it was a part of composition with graphite powder and cut carbon fibers, to precisely determine the time and temperature of gelation. The material for the research is a set of commercial epoxy resins with a gelation time not exceeding 100 min. The curing process was characterized for the neat resins and for resins with 10% by weight of flake graphite and cut carbon fibers. The results recorded in the analysis of temperature derivative (ATD) method unequivocally showed that the largest first derivative registered during the test is the gel point of the resin. The innovative approach to measuring the gelation time of resins facilitates the measurements while ensuring the stability of the curing process compared to the normative tests that introduce mechanical interaction. In addition, it was found during the research that the introduction of 10% by weight of carbon particles in the form of graphite and cut carbon fibers rather shortens the gelation time and lowers the temperature peak due to the effective absorption and storage of heat from the cross-linking system. The inhibiting (or accelerating) action of fillers is probably dependent on chemical activity of the cross-linking system.

Characterization and modeling of an epoxy vitrimer based on disulfide exchange for wet filament winding applications

“…The GP of a thermosetting polymer corresponds to the material‐specific DOC of incipient percolated network formation. This point becomes relevant from an engineer's perspective as viscosity increases exponentially, 76,77 preventing further processing 78 . Further from the GP onward, the formation of the mechanical modulus commences most residual stresses in the composite material 28,29 .…”

“…This point becomes relevant from an engineer's perspective as viscosity increases exponentially, 76,77 preventing further processing. 78 Further from the GP onward, the formation of the mechanical modulus commences most residual stresses in the composite material. 28,29 Before GP, the development of stresses is of secondary importance, as they relax immediately.…”

Thermo-rheological and kinetic characterization and modeling of an epoxy vitrimer based on polyimine exchange

“…This point becomes relevant from an engineer's point of view as viscosity increases exponentially, 44,45 which prevents further processing. 46 Further, the formation of the mechanical moduli at the GP commences most residual stresses in the composite material, 47,48 whereas, before gelation, the development of stresses is of secondary importance, as relaxation occurs immediately. 49 Different rheological 49,50 and dielectric 51,52 evaluation methods have been proposed for detecting gelation.…”

Application of Mathematical and Experimental Approach in Description of Sedimentation of Powder Fillers in Epoxy Resin

“…In such a scenario, V can be presented as a function of sedimentation distance h and resin pot life (gel time) t gel . In this study, the gel time of raw resin was assumed as 3709 s. The gel time of resin was determined using the Analysis of Temperature Derivative (ATD) method [47]. In the case of sedimentation distance, it was optimized based on quantitative metallography results and linked with the particle mean diameter d. The data collected in the research process and their interpretation allowed for a mathematical description of the filler sedimentation in the composite, which was verified by producing a sample and describing it quantitatively with the SEM/LM technique and hardness testing, showing the correctness of the mathematical model.…”