Following network formation in an epoxy/amine system by ultrasound, dielectric, and nuclear magnetic resonance measurements: A comparative study

Abstract

This article presents a comparison of data obtained from a low-temperature cure of an epoxy/amine system by three independent cure monitoring techniques: ultrasonic wave propagation, dielectric permittivity, and nuclear magnetic resonance. The sizes and thermal histories of the samples studied by the three techniques were controlled for comparability between the methods. The three techniques gave consistent information on the progress of cure and were complementary, in that each was particularly sensitive to different stages of the cure process.

Monitoring cure and detecting damage in composites with inductively coupled embedded sensors

“…The bulk wave measurements recorded by the ICTS are in agreement with those made using external transducers; the attenuation experienced by the ultrasonic waves decreased, and the velocity of sound increased as the part cured [12,15,19,20]. The bulk wave ICTS displayed a high sensitivity to the final stages of the curing process, with the ultrasonic amplitude data plateauing later than the degree of conversion, and IIM measurements.…”

“…The progress of cure was followed by monitoring the reflection received from the back wall of the thick glass fibre laminate. This method of cure monitoring is similar to conventional ultrasonic cure monitoring methods, in which external transducers are used to make bulk wave measurements across the thickness of a curing part [12,15,19,20]. The cure of a large glass fibre plate (Figure 2b) was monitored using an embedded guided wave sensor (165 KHz operating frequency, Table 1).…”

“…The high cost and complexity associated with autoclave processes (and many other methods of composite manufacture), have created demand for techniques capable of providing real time data during cure, to ensure that parts are fully cured in the minimum amount of time. Numerous cure monitoring methods exist of which measurements of the dielectric permittivity [11,12,13,14], and ultrasonic techniques [12,15,16] are two of the most prominent macroscopic scale approaches, whilst differential scanning calorimetry (DSC), can be used to analyse the behaviour during cure of small laboratory samples (measuring tens of milligrams) [15,17,18]. All of these techniques can provide detailed analysis of the curing process, but each requires specialist equipment which can be of considerable expense; ultrasonic techniques often require transducers to be embedded into the tooling [19,20], whilst measurements of the dielectric permittivity are typically recorded by embedded sensors which become redundant post manufacture [14,21].…”

"Novas aplicações da precessão livre em onda contínua em ressonância magnética nuclear de baixa e alta resolução"

“…Um exemplo da potencialidade do uso desta técnica é o acompanhamento do tempo cura de resinas, inclusive com aplicações em odontologia 33,34 . Várias técnicas têm sido utilizadas para o estudo deste processo 35 e a RMN têm se mostrado como uma importante e mais versátil ferramenta 36,37,38,39,40 .…”

“…Através da RMN é possível acompanhar a reação de polimerização, tanto do ponto de vista cinético, quanto no que diz respeito a variações na mobilidade das cadeias, e interações entre elas 38,40 . .…”