Morphological, optical and thermal characterisation of aerogel-epoxy composites for enhanced thermal insulation

The present work explores the possibility of introducing aerogel at different stages of the epoxy resin cure to identify the most effective method that ensures minimal destruction of the aerogel particles. The aerogel particles are added at 0.5 h, 1 h and 1.5 h after the resin and the hardener are mixed together. Additionally, the effect of a wetting agent that improves the interface between the aerogel and the resin is also investigated. The different materials are characterised using optical images and ESEM-EDX to determine the most effective processing route. Additional data are also provided by determining the different material’s optical transmittance and reflective characteristics. From the experimental results, it is observed that the addition of aerogel at the 1-h mark proves to be the most efficient route to follow. In addition, the wetting agent displays a negligible effect on the samples in the study; hence, its usage is advocated due to its influence on the interface strength. Therefore, the aerogel/epoxy/wetting agent sample with the aerogel added at the 1 h mark looks promising. A 13.3% decrease in thermal conductivity when compared with the pure resin/hardener sample along with the damage coefficient value of 0.183 demonstrates the material’s potential for thermal insulation applications.

Quantitative Analysis of Epoxy Resin Cure Reaction: A Study by Near-Infrared Spectroscopy

Near-infrared spectroscopy was used to quantify the cure reaction of 4,4′-methylene- bis-(2,6-diethylaniline) (MDEA)–epoxy resins (E/A = 1.4) carried out at 72 and 160 °C. The absorption bands of the functional groups of interest in MDEA–epoxy resins are assigned according to the literature. A new assignment at 6580 cm−1 is also proposed for the secondary amine: it was supported by a synthesized model compound. Two different spectrum treatments were proposed. The first one is based only on a normalization at 4610–4620 cm−1, while the second one needs the subtraction of the normalized spectrum of a post-cure sample. To follow the curing process, amines and epoxy were studied at the same time in the combination and the overtone regions. The results are compared. In the combination region, quantitative results are obtained from absorbance measurements, while in the overtone region spectrum decompositions and area measurements are necessary. Complementary and reliable information are so obtained and allow us to calculate conversions of epoxide and amine I and concentrations in amine II, amine III, hydoxyl groups, and ether links. Kinetics are also established. The curing process mechanism is at last discussed for both curing temperatures.

Application of Near-Infrared Attenuated Total Reflectance Spectroscopy for Monitoring Epoxy Resin/Amine Cure Reactions

Product quality in composite processing will be improved by dependable methods for monitoring the process. In this paper, the feasibility of using near-infrared attenuated total reflection (NIR ATR) spectroscopy as a sensor for monitoring epoxy resin cure is demonstrated. An ATR crystal serves as a contact sensor, which has several potential advantages over embedded optic fiber techniques previously reported. NIR ATR spectra obtained from several epoxy/amine systems show that both primary amine and epoxy functional groups have well-isolated absorption peaks in the near-infrared region. The utility of NIR ATR spectroscopy for in situ cure monitoring is demonstrated by following the reaction between phenyl glycidyl ether and butylamine at ambient temperature.