New approaches of curing and degradation on epoxy/eggshell composites

Jaques, Nichollas Guimarães; Barros, Janetty Jany Pereira; Silva, Ingridy Dayane dos Santos; Popp, Matthias; Kolbe, Jana; Wellen, Renate Maria Ramos

doi:10.1016/j.compositesb.2020.108125

Cited by 23 publications

(11 citation statements)

References 37 publications

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“…Additionally, to afore mentioned for the heating rates 5, 10 and 20 °C/min an endothermic peak is observed previously to the curing one (exothermic peak), which may be associated with the hardener (MTHPA) decomposition which starts at T i = 120 °C and finishes at T f = 275 °C, assuming nitrogen atmosphere and 10 °C/min as the heating rate, as reported elsewhere [18] . For S 5 (synthetic catalyst added), Figure 1b, the curing presented a bell shape without discontinuities, indicating that for this system the reaction occurs through one mechanism, despite presenting lower time and temperature curing ranges [24][25][26] .…”

Section: Resultssupporting

confidence: 64%

“…Eggshell and eggshell membranes as potential enhancers for epoxy systems were previously investigated by our research group, the results showed that the membrane increased the curing rate, and may be used as a low-cost substitute for synthetic catalysts. Regarding the thermal properties, composites with natural catalysts showed less stability [18] . Aware that the final properties of epoxies depend on their cross-linking process, and this process is influenced by the cross-linkers, the processing variables (time, temperature, pressure), and knowing the influence that using a natural catalyst may provide in the epoxy curing, it is essential to investigate their curing kinetics.…”

Section: Introductionmentioning

confidence: 99%

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Tailoring sustainable compounds using eggshell membrane as biobased epoxy catalyst

et al. 2022

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In this work eggshell membrane was added as biobased curing catalyst to epoxy (DGEBA), for comparison purposes the synthetic catalyst DEH 35 data was reported, the curing of compounds was followed through differential scanning calorimetry (DSC) under dynamic conditions and their kinetics were modeled using Kissinger, Friedman, Friedman model based and Málek approaches. From evaluated E A and ln A two steps of curing were verified, for the synthetic catalyst compound (S 5 ) E A abruptly increased for the degree of conversion 0.7 α > the opposite trend was observed for the eggshell membrane compound (M 10 ). It is supposed for S 5 E A increases due to the competitive reactions leading to viscosity increase until reach the solid phase with decrease of the reactive groups availability, hampering the crosslinking, whereas for M 10 E A decreases at 0.7 α > , hence invalidating the Kissinger model which assumes constant E A .

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Section: Resultssupporting

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Tailoring sustainable compounds using eggshell membrane as biobased epoxy catalyst

et al. 2022

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“…After the analysis, 50% of the sample remained at 900 C. Similar TGA profile of QES was also supported by. [28] On the other hand, both pristine PANI and PANI/QES composites generally had almost similar thermal degradation profiles. However, PANI/QES composites exhibited a higher degradation temperature as compared to pristine PANI due to the presence of QES fillers in PANI/QES composites.…”

Section: Tga Analysismentioning

confidence: 99%

Optimization of waste quail eggshells as biocomposites for polyaniline in ammonia gas detection

Norsham

Baharin

Raoov

et al. 2020

Polymer Engineering & Sci

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A simple, cost‐effective, and novel chemical sensor for ammonia (NH3) gas detection was developed from polyaniline (PANI)/quail eggshell (QES) composites. QES is a natural waste enriched in calcium carbonate. In this work, pure PANI was synthesized from chemical oxidation method and PANI/QES composites were prepared from physical mixing of QES with the synthesized PANI at different mass ratio. A series of complementary techniques including Fourier transform infrared and ultraviolet‐visible spectrometers, scanning electron microscope with energy dispersive detection coupled with mapping, thermogravimetric analysis, and X‐ray diffractometer were used to characterize the physicochemical and textural properties of the biocomposites. From the results, PANI/QES composite with a mass ratio of 1 exhibited the lowest NH3 detection limit of 5.24 ppm with a linear correlation coefficient (R2) of close to unity (0.9932) between the signal and NH3 gas concentration. As a whole, the PANI/QES biocomposites synthesized from this work exhibited excellent selectivity toward NH3 gas even in the presence of other gas impurities, such as acetone, ethanol, and hexane. For the sensor reusability, the PANI/QES biocomposites can be reused in the application of NH3 gas detection for at least 4 cycles.

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“…• 2nd stage, 5 < α < 90%, fast curing rate increases due to the greater functional groups availability and easier molecular movement, improving the crosslinking advance; • 3rd stage, 90 < α < 100%, at final stage the curing rate slows down due to the high viscosity and lower reactive functional groups content. 45 The curing parameters, that is, the maximum curing rate (C max ) and released enthalpy (ΔH) and characteristic temperatures computed from DSC scans for ESO/ MTHPA/DEH 35 compounds are shown in Table 2. Increasing the heating rates resulted in higher C max which also increased under MTHPA addition, indicating that ESO 87:10 and ESO 87:5 cured faster.…”

Section: Ftir Measurementsmentioning

confidence: 99%

Effect of hardener and catalyst contents on curing and degradation of epoxidized soybean oil

Albuquerque

Almeida

Barreto

et al. 2022

J of Applied Polymer Sci

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Epoxidized soybean oil (ESO) compounds were cured with methyl tetrahydrophthalic anhydride (MTHPA) as hardener and 2,4,6-tris (dimethylaminomethyl) phenol (DEH 35) as catalyst. To figure out MTHPA and DEH 35's influence during curing and degradation, ESO/MTHPA/DEH 35 compounds were investigated using Fourier-Transform Infrared Spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetry (TG).FTIR spectra of uncured resin showed the secondary interactions among ESO's carbonyl groups with MTHPA and DEH 35's hydroxyls and amines. Curing progress was followed tracking the evolution of reactive groups, that is, epoxy and carbonyl bands and corroborated with released heat of DSC scans. ESO 87:5 and ESO 87:10 compounds cured using higher heating rates presented higher released enthalpy suggesting denser reticulation, and they also displayed lower activation energy E a ð Þ for curing, which was evaluated using the Friedman model. Increasing the hardener and catalysts contents promoted higher thermal stability and lower degradation rates, while higher E a for degradation was verified.

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New approaches of curing and degradation on epoxy/eggshell composites

Cited by 23 publications

References 37 publications

Tailoring sustainable compounds using eggshell membrane as biobased epoxy catalyst

Tailoring sustainable compounds using eggshell membrane as biobased epoxy catalyst

Optimization of waste quail eggshells as biocomposites for polyaniline in ammonia gas detection

Effect of hardener and catalyst contents on curing and degradation of epoxidized soybean oil

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