Thermal and dynamic mechanical behavior of epoxy composites reinforced with post‐consumed yerba mate

Abstract

Yerba mate (YM) is widely consumed in Latin American countries, and its residues can be used as bio‐resources such as reinforced in epoxy composites. The present work aims to produce epoxy resin composites and evaluate the influence of post‐consumed YM as reinforcement. The concentrations of YM used were 5, 10, and 20% (wt/wt). Chemical, thermal, morphological, and dynamic mechanical behaviors were explored. The YM incorporation did not influence chemically on the epoxy structure and a pull‐out phenomenon was observed as YM content increased. The YM at lower concentrations (5 and 10%) led to higher values of activation energies calculated from model‐free isoconversional methods. On the other hand, the composite e/YM 20 wt% improved all dynamic‐mechanical properties. YM proved to be a suitable and cheap reinforcement for epoxy resin.

Modeling of the creep behavior of epoxy/yerba-mate residue composites

“…[35][36][37] However, it is noteworthy to mention that a rougher and a high number of holes are formed when the composite is cryogenically fractured with a greater reinforcement content (e/YM 10% and 20%), due to the pull-out mechanism. 38 This result might be related to the non-chemical interaction between epoxy resin and YM particles, observed in a previous work 39 where it was shown in FTIR spectra that the incorporation of YM onto epoxy did not altered the spectrum. Moreover, when particulate fillers are used above their saturation, the surface touching each other starts to be more pronounced in the polymer matrix, decreasing the adhesion and filler/matrix interface area.…”

“…Since the aim was to verify the influence of YM content in the glassy region, therefore the tests were performed between 30 and 90°C, based on the storage modulus curves of the composites. 1 Creep tests were performed based on previous studies. 14,17,33 The temperature was set at 30°C and three different loads were applied: 1.5, 3.0, and 6.0 MPa, using a pre-load force of 0.1 N. The tests were carried out in creep mode and each load was applied at the center of the sample, through the sample thickness, for 30 min, aiming to reach equilibrium.…”

“…Brazil plays an important role in YM production and consumption since they produced around 390 thousand tons, of which 80% was destined for the internal market, in 2018. 1,2 It is estimated that the per capita consumption of yerba mate in Brazil lays around 1.2–5 kg per year. 3 Due to its high consumption, a huge amount of waste is produced.…”

Epoxy-based composites reinforced with imidazolium ionic liquid-treated aramid pulp

“…Table 1 summarizes the main temperatures related to the curing of the epoxy and epoxy IL-treated AP composites. No significant differences on T onset and T peak are presented for all composites or neat epoxy, which means that AP does not influence on the beginning of epoxy curing [31]. On the other hand, the heat realized (ΔH) during the cure presents a slight increment, when AP is used, which may be attributed to the catalytic effect of AP in the ring opening reaction of epoxy, by the presence of amine groups on the AP surface [32].…”

“…All samples presented an exothermic peak during curing, indicating the formation of a high crosslinking density, as expected. Moreover, according McCoy et al [30], the curing kinetic of a DGEBA epoxy resin is a complex reaction system and the use of fillers may promote different events in the DSC curve shape [31]. Table 1 summarizes the main temperatures related to the curing of the epoxy and epoxy IL-treated AP composites.…”