Search Results (6)

Epoxy chip seals are widely used to improve the skid resistance of cement concrete pavements, which is significantly affected by surface texture. However, current methods for characterizing the surface texture structure are not precise, and the standard is not uniform. Therefore, a high-toughness modified epoxy resin chip seal structure was developed to conduct an indoor accelerated abrasion test. The elevation data of the epoxy chip seal under different abrasion times and different abrasion loads were obtained using laser scanning, and the Density/Sharpness combination parameters were obtained using the Hilbert–Huang transform and spectral analysis. The correlation between the texture parameters and the dynamic friction coefficient was analyzed using a stepwise multivariate quadratic polynomial method. The results showed that the texture structure of the epoxy chip seal surface is positively distributed, and the macroscopic texture occupies 49.45%, while the probability of the microscopic texture is only 4.55%. Meanwhile, the correlation coefficient between the texture parameters and the dynamic friction coefficient is 0.9307, which demonstrates that the selected texture parameters discard the texture components unrelated to skid resistance performance and reflect the distribution of the pavement texture and the skid resistance performance well. Full article

With the swift progress of the electronics industry, discarded circuit boards have become an important source of non-degradable waste. In this work, discarded epoxy resin was collected as a precursor to prepare activated carbon (AC) through stepwise carbonization/activation methods. The rough carbon materials with a certain graphite and amorphous structure reveal the multiple oxygen-containing groups on their surface. In the process of studying the adsorption of methyl orange by activated carbon, it is found that the adsorption is in accordance with the quasi-secondary kinetic model, and equilibrium adsorption amounts can reach 41.051 mg/g. The adsorption isotherm of AC is more in line with the Langmuir model, and the saturation adsorption amount at three different temperatures is 23.137 mg/g, 30.358 mg/g, and 37.202 mg/g, respectively. The enthalpy (ΔH) is 17.30 KJ/mol in the adsorption process, which indicates that is a physical process with heat-absorbing capabilities. This work is of great significance with regard to the recycling of waste to reduce pollution and in terms of gaining economic benefits. Full article

Composites with natural lignocellulosic fillers are being cited as a viable and sustainable alternative to conventional materials, as they combine lower costs with lower weight. In many tropical countries, such as Brazil, there is a considerable amount of lignocellulosic waste that is improperly discarded, which causes pollution of the environment. The Amazon region has huge deposits of clay silicate materials in the Negro River basin, such as kaolin, which can be used as fillers in polymeric composite materials. This work investigates a new composite material (ETK) made of epoxy resin (ER), powdered tucumã endocarp (PTE), and kaolin (K), without coupling agents, with the aim of producing a composite with lower environmental impact. The ETK samples, totaling 25 different compositions, were prepared by cold molding. Characterizations of the samples were performed using a scanning electron microscope (SEM) and a Fourier-transform infrared spectrometer (FTIR). In addition, the mechanical properties were determined via tensile, compressive, three-point flexural and impact tests. The FTIR and SEM results showed an interaction between ER, PTE, and K, and the incorporation of PTE and K reduced the mechanical properties of the ETK samples. Nonetheless, these composites can be considered potential materials to be used for sustainable engineering applications in which high mechanical strength is not a main requirement of the material. Full article

Surface-Enhanced Raman Spectroscopy (SERS) was employed as a spectroscopic tool to detect Bisphenol A (BPA), a building block in polycarbonate and epoxy resins or an additive in other polymer plastics like PVC, which has an endocrine disruptor effect. Silver nanoparticles (AgNPs) synthesized by using different reducing agents such as hydroxylamine (Ag@HX), citrate (Ag@Cit), borohydride (Ag@BH), and β-cyclodextrin (Ag@βCD) were employed, aiming to select the best standard SERS substrate. The lowest limit of quantification was reached at a concentration of 0.01 mM (2.3 μg/mL) of a sonicated aqueous solution by using Ag@Cit NPs and identifying two enhanced bands recorded at about 350 and 460 cm⁻¹. In order to gain insight into the nature of the enhanced bands, and therefore into which mechanism governs the SERS signal, electrochemical spectra recorded at different electrode potentials were acquired and TD-DFT calculations were applied to a neutral silver complex of BPA, Ag₂-BPA, and to its monohydroxylated chemical specie, Ag₂-BPA(OH), which is present in sonicated solution. The calculated electronic structure and the resonance Raman spectra point out that a surface plasmon-like resonance inside the silver cluster dominates the SERS spectrum corresponding to the physisorbed BPA(OH) species, a charge transfer enhancement mechanism or an intramolecular resonance transition localized in the phenolic framework was then discarded. Full article

Waste tires have emerged as a severe environmental threat worldwide as they create a number of disposal and landfill burden issues. In the present study, environmental pollutant crump rubber derived from waste discarded tires was reinforced with epoxy resin and prepared by means of an open-mold casting method to assess its mechanical properties. The impact of crump rubber content (0, 10, 20 and 30 vol.%) on the mechanical behavior of the composites was assessed using three-point bending tests at a constant strain rate of 0.1 and 0.01 mm/s. The stress–strain profiles of the 0.01 mm/s specimens revealed higher strains to failure compared with the 0.1 mm/s tested specimens and all the specimens showed brittle failure. Irrespective of the strain rates, tests revealed a marginal increase in the strength values of the composites and a significant increase in the modulus of all the composites compared with neat epoxy specimens. The results suggest that crump rubber can be effectively used in utilitarian composites requiring good flexural modulus and strength properties. Crump rubber epoxy composites with 30 vol.% of crump rubber showed higher modulus and strength compared with neat epoxy and other composites owing to the toughening phase induced by the crump rubber particles. The failure and fracture features of the specimens were analyzed using scanning electron microscopy. Full article

A sustainable alternative to the destination of polyethylene (PE) residue from the prepreg package was established. This work intends to develop nanocomposites for packaging containing neat low-density polyethylene (LDPE), a compatibilizer agent (maleic anhydride grafted-LDPE, LDPE-g-MA), recycled LDPE obtained from the protective films of prepreg (rLDPE) and montmorillonite (MMT). The rLDPE, from the prepreg shield, has a primary role during the transport and storage of prepreg, which can be composed of epoxy resin and carbon fiber or glass fiber. However, this rLDPE is withdrawn and discarded, besides, it is estimated that tons of this material are discarded monthly by the company Alltec Materiais Compostos Ltd. (São José dos Campos-SP, Brazil). Due to several factors, including the lack of technology for recycling, the majority of this material is incinerated. In this context, this work presents a technical and ecologically viable alternative for the use of this discarded material. Nanocomposites of LDPE/rLDPE blends and montmorillonite (MMT) with different contents (0.0, 1.0, and 3.0 wt%) and with the addition of compatibilizer agent (LDPE-g-MA) were prepared by extrusion process. Test specimens were obtained by hot pressing in a hydropneumatic press followed by die-cutting. The nanocomposites produced using rLDPE presented good mechanical, thermal, and morphological properties, being the ideal concentration of 1 wt% MMT. Thus, the results obtained confirmed the viability of recycling LDPE from the prepreg package which contributes to the reduction of waste and the use of this material in technological applications. Full article