Hybrid composites of novolac resin were prepared by using graphene oxide (GO) which was functionalized with furfuryl alcohol and silica nanoparticles (SiO2). For this purpose, SiO2 was modified with ...silane coupling agent of (3-aminopropyl)triethoxysilane (APTES) to obtain SiO2-NH2 and subsequently attached at the surface of furfuryl alcohol-modified GO (GOFA) to obtain SGOFA. The SGOFA was incorporated into the novolac resin matrix in two different contents of 4 and 8 wt% of the matrix. Successful modification processes of GO with furfuryl alcohol, SiO2 with APTES, and GOFA with SiO2-NH2 were confirmed by Fourier-transform infrared spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. TGA results showed that char residue of novolac resin was increased by incorporation of SGOFA from 58.4 to 61.3 and 65.4% by the addition of 4 and 8 wt% of SGOFA, respectively. Additionally, degradation temperature of novolac resin was increased by incorporation of SGOFA from 445.4 to 460.0 and 467.4 °C by the addition of 4 and 8 wt% of SGOFA, respectively.
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•Surface modification of GO by furfuryl alcohol and APTES-modified silica resulted in SGOFA.•Novolac-type phenolic resin composites were prepared by incorporation of 4 and 8 wt% of SGOFA.•Char residue was increased by incorporation of SGOFA to 65.4% by the addition of 8 wt% of SGOFA.•Degradation temperature was increased to 467.4 °C by the addition of 8 wt% of SGOFA.
The current research focuses on investigating the effect of using reclaimed asphalt pavement (RAP) on performance of hot mix asphalt (HMA) prepared with polymer modified bitumen (PMB) binder. This ...PMB used for the first time with HMA contained RAP. The mechanical properties and performance of HMA were assessed using several standard tests including Marshall, indirect tensile strength, creep compliance, and wheel track test. The RAP replacement was conducted up to 70% of total aggregate in HMA with an increment of 10%. The results of investigation showed, that the use of PMB binder prepared by addition novolac (phenol formaldehyde solid resin) and hexamine to conventional bitumen, significantly improved the performance of HMA contained RAP. Also, the optimum percentage of RAP replacement was found to be 50% of total aggregate in HMA. For this level of replacement, the rut depth reduced up to 38% of its original value.
On a global scale, methanol is one of the most important feedstocks and is used widely as solvent and co-solvent. However, due to the polar nature and associated ability to conduct current, the small ...molecule can take part in galvanic corrosion of metal storage tanks and degrade the barrier properties of protective coatings. In the present work, we investigated the degradation of two novolac epoxy coatings and a polyurethane (PU) coating exposed to methanol with the aim of quantifying the various degradation paths. Absorption and desorption rates were measured and the thermomechanical properties followed by dynamic mechanical analysis. For evaluation of the coating barrier properties (i.e., breakthrough time and steady state permeation rates of methanol), permeation cells were applied. During methanol absorption, simultaneous leaching of certain coating ingredients and bonding of methanol to the binder matrix via hydrogen bonds was evidenced. In terms of classification, the bonding of methanol took place by two types of mechanisms. In Type I, the methanol molecule forms a single hydrogen bond to the coating network, thereby acting as a plasticizer, which decreases the coating storage modulus and glass transition temperature. For Type II bonding of methanol, on the other hand, two hydrogen bonds to the coating network form per molecule, resulting in so-called physical crosslinking. The Type I mechanism boosted segmental mobility and contributed to the leaching of the plasticizer benzyl alcohol from the novolac epoxy coatings and residual solvents (i.e., naphtha and xylene) from the PU coating. Following the methanol desorption, and attributed to an increased effective crosslinking density from Type II bound methanol, the novolac epoxy and PU coatings exhibited significant increases in the glass transition temperatures. In addition, for the three coatings, a gradual decline in the permeability rate of methanol was observed over time. These enhanced (and unexpected) barrier properties result from a combination of effects ascribed to Type II bound methanol and the leaching process.
► A piecewise kinetic method is developed and described well the cure behavior of novolac resin. ► The mechanism changes from autocatalytic to
n-order kinetic gradually during the cure reaction. ► ...Model-free kinetic results show the same reaction mechanism with the model fitting model. ► Model-free kinetic methods do better in the prediction of isothermal curing behavior.
The curing behavior of novolac type phenolic resin was studied through differential scanning calorimetry (DSC) using model fitting and model-free (isoconversion) kinetic methods. For the model fitting kinetic study, a piecewise fitting approach was developed to describe the dependence of cure reaction rate on temperature and curing degree. The piecewise model displayed excellent modeling ability. In the model-free kinetic study, Friedman, and Kissinger–Akahira–Sunose methods were used to calculate the curing activation energy. The dependence curve of activation energy on conversion and the piecewise model fitting results both displayed a change in the kinetic reaction mechanism from the autocatalytic to
n-order regime. According to the isothermal prediction results, the model-free kinetic methods show much better prediction ability, compared with the model fitting methods. Also, Friedman and Kissinger–Akahira–Sunose methods were found to show similar results in predicting the isothermal curing behavior of this novolac resin.
The influence of carbonization temperature on the permeation properties and aging of thin (4 μm) supported carbon molecular sieve membranes (c-CMSM), prepared from in house synthesized novolac ...phenolic resin loaded with boehmite nanoparticles, were studied. Just after membrane carbonization (fresh membrane), high permeance to N2 and O2 and low O2/N2 permselectivities were observed; the highest permeations were observed for carbonization end temperatures between 500 °C and 700 °C. After leaving the c-CMSM 1 day in the air, a large decrease in the permeation and considerable increase in the permselectivity were observed due to the reduction of the pore size by oxygen chemisorption and water physical adsorption; the permeability to H2 and H2/N2 ideal permselectivity for a membrane carbonized at 550 °C are close to palladium membranes for low temperature (<100 °C). The effect of the permeation characteristics of the membranes carbonized at various temperatures and the removal of water adsorbed in the pores by heat treatment were studied.
•Supported c-CMSM was prepared in a single coating-drying-carbonization step from novolac.•Effect of the carbonization temperature on the permeation characteristics of c-CMSM are studied.•From 700 °C the pores are small, the mechanism of permeation of gases is by molecular sieving.•For carbonization between 500 and 650 °C, good H2 permeation and H2/N2 selectivities are obtained.•Aging and activation of c-CMSM carbonized at different T was studied.
Choosing the amount of binder resin in a brake lining composition is important in terms of avoiding structural deterioration of the brake lining composite and resisting mechanical and thermal ...stresses at different temperatures. This study evaluated the performances of new brake lining composites with 15% and 20% novolac resin additives by performing wear tests in different temperature environments. Friction wear tests were performed according to ASTM G99 using pin-on-disc test devices at temperatures of 23°C, 150°C and 300°C. The hardness and density of the samples increased by 2.4% and 3.7%, respectively, with the increase of the novolac resin ratio in the composition. In general, it was observed that the friction coefficient, thermal conductivity and vibration increased in parallel with the resin ratio. In addition, increasing the test temperature led to an increase in the friction coefficient.
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In this paper, porous microcapsules with tunable pore sizes were prepared using interfacial polymerization by employing a temperature-responsive cross-linking agent above its ...so-called cloud point temperature (Tscp). The influences of porosity on the surface morphology, release profile and biological activity of the microcapsules were investigated. The results showed that both pore size and pore density could be controlled by regulating either the amount of cross-linking agent or the ratio of core material to shell material. Furthermore, the porosity of the microcapsules determined their release properties and further regulated the bioactivity of the microcapsules. In addition, the mechanism of pore formation was confirmed by investigating the morphology of microcapsules below the Tscp. The microencapsulation methodology described here is convenient and versatile, which can be easily extended to encapsulate a broad range of lipophilic core materials.
In the present study, vinyltrimethoxysilane was used to modify high-ortho novolac resin (NR) to obtain a vinyl silicone-modified phenolic oligomer (Si-mod NR). Subsequently, this oligomer is ...polymerized with methyl methacrylate. The mid-products (NR and Si-mod NR) and synthesized silicone-modified phenolic/acrylic resin (Ac/Si-mod NR) were characterized by Fourier transform infrared spectroscopy, and thermal properties were investigated by using thermal gravimetric analysis and differential scanning calorimetry techniques. In addition, the surface coating properties, including drying, hardness, adhesion, impact resistance, gloss, acid, alkaline, water, and solvent resistance of the films prepared from these products, were comparatively investigated. The results showed that the modification reactions yield a novel resin (Ac/Si-mod NR), which can be easily used as a surface coating material with high thermal resistance, flexibility, and excellent film properties.
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