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•The NC dispersion in epoxy matrix was enhanced by graphene oxide nanosheets.•The G/N:34/66 loaded coating showed the highest corrosion protection degree.•The G/N:34/66 loaded coating ...resulted in the lowest coating cathodic delamination.
In this study, Graphene oxide (GO) nanosheets were studied to improve nanoclay (NC) exfoliation in a phenol novolac glycidyl ether and improve coating performance. Particle characterizations are performed by FT-IR, Raman spectroscopy, and FE-SEM methods. EIS measurements confirmed denotative stability in impedance values, more significant than 1010 ohm·cm2, after prolonged immersion time (18 weeks). Complementary characterizations, salt spray test, pull-off, and cathodic disbondment test, revealed that such enhancement in the clay dispersion has significantly improved the coatings protection function.
Each composite energetic material (CEM) has specific electrical resistivity (ER) and electrostatic discharge (ESD) sensitivity. These parameters depend on the concentration of composite ingredients. ...The effect of different mole ratios of ingredients on the ER and ESD sensitivity of Mg/Ba(NO3)2/novolac resin composite was modeled by response surface methodology (RSM) and central composite design (CCD). Nonlinear regression analysis and analysis of variance (ANOVA) indicated that the predicted responses were in good agreement with the experimental results. The results showed an inversely proportional correlation between increasing the mole ratio of Mg with ER and the minimum ignition energy (MIE) of ESD ignition. Similarly, there is a directly proportional correlation between increasing the mole ratio of Ba(NO3)2 and the novolac resin with increasing ER and MIE. A composite with low ER will conduct electrical energy and accumulate joule heating to begin ESD ignition. Therefore, increasing the conductive Mg ratio in the composite decreases joule heating. Thus, the MIE decreases with an increase in the Mg concentration. Similarly, increasing the concentration of electrical insulated novolac resin or Ba(NO3)2 in the composite increases the joule heating and the MIE. Therefore, a correlation was made to predict the ESD sensitivity of composites with different mole ratios of ingredients according to the values obtained from their ER measurements.
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•There is a correlation between electrical resistivity and ingredients ratio of a CEM.•There is a correlation between the ESD sensitivity and ingredients ratio of a CEM.•The ESD sensitivity of a CEM can be predicted by measuring its electrical resistivity.
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•Chemical modification of epoxy and novolac resins for incorporation into silica/siloxane networks.•Functionalization of CNT with silica nanoparticles to form CNT-SiO2 particle as a ...nonofiler.•Hybrid nanocomposites prepared by mixing of modified resins with CNT-SiO2 nonofiler and sol-gel method.•Increase of thermal stability and char yield by novolac-based resins and CNT-SiO2.•High char yield of 59.3% obtained from nanocomposites based on modified and epoxidized novolac resins containing CNT-SiO2.
Hear, three hybrid composites with high char yield and thermal stability were prepared form tetraethyl orthosilicate (TEOS)-modified epoxy resin (MER), (3-glycidyloxypropyl) trimethoxysilane (GPTES)-modified novolac resin (MNR), epoxidized novolac resin (ENR), and silica-grafted carbon nanotube (SFCNT) by a sol-gel method. The first class was prepared from MER and SFCNT. The second class was prepared from MER, MNR, and SFCNT. And the third class was prepared from MNR, ENR, and SFCNT. TEOS was used as covalent coupling agent in the sol-gel process. Results of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed successful modification of epoxy and novolac resins, modification of silica nanoparticles with (3-Aminopropyl)triethoxysilane (APTES), and also functionalization of CNT with amine-modified silica nanoparticles. Results of thermogravimetric analysis confirmed that the hybrid composite containing 4 wt% of SFCNT, MNR, and ENR shows the highest char yield of 58.4%. The hybrid composite containing 4 wt% of SFCNT and MER shows the highest degradation temperature of 442.7 °C. Finally, the hybrid composite formed from 4 wt% of SFCNT, MER, and MNR shows degradation temperature of 439.0 °C and char yield of 47.2%. Microscopic images and X-ray diffraction results confirmed attachment of silica particles at the surface of CNT by chemical bonding.
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•Carbon molecular sieve membranes were developed for ethanol dehydration.•alumina supports result in 48% thicker membranes than zirconia supports.•Higher performance compared with ...other membranes are reported.•Membranes are stable over a long period of time in permeation mode.
Tubular supported carbon molecular sieve membranes (CMSMs) with high hydrophilicity and perm-selectivities for water suitable for ethanol dehydration were developed from a Novolac oligomer phenolic resin as precursor. Alpha alumina supported CMSMs resulted in 1.69 times higher surface roughness than zirconia supports. The higher surface roughness resulted in 48% higher selective layer thickness. According to pervaporation results, water permeance decreased by the increase in selective layer thickness and mole based selectivity of water- ethanol was enhanced. The oligomer with 3982 g/mol molecular weight enabled membrane to reach high selectivity with one-layer coating. Performance of the membranes are compared with literature data in terms of mole-based selectivity vs. water permeance. CMSMs could be a potential substitution for traditional ethanol dehydration methods with offering higher performance and as a result reducing the final price of bioethanol to be used as a sustainable energy source.
Microcapsules (MCs) containing isocyanate compounds for use as self-healing materials in waterborne polyurethane coatings have been synthesized, in the presence of modified Novolac resins. With ...modification of Novolac resin, it is succeeded partial or total protection (Benzylation and Acetylation) of its hydroxyl groups. The idea here is to use a protected Novolac resin as the organic substrate for the encapsulation of the less reactive Isophorone isocyanate (IPDI) while the more reactive one, Methylene diphenyl diisocyanate (MDI), is used for the shell formation. Based on that strategy microcapsules of different morphologies and sizes were obtained, depending on the agitation conditions, as revealed using SEM and optical microscopy. Selective extraction was performed to determine the amount of the less reactive isocyanate (IPDI) stored inside the capsules through FTIR-ATR spectroscopy and isocyanate titration as well as the stability of IPDI inside the capsules over time. As determined, microcapsules based on Acetyl-modified Novolac resin encapsulated 96 wt% of IPDI monomer; this amount is about five and ten times higher than that encapsulated in MCs based on by Benzyl-modified Novolac resin or unprotected Novolac resin, respectively. At the same time, MCs based on Acetyl-modified Novolac resin were stable, maintaining approximately 80 % of the initial isocyanate content after two months of storage under inert conditions. Finally, the self-healing ability of the microcapsules was tested by adding selected IPDI-loaded microcapsules in waterborne polyurethane dispersions. It was proven that the Acetyl-modified Novolac-based MCs showed efficient healing behavior, in the absence of any catalyst, on the polyurethanes’ surfaces when scratched artificially.
•Two derivatives of Novolac resin through benzylation and acetylation were prepared•Novolac-based microcapsules (MCs) loaded with isocyanates (IPDI) were synthesized•High IPDI loading and stability has been found for acetyl-modified Novolac MCs•MCs can be well incorporated into waterborne polyurethane films•Acetyl-modified Novolac-based MCs were proved efficient self-healing materials
Phenolic novolac-type epoxy (EPN) resin composites were fabricated by reinforcing with cotton waste (CtW), along with aluminum hydroxide (AH), and boric acid (BA) particles under different filler ...loadings. For characterization, thermogravimetric analysis, scanning electron microscopy, differential scanning calorimetry, and water sorption tests were performed on the composites. The effects of the CtW, AH, and BA contents on the thermal, flame-retardant, and mechanical properties of the composites were investigated. The triple hybrid additive (CtW:BA:AH) with a ratio of 20:5:10 wt% exhibited the best mechanical and combustion properties. The tensile strengths of this composite and the neat EPN were determined as 95.7 ± 6.92 and 96.6 ± 4.77 MPa, respectively. The
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temperatures of the BA- and AH-doped composites were higher than that of neat EPN. The highest char percentages were observed in the triple composites, while the lowest were observed in the EPN/CtW composites. The combustion of the triple composite with a CtW:BA:AH ratio of 20:5:10 wt% was spontaneously extinguished in 37 s. Horizontal flammability testing also showed better fire resistance for the CtW/BA/AH composites over their CtW counterparts, with the highest estimated limiting oxygen index of 32.3 obtained for the 20:5:10 wt% composite. The water sorption test results show that the CtW composites had the highest hydrophilicity, especially those with 30 wt% CtW or higher, in the presence of water at room temperature.
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Reinforcing the novolac matrix with glass fiber (GF) and graphite (Gr) was a promising method for producing high‐performance friction composites. In this context, the morphology of the matrix and ...additive particles used in the production of friction composites, microstructures, wear surfaces, and wear debris of friction composites were examined by scanning electron microscopy‐energy dispersive spectroscopy, while the crystal phases of the materials were scanned by X‐ray diffraction. Density measurements (Archimed's method), hardness, tensile behaviors, and thermal analyses (thermogravimetric analysis and differential scanning calorimetry) of friction composites were performed. The variations in coefficient of friction (COF) and temperature with the change in sliding time were observed in detail at different additive ratios. The tribological behaviors of these composites were tested using a computer supported block‐on ring machine at sliding speeds of 200, 250, 300, and 350 rpm, applied loads of 50, 100, 150, and 200 N and constant time of 1800 s under dry conditions. Results indicated that with increase in the GF and Gr content, the stability of the (COF) became more stable and effectively reduced the specific wear rate. In addition, the wear resistance increased in parallel with the increase in normal loads and sliding speeds for all conditions.
Fabrication of novolac/graphite (Gr)/glass‐fiber (GF) friction composites. Investigate the effect of glass fiber and graphite contents on wear behavior. Obtaining advanced tribological properties with the reinforcement of Gr and GF.
In this study, effect of recycled zinc powder reinforcement ratios and ball milling time on novolac matrix hybrid composites were investigated. The ball milling time of 2 h showed a positive effect ...on the hardness of the composites up to 100 HRM. Thermal analysis results showed that the increasing zinc reinforcement ratio was increased thermal stability of the composite powders. The assessment of wear resistance was conducted using a block-on-ring tribometer, and the results demonstrated that the incorporation of zinc particles significantly decreased wear rates. Additionally, 2 h ball milling times showed superior wear resistance. Specimens with 20 wt% Zn reinforcement and subjected to 2 h ball milling time exhibited approximately 93% less wear loss than Zn-free specimens.
•Zinc powder recycled from waste Zinc anode.•Novolac matrix Zinc reinforced hybrid composites synthesized.•Thermal stability was increased with increasing Zinc reinforcement ratio.•The highest hardness value was obtained as 100 HRM.•The minimum wear rate in this study was obtained as 0.39 × 10−5 mm3/N.m.
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