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.
•A batch-like reactor (autoclave) capable of simulating the HPHT conditions is utilized.•A mixture of N2 and CO2as the gas phase had no detrimental effects on the epoxy novolac and bisphenol F ...networks at HPHT.•Hydrocarbon interactions with epoxy novolac and bisphenol F coatings resulted in softening of their network at HPHT.•Synergistic action of hydrocarbon and seawater resulted in an underfilm-corrosion for epoxy novolac and bisphenol F coatings. 5. Epoxy novolac exhibited superior seawater resistance compared to Bisphenol F at HPHT.
Projections of continued growth in the global hydrocarbon demand and fast depleting resources push the oil and gas industry to explore and produce in geological formations with abnormal high pressures and temperatures, so-called HPHT conditions. In the present study, the largely unexplored degradation mechanisms for amine-cured epoxy novolac (EN) and bisphenol F (BPF) epoxy resins are investigated at lower limits of HPHT.
Using a batch-like reactor encompassing the three relevant phases (a gas mixture of nitrogen and carbon dioxide, a hydrocarbon phase of aromatic para-xylene, and an artificial seawater phase), the conditions of high pressures and high temperatures were simulated. The EN and BPF coated steel panels were placed inside the batch reactor.
In the gas phase-exposed zone, both EN and BPF remained essentially intact with no major defects. However, due to para-xylene uptake that resulted in a free volume increase (i.e. lowering of the glass transition temperature), the hydrocarbon-exposed zones of EN and BPF were partly covered by an oxide of iron, the origin of which was found to be diffusion of anodically-dissolved iron from the steel-coating interface. The enhanced resin chain mobility at the hydrocarbon-seawater interphase allowed higher rates of diffusion of seawater ions to the steel-coating interface with clear signs of coating degradation. Finally, the seawater phase induced small blisters in the EN coating, whereas for BPF, a complete loss of adhesion between the coating and the substrate was observed.
Simulation of Rapid Gas Decompression (RGD), uncovered the role of RGD in the iron oxide formation process for both EN and BPF coatings.
In summary, when compared to BPF, the EN network showed superior performance under conditions of HPHT.
The present work intended to synthesize a composite material exhibiting self-healing and enhanced anticorrosion properties. In this context, MWCNT incorporated nanocapsule (NC) filler material was ...synthesized, then it is blended with phenol novolac resin (PNR). The surface characterization studies of MWCNT/NC-PNR composite material signify the nano-size, spherical, and multiwalled structures of NC and CNT. The composite materials consisting of different weight percentages of MWCNT inserted NC were coated on the mild steel (MS) surface by the doctor blade method. The 0.3 wt% MWCNT/NC blended PNR showed significantly enhanced hydrophobicity of the coating which is evidenced by the high value of water contact angle (98.2°) amongst the coating materials prepared. Further, electrochemical impedance spectroscopy (EIS) tests of the coating confirm a high impedance value of 3.039× 107 ohm cm2 at the low frequency region for 50 days of immersion in 3.5 wt% NaCl solution. Thus, it was found that 0.3 wt% MWCNT incorporated NC filler increased the corrosion protection efficiency of NC/PNR coating by 32.61%. Therefore, the results show that the MWCNT/NC-PNR composite coating exhibits significantly elevated corrosion resistance, and can be used as a self-healing inhibitor coating material for long-term anti-corrosion shield.
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•MWCNT/NC-PNR exhibiting both self-healing and elevated anticorrosion properties.•MWCNT/NC strongly tortures the electrolyte to reach the MS surface.•The active agent released by the capsule can fill the loophole thereby self-healing the coating surface.•TEM show the spherical structured smooth surface of NC, and its diameter seems to be 230 nm.•The EIS results validate the excellent healing nature of the capsules.
Novolac vinyl ester (NVER) often serves as film-forming material in severe corrosion environment. Unfortunately, major hydrophilic groups gathering on the surface and voids are produced in the ...solidifying process, which is an intrinsic defect. In order to fulfill the hydrophobicity and promote antiseptic performance, the fluorinated NVER coatings (F-NVERs) was modified with dodecafluoroheptyl methacrylate (DFHMA) by chain polymerization reaction and different loading ratio of β-Si3N4 nanoparticles was introduced to the polymeric matrix through ultrasound approach to fabricate DFHMA modified NVER-based nanocomposite coatings (S/F-NVERs) protection system. The chemical structure, hydrophobicity and morphology were examined by Fourier-transform spectroscopy, contact angle measurement and scanning electron microscope, respectively. Moreover, the corrosion barrier property of coatings on mild steel was also evaluated through immersion and electrochemical impedance spectroscopy. According to the findings, the nanocomposite coatings prepared via addition of 8 wt% DFHMA and 3 wt% β-Si3N4 were confirmed with decent hydrophobicity and optimal corrosion protection ability. Also, the effect of dispersity on corrosion resistance, among disparate addition of β-Si3N4, was systematically discussed.
In order to enhance anti-corrosion property of novolac vinyl ester coatings (NVERs), the NVERs was modified by introducing of dodecafluoroheptyl methacrylate (DFHMA) and β-Si3N4 particles. DFHMA is an organic monomer with long fluorinated chains tails and CC double bond, which will improve the hydrophobicity of the top coating. β-Si3N4 particles create a “labyrinth effect”, which is responsible for the barrier performance of the coating. Moreover, the anti-corrosion mechanism of the S/F-NVERs was also discussed. Display omitted
Phthalonitrile resins (PN) are known for their incredible heat resistance and at the same time poor processability. Common curing cycle of the PN includes dozens hours of heating at temperatures up ...to 375 °C. This work was aimed at reducing processing time of phthalonitrile resin, and with this purpose, a novolac oligomer with hydroxyl groups fully substituted by phthalonitrile moieties was synthesized with a quantitative yield. Formation of the reaction byproducts was investigated depending on the synthesis conditions. The product was characterized by
H NMR and FT-IR. Curing of the resins with the addition of different amounts of novolac phenolic as curing agent (25, 50 and 75 wt.%) was studied by rheological and DSC experiments. Based on these data, a curing program was developed for the further thermosets' investigation: hot-pressing at 220 °C and 1.7 MPa for 20 min. TGA showed the highest thermal stability of the resin with 25 wt.% of novolac (T
= 430 °C). The post-curing program was developed by the use of DMA with different heating rates and holding for various times at 280 or 300 °C (heating rate 0.5 °C/min). Carbon and glass fiber plastic laminates were fabricated via hot-pressing of prepregs with T
's above 300 °C. Microcracks were formed in the CFRP, but void-free GFRP were fabricated and demonstrated superior mechanical properties (ILSS up to 86 MPa; compressive strength up to 620 MPa; flexural strength up to 946 MPa). Finally, flammability tests showed that the composite was extinguished in less than 5 s after the flame source was removed, so the material can be classified as V-0 according to the UL94 ratings. For the first time, fast-curing phthalonitrile prepregs were presented. The hot-pressing cycle of 20 min with 150 min free-standing post-curing yielded composites with the unique properties. The combination of mechanical properties, scale-up suitable fast-processing and inflammability makes the presented materials prospective for applications in the electric vehicle industries, fast train construction and the aerospace industry.
Enhancement of thermal stability‐insulation performance of hyper porous materials is the premier issue to design of novel porous thermal protection systems. Boron‐containing monolithic novolac ...xerogels (BCNXs) were synthesized using sol–gel networking of novolac resin with hexamethylenetetramine (HMTA) and boric acid at the solvent saturated vapor atmosphere (SSVA). The aim was to elucidate the effect of higher crosslinking density and thermal stable boron containing chemical bonds on the microstructure, thermal conductivity, and thermal oxidation stability of novolac xerogels. The results of FESEM and BET analysis showed that the microstructural characteristics of xerogels are significantly depend on the HMTA and boric acid concentration. The thermogravimetric results were analyzed using characteristic kinetic temperature (CKT)‐characteristic kinetic temperature range (CKTR) approximations. The effect of micromorphology of xerogels on the thermal conductivity was investigated. The effective thermal conductivity of samples were in the range of 0.031–0.048 W/m K.
The encapsulation of active components is currently used as common methodology for the insertion of additional functions like self-healing properties on a polymeric matrix. Among the different ...approaches, polyurea microcapsules are used in different applications. The design of polyurea microcapsules (MCs) containing active diisocyanate compounds, namely isophorone diisocyanate (IPDI) or hexamethylene diisocyanate (HDI), is explored in the present work. The polyurea shell of MCs is formed through the interfacial polymerization of oil-in-water emulsions between the highly active methylene diphenyl diisocyanate (MDI) and diethylenetriamine (DETA), while the cores of MCs contain, apart from IPDI or HDI, a liquid Novolac resin. The hydroxyl functionalities of the resin were either unprotected (Novolac resin), partially protected (Benzyl Novolac resin) or fully protected (Acetyl Novolac resin). It has been found that the formation of MCs is controlled by the MDI/DETA ratio, while the shape and size of MCs depends on the homogenization rate applied for emulsification. The encapsulated active compound, as determined through the titration of isocyanate (NCO) groups, was found to decrease with the hydroxyl functionality content of the Novolac resin used, indicating a reaction between NCO and the hydroxyl groups. Through the thorough investigation of the organic phase, the rapid reaction (within a few minutes) of MDI with the unprotected Novolac resin was revealed, while a gradual decrease in the NCO groups (within two months) has been observed through the evolution of the Attenuated Total Reflectance-Fourier-Transform Infrared (ATR-FTIR) spectroscopy and titration, due to the reaction of these groups with the hydroxyl functionalities of unprotected and partially protected Novolac resin. Over longer times (above two months), the reaction of the remaining NCO groups with humidity was evidenced, especially when the fully protected Acetyl Novolac resin was used. HDI was found to be more susceptible to reactions, as compared with IPDI.
•Post-consumer denim was collected from municipal waste sorting plants and recycled.•Efficient sound-absorbing construction material was produced.•Prediction of sound absorption was performed using ...logarithmic and JCA models.•Recycled denim composites successfully compete with commercial glass wool samples.•Recycled denim composites are environmentally friendly and economically viable.
Recently, a growing interest has been focused on utilizing alternative recycled sound-absorbing construction materials. This study investigates phenolic resin-bonded recycled denim as a potential replacement to synthetic sound absorbers. To this end, the discarded denim was collected from municipal waste sorting plants and shredded to back down into fiber form. Solid novolac resin and fibers were fed to the air-laid machine. The hybrid structures were then introduced to an oven to cure the resin and form an integrated flexible structure. Nonwoven composites at different bulk densities (61–102 kg/m3) and resin contents (10–35%) were produced. The sound absorption coefficient (SAC) of composite samples was determined using the impedance tube method. The relationship between SAC versus frequency was modeled using a logarithmic regression and the phenomenological model of Johnson-Champoux-Allard (JCA). Additionally, the noise reduction coefficient (NRC) values of the samples were compared with those of some commercially available glass wool nonwovens of the same physical properties. The results showed that the mechanism of sound absorption for samples is viscosity resistance, in which SAC at low frequencies is low, however at high frequencies is quite significant. The results of the statistical analysis confirmed that both the bulk density and resin content have a significant effect on the SAC. It was found that SAC rises with increasing the areal density and bulk density, and this raise is more pronounced at higher bulk densities. It was also observed that for samples of the same bulk density, SAC increases with increasing the resin content. The results indicated that resin-bonded recycled denim composites could successfully compete with commercial glass wool samples for noise control, apart from being environmentally friendly and economically viable.
