In this paper, in order to further improve the heat resistance of UV-curing epoxy cresol novolac (EOCN), 2,2-bis(hydroxymethyl)propionic acid (DMPA) was firstly introduced to open epoxy groups in ...EOCN and then the hydroxyl groups reacted with acryloyl chloride to make sure the resin has sufficient UV-curing double bonds. Compared with the system that uses acrylic acid to open epoxy group and the secondary hydroxyl group reacting with unsaturated anhydride, up to 1.5 times double bonds were potentially introduced. The structure of the resins was characterized by FT-IR and
1
H-NMR. Influences of double bond content on thermal behavior, photopolymerization kinetic behavior, and basic properties of the cured films were investigated. Thermal performance analysis demonstrated that the glass transition and the initial decomposition of the cured films were increased with the rising proportion of acryloyl group. Moreover, doping of abundant acryloyl chloride caused a significant increase of unsaturated double bond conversion, though the initial photopolymerization rates declined. Cured films with less acryloyl chloride modified showed better adhesive. For solvent-resistant test, with the increase of the acryloyl group, the cured film displayed good resistance to strong acids and alkalis. These attractive features give this process potential applications in soldering ink and protective coatings.
A phenolic novolac resin has been chemically reacted with 4-vinylbenzyl chloride to introduce polymerizable vinyl benzyl groups. The modified novolac spontaneously polymerizes like styrene, is ...physically and chemically compatible with a typical unsaturated polyester (UP) resin, and can be free-radically cured (crosslinked) alone and in mixtures with UP using styrene as a reactive diluent. The cured vinylbenzylated novolac and co-cured blends of it with UP show superior flame retardance to cured UP alone and have potential applications as matrix resins in glass-reinforced composite laminates especially for marine structures.
With a growing interest in hydrogen as energy carrier, the efficient purification of hydrogen from gaseous mixtures is very important. This paper addresses the separation of hydrogen using Carbon ...Molecular Sieves Membranes (CMSM), which show an attractive combination of high permeability, selectivity and stability. Supported CMSM containing various amounts of aluminium have been prepared from novolac and aluminium acetyl acetonate (Al(acac)3) as carbon and alumina precursors. The thickness of the CMSM layers depend on the content of Al(acac)3 in the dipping solution, which also has influence in the pore size and pore size distribution of the membranes. The permeation properties of the membranes against the Al content in the membrane follows a volcano shape, where the membrane containing 4 wt (%) of Al(acac)3 has the best properties and was stable during 720 h for hydrogen at 150 °C and 6 bar pressure difference. All the CMSM have permeation properties well above the Robeson Upper limit.
•Defect free CMSMs were developed from Novolac and various contents of Al(acac)3.•Membrane thickness depends on the content of Al(acac)3 in the dipping solution.•Elemental analysis shows that the O and H content in the CMSM increases with the Al content.•Membranes were stable for H2 permeation for 720 h at 150 °C and 6 bar ΔP.
Novolac/silica hybrid gels (N/SiO2) are synthesized using the sol–gel polymerization method under a solvent-vapor saturated atmosphere, followed by an ambient-pressure drying technique. Moreover, ...prepared N/SiO2 aerogels are converted to carbon/silica (C/SiO2) and carbon/silica/silicon carbide (C/SiO2/SiC) nanocomposite aerogels through pyrolysis and carbothermal reduction at 800 and 1500°C, respectively. X-ray diffraction studies reveal the formation of graphite, cristobalite and β-SiC portions in the structure of prepared C/SiO2/SiC aerogels. Mercury porosimetry and scanning electron microscopy results demonstrate that the structural characteristics of fabricated nanocomposite aerogels retained after heat treatment steps. Thermogravimetric analysis and compressive strength measurements are used to investigate thermal and mechanical properties of prepared aerogels, respectively. The maximum oxidation rate temperature increased from 588°C for carbon aerogel to about 750°C for C/SiO2/SiC aerogels. The thermal conductivity coefficient of C/SiO2 and C/SiO2/SiC aerogels at room temperature are about 0.058 and 0.121 (Wm−1K−1), respectively. Compressive strength of C/SiO2/SiC aerogels is in the range of 1.8–2.3MPa. This is very impressive as the compressive strength of novolac/silica aerogels is in the range of 0.2–1.4MPa.
•Sol–gel polymerization in vapor of solvent saturated atmosphere is developed.•Highly porous carbon-silica-SiC composite aerogels are synthesized by pyrolizing novalac-silica composite aerogels.•The incorporation of silica resulted in higher porosity and lower density in carbon and polymer aerogel composites.•Presence of silica decreased the shrinkage during drying stage and increased shrinkage during the ultimate pyrolysing step.•By adding silica the oxidation temperature increased and the rate of oxidation decreased in carbon composite aerogels.
Low temperature curable propargyl novolac resin containing phthalonitrile moieties was realized through click chemistry approach. Towards this, propargylated novolac phthalonitrile and azide novolac ...functionalized resins were coupled through click reaction leading to triazole linked networks. The Cu
2
I
2
catalyzed reaction was initiated at 80 °C and the click coupled products showed excellent thermal stability up to 400 °C. The kinetics of click reaction was monitored using FT-IR spectroscopy and click coupling has been assumed to be second order with activation energy of 50 kJ mol
−1
. The possibility of formation of coupled products were theoretically evaluated using Density Functional Theory (DFT/B3LYP) method with 6-311G (d,p) basis set. Activation energy for the triazole ring formation was found to be 67 kJ mol
−1
which was closely matching with kinetic studies. The click cured samples found to form firm coating on glass substrates capable of withstanding elevated temperature without property deterioration unlike the generally used epoxies and silicones. The attempts through click-coupling may ease the sluggish curing restrictions of phthalonitriles that limits its potential applications.
In this study, the flame-retardant, thermal and mechanical properties of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and nano-SiO2 modified epoxy novolac resin is evaluated, and the ...combinational effects of both additives are verified. As a hardener, an isophorone diamine (IPDA) and polyetheramine blend is stoichiometrically added to obtain a low viscous epoxy resin system, suitable for resin injection and infusion techniques. The glass transition temperature (Tg) and the silica dispersion quality is affected by the DOPO modification and the nano silica particles. The flame-retardant (FR) and mechanical properties of the additives are investigated separately. The fracture toughness could be increased with the incorporation of both FR additives; however, the effect is deteriorated for higher DOPO amount which is referred to silica particle agglomeration and consequently reduced shear yielding mechanism. Flame-retardant properties, especially the peak heat release rate (pHRR) and the total heat release (THR) could be decreased from 1373.0 kW/m2 of neat novolac to 646.6 kW/m2 measured by resins with varying phosphorous and silica content. Thermogravimetric analysis (TGA) measurements show the formation of a high temperature stable char layer above 800 °C which is attributed to both additives. Scanning electron microscopy (SEM) images are taken to get deeper information of the flame-retardant mechanism, showing a dense and stable char layer for a certain DOPO silica mixture which restrains the combustible gases from the burning zone in the cone calorimeter test and influences the fire behavior of the epoxy resin.
The multifunctional novolac epoxy/Al2O3 nanocomposites were fabricated by high-speed mechanical mixing of epoxy resin with varying concentration of nano Al2O3 (0–5 wt%) of particle size 13 nm for 30 ...min, followed by curing with triethylenetetramine (TETA) at 110°C for 1 h and post-curing at 80°C for 5 h. The fabricated nanocomposite samples were characterized for mechanical properties (viz., tensile strength, elongation-at-break, impact strength, toughness, and hardness shore D), thermal stability, and fire retardancy. It was observed that the 3 wt% nano-Al2O3 containing sample showed significant enhancement in the tensile strength, elongation-at-break, impact strength, hardness shore D, thermal stability, and fire retardancy compared to the neat epoxy sample. The Differential Scanning calorimetry (DSC) confirmed the 3-D curing reaction between TETA and nano-alumina modified epoxy and neat epoxy samples. The reactivity effect of alumina towards resin was investigated by Fourier Transform Infrared (FTIR) spectroscopy. The morphological studies of nanocomposite samples were investigated by Scanning Electron Microscopy (SEM) to justify the enhancement of mechanical properties via dispersion of nanoparticles.
We have developed a three-component novolac resist incorporating a chemical amplification mechanism. The three components are a novolac resin, a dissolution inhibitor, and a photoacid generator. In ...this study, we investigated the change in dissolution rate and resist characteristic by reducing the number of protecting groups on the dissolution inhibitor. The dissolution inhibitor is a compound obtained by protecting some of the three hydroxyl groups of the dissolution accelerator (DA), which is a phenol derivative, with tBoc groups. From the dissolution rate of the polymer film, tBoc-DI-1(33%) in which one of the three hydroxyl groups was protected with tBoc group and DA showed dissolution promoting ability. tBoc-DI-2(67%) in which two of the three hydroxyl groups were protected with tBoc groups and tBoc-DI(100%) in which the three hydroxyl groups were completely protected exhibited dissolution inhibition ability. Mixtures of fully protected tBoc-DI(100%) and DA and tBoc-DI(X%) with randomly protected hydroxyl groups on DA have the same sensitivity, but the resolution of tBoc-DI(X%) was better. This is probably because tBoc-DI(100%) has a very large ability to suppress dissolution.
This work introduces coal char prepared by pyrolysis of subbituminous coal as a filler for compression-molded phenolic resin composites to improve the physical properties along with reducing material ...costs. The effects of filler concentration, particle size, and blending method on mechanical and thermal properties as well as morphology were comprehensively studied in comparison to reference materials. When simply blending resin and char powders, the highest compressive strength of 246 MPa with a Young's modulus of 5.0 GPa was reached using 50 wt% coal char, outperforming an equal amount of wood fiber (sawdust) as a filler with 198 MPa compressive strength and 3.2 GPa Young's modulus. Subsequently, different solvents were employed as dispersants to improve particle dispersion allowing for higher filler loads. Tetrahydrofuran (THF) enabled the best dispersion and led to compressive/tensile strengths reaching 288 MPa/75 MPa for 60 wt% coal char and 307 MPa/37 MPa for 70 wt% coal char. In addition, the phenolic/coal char composites showed a significantly higher thermal stability over the sawdust composite as well as a commercial phenolic composite. Water absorption studies also illustrated improved performance of coal char with and without the THF dispersant over sawdust in reducing moisture absorption. The findings of this work suggest that coal char has significant potential to be used as a filler in novolac composites for applications such as load-bearing building materials where high compressive strength, stiffness, thermal stability, water resistance, and low cost are required.
The combination of fractional condensation and water extraction methods is proposed to produce phenol rich beech wood pyrolysis bio-oil fractions, which have great potential to replace ...petroleum-based phenol in polymerization of novolac resin. The polymerization of model phenol acetaldehyde (MPA) resins, mimic acetaldehyde (mimic) resin which base on the composition of phenol compounds in bio-oil, and bio-oil acetaldehyde (BOA) resins were studied. MPA and mimic resins were used to compare with the BOA resins to determine the feasibility of using bio-oil. Bisphenol A type epoxy resin (DGEBA) was used, for the first time, as a formaldehyde-free cross-linker for bio-oil based novolac resins. The kinetic parameters of the curing reaction with model-free methods were obtained using data from a differential scanning calorimeter (DSC). The BOA resin showed curing activation energy was close to that of the phenol-acetaldehyde (PA) resin (95.5 and 94.9 kJ/mol by Kissinger method). The physicochemical and thermal properties of the novolac resins before and after curing are compared, and the potential of treated bio-oil products to effectively replace commercial phenols is demonstrated.
•Bio-oil fractions obtained by condensation were used to prepare novolac resin•Water insoluble bio-oil fraction has a potential to replace phenol•A formaldehyde-free cross-linker was used for bio-oil based novolac resins•The curing kinetic parameters were studied using differential calorimetry•A lower curing initial temperature was obtained using bio-oil resin
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