Semiconductors have continued to grow smaller alongside the development of shorter wavelength exposure sources and the development of photoresists optimized for such exposure wavelengths. For the ...g-line (436 nm) and i-line (365 nm) exposure wavelengths, novolak resists made of novolak resin have been used for patterning at pattern sizes of 0.5 μm-1 μm. For the exposure wavelength of 248 nm (KrF excimer laser), polyhydroxystyrene (PHS) has been used for patterning at pattern sizes of 0.2 μm-0.35 μm. For the exposure wavelength of 193 nm (ArF excimer laser), acrylic-based resin has been used for patterning at pattern sizes of 30 nm-0.2 μm. With the most advanced current lithography technologies, patterning at pattern sizes finer than 20 nm can be performed using exposure wavelengths of 13.5 nm (EUV). Apparently, then, lithography using novolak resists made of novolak resins is an outdated technology. However, it continues to be employed in LCD processes that involve TFT technology, where the development of higher definition LCDs continues to drive miniaturization. We studied the novolak resist, from synthesis to formulation and to evaluation of its resolution, to reexamine which factors are key to achieving high resolution in novolak resists.
Polybenzoxazines, as a kind of phenolics, are high performance thermosets with a range of features and overcoming some drawbacks of resole and novolac type phenolics. Most of the polybenzoxazines ...exhibit high Tg, high char yield, flame resistance, low water absorption, low shrinkage and also limited or no release of by-products during curing, they have good mechanical performance and are effective contender of high performance polymers such as bismaleimide resins. Thus, the interest in polybenzoxazines is continuously increasing in the polymer science as reflected by the number of scientific publications and patents. In this mini review, an overview about polybenzoxazines is reported highlighting the current advances and progress in the synthesis of benzoxazine based materials for unconventional uses that can be considered as smart applications ranging from self-healing materials to electrochromic devices.
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Polybenzoxazine is a newly developed addition polymerized phenolic system, having a wide range of interesting features and the capability to overcome several shortcomings of conventional novolac and ...resole type phenolic resins. These materials exhibit (i) near-zero volumetric change upon curing, (ii) low water absorption, (iii) for some polybenzoxazines
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g much higher than cure temperature, (iv) high char yield, (v) no strong acid catalysts required for curing, and (vi) release of no toxic by-product during curing. The molecular structure of polybenzoxazines offers enormous design flexibility, which allows tailoring the properties of the cured materials for a wide range of applications. In this review article, different synthetic strategies for the preparation of benzoxazine monomers and blends, their polymerization reaction mechanisms, and the structure–property relationships of the cured materials have been discussed.
We pyrolyzed and activated novolac beads in one single step with ammonia at different temperatures (750–950 °C), which leads to a highly porous carbon with nitrogen-doping. The chemical and physical ...properties were characterized and correlated with the electrochemical performance as supercapacitor electrodes. The average pore size varied at 0.6–1.4 nm dependent on the synthesis temperatures. Three different electrolytes (aqueous, organic, and an ionic liquid) were tested. The specific capacitance in a symmetrical supercapacitor reached up to 173 F g−1 and was strongly dependent on the porosity of the electrode material and the kind of electrolyte. We found that the presence of nitrogen enhanced the electrochemical performance stability and led to a high specific energy of 50 Wh·kg−1 using an ionic liquid as electrolyte.
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•Two kinds of encapsulated ceramsite-supported phase change materials have been successfully prepared.•E-PEG/CS has the better thermal reliability and chemical stability.•The maximum peak temperature ...reduction of upper surface can reach 9.1 °C.
Two kinds of phase change materials (PCMs), poly(ethylene glycol) (PEG) and ethylene glycol distearate (EGD), were incorporated with ceramsite (CS) to obtain the composite PCMs (CPCMs) by vacuum impregnation method. The morphology of the samples was observed using scanning electron microscope (SEM) and the chemical compatibility was characterized by X-ray diffraction (XRD) and Fourier transformation infrared (FTIR). The PEG and EGD could be retained by 42.1 wt% and 34.0 wt% into pores of the CS, which was calculated according to the curves of the thermogravimetric (TG) analysis. The thermal properties and thermal reliability of the CPCMs were investigated via differential scanning calorimetry (DSC). The phase change temperature (Tm) and heat of fusion (ΔHm) of prepared CPCMs are in the range of 54–60 °C and 29–50 J/g, respectively. The ΔHm of the CPCMs decreased obviously after 100 melting/freezing cycling, which was improved by encapsulating the prepared CPCMs with novolac epoxy resins (NER) to produce the encapsulated CPCMs (E-CPCMs). The results of the leakage experiment and storage/release test also show that the E-CPCMs have good thermal exudation stability and thermal storage/release properties. Based on all the results of the experiment, the encapsulated PEG/CS composite (E-PEG/CS) was added into the asphalt mixture to substitute the corresponding aggregate for simulating the actual temperature-adjusting effects. The results indicate that the maximum temperature reduction of the upper surface reaches about 9.1 °C at 210 min. Therefore, the E-CPCMs have the potential to decrease the high temperatures and temperature fluctuations in the asphalt pavements.
Graphene oxide (GO) modified with furfuryl alcohol and (3-aminopropyl) triethoxysilane (GOFASi) was used in two separate ways for preparation of novolac resin nanohybrids. In the first procedure, ...graphene-containing silica aerogel (GA) was obtained by incorporation of GOFASi into silica aerogel network using tetraethyl orthosilicate (TEOS). Then, GA was used as an additive in novolac resin matrix. In the second procedure, the synthesis of a hybrid novolac resin was accomplished by network formation via the reaction of GOFASi with (3-glycidyloxypropyl)trimethoxysilane-modified novolac resin and TEOS. The thermal stability and the carbon yield of the hybrid resins obtained by the two procedures were compared. Fourier transforms infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis showed that both GO and the novolac resin were successfully modified. Aerogel formation was proved by Raman, X-ray diffraction, N2 adsorption and desorption isotherms, and by scanning and transmission electron microscopies.
The nanometer-sized and stable waterborne epoxy dispersions are achieved by phase inversion method using the reactive emulsifier.
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•A reactive emulsifier for emulsifying epoxy resins ...with tunable Krafft point and HLB is fabricated.•Three nanometer-sized and stable waterborne epoxy dispersions are achieved.•The 2 K waterborne epoxy coatings films possess excellent properties.
Waterborne epoxy dispersions have excellent permeability and adhesion to various polar substrates and they are widely used as coatings and adhesives in industrial applications. Herein we present experimental schemes of a reactive emulsifier and three waterborne epoxy dispersions prepared for waterborne epoxy coatings. First, the epoxy groups in polyethylene glycol diglycidyl ether (PEGDGE) and epoxy resin E20 are ring-opened with amino hydrogen in ethanolamine, followed by neutralizing with glacial acetic acid (HAc) to obtain an emulsifier for emulsifying epoxy resins. Then two bisphenol A epoxy resins E20, E51 and a novolac epoxy resin NPPN631 are employed as emulsified oil phase to prepare waterborne epoxy dispersions with the above emulsifier. And finally the as-prepared waterborne epoxy dispersions are applied in 2K waterborne epoxy coatings. The results indicate that when the molar ratio of PEGDGE with an epoxy equivalent of 109 g▪mol−1 and epoxy resin E20 is 2:1, the synthesized emulsifier possesses the optimal emulsifying ability for epoxy resin, with the Krafft point of 56°C, and the HLB of 16. The coating films from 2K waterborne epoxy coatings occupy excellent wear resistance, thermal stability, hardness and mechanical properties. By exploring the curing mechanism, the superior performances of the coatings film prepared by waterborne epoxy dispersion and waterborne epoxy curing agent are presented.
Novolac is a low-cost carbon precursor which can be used to derive nanoporous carbon beads in sub-micrometer size. In this study, we introduce this material as a novel electrode material for ...capacitive deionization (CDI) with high performance stability and superior desalination rate. The polymer beads were synthesized employing a self-emulsifying system in an autoclave, pyrolyzed under argon, and activated with CO2, yielding a specific surface area of 1905 m2 g−1 with a high total pore volume of 1.26 cm3 g−1. After CO2 activation, the material shows a salt sorption capacity of ∼8 mg g−1, but the performance is highly influenced by functional groups, causing an inversion peak and fast performance decay. However, de-functionalization via hydrogen treatment is outlined as an effective strategy to improve the CDI performance. After hydrogen treatment of novolac-derived carbon beads, we obtained a salt sorption capacity of 11.5 mg g−1 with a charge efficiency of more than 80% and a performance stability of around 90% over more than 100 cycles. Particularly attractive for practical application is the very high average salt adsorption rate of 0.104 mg g−1 s−1, outperforming commercial activated carbons, which are commonly used for CDI, by at least a factor of two.
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