The pore formation in the system resol resin – ethylene glycol – p-toluenesulfonyl chloride based on polymerization induced phase separation (PIPS), post-curing and pyrolysis techniques are studied ...by thermal analysis methods, pyrolysis gas chromatography mass spectrometry and electron microscopy. The presence of p-toluenesulfonyl chloride leads to accelerating of curing reaction and reaction order increasing. It was shown that PIPS step determines the texture and morphology of final carbon matrix precursors. The increasing of PIPS step temperature results in decreasing of the segregation scale and increasing of segregation intensity of phase separation. The decreasing of PIPS step temperature leads to increasing of macropores sizes, but decreasing of mesopores cumulative volumes. The increased mesopores content at high PIPS temperature is supposed to be resulted and from the oligoethylene glycol formation. Insufficient PIPS step time leads to partial collapsing of formed porous structure during pyrolysis.
An asymmetric carbon membrane was prepared by coating alcohol solution of novolac phenol–formaldehyde resin containing a little hexamine on a porous resin support from the same material. After drying ...in air for two days at room temperature, the coated support was heated at 150
°C for 1
h in air (heating rate: 0.5
°C/min) and then carbonized at 800
°C (heating rate: 0.5
°C/min) in Ar atmosphere. The support and the membrane layer were carbonized simultaneously. The coating–pyrolysis cycle only needed one time. SEM photographs showed the carbon membrane had an asymmetric structure formed by a dense skin layer with a thickness of around 35
μm and a porous substrate. Pure gases of different molecular size (H
2, CO
2, O
2, N
2 and CH
4) were used to test the carbon membrane permeance property. The membrane has a good selectivity for H
2/N
2 and H
2/CH
4 with H
2 permeance of 4.05
×
10
−6
cm
3
cm
−2
s
−1
cmHg
−1. The permeance is independent of pressure. The results indicate that the gases transport through the membrane according to molecular sieve mechanism.
A facile hydrothermal method was employed to synthesize the core-shell structure up-conversion Cit-NaYF4:Yb, Tm (UC)@phenolic formaldehyde resin (PFR) nanoparticles (NPs). UC NPs can enhance the ...emission intensity of the PFR shell, which contributes to improving the fluorescence detection sensitivity of UC@PFR NPs. Au NPs were loaded onto the surface of PFR shell in situ through the good reduction of the hydroxyl group in PFR. The emission intensity of UC@PFR decreased greatly in the presence of Au nanoparticles due to fluorescence resonance energy transfer (FRET) mechanism between UC@PFR and Au NPs. However, the mixture of H2O2 and SCN− could prevent the decrease of emission intensity of UC@PFR@Au composites because of the oxidation reaction between H2O2 and Au nanoparticles in the presence of SCN−. Also, Cu2+ can prevent the oxidation reaction to occur, which results in the slight change of emission intensity of UC@PFR@Au in the presence of H2O2 and SCN−. Thus, the as-synthesized UC@PFR@Au particles were used to detect Cu2+ sensitivity. The good linear correlation equation between the fluorescence intensity of UC@PFR@Au particles and the concentration of Cu2+ in the range of 4–90 nM (R2 = 0.99) was established with the low detection limit (LOD) of 0.54 nM. Furthermore, the as-synthesized particles were employed to detect Cu2+ in the actual water sample with satisfying results.
•The core-shell nanoparticles of Cit-NaYF4:Yb,Tm@PFR were synthesized by facile method.•Au nanoparticles were loaded onto the PFR shell through the reduction of hydroxylgroup in PFR.•A fluorescence resonance energy transfer system was established between UC@PFR and Au.•The as-synthesized nanocomposites were used to detect Cu2+ sensitively.
Phenol-formaldehyde resin (PF) composites with a nano-porous graphite additive (NPGA) in various contents were fabricated and the wear behaviors under low and high sliding speeds were studied. The ...addition of NPGA significantly improved the wear resistance of the PF. The specific wear rates of PF composites under low sliding speed first decreased with increasing NPGA and then slightly increased when the NPGA content surpassed 15 wt%; the specific wear rate of the composite with 15 wt% NPGA was reduced by 77% compared with the neat PF. Under high sliding speed the specific wear rates of the composite material decreased continuously with increasing NPGA content and the maximum wear resistance of the composite with 20 wt% NPGA was more than 12 times that of the neat phenolic resin. The results are attributed to the combined effects of load-capacity and the lubrication role of the included NPGA. The surface morphology of the worn surface was characterized, and the wear mechanism for the composites is discussed.
In this work, sodium lignosulfonate (SL) was introduced in the hydrothermal preparation of phenol-formaldehyde (PF) resin sphere that was subsequently used as a green reducer and support for ...synthesis of Ag nanoparticles (Ag NPs). The results showed that the addition amount of SL had a remarkable effect on the size of the SL incorporated PF (SLPF) spheres and the smallest particle size was obtained when 20% of SL (based on phenol mass) was added. The addition of SL increased the surface area and negative charge of SLPF spheres, which enhanced the Ag NPs loading amount accordingly. Moreover, SL also prevented Ag NPs from aggregating effectively, resulting in the high-density loading of small size Ag NPs on the SLPF spheres. Therefore, the as-prepared Ag@SLPF composites exhibited significantly enhanced catalytic activities in the 4-nitrophenol reduction than that of SL-free Ag@PF. Besides, the Ag@SLPF catalyst demonstrated superior recyclability owing to strong anchoring between the Ag NPs and the support. Consequently, the work demonstrates the incorporation of SL enables the green formation of high-density and tunable Ag NPs on the SLPF support and then endows the composite catalyst with enhanced catalytic performance, which presents a promising value-added application of lignosulfonate for functional catalyst preparation.
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•The addition of sodium lignosulfonate (SL) decreases the size of SLPF spheres significantly.•SL enhances the adsorption amount of Ag+ on SLPF spheres, resulting in high-density loading of Ag NPs.•SL prevents the aggregation of Ag NPs effectively, leading to the formation of small Ag NPs.•SL incorporation enables the formation of high-density and small Ag NPs on SLPF support.•The as-prepared Ag@SLPF exhibited significantly enhanced catalytic activities compared with the SL-free Ag@PF.
Test results of changing the thermo-rheological properties of coal-tar pitch under influence of phenol-formaldehyde resin are presented in this research work. Influence of modifying agent amount and ...crosslinking conditions (time) of resin in bitumen was evaluated. Tests were carried out using the rheometer in oscillation mode. They enabled the evaluation of changes in bitumen viscous and elastic properties and draw the conclusions about changes in bitumen structure on that basis. Compositions of the coal-tar pitch with phenol-formaldehyde resin show increased thermal and mechanical resistance. Furthermore, phenol-formaldehyde resin has an effect on increase in the coal-tar pitch viscosity. It probably results from the increased content of components of higher average molecular mass in the pitch and lower solubility in organic solvents.
Graphene oxide (GO) modified urea-melamine-phenol formaldehyde resin was reinforced by R-glass fiber woven (RFW-GO/UMPF). The influence of GO content on the tensile, flexural, and drilling properties ...was investigated. Polytetrafluoroethylene (PTFE) coatings was applied onto individual glass fibers to evaluate the reinforcement mechanism of GO sheets on the tensile and flexural properties of RFW-GO/UMPF composites laminates. Compared to the R-glass fiber woven reinforced urea-melamine-phenol formaldehyde resin (RFW-UMPF), the tensile strength and modulus of RFW-GO/UMPF with 0.6 wt% GO contents increased by 28.1% and 200.3%, respectively. The flexural strength and modulus of RFW-GO/UMPF with 0.4 wt% GO loadings improved to 51.8 MPa and 716.7 MPa, respectively. Moreover, when the content of GO increased from 0 wt% to 0.8 wt%, the delamination factor of RFW-GO/UMPF decreased by 0.2. Morphology analysis of failure surface was systematically revealed by SEM.
Batch pyrolysis of a commercial resole type phenol-formaldehyde resin was performed using a step-wise heating procedure in a temperature increment of 50 K from 320 to 1290 K. A resin sample of 50 mg ...was loaded in a reactor assembly specifically designed and built for this study. Mass loss was measured after each 50 K step and the production of pyrolysis products was quantified using gas chromatography techniques. The overall mass loss from the samples reached 39.2% after the entire procedure. Three major product families were identified: 1) water is the most dominant product at a pyrolysis temperature below 800 K; 2) phenol derivatives (aromatic alcohols) have significant yields at a pyrolysis temperature between 500 and 850 K; 3) permanent gases such as hydrogen, methane, carbon monoxide, and carbon dioxide have the highest yields at a temperature above 800 K. Minor products observed include aromatics, which are formed between 700 and 850 K, and C2 to C4 light hydrocarbons, which are only formed above 800 K and peak at 1000 K.
► Sub-/super-critical water–ethanol proved to be very effective for de-polymerization of organosolv lignin (OL). ► Ni10/AC and Ru10/γ-Al2O3 as catalysts effectively inhibited char formation, and ...increased degraded lignin (DL) yield. ► A high yield of DL (80.7%) with Mw (568g/mol) and Mn (181g/mol) was obtained at 340°C for 2h with Ni10/AC. ► OL phenol-formaldehyde resins (OLPF) and DLPF resins with OL/DL substituting up to 75% phenol were produced. ► Lignin-based PF resins have higher dry and wet tensile strength than PF resole resin when using as plywood adhesive.
The objective of this study was to produce green phenolic resins and adhesives using bio-phenolic compounds produced from lignin/forestry residuals. To produce bio-phenolic compounds, an organosolv lignin (OL) was catalytically degraded in 50/50 (v/v) water–ethanol and pure ethanol media under sub/supercritical condition in hydrogen atmosphere. Effects of lignin degradation process conditions (catalyst, temperature, type of reactor, etc.) on the yields and properties (molecular weights) of the degraded lignin (DL) products were examined in this study. The DL products were used to substitute for phenol in the synthesis of bio-phenol formaldehyde resins, denoted as degraded lignin phenol-formaldehyde (DLPF) resins, whose properties (such as viscosity, non-volatile contents, storage time, free formaldehyde contents, curing behavior, and thermal stability) were compared with pure PF resin and organosolv lignin phenol-formaldehyde (OLPF) resins. Plywood samples glued with the OLPF and DLPF adhesives with a phenol replacement ratio up to 75wt% showed higher dry and wet tensile strengths than those of PF adhesives. Although the OLPF adhesives have better bond strengths and thermal stability than DLPF adhesives, the DLPF resins have a lower free formaldehyde content and can be cured at a lower temperature.
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