Structural properties of nanocomposites based on resole-type phenol-formaldehyde oligomers and detonation nanodiamonds

Using the methods of infrared spectroscopy (IRS) and X-ray photoelectron spectroscopy (XPS), it was shown that short-term high-energy machining of detonation nanodiamonds (DND) leads to structural changes in the crystal structure and functional composition of the surface layer on particles. The possibility of spontaneous formation for stable colloidal systems with a narrow size distribution of mechanically activated DND in phenol-formaldehyde oligomers (PFO) was established. By molecular spectroscopy it was revealed that π → π* interactions of the aromatic rings of PFO are caused by orientational phenomena as a result of hydrogen bonds between an activated DND surface and functional groups of PFO. The effect of DND concentration on the curing reaction parameters ofpsgr the phenol-formaldehyde oligomer was determined by differential scanning calorimetry (DSC). The concentration effect of mechanically activated nanodiamonds on the physical and mechanical characteristics of a composite material based on phenol-formaldehyde binder and polyamide paper (Nomex) was studied. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48582.     

Thermal cure monitoring of phenolic resole resins based on in situ fluorescence technique

The thermal curing reaction of two phenolic resole resins is monitored using the fluorescence technique. The intrinsic fluorescence can be used as an indicator for cure monitoring for the first resole. As the thermal curing proceeds, the intrinsic fluorescence intensity of the resole resin decreases and exhibits a few nanometers of redshift. The fluorescence intensity of the emission maxima is correlated with the conversion measured by differential scanning spectroscopy. A linear correlation is found at three different temperatures. The intrinsic fluorescence cannot always be used for monitoring the curing process of phenolic resole resins. Thus, three intramolecular charge transfer compounds and two organic donor–π‐acceptor salts are selected and applied for the cure monitoring of the second phenolic resole resin. As the curing reaction proceeds, the fluorescence emission spectra of the probes exhibit a blue spectral shift and the intensity changes because of environmental changes. An intensity ratio method is applied in which the ratios of the low‐ to high‐intensity changes in the emission bands are used to determine the degree of the curing process. There is a smooth correlation between the intensity ratio method and the degree of cure. The method enables one to follow the changes in the polymer structure at low and intermediate degrees of the curing process (below 70%) and obtain comparable results from different types of probes during the same curing process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1773–1780, 2002     

新一代酚醛树脂木材胶粘剂

介绍一种浅色酚醛乳液的实用制备方法(酚醛树脂乳液技术)解决了酚醛树脂颜色深的问题。研究分析了酚醛乳液和传统甲阶酚醛树脂性能的相似点和不同点。     

中空酚醛微球的合成与表征

提出了一种在石蜡油浴中搅拌状态下制备中空酚醛微球的新方法,研究了甲醛苯酚单体配比、制备温度对固化速率与发泡速率的影响。结果表明以单体配比n(甲醛)∶n(苯酚)=1.6合成的甲阶酚醛树脂,160℃时能达到固化速率与发泡速率的匹配。SEM照片及物性测试结果反映出微球体具有较好的中空结构及粒径分布,通过测定树脂凝胶时间求得基体树脂的固化反应活化能。     

Thermomechanical properties and morphology of polyethylene oxide and phenolic resole blends

Blends of poly(ethylene oxide) (PEO) and resole type phenolic resin were prepared by a solution cast method using water as a solvent. The cured blends were made by heat curing without using any catalyst. The blends were characterized by dynamic mechanical analysis (DMA), which indicated that PEO forms compatible blend with the resole. The glass transition values, read from the DMA traces, showed a positive shift as compared to the theoretical values calculated by the Fox equation. This suggests a strong H‐bonding interaction between the phenolic resole and PEO as established by Fourier transformed infrared spectroscopy. Flexural test indicated an enhanced flexibility of the blends when compared to the neat phenolic resin. The fracture surface analysis by using a scanning electron microscope (SEM) revealed an increase in plastic deformation with increasing PEO concentration in the blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Resole-cured NR vulcanizates with thermally reacted p-t-octylphenol formaldehyde resole

Crosslink dissociation of resole-cured NR vulcanizates was studied using steam aging. Four carbon black-filled NR vulcanizates were prepared to investigate the influence of heated p-t-octylphenol formaldehyde resole (at 160°C for 0.0, 1.5, 3.0, and 6.0 h) on the cure characteristics and stability of the crosslinks. By increasing the heating time of the resole, dimethylene ether linkages of the resole decrease while o-methylene quinone intermediates increase. The cure rate of the NR vulcanizates with the heated resole for 1.5 h is faster but those for 3.0 and 6.0 h are slower than that with the unheated resole. In comparison with the vulcanizates containing the nonheated resole, the delta torque of the NR vulcanizate with the heated resole for 1.5 h increases, while those for 3.0 and 6.0 h decrease. The swelling ratios of the four NR vulcanizates decrease after steam aging at 95°C for 7 days. The differences of the swelling ratios before and after steam aging decrease with increase of the heating time of the resole. The decrease of the swelling ratio after the steaming is due to the dissociation of the dimethylene ether linkage in the vulcanizates. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1811–1819, 1998     

High temperature ablation of highly filled polymer‐layered silicate nanocomposites

At instantaneous thermal shocks and high temperature conditions, using the charring ablative heat shields is more effective than the other heat protection methods. In recent years, low‐filled layered silicate polymeric nanocomposites were introduced as new class of ablative materials. In this work, highly filled ablative polymeric nanocomposite is prepared and its thermal stability and ablation mechanism is studied under high external heat flux. The thermal degradation kinetics during pyrolysis, the variation of thermophysical properties as a result of ablation process and mathematical modeling of ablation process are performed for highly filled ablative polymeric nanocomposite samples compared with those of their composite counterparts under oxyacetylene flame test. The results show that the ablation performance of highly filled polymeric nanocomposite is higher than that of the composite, and the mathematical model is adequately confirmed by the experimental data of the thermophysical and ablation properties of highly filled nanocomposites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation,Acid Curing,and Thermal Stability of Various Formulated Phenolic Resole Resins: Unfilled and Nanocomposites

Several phenol-formaldehyde resole resins were prepared with variety in monomers ratio, catalyst type, and content, having different nanoclay levels; then they were cured using various acids in the wide range of concentration. The acid-curing process was studied, considering gel time (t_G) and cure time (t_C). In addition, the thermal stability was investigated before and after cure for all samples. With increasing F/P ratio, t_G, t_C and t_G-t_C decreased and also C_C (critical concentration). By using more catalyst in the synthesizing step, the curing was done more rapidly in the order of NaOH, Ba(OH)₂ and NH₃. Stronger acids having smaller pK_a made a more realizable cure. However, the weak boric acid had no curing effect. Nanocomposites had shorter t_G and t_C, mainly at lower acid concentration. The structure peak of nanoclay shifted to the lower angles in nanocomposites, especially in the cured state. Crosslinked samples had higher degradation temperature (T_D) and lower weight decrease (Δ_w) related to the primary resoles. For uncured resins, thermal stability increased with decreasing of F/P ratio, and the inverse effect was found for the cured resins. Resins cured with HCL had higher T_D and lower Δ_w. However, at 30% concentration the sample cured by H₂SO₄ was more stable. With increasing catalyst amount and reactivity, T_D increased and Δ_w decreased. In all acid concentrations, at the presence of nanoclay the better thermal resistance was observed. T_D increased and Δ_w decreased as the nanoclay level increased.     

J—147汽车刹车蹄片用胶粘剂的研究

本工作以热固性酚醛做主体树脂,含Ｂ树脂做改性树脂,丁腈橡胶做增韧剂,制备了Ｊ－１４７刹车蹄片用胶粘剂,并讨论了各组份对胶接性能的影响。     

Jute Fiber Composites from Coal,Super Clean Coal,and Petroleum Vacuum Residue–Modified Phenolic Resin

Jute fiber composites were prepared with novolac and coal, phenolated-oxidized super clean coal (POS), petroleum vacuum residue (XVR)–modifiedphenol-formaldehyde (novolac) resin. Five different type of resins, i.e., coal, POS, and XVR-modified resins were used by replacing (10% to 50%) with coal, POS, and XVR. The composites thus prepared have been characterized by tensile strength, hardness, thermogravimetric analysis (TGA), Fourier-transfer infrared (FT-IR), water absorption, steam absorption, and thickness swelling studies. Twenty percent POS-modified novolac composites showed almost the same tensile strength as that of pure novolac composites. After 30% POS incorporation, the tensile strength decreased to 25.84 MPa from 33.96 MPa in the case of pure novolac resin composites. However, after 50% POS incorporation, the percent retention of tensile strength was appreciable, i.e., 50.80% retention of tensile strength to that of pure novolac jute composites. The tensile strength of coal and XVR-modified composites showed a trend similar to that shown by POS-modified novolac resin composites. However, composites prepared from coal and XVR-modified resin with 50% phenol replacement showed 25.4% and 42% tensile strength retention, respectively, compared to that of pure novolac jute composites. It was found that the hardness of the modified composites slightly decreased with an increase in coal, POS, and XVR incorporation in the resin. The XVR-modified composites showed comparatively lower steam absorption than did coal or POS-modified composites. The thermal stability of the POS-modified composites was the highest among the composites studied. The detailed results obtained are being reported.