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Phenol formaldehyde resins of resol type were prepared under molar ratio phenol: formaldehyde: calcium hydroxide 1:2.7:0.1. The reaction products contained in all cases about 3.8% free formaldehyde and 1.5% free phenol. A 36% solution of formaldehyde was used for synthesis. The course of synthesis, expressed by drop of free formaldehyde contents in the reaction mixture, is presented. In aqueous resol solutions, prepared by this way, the decrease of miscibility with water was examined during storage at 10°C. It was found that the resol synthesized at lower temperature had better shelf life than that prepared at higher temperature. The presented results are of practical importance in the cases where compatibility with water is a significant processing parameter. 相似文献
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Urea formaldehyde resin with low formaldehyde content modified by phenol formaldehyde intermediates and properties of its bamboo particleboards
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Phenol formaldehyde reaction solution (PFS) was used to synthesize urea–formaldehyde resins (PFSUF resins) with low formaldehyde content. In addition, the prepared PFSUF resins were used as adhesives to bond bamboo particleboards. Mechanical properties, fracture morphology, water absorption ratio, and dimensional stability of bamboo particleboards have been studied by tensile tests, SEM tests, water absorption analysis, and swelling ratio analysis, respectively. The results demonstrate that the main ingredient of PFS is phenol formaldehyde intermediate 2,4,6‐trimethylolphenate and proper amount of PFS can be used to reduce the formaldehyde content of UF resins effectively. The results also show that bamboo particleboards bonded with PFSUF resins exhibit better mechanical properties, water resistance, and dimensional stability than that bonded with pure UF resin. However, the results of TG and mechanical properties analysis exhibit that alternative curing agents to ammonium chloride should be studied to improve the curing properties of the PFSUF resins with low formaldehyde content. Taken together, this work provides a method of preparing environment‐friendly PFSUF resins with low phenol and low formaldehyde content and the prepared resins have potential application in wood industry. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42280. 相似文献
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本文主要研究了铸造砂芯粘合剂苯基苯酚甲醛树脂的合成路线。以邻苯基苯酚和甲醛为原料,乙醇为溶剂,碱性阴离子交换树脂为催化剂。通过催化缩合、真空抽滤、蒸馏等过程,制得苯基苯酚甲醛树脂。实验结果表明,邻苯基苯酚用量为100 g时、使用145 m L甲醛、50 g催化剂、35℃反应温度、6.5 h反应时间所得产品的质量最好。粘度在300 MPa·s以上,甲醛含量低于2%,固化时间在210 s左右。是一种耐水和酸碱、稳定性较好的苯基苯酚甲醛树脂。 相似文献
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Wood liquefaction was conducted at a 2/1 phenol/wood ratio in two different reactors: (1) an atmospheric three‐necked flask reactor and (2) a sealed Parr reactor. The liquefied wood mixture (liquefied wood, unreacted phenol, and wood residue) was further condensed with formaldehyde under acidic conditions to synthesize two novolac‐type liquefied wood/phenol/formaldehyde (LWPF) resins: LWPF1 (the atmospheric reactor) and LWPF2 (the sealed reactor). The LWPF1 resin had a higher solid content and higher molecular weight than the LWPF2 resin. The cure kinetic mechanisms of the LWPF resins were investigated with dynamic and isothermal differential scanning calorimetry (DSC). The isothermal DSC data indicated that the cure reactions of both resins followed an autocatalytic mechanism. The activation energies of the liquefied wood resins were close to that of a reported lignin–phenol–formaldehyde resin but were higher than that of a typical phenol formaldehyde resin. The two liquefied wood resins followed similar cure kinetics; however, the LWPF1 resin had a higher activation energy for rate constant k1 and a lower activation energy for rate constant k2 than LWPF2. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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The lignin separated from the spent liquor of soda pulping of rice straw can replace a part of phenol in the condensation reaction with formaldehyde in a basic medium to form phenol lignin–formaldehyde (PL–F) resol resin. The production of phenol lignin–formaldehyde resol resin was carried out in two stages: First was the formation of the adduct (lignin phenol) using different lignin percentages; second was the condensation of the adduct with formaldehyde. Reaction variables, i.e., molar ratio of formaldehyde to phenol lignin, polymerization time, amount of sodium hydroxide as a catalyst, and polymerization temperature in the polymerization step were studied. Solubility of the produced resol resin in different solvents, its viscosity, and yield were determined. Lignin could replace up to 40% of phenol in the produced resin. Infrared spectra of the prepared resin were determined. Structural similarity of phenol–formaldehyde to phenol lignin–formaldehyde resin was shown. Also, relative absorbance of characteristic bands of the resins were calculated and claimed too much on the effect of reaction parameters on the prepared resins. 相似文献
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采用多聚甲醛代替37%甲醛溶液与苯酚逐步加成聚合,合成可发性甲阶酚醛树脂。通过粘度、固含量、游离苯酚和甲醛含量及凝胶时间测定以及IR,GPC和TG分析研究了多聚甲醛-苯酚物质的量比为1.8∶1条件下,缩聚反应温度及催化剂加入量对可发性甲阶酚醛树脂性能的影响。结果表明,缩聚反应温度为90℃,催化剂质量分数为5%(以苯酚质量计)时,可得到性能优良的可发性甲阶酚醛树脂,其性能如下:粘度2.6 Pa·s,游离甲醛质量分数1.23%,游离苯酚质量分数5.13%,热失重质量残留率50%以上。 相似文献
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《Journal of Adhesion Science and Technology》2013,27(9):833-839
One of the main drawbacks that has prevented a wider use of phenol–formaldehyde (PF) resins in the manufacture of impregnated paper and wood composite panels is their relatively slow cure rate. In this study, the curing characteristic of PF resol resins catalyzed with MgO was studied with various formaldehyde (F)/MgO/phenol (P) ratios at various pH values. The results indicated that the pH value, nature of pH regulator and synthesis parameters, including the F/P ratio and MgO content, all influence the rate of cure. The pH value played an important role in affecting both the cure rate and cure time. The cure rate was fast when pH was below 7.5. The cure time decreased as the pH value decreased at all F/MgO/P ratios. The MgO/P ratio had a definite influence on the cure rate, the cure time decreased with the increase of MgO/P molar ratio, and the F/P ratio had no significant influence on the cure rate. Differential scanning calorimetry (DSC) results showed that MgO catalyzed PF resin can cure at a low temperature. 相似文献
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采用多聚甲醛代替37%的甲醛溶液,在20%NaOH水溶液催化下与苯酚逐步加成聚合,合成了可发性甲阶酚醛树脂。研究了多聚甲醛与苯酚物质的量比(F/P)对合成树脂固含量、粘度、游离苯酚、游离甲醛、凝胶时间、分子结构、分子质量、树脂热性能及泡沫性能的影响。结果表明,F/P值为1.8时,可得到性能优良成本较低的可发性甲阶酚醛树脂,树脂粘度1.4 Pa.s,游离甲醛质量分数1.17%,游离苯酚质量分数6.72%,羟甲基指数1.41,树脂分子质量在240左右,耐热性较好。 相似文献
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The effect of wood flour on the cure kinetics of commercial phenol‐formaldehyde resins used as oriented strandboard face and core adhesives was studied using differential scanning calorimetry. The wood flour did not change the cure mechanism of the face resin, but lowered its cure temperature and activation energy and increased its cure reaction order. For the core resin (CR), the wood flour lowered the onset cure temperature, and caused separation of the addition and condensation reactions involved in curing of CR. Compared with neat CR, the addition reaction of CR/wood mixture also followed an nth‐order reaction mechanism but with a lower reaction order, while the condensation was changed from an autocatalytic reaction to an nth‐order one. The addition reaction happened at temperatures lower than 90°C, and the condensation reaction was dominant at temperatures higher than 110°C. The proposed models fitted the experimental data well. Relationships among cure reaction conversion (cure degree), cure temperature, and cure time were predicted. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3774–3781, 2006 相似文献
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Mozaffar Alam Khan Sayed Marghoob Ashraf Ved Prakash Malhotra 《International Journal of Adhesion and Adhesives》2004,24(6):485-493
Bagasse is spent fiber left after extraction of sugar. It is mainly used as a fuel to concentrate sugarcane juice. In the present work, the possibility of preparing wood adhesives from bagasse has been explored. The parameters for the preparation of a lignin phenol formaldehyde (LPF) adhesive, (lignin concentration, formaldehyde to phenol molar ratio, catalyst concentration, reaction time and reaction temperature) have been optimized. It was found that up to 50% of phenol can be substituted by bagasse lignin to give LPF wood adhesive having better bonding strength in comparison to a control phenol formaldehyde (CPF) wood adhesive. Prepared resins were characterized using IR, DSC and TGA. IR spectra of LPF resin showed structural similarity with CPF resin. Thermal stability of LPF resin was found to be lower as compared to CPF resin. DSC studies reveal a lower curing temperature for LPF adhesive in comparison to CPF adhesive. A shelf-life study reveals that LPF exhibits consistent behavior as compared to CPF in respect to adhesive strength. 相似文献
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一种低甲醛含量水溶性酚醛树脂的制备 总被引:1,自引:0,他引:1
以苯酚和甲醛为原料,采用两步碱合成工艺,制备了水溶性酚醛树脂,考察了原料配比、反应温度、催化剂用量对产品性能的影响。结果表明,最佳工艺条件为:苯酚∶甲醛=1∶1.5(摩尔比),在45~96℃程序下升温,连续反应4.5 h。该工艺可使产品的固含量达到49%,甲醛残留量为2.3%。 相似文献
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《Polymer-Plastics Technology and Engineering》2013,52(4):689-699
Abstract Lignin (poly‐phenylpropane units) was precipitated from waste black liquor produced by paper manufacture from rice straw. The use of this lignin as partial substitution of phenol in phenol formaldehyde resin is investigated. The effect of different variables [e.g., lignin concentration, ratio of formaldehyde to phenol lignin (phenol + lignin), temperature, and polymerization time on the properties of the produced resin is studied]. The effect of the chemical modification of lignin by oxidation, reduction, and hydrolysis on the properties of the produced phenol lignin formaldehyde resin is also studied. Hydrolysis of lignin by hydrochloric acid increases the reactivity between lignin, formaldehyde, and phenol in producing resin with good properties more than untreated lignin. Also, the percent of replaced phenol with lignin in the resin can be increased by hydrolysis of lignin with hydrochloric acid. So, the reactivity of lignin toward resin formation has the following sequence: hydrolyzed lignin > oxidized lignin with dichromate > treated lignin with sodium hydrosulfite. 相似文献