Cyanate esters based on cardanol modified-phenol-formaldehyde resins: Syntheses and thermal characteristics

Cardanol incorporated-phenol-formaldehyde novolac resins were synthesized by acid and base catalyzed reactions. The novolacs were transformed to their cyanate esters. The thermal cure characteristics of the cyanate esters depended upon the composition. The presence of cardanol proportionately facilitated the curing. The thermal characterization of the novolacs and the corresponding cured phenolic-triazine networks indicated a dedicated a detremental effect of cardanol on the thermal stability and char residue of the resins. © 1995 John Wiley & Sons, Inc.     

Structural characteristics of phenol formaldehyde novolak resin depending on polycondensation type using molecular simulation

Phenol formaldehyde novolak resins have various structures depending on the polycondensation types. Their structures were characterized using molecular mechanics and molecular dynamics. Dimer, tetramer, hexamer, octamer, and decamer of the resins with the ortho–ortho, ortho–para, and para–para sequences were calculated. The ortho–ortho resins have the structural characteristics of intramolecular hydrogen bonds between hydroxyl groups of the adjacent phenolic units. For the ortho–para and para–para resins, the intramolecular hydrogen bonds are formed mainly between hydroxyl groups of the backbone phenolic units. The para–para resins also have intramolecular hydrogen bonds between hydroxyl groups of the branched phenolic units. A factor determining the structural characteristics of the resins was found to be the geometry of the basic unit (dimer). The order of the end‐to‐end distances between hydrogen atoms on the para‐position of the basic units of the resins is ortho–ortho resin < ortho–para resin < para–para resin. The calculational results were found to be consistent with the gel permeation chromatography (GPC) analysis. Copyright © 2001 John Wiley & Sons, Ltd.     

聚丙烯酰胺/酚醛树脂的胶凝反应动力学探讨

两性聚丙烯酰胺;水溶性酚醛树脂;聚合物水凝胶;聚丙烯酰胺/酚醛树脂的胶凝反应动力学探讨     

Preparation,Morphology, and Structure of Thermotropic Liquid Crystalline Polyester-imide/Phenol-formaldehyde Resin Blends

As a novel toughening agent, thermotropic liquid crystalline polymers (TLCPs) possess excellent properties of high strength, high modulus, low expanding coefficient, and high thermal stability. In this study, a thermotropic liquid crystalline poly(ester-imide) derived from N,N’-hexane-1,6-diylbis(tri-millitimide) (IA6), p-hydroxylbenzoic acid (PHB), and 4,4’-dihydroxybenzophenone (DHBP) was synthesized by the Higashi's direct polycondensation method. The structure and properties of the TLCP were studied using Fourier transformed infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetic analyses (TGA), polarized light microscopy (POM), and wide angle X-ray diffraction (WAXD). The results revealed that the synthesized polyester-imide is a nematic TLCP with good thermal stability and its starting decomposition temperature is up to 439°C. Additionally, polymer blends of phenol-formaldehyde (PF) resin with different contents of polyester-imide were prepared and characterized by POM and WAXD. POM results demonstrated that two-step blending is an ideal method for blending TLCP and PF resin. By this method, continuous filamentous stripes can be clearly observed at 230°C for TLCP/PF blend of 10 wt% poly(ester-imide).     

硼酸与甲阶酚醛树脂的配位反应及配合物的结构

本文通过对溶液pH值的测定和外光谱分析,研究了硼酸与甲阶酚醛树脂的配位反应。结果表明：在室温下硼酸能与甲阶酚醛树脂中的羟基发生配位反应,并产生H^ 使溶液的pH值降低;溶液的酸性强弱与甲阶酚醛树脂中的羟甲基含量和硼酸的用量有关;硼酸以硼酸根离子的形式与树脂中的酚羟基和邻位羟甲基发生配位反应,形成了一个含有两个氧原子和一个硼原子的六元环,使甲阶酚醛树脂发生交联。     

多孔酚醛树脂热解碳材料的制备与结构

用苯酚和甲醛在氨水催化下合成了可溶性酚醛树脂, 经掺杂不同质量比发泡剂(氯化锌)后在惰性气氛下进行热裂解(500～900 ℃), 制备了多孔热解碳导电材料(PPAS); 用FTIR, XRD, TG, SEM, BET等方法对所制备材料进行了结构表征, 详细讨论了发泡剂的加入对热解碳导电材料结构和性能的影响. 研究发现: 酚醛树脂经掺杂一定量发泡剂后再进行热裂解, 一方面加快了酚醛树脂分子间的脱水速度, 降低了热裂解温度范围; 另一方面, 裂解产物内部结构的微晶尺寸和层间距发生了明显变化, 未掺杂发泡剂的裂解产物呈现尖锐棱角的无定形结构, 而掺杂发泡剂的裂解产物则为多孔的球形和椭球形结构; 表面吸附实验测试结果表明, 当酚醛树脂与发泡剂的质量比为1∶3, 升温速率为30 ℃/h, 热裂解温度为600 ℃时, 热裂解产物的比表面积可达2150 m2&#8226;g－1, 平均孔径在11 Å左右.     

公共场所空气中甲醛的测定——酚试剂分光光度法

采用酚试剂分光光度法对室内空气环境中甲醛含量进行了分析。研究表明,酚试剂分光光度法具简便、易控制、迅速、成本低等优点,在普通室内检测时应优先选用。     

DSC by the TGA/SDTA851e Considering Mass Changes

DSC measurements in open pans are often disturbed by mass losses such as sublimation during melting or release of water during chemical reactions. By simultaneous DSC and TG measurements the DSC signal can be corrected. For this purpose, a temperature dependent calibration function has to be determined by which the SDTA signal from the TGA/SDTA851^e measuring cell can be converted into a heat flow curve (DSC). By this procedure, accurate heat of melting can be determined despite ongoing sublimation in open pans. This method is illustrated with reference of the melting of anthracene. Additionally, condensation reactions were investigated and analyzed by DSC/TG even under ambient pressure, knowing the heat of evaporation. Using phenol formaldehyde resins the influence of the presence or the release of volatile reaction products on the reaction rate and kinetic parameters were studied. In general, the method can be used to correct DSC curves for thermal effects related to mass change. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of heat treatment conditions on the porosity changes of sulfonated styrene/divinylbenzene copolymers

Sulfonic cation exchangers with two ion exchange group concentrations (0.5 and 2.4 mmol/g, samples A and B, respectively) were obtained by sulfonation of a porous styrene (S) and divinylbenzene (DVB) copolymer with chlorosulfonic acid. Strong thermal decomposition of the sulfonated copolymer A, accompanied by significant changes in its porous structure, starts at ca. 400°C. The char has no sulfonic groups. After heat treatment at 400°C in steam, a sorbent was obtained (yield 65%) that shows higher phenol sorption than the untreated sample when related to the bed volume. The chlorosulfonic derivatives of the initial copolymer were less thermally resistant than the sulfonic ones obtained by hydrolysis. Pyrolysis of the cation exchanger B, in its H+ and Ca²⁺ forms, was carried out at 900°C (yield of both chars close to 30%). By subsequent steam activation at 800°C to a 50% burn-off of the char, sorbents with well-developed, but distinctly different, porous structures were obtained. The activated char from the sulfonated copolymer in its hydrogen form was highly microporous and indicated an effective surface area of 1180 m²/g. However, because of a low contribution of mesopores, its ability to adsorb phenol from the liquid phase was not very high. The activated char from the calcium-doped copolymer, indicating a smaller surface area (580 m²/g) but characterized by a well-developed mesoporosity, was a better sorbent for phenol. © 1994 John Wiley & Sons, Inc.     

双环戊二烯苯酚树脂的合成新工艺

以双环戊二烯（DCPD）和苯酚为原料,甲磺酸为催化剂,合成了双环戊二烯苯酚树脂。适宜工艺条件:苯酚与DCPD摩尔比为5、反应温度120 ℃、反应时间5 h、催化剂质量分数为1.5%,收率89%。所得的双环戊二烯苯酚树脂（DPR）经催化加氢法在H2气压力1.5 MPa、催化剂Pd/Al2O3用量为原料质量分数的0.5%、反应温度80 ℃条件下对树脂进行脱色处理。 得到浅黄色双环戊二烯苯酚树脂,收率89%,经IR和1H NMR表征分析其为目的产物,产物指标达到国际同类产品的质量标准。     

Cocondensation of urea with methylolphenols in acidic conditions

The reactions of urea with methylolphenols under acidic conditions were investigated using 2- and 4-hydroxybenzyl alcohol and crude 2,4,6-trimethylophenol as model compounds. The reaction products were analyzed with ¹³C-NMR spectroscopy and GPC. From the reaction of urea with 4-hydroxybenzyl alcohol, the formations of 4-hydroxybenzylurea, N,N′-bis (4-hydroxybenzyl) urea, and tris(4-hydroxybenzyl) urea were confirmed and the formations of N,N-bis(4-hydroxybenzyl) urea and tetrakis (4-hydroxybenzyl) urea were suggested. From the reaction of urea and 2-hydroxybenzyl alcohol, 2-hydroxybenzylurea and N,N′-bis(2-hydroxybenzyl) urea were identified. Further, the alternative copolymer of urea and phenol could be synthesized by the reaction of urea with 2,4,6-trimethylophenol. It was also found that the cocondensation between p-methylol group and urea prevails against the self-condensation of the methylolphenol even at the low pH below 3.0, and that p-methylol group has the stronger reactivity to urea than o-methylol group. © 1992 John Wiley & Sons, Inc.     

Multifunctionality in Epoxy Resins

Abstract

Epoxy resin will continue to be in the forefront of many thermoset applications due to its versatile properties. However, with advancement in manufacturing, changing societal outlook for the chemical industries and emerging technologies that disrupt conventional approaches to thermoset fabrication, there is a need for a multifunctional epoxy resin that is able to adapt to newer and robust requirements. Epoxy resins that behave both like a thermoplastic and a thermoset resin with better properties are now the norm in research and development. In this paper, we viewed multifunctionality in epoxy resins in terms of other desirable properties such as its toughness and flexibility, rapid curing potential, self-healing ability, reprocessability and recyclability, high temperature stability and conductivity, which other authors failed to recognize. These aspects, when considered in the synthesis and formulation of epoxy resins will be a radical advance for thermosetting polymers, with a lot of applications. Therefore, we present an overview of the recent finding as to pave the way for varied approaches towards multifunctional epoxy resins.     

Addition Mechanisms of Phenol toward Formaldehyde under Acidic Condition： a Theoretical Investigation

The reaction mechanisms of phenol with formaldehyde in the first and second addition at the ortho- and para-position in acid solution were theoretically investigated at the PW91/DNP level with solvent effects included. The reaction of phenol with protonated methanediol firstly forms an adduct intermediate, via a SN2 mechanism with a water molecule as the leaving group. From the adduct intermediate, there are two reaction channels involving a proton transfer to form the addition products. One is that a proton directly transfers via a four-membered ring transition state with a notable energy barrier (Four-member mechanism). Another mechanism involving a water molecule as catalyst to mediate the proton transfer (WCP mechanism), is a barrierless process, indicating that the formation of the adduct intermediate, the first reaction step, is rate-limiting. The reaction products are free hydroxymethyl phenols and/or hydroxybenzy carbocation (HOC6H4CH2+) which plays an important role in the following formation of methylene and methylene ether linkages. The second addition reactions between formaldehyde and hydroxymethyl phenol at all possible reaction sites of the phenol ring in acid solution were also investigated and discussed.     

Effect of HAP on Stability and Plugging Property of LPFR Dispersion

To improve the stability and plugging property of low-solubility phenol formaldehyde resin (LPFR) in the injection water from Daqing Oilfield, hydrophobically associating polymers (HAP) as a stabilizing agent were used. The size and zeta potential of LPFR, LPFR/HAP molecule aggregates, and turbidity and plugging properties of LPFR dispersions were measured in deionized water, simulation water, and injection water, respectively. The results show that the hydrophobic grouping on the HAP molecule has a similar molecular structure as LPFR, and HAP and LPFR can form complex molecule aggregates in the injection water. The zeta potential of LPFR/HAP molecule aggregates is larger than that of LPFR molecule aggregates. Therefore, the repulsive force operating between LPFR/HAP complex molecule aggregates is increased. HAP enhances the stability of LPFR in the injection water and plugging property of LPFR dispersion in porous medium.     

三聚氰胺甲醛树脂增韧改性的研究进展

三聚氰胺甲醛树脂具有良好的耐热性和胶接强度大等特点,因此被广泛应用于木材加工用的胶粘剂、涂料的固化剂、纸张湿强剂中。但是三聚氰胺的刚性三嗪环结构会导致三聚氰胺甲醛树脂存在硬脆、力学性能差、强度低、拉伸和弯曲性能差等缺陷。上述缺陷限制了三聚氰胺甲醛树脂在某些领域中的应用。为了扩大其应用范围,三聚氰胺甲醛树脂的增韧问题得到了越来越多的关注。本文主要综述了小分子增韧和高分子增韧两种主要方法,其中小分子增韧又包括异氰脲酸酯增韧、二元醇增韧、二元醛增韧、胺类增韧以及多种小分子协同增韧。高分子增韧包括聚多元醇增韧和聚氨酯增韧。此外,还介绍了生物质增韧、硅烷增韧等其他几种方法,并阐述了上述方法的增韧机理。     

应用阳离子交换树脂催化水解蔗糖──Ⅱ.蔗糖水解最佳反应条件选择

本文研究H+型强酸性阳离子交换树脂为蔗糖水解催化剂时，催化剂柱温、蔗糖进料浓度和空速等工艺条件对蔗糖水解的影响．结果表明，蔗糖在离子交换树脂柱内的较佳水解温度段为40～54℃；在相同蔗糖水解率下，空速随蔗糖进料浓度的增高而增高、较高的进料浓度有利于充分发挥催化剂效能；若适当降低蔗糖水解程度，可明显提高空速，提高生产率。