粒径可控单分散三聚氰胺-甲醛(MF)树脂微球的制备研究

利用甲酸催化水溶液中的三聚氰胺与甲醛发生缩聚反应,制备出单分散性的三聚氰胺-甲醛(MF)树脂微球。红外光谱(FT-IR)、扫描电子显微镜(SEM)、激光粒度仪(LPA)分析表明:生成了粒径分布均一、表面光滑的微米级MF树脂微球。在一定范围内,MF树脂微球的粒径随甲酸用量的增加而减小,粒径分布变窄。然而加入过量的甲酸,反而导致微球粒径分布不均,甚至得不到MF树脂微球。     

MF/FEA-1100混合发泡剂对聚氨酯泡沫泡孔结构和性能的影响

以甲酸甲酯(MF)和1,1,1,4,4,4-六氟丁烯(FEA-1100)为混合发泡剂,制备了密度为30~35kg/m~3的硬质聚氨酯泡沫塑料,研究了发泡剂配比对泡孔结构和泡沫性能的影响。结果表明,随着FEA-1100比例的增加,泡沫的拉丝时间和脱粘时间延迟、泡沫流动性能提高;泡沫的压缩强度提高、导热系数降低。扫描电子显微镜(SEM)分析表明,采用MF和FEA-1100混合发泡剂,可使泡沫的泡孔结构更加均匀细腻;泡沫导热系数和压缩强度的各向异性与泡沫泡孔结构的各向异性相关。     

甲酰胺的生产方法

<正> 甲酰胺的生产方法有:①一步法——CO和NH_3直接进行合成反应(需高压)。②羰基合成MF进而氨解法—CO和甲醇进行羰基合成,生成的MF再与氨反应生成甲酰胺。③甲醇脱氢制MF进而氨解法。④传统法—用焦炭发生煤气,将煤气净化,用NaOH溶液吸收煤气中的CO制得甲酸钠,甲酸钠酸化制得甲酸,甲酸与甲醇反应生成MF,MF氨解得甲酰胺。传统     

PVA/SA/MF阻燃复合纤维的制备和性能研究

以聚乙烯醇(PVA)、海藻酸钠(SA)和三聚氰胺-甲醛树脂(MF)混合液为纺丝原液,采用湿法纺丝工艺制备PVA/SA/MF复合纤维。研究了PVA与SA及MF的共混比例对复合纤维阻燃性能和力学性能的影响。结果表明:PVA/SA/MF复合纤维的表面均匀光滑,其内部为网状结构;随着MF含量的增加,复合纤维阻燃性能增强,但其断裂强度呈现先增加后降低的趋势;当PVA∶SA∶MF质量比为10∶1∶4时,复合纤维的阻燃性能和力学性能均较好,其极限氧指数(LOI)为29. 8%,断裂强度为3. 19 c N/dtex;当PVA∶SA∶MF质量比为10∶1∶6时,复合纤维的阻燃性能、热性能及耐阻燃耐久性最好,其LOI为32. 0%,600℃时的质量保持率为24%左右,水洗50次后的LOI为25. 9%。     

含二氧化钛连铸保护渣的黏性特征

采用旋转黏度计并借助岩相分析系统探讨了二氧化钛(TiO2)对不锈钢连铸保护渣(mold fluxes,MF)黏性特征影响的作用机制.研究表明:随着TiO2加入量的增加,MF的黏度和凝固温度(θs)先逐渐减小而后迅速增大.在实验条件下,当TiO2加入量(质量分数,下同)为10%时,MF的黏度(1 300℃)和θs达到最小值,分别为0.30Pa·s和1 198℃.当TiO2加入量较小时,TiO2作为网络抑制体可以降低MF的黏度.当TiO2加入量较大时,TiO2促进钙钛矿晶体的析出,使MF的表观黏度增加.TiO2可以抑制MF中枪晶石和硅灰石的生长,促进黄长石和钙钛矿的析出.在实验条件下、1 350℃时,MF的TiO2溶解度大于20%.     

甲醚化MF改性MF/PVA阻燃纤维的结构与性能

以甲醚化三聚氰胺甲醛(MF)树脂、MF树脂和聚乙烯醇(PVA)在一定条件下制得纺丝原液,经湿法纺丝得到甲醚化MF改性的MF/PVA纤维;研究了纺丝过程中氮流失率和纤维的形貌结构、力学性能、热性能以及阻燃性能.结果表明:甲醚化MF的加入可以降低MF树脂在凝固浴中的溶出;随甲醚化MF比例的增加,氮流失率逐渐降低,纤维表面更...     

HO-PDMS改性酚醛泡沫材料的性能研究

研究了低聚羟基封端聚硅氧烷(HO-PDMS)改性酚醛泡沫的性能,考察了HO-PDMS含量对改性酚醛泡沫表观密度、吸水率、压缩强度和阻燃性的影响。结果表明:含10%HO-PDMS改性酚醛树脂制成的泡沫压缩强度达到336 k Pa,是改性前的1.9倍左右;泡沫的阻燃性随HO-PDMS含量的增加而下降,在HO-PDMS含量为25%时,泡沫的氧指数仍保留在40%以上;改性泡沫的表观密度随增韧剂含量的增加而增加;HO-PDMS的添加有效降低了酚醛泡沫的吸水率。     

泡沫复合驱用癸基糖苷磺酸盐的合成及性能研究

以癸基葡萄糖苷(C_(10)APG)和3-氯-2-羟基丙烷磺酸钠为原料反应制得癸基糖苷磺酸盐(C_(10)APGS),用FT-IR和ESI-MS对产物进行了表征,并对其泡沫性能和吸附性进行了测定。结果表明:C_(10)APGS表现出良好的发泡能力和泡沫稳定性,其发泡率和排液半衰期随C10APGS质量分数的增加而增加,当质量分数增加到0.4%后,发泡率和排液半衰期增速变缓;随着二价盐质量分数的增加,C10APGS的发泡率变化不大,但对泡沫稳定性产生明显的影响,当二价盐质量分数增加到8%时,C10APGS仍表现出良好的耐盐性能;相对于C_(10)APG,C10APGS的饱和吸附损失量降低了14.4%,可作为较理想的发泡剂应用于高盐油藏的泡沫复合驱。     

十二烷基醇聚氧乙烯醚羧酸钠及其复配体系的泡沫性能

采用气流法研究了十二烷基醇聚氧乙烯醚羧酸钠(C12E3C)水溶液的泡沫性能,并考察了不同添加剂(氯化钠、聚合物、脂肪醇、烷醇酰胺)对泡沫性能的影响.结果表明,电解质的加入显著降低了泡沫的稳定性,泡沫半衰期从85 min降低至45 min,而起泡能力随电解质浓度的增加先增强后减弱;聚合物的加入降低了起泡能力,但明显增加泡沫稳定性;短链醇的加入可以明显提高溶液的起泡能力及泡沫稳定性,泡沫体积从218 mL最高可增至240 mL,泡沫半衰期从85 min最高可增至108 min;而不同链长的长链醇对泡沫性能影响效果不同;烷醇酰胺的加入则可以增加泡沫稳定性,但对起泡能力影响不大.     

反应型磷氮阻燃剂/可膨胀石墨复配阻燃聚氨酯泡沫

将反应型阻燃剂六(4-磷酸二乙酯羟甲基苯氧基)环三磷腈(HPHPCP)和可膨胀石墨(EG)复配,制备了阻燃聚氨酯泡沫,详细研究了复配阻燃剂对聚氨酯泡沫的物理力学性能、热稳定性以及阻燃性能的影响。结果表明,阻燃聚氨酯泡沫的密度和热导率随着复配阻燃剂中EG含量的增加而升高;压缩强度随着EG含量的增加呈现先增加后降低的趋势。热失重表明复配阻燃剂大大提高了聚氨酯泡沫的热稳定性。聚氨酯泡沫的初始分解温度(T_10%)从212.9℃,分别提高到222.0、231.2和243.2℃;700℃残炭量从7.6%分别提高到26.3%、31.6%和37.9%。聚氨酯泡沫的阻燃性能随着复配阻燃剂中EG含量的增加而提高。阻燃聚氨酯泡沫的极限氧指数从19%提高到29%,均能通过UL-94水平燃烧HF-1等级和垂直燃烧V-0等级。     

A flame‐retardant composite foam: foaming polyurethane in melamine formaldehyde foam skeleton

A composite foam, polyurethane–melamine formaldehyde (PU/MF) foam, was prepared through foaming PU resins in the three‐dimensional netlike skeleton of MF foam. The chemical structure, morphology, cell size and distribution, flame retardancy, thermal properties and mechanical properties of such composite foam were systematically investigated. It was found that the PU/MF foam possessed better fire retardancy than pristine PU foam and achieved self‐extinguishment. Moreover, no melt dripping occurred due to the contribution of the carbonized MF skeleton network. In order to further improve the flame retardancy of the composite foam, a small amount of a phosphorus flame retardant (ammonium polyphosphate) and a char‐forming agent (pentaerythritol) were incorporated into the foam, together with the nitrogen‐rich MF, thus constituting an intumescent flame‐retardant (IFR) system. Owing to the IFR system, the flame‐retardant PU/MF foam can generate a large bulk of expanded char acting as an efficient shielding layer to hold back the diffusion of heat and oxygen. As a result, the flame‐retardant PU/MF foam achieved a higher limiting oxygen index of 31.2% and exhibited immediate self‐extinguishment. It exhibited significantly reduced peak heat release rate and total heat release, as well as higher char residual ratio compared to PU foam. Furthermore, the composite foam also showed obviously improved mechanical performance in comparison with PU foam. Overall, the present investigation provided a new approach for fabricating a polymer composite foam with satisfactory flame retardancy and good comprehensive properties. © 2018 Society of Chemical Industry     

Electrodeposited porous Pb electrode with improved electrocatalytic performance for the electroreduction of CO2 to formic acid

A porous Pb foam was fabricated electrochemically at a copper substrate and then used as the cathode for the electroreduction of CO₂. The surface morphology and composition of the porous Pb electrode was characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and selected area electron diffraction. The honeycomb-like porous structure was composed of needle-like Pb deposits. Cyclic voltammetry studies demonstrated that the porous Pb electrode had better electrocatalytic performance for the formation of formic acid from CO₂ compared with a Pb plate electrode. The increase in current density was due to the large surface area of the porous Pb electrode, which provides more active sites on the electrode surface. The improved formic acid selectivity was due to the morphology of the roughened surface, which contains significantly more low-coordination sites which are more active for CO₂ reduction. The highest current efficiency for formic acid was 96.8% at -1.7 V versus saturated calomel electrode at 5 °C. This porous Pb electrode with good catalytic abilities represents a new 3D porous material with applications for the electroreduction of CO₂.     

轻质密胺泡沫制备工艺优化

基于红外光谱分析和反应过程树脂黏度及泡孔结构的变化, 说明了三聚氰胺和甲醛为主要原料制备热固性泡沫的机理, 物理发泡过程还发生交联固化, 不同条件下制备不同泡孔大小和长径比的泡沫。为获得轻质、降噪和回弹好的发泡材料, 设计了正交实验优化工艺, 得到最佳工艺为:发泡液黏度1500 mPa·s, 树脂液、表面活性乳化剂、正戊烷发泡剂、固化剂质量配比为50:2:16:4, 微波加热60 s, 制得密度5 kg·m^-3的密胺泡沫。     

Determination and Correlation of Solubility for D-Xylose in Volatile Fatty Acid Solvents

The solubility of D-xylose in formic acid and binary solvents of formic acid with formic acid and acetic acid, propionic acid, n-butyric acid or isobutyric acid was measured in the temperature range from 300.35 to 325.05 K using the synthetic method by a laser monitoring technique at atmospheric pressure. The solid-liquid equilibrium data will provide essential support for industrial design and further theoretical study. The experimental data show that the solubility of D-xylose in formic acid and in the mixtures of formic acid＋acetic acid （1︰1）, formic acid＋propionic acid （1︰1）, formic acid＋n-butyric acid （1︰1）, and formic acid＋isobutyric acid （1︰1） increases with temperature. The Apelblat equation, theλh model, and the ideal solution equation correlate the solubility data well.     

Intrinsically flame retarded foams based on melamine − formaldehyde condensates: thermal and mechanical properties

Two kinds of foam based on melamine ? formaldehyde (MF ) condensates (PVA /MF (PVA , polyvinyl alcohol), PVA /APTES /MF (APTES , 3‐triethoxysilylpropylamine)) were prepared by chemical modification. Pure MF foam has the serious disadvantage that it is very hard and brittle, breaks easily and crumbles when handled. After modification, PVA /MF and PVA /APTES /MF display excellent resilience. The structures of the foams were characterized by Fourier transform infrared (FTIR ), SEM and XRD . XRD data indicate that modifiers hinder the crystallization of MF , which might contribute to the improvement of resilience. Flame retardancy of the foams was characterized by limiting oxygen index testing, and the thermal degradation behavior was studied using TGA . The mode of flame retardant action is suggested by gaseous and solid phase analysis. TGA‐FTIR results demonstrate that the sublimation of the melamine of MF and foams based on MF occurs during thermal decomposition, which contributes to the high flame retardancy. © 2016 Society of Chemical Industry     

Highly effective anode structure in a direct formic acid fuel cell

We report the mass transport characteristics of formic acid and performance enhancement in a direct formic acid fuel cell in terms of the property of anode components. The effect of hydrophobicity of anode diffusion media as well as catalyst layer was investigated applying different cell temperature and fuel concentration. The operation over 80 °C and concentrated formic acid is of great advantage to the enhancement of catalytic activity and better water management. On the other hand, the conductivity of formic acid decreases by means of the formation of more complex chains of formic acid and the fuel cell resistance increases by membrane dehydration effect due to the hygroscopic property of formic acid, resulting in overall decrease of cell performance and long-term stability. Optimizing operating conditions, the use of 60% PtRu/C with only 1 mg/cm² on plain carbon paper can be one of the good choice to achieve both sustainable power performance and higher utilization of anode catalysts keeping cell resistance.     

Vapour phase hydrogenation of olefins by formic acid over a Pd/C catalyst

It has been found that ethylene and propylene could be effectively hydrogenated by formic acid vapour over a Pd/carbon catalyst at low temperatures (<440 K). Surface hydrogen formation from formic acid is the rate-determining step for this hydrogenation reaction. Interaction of this hydrogen with the olefins is then fast. The conversion of formic acid in the presence of either of the olefins at any temperature is higher than in their absence. This has been explained by a much lower surface hydrogen concentration in the presence of the olefins. Direct experiments have confirmed that hydrogen inhibits the formic acid decomposition. Water vapour addition has a small positive effect on the decomposition of formic acid as well as on the hydrogenation of the olefins with formic acid. Catalysts consisting of gold supported on carbon or titania are both active in the production of hydrogen from formic acid. However, in contrast to the Pd/C catalyst, neither gives hydrogenation of the olefins with this acid.     

Formation of formic acid from glycerine using a hydrothermal reaction

BACKGROUND: Glycerine, a main by‐product of the biodiesel manufacturing process, has potential to be an important biorefinery feedstock with the rapid increase in biodiesel production all over the world. Hydrothermal experiments with glycerine were carried out at 250 °C using H₂O₂ as an oxidant. RESULTS: Glycerine was converted into formic acid with a yield of 31.0% based on the starting mass of carbon in glycerine. A possible oxidation pathway for the formation of formic acid from glycerine is proposed. In the proposed pathway, glycerine may first be oxidised and then decomposed into formic acid and oxalic acid. Oxalic acid was indirectly attributed to the increase of formic acid production from glycerine, but it instead acts as a retardant to prevent further oxidation of formic acid. However, when an alkali was added to the experimental conditions, the yield of formic acid was not greatly improved, reaching only 34.7%. CONCLUSION: The present work should help to facilitate further studies to develop a new green process for the production of formic acid from renewable biomass. © 2012 Society of Chemical Industry     

浅析苯菲尔溶液泡沫特性与有机物含量的关系

苯菲尔溶液泡沫特性与有机物含量之间的关系没有具体的相关资料说明,本文通过对苯菲尔溶液泡沫特性与有机物含量的关系研究,从分析的角度,结合工艺流程,对苯菲尔溶液中甲醛、甲醇、甲酸、黏度、COD等项目进行测定,通过实验确定引起消泡时间超标的重要因素。     

多指标正交实验优化可发性三聚氰胺甲醛树脂的制备

用己内酰胺作改性剂,通过正交实验设计考察了甲醛和三聚氰胺摩尔比(F/M)、溶液pH值、反应温度(T)和反应时间(t)对可发性三聚氰胺甲醛(MF)树脂的储存期、固含量、黏度、MF泡沫密度及泡孔尺寸均匀性的影响,运用综合评分法和综合平衡法对正交实验结果进行了分析,得出最优水平组合:F/M=2.5,pH=8.0,T=90℃,t=60min。最优条件下合成的MF树脂可发泡性良好,制得的泡沫性能优良。