Investigation of alkaline hydrolysis of polyethylene terephthalate by differential scanning calorimetry and thermogravimetric analysis

The hydrolytic depolymerization of polyethylene terephthalate (PET) with alkaline hydroxides was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The reactions of the mixtures were conducted in their solid states under nitrogen atmosphere. The experimental results showed that potassium hydroxide possessed the hydrolytic activity of depolymerizing PET into small molecules such as ethylene glycol; in contrast, sodium hydroxide did not. The production rate of ethylene glycol was enhanced by increasing charge ratio of potassium hydroxide to PET. The presence of water facilitated the alkaline hydrolysis of PET; however, the presence of metal acetates decreased the hydrolysis rate. The activation energy for alkaline hydrolysis of PET determined by the thermograms was in good agreement with the value obtained from the experiments in a batch reactor. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1939–1945, 1998     

Degradation of poly(vinyl alcohol) in strongly alkaline solutions of hydrogen peroxide

The action of hydrogen peroxide and sodium hydroxide independently as well as in combination together with stabilizer formulation–consisting of magnesium sulphate (5 g/L), ethylenediamine tetraacetic acid (2 g/L), gluconic acid (2 g/L), and nonionic/anionic wetting agent (1.5 g/L)–on poly(vinyl alcohol) (PVA) was investigated at 30°C and 95°C. The effect of sodium hydroxide (5–25 g/L) alone was to bring about an enhancement in the viscosity of PVA most probably due to gel formation. The latter was favored at higher sodium hydroxide concentrations and longer duration (30 min) of treatment. The opposite holds true when hydrogen peroxide (35% w/v) was used alone at concentrations ranging from 2 to 20 mL/L. The viscosity of PVA decreased as the hydrogen peroxide concentration increased. Nevertheless, hydrogen peroxide alone could not cause complete dissolution of PVA even at 95°C for 30 min. On the other hand, complete dissolution of PVA could be achieved under the influence of stabilized alkaline solutions of hydrogen peroxide at 95°C in less than 10 min. It was postulated that, under the conditions used, oxidation of PVA by hydrogen peroxide prevailed over gel formation under the influence of sodium hydroxide.     

Thermal and flammability studies of poly(vinyl alcohol) composites filled with sodium hydroxide

Poly(vinyl alcohol) (PVA) is a polymer of great value due to its wide spread applications. The present article describes the effect of sodium hydroxide on the flammability, thermal degradation, and tensile strength properties of PVA. The PVA/sodium hydroxide composite films at different loading levels of sodium hydroxide, i.e., 0.5, 1, 2, 3, and 4.5 wt % were prepared by solution casting technique. Dynamic thermogravimetry was used to study the thermal degradation behavior of samples at four different linear heating rates, i.e., 2.5, 5, 10, and 20 °C min^?1 under nitrogen atmosphere. The degradation activation energy values were calculated using reliable and preferred multiple‐heating rate methods. Limiting oxygen index (LOI) and UL 94 tests were carried out to check the flammability behavior of the samples. The presence of sodium hydroxide in PVA brought significant changes in the thermal and flammability performance. PVA/sodium hydroxide samples though showed lower initial decomposition temperature, but overall more thermal stability results as evidenced from the higher activation energy and char residue values. LOI and UL 94 tests indicate that sodium hydroxide greatly enhanced the flame retardancy of PVA/sodium hydroxide films. Based on the thermal and flammability level, the optimum concentration of sodium hydroxide is worked out. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Linear polythioesters. IV. The effect of hydrogen chloride acceptor on interfacial polycondensation of 4,4′-di(mercaptomethyl) benzophenone with isomeric phthaloyl chlorides

New polythioesters of better physicochemical and mechanical properties have been obtained by interfacial polycondensation of 4,4′-di(mercaptomethyl)benzophenone with terephthaloyl, isophthaloyl, and phthaloyl chlorides with the use of sodium hydroxide excess as a hydrogen chloride acceptor. According to preliminary experiments, the best yield and the highest reduced viscosity are reached when the polycondensation at a 1:l ratio of the aqueous to the organic phase is carried out at a temperature of 5–7°C with a little excess of acid chloride with addition time of 0.5–2 min in the presence of 100% excess of NaOH as hydrogen chloride acceptor. The structure of the polythioesters was determined from elemental analysis and infrared spectra. Thermal properties of all polythioesters were determined. Mechanical and electrical properties of only the most interesting polythioesters obtained from isophthaloyl chloride were determined.     

不同浸渍方法制备生物质活性炭及其活化机理的研究

利用生物质废料——棕榈壳,采用不同的浸渍方法制备高效活性炭。详细探讨了活化温度和浸渍剂(氢氧化钠)浓度对活性炭性能的影响。采用固定床吸附二氧化硫气体,评价了制备样品的吸附能力。还开展了解吸过程的研究,证明了二氧化硫与活性炭表面之间发生的化学吸附或化学反应。研究表明,采用前期浸渍方法制备活性炭时,原料表面的氢基团被钠置换,形成交联体,从而可获得较高的活性炭收率。而且,这些钠离子在二氧化碳活化阶段还起到催化作用。采用中期浸渍方法,氢氧化钠脱水后生成单质钠,夹杂在碳层中有利于微孔的形成,活化时与二氧化碳生成碳酸钠,可防止试样的过度烧失。采用后期浸渍方法时,由于氢氧化钠颗粒阻挡了活性炭的微孔通道,改变了活性炭的结构特性。但附着的氢氧化钠可通过生成亚硫酸钠,提高对二氧化硫的除去效果。     

固相萃取-液质联用法测定食品中两种苯氧乙酸类除草剂含量

建立了固相萃取-液质联用法测定食品中2,4-二氯苯氧乙酸(2,4-D)和2-甲-4-氯苯氧乙酸(MCPA)含量的方法。样品经0.01 mol/L氢氧化钠碱液提取后,用甲酸溶液调至酸性(pH=3.0),以Oasis HLB柱净化富集,在HPLC-MS(SIR)模式下进行定性定量分析。结果表明,2,4-D和MCPA溶液在0.005~0.32μg/mL内呈良好的线性关系,相关系数r分别为0.999 3和0.999 6,检出限(S/N=3)分别为1.35,1.31μg/L,富集倍数为49和51,加标回收率为78.75%~103.75%。本法操作简便、结果准确、重复性好,是测定食品中残留2,4-D和MCPA含量的有效方法。     

Graft copolymerization of acrylamide onto carboxymethylcellulose with the xanthate method

Acrylamide was grafted to an xanthate mixture of carboxymethylcellulose with a sodium bisulfate/ammonium persulfate redox initiator system in water, sodium hydroxide, potassium hydroxide, and dioxane at 40, 50, 60, 70, and 80°C during a reaction period of 2 h. The grafted polymer and homopolymer were isolated with diethyl ether from the reaction mixture, dried, and weighed. The grafted polymer was characterized with IR and mass spectrometry methods, and the microscopic morphology was detected with electron scanning microscopy. The graft level percentage distinctly increased with the use of sodium hydroxide, potassium hydroxide, and dioxane over that of a reaction carried out completely in an aqueous medium. Also, the graft level decreased as the reaction temperature increased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 271–278, 2004     

Rendering flax fibre dyeable with basic dyes via partial carboxymethylation

Carboxymethylation of flax has been carried out by first treating the fibres with sodium hydroxide followed by the sodium salt of monochloroacetic acid. The treatment was carried out under a variety of conditions. Variables studied included concentrations of monochloroacetic acid and sodium hydroxide in the impregnating solutions, as well as duration and temperature of the reaction. it was found that the extent of carboxymethylation increased substantially by controlling the concentrations of alkali and monochioroacetic acid, and by reacting for 6d min at 70d?C. The behaviour of selected samples of partially carboxymthylated flax towards basic dyes was also studied.     

膨润土与碱反应的初步研究

将经焙烧与不经焙烧的膨润土与氢氧化钠反应，考察了反应时间和氢氧化钠浓度对膨润土中硅铝浸出的影响. 测定了不同焙烧温度和焙烧时间条件下膨润土与碳酸钠固相反应生成物中可溶性硅铝的含量，并通过热重分析实验对此固相反应进行了研究. 结果表明：接近碳酸钠熔点时固相反应最剧烈，膨润土中63.85%的SiO2和96.78%的Al2O3可被浸出转变为水溶性物质.     

Preparation procedures for woven cotton and polyester/cotton fabric. Part 2 — oxidative desizing with hydrogen peroxide

Oxidative desizing with sodium hydroxide in the presence of hydrogen peroxide has been investigated as a preparatory treatment for dyeing and printing cotton and polyester/cotton woven fabric. Using statistically designed experiments, the effect of time and temperature of treatment, and peroxide and sodium hydroxide concentrations on degree of desizing, whiteness, fabric absorbency and mote removal has been determined. The major factor determining desizing rate was sodium hydroxide concentration. As peroxide concentrations increased above 0.1% o.w.f. of 35% solution desizing was retarded. Desizing was thus seen to be a hydrolytic process initiated by hydrogen peroxide. Whiteness achieved during desizing was not correlated with sodium hydroxide concentration and adequate whiteness was not achieved with the 100% cotton fabric. Whiteness of the blend was significantly influenced by all the desizing factors, while absorbency was affected by treatment time and temperature. Pure cotton was not rendered absorbent at all at below 65°C, in contrast with enzymatic desizing. Treatment for a short time in the temperature range 65–95°C gave a generally unsatisfactory level of mote removal.     

Electrosynthesis of ammonia in hydrogen-producing sorption-active electrochemical matrix

A fundamentally new low-temperature method of synthesizing ammonia has been suggested, which is carried out directly in a hydrogen-producing matrix with a material made of cellulose fabric with porous layers of ethanol–cyclam PVC derivatives with activated carbon with aquacomplexes of sodium hydroxide grafted onto its fibers. Complexes of zero-valent nickel and iron within the cyclam structure are formed in the matrix. Hydrogen is formed on the cathode in the course of electrolysis of water from sodium hydroxide aqua complexes on particles of activated carbon as microelectrodes. Hydrogen forms bonds with complexes of zero-valent nickel. Nitrogen from adsorbed air is bound in complexes of zero-valent iron and interacts with active atomic hydrogen. Water is transported to carbon particles through the fabric onto which the layer is grafted. The process is carried out at the room temperature. It has been found that the forming hydrogen is almost completely used. As opposed to the existing methods of synthesis of ammonia, the suggested process is carried out at room temperature and normal pressure.     

Benign and ecofriendly depolymerization of polycarbonate wastes into valuable diols using micro- and nano-TiO<Subscript>2</Subscript> as the solid supports

Hydroglycolysis of polycarbonate (PC) wastes received from optical (CDs) and digital optical discs (DVDs) to the diols derivatives of bisphenol-A (BPA), namely, bis(4-hydroxybutyl hydrogen carbonate) of BPA (DHB–BPA), mono(4-hydroxybutyl hydrogen carbonate) of BPA (MHB–BPA), and BPA itself as the major and oligomeric minor products were developed under mild and convenient conditions. Experiments were performed with the mixture of green solvents, including 1,4-butanediol and water in the presence of nanoparticles TiO₂ (NPs-TiO₂) and microparticles TiO₂ (MPs-TiO₂) as the solid supports, and sodium hydroxide as the catalyst under simple heating method and the obtained results were compared with together. In the developed procedure, DHB–BPA achieved and selectively converted into the MHB–BPA and BPA, respectively, when left in the moisturized environment. In these reactions, the effects of various parameters such as concentration of sodium hydroxide, the role of water as co-solvent, and nano-solid support on reaction progress are considered. The obtained results showed that by increasing the amount of water (0 up to 30 pbw based on total solvent weights) and catalyst as well (0 up to 2 pbw based on total solvents and PC wastes weights), the depolymerizing reaction was performed in high yields. In the meantime, DHB–BPA was recovered in 80% yield, using NPs-TiO₂ as the solid support in the 30 pbw aqueous 1,4-butanediol. The depolymerization reaction time shortened in using NPs-TiO₂ as the solid support when the data compared with the experiments performed by MPs-TiO₂. Finally, the recyclability and efficiency of the NPs-TiO₂ were studied and the data showed the usability of this solid support for four cycles. The recovered products were characterized using ¹H NMR, ¹³C NMR, Fourier-transform-infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and gas chromatography–mass spectrometry (GC–MS) methods.     

利用硫酸镍制备超细球形镍粉的实验研究

针对硫酸镍液相通氢还原制得球状超细镍粉品位较低（仅在96%左右）的问题,提出一条通过火法-湿法联合还原提高镍粉品位的工艺路线。首先由硫酸镍和氢氧化钠水溶液在室温下混合而成氢氧化镍浆料,不经过过滤洗涤,转入高压釜进行悬浮态氢还原。反应结束后,液固分离,获得品位在96%左右的半成品镍粉。将半成品镍粉在氢还原炉中进行二次还原,控制还原温度为400 ℃,还原时间为2 h,获得的产品镍质量分数大于99.5%,粒度小于2.0 μm,满足金刚石工具、硬质合金等行业需求的超细镍粉性能指标要求。     

5-乙酰基-2-氨基二苯甲酮的超声合成

利用超声振荡,以对硝基苯乙酮为原料,在原甲酸三乙酯和对甲苯磺酸的催化作用下和乙二醇醚化保护酮基,然后在氢氧化钠甲醇溶液的碱性条件下和苯乙腈环化加成,再用w(Pd)=5%的Pd-C催化加氢,最后在浓度为1mol/L的高氯酸的强酸作用下恢复酮基,合成出5 乙酰基 2 氨基二苯甲酮,用IR和1HNMR对其结构进行了表征。与非超声合成方法比较,反应时间由44h缩短到32h,目标产物总收率由39 5%提高到69 6%。     

Using ecological reducing agents instead of sodium sulphide in dyeing with CI Sulphur Black 1

Although low‐cost sodium sulphide is used as a reducing agent in most sulphur dyeing processes, it is considered to be environmentally unfavourable because of the resultant contaminated wastewater and the toxic hydrogen sulphide generated during the dyeing process. In the present paper, hydrazine sulphate, glucose, and sodium borohydride in the presence of sodium hydroxide were used as ecologically safe reduction systems for the CI Sulphur Black 1 dyeing of cotton fabric, and results were compared with those obtained using sodium sulphide. Dyeing processes were carried out at 90 °C for 60 min, and the colour yield (the K/S value), dyeing fastness, and breaking strength of dyed fabrics after soaping were measured. Response surface methodology was employed for experimental design and optimisation of results. Mathematical model equations were derived and statistical analysis carried out by computer simulation programming using Minitab v.15. At a dosage of 0.8 g l^?1 of CI Sulphur Black 1, the optimum sodium borohydride reduction system (sodium borohydride 0.47 g l^?1, sodium hydroxide 0.65 g l^?1) exhibited the highest colour yield and the lowest chemical oxygen demand of the residual dyebath.     

Rapid,efficient and selective conjugate addition of thiols to α, β-unsaturated carbonyl compounds using silica supported sodium hydrogen sulfate under solvent-free conditions†

The conjugate addition of thiols to α, β-unsaturated carbonyl compounds was carried out rapidly (within 2–5 min) and selectively in the presence of silica supported sodium hydrogen sulfate (NaHSO₄·SiO₂) to form the corresponding Michael adducts in excellent yields (86–95%) at room temperature and under solvent-free conditions.     

Monitoring and control of hydrogen peroxide dosing

A new method is described for continuously monitoring hydrogen peroxide and sodium hydroxide concentrations in impregnation baths used for bleaching woven cotton fabrics. A series of industrial tests were carried out using this new method in which concentrations were monitored and then controlled by regulated dosing.     

Properties of trialkylamines as catalysts of resoles synthesis

A series of the syntheses of phenol–formaldehyde resoles was carried out in the presence of trimethyl‐, triethyl‐, tripropyl‐, and tributylamines and sodium hydroxide as catalysts for this process. The rate constants were calculated for the partial reactions identified in the synthesis. Also, the performance properties of the resins obtained and the hardened resin samples were estimated in simple tests. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 898–902, 2000     

Chemical Recycling and Kinetics of Aqueous Alkaline Depolymerization of Poly(Butylene Terephthalate) Waste

Depolymerization reactions of poly(butylene terephthalate) (PBT) waste in aqueous sodium hydroxide solution were carried out in a batch reactor at 80–140 °C at atmospheric pressure by varying PBT particle size in the range of 50–512.5 μm. Reaction time was also varied from 10–110 min to understand the influence of PBT particle size and reaction time on the batch reactor performance. Agitator speed, particle size of PBT and reaction time required were optimized. Disodium terephthalate (salt) and 1,4‐butanediol (BD) remain in the liquid phase. BD was recovered by the salting‐out method. Disodium terephthalate was separated by acidification to obtain solid terephthalic acid (TPA). The produced monomeric products (TPA and BD) and PBT were analyzed. The yields of TPA and BD were in agreement with PBT conversion. The depolymerization reaction rate was first order to PBT concentration as well as first order to sodium hydroxide concentration. The acid value of TPA changes with the reaction time as well as particle size of PBT. This indicates that PBT molecules get fragmented and hydrolyze simultaneously with aqueous sodium hydroxide to produce BD and disodium terephthalate. Activation energy, Arrhenius constant, equilibrium constant, Gibbs free energy, enthalpy and entropy were determined. The dependence of the hydrolysis rate constant on reaction temperature was correlated by the Arrhenius plot, which shows an activation energy of 25 kJ/mol and an Arrhenius constant of 438 L/min/cm².     

Improvement of the phase-transfer catalysis method for synthesis of glycidyl ether

A convenient procedure for the synthesis of aliphatic alkylglycidyl ether has been studied. It has been found that the improved preparation of the alkylglycidyl ether can be achieved by using fatty alcohol such as octanol and octadecanol with epichlorohydrin in the presence of phase-transfer catalyst (PTC) such as 1-alkyloxypropan-2-ol-3-trimethyl ammonium methylsulfate, 1-alkyloxypropan-2-ol-3-methyldiethanolammonium methylsulfate, alkyloxy-2-hydroxypropyldimethylamine and alkyloxy-2-hydroxypropyldiethanolamine, tetrabutylammonium bromide, etc. without water and other organic solvents. This method, carried out in solid phase/organic phase (reactants and product themselves), has the following merits: (i) producing the solid by-products such as sodium chloride and sodium hydroxide which are easily removed by simple filtration, (ii) saving the amount of reactants used such as sodium chloride and phase-transfer catalyst, and (iii) increasing the yields of glycidyl ethers. The yields of octylglycidyl ether and octadecylglycidyl ether are 92.0 and 91.7%, respectively. The amount of sodium hydroxide used can be saved by from 1.5 to 0.7 molar ratio with respect to octanol in comparison with those in the conventional method using PTC.