On the Structure and Strength of Solvent-Welded Joints: The Intrinsic Joint Strength and the Effect of Dissolved Polymer in the Solvent Cement

It is proposed that the intrinsic strength of a solvent-welded joint can be represented by the magnitude of its critical principal strain. A large critical principal strain implied a high intrinsic weld strength. With poly(vinylchloride) adherends, solvent welds formed using pure tetrahydrofuran (THF) and cyclohexanone bonding solvents had high intrinsic joint strengths while solvent welds from pure methyl ethyl ketone (MEK) bonding solvent had lower intrinsic joint strength. In the THF bonding system, the introduction of dissolved polymer in the bonding agent led to significant decreases in the strength of the solvent-welded joint. Additions of up to 2% by weight of dissolved polymer in the MEK bonding agent increased the strength of the solvent weld. However, further increases in the dissolved polymer content in MEK bonding agent also led to decreases in strength.     

On the Structure and Strength of Solvent-Welded Joints: The Intrinsic Joint Strength and the Effect of Dissolved Polymer in the Solvent Cement

It is proposed that the intrinsic strength of a solvent-welded joint can be represented by the magnitude of its critical principal strain. A large critical principal strain implied a high intrinsic weld strength. With poly(vinylchloride) adherends, solvent welds formed using pure tetrahydrofuran (THF) and cyclohexanone bonding solvents had high intrinsic joint strengths while solvent welds from pure methyl ethyl ketone (MEK) bonding solvent had lower intrinsic joint strength. In the THF bonding system, the introduction of dissolved polymer in the bonding agent led to significant decreases in the strength of the solvent-welded joint. Additions of up to 2% by weight of dissolved polymer in the MEK bonding agent increased the strength of the solvent weld. However, further increases in the dissolved polymer content in MEK bonding agent also led to decreases in strength.     

Screening of Binary Solvent Mixtures and Solvate Formation of Indomethacin

The applicability of solubility parameters and solvent activity in the screening of binary solvent mixtures was studied. The solubility of indomethacin was measured in binary mixtures of dichloromethane, acetone, and ethyl acetate with methanol and ethanol. Solubility extremes in the mixed solvents were observed. The solubility maxima were related to the excess Gibbs free energy of the solvents and the hydrogen bonding term of the Hansen solubility parameter. The solvates of indomethacin were characterized with a confocal Raman spectrometer, and the desolvation of the solvates was investigated with thermogravimetry.     

Vaporized solvent bonding of polymethyl methacrylate

This investigation highlights rationale of vaporized solvent bonding for fabrication of transparent polymers such as polymethyl methacrylate (PMMA) in terms of optical transparency and bond strength. Vaporized solvent bonding is employed to fabricate the polymer, and its bonding characteristics with appropriate solvents are analyzed. It is observed that chloroform exhibits superior bonding characteristics in comparison with other solvents such as acetone, ethanol, and dichloromethane. In order to see the effect of prior surface modification carried out by ultraviolet (UV) irradiation and low-pressure plasma, surface energy of the polymer was estimated. It is observed that due to surface modification of PMMA by UV irradiation and low-pressure plasma, surface energy of the polymer increases considerably. However, due to exposure under UV irradiation and low-pressure plasma, molecular weight of PMMA decreases and atomic force microscopy (AFM) studies reveal that the topography of PMMA changes significantly resulting in deterioration of vaporized solvent bonding strength. Therefore, in the case of vaporized solvent bonding, increase in surface energy of the polymer is not a primary factor rather retention of molecular weight is more necessary.     

Experiments on the induction welding of thermoplastics

In induction welding of thermoplastics, induction heating of a gasket, made of a ferromagnetic‐powder‐filled bonding material and placed at the interface of thermoplastic parts to be joined, is used to melt the interface; subsequent solidification of the melt results in a weld. Tensile tests on induction butt‐welds of polycarbonate (PC), poly(butylene terephthalate) (PBT), and polypropylene (PP) are used to characterize achievable weld strengths, and microscopy is used to correlate weld strength with the morphology of failure surfaces. In PC, PBT, and PP relative weld strengths as high as 48%, 43%, and 55% of the respective strengths of PC, PBT, and PP have been demonstrated. Relative weld strengths on the order of 20% have been demonstrated in PC‐to‐PBT welds.     

Vibration welding of nano‐TiO2 filled polypropylene

Polypropylene (PP)‐based nanocomposites compounded by a twin‐screw extruder and injection molded into plates those were then joined by linear vibration welding. The mechanical performances of the welds and bulk materials were examined. While the incorporation of rigid particles slightly improves the impact strength of the bulk PP, the mechanical properties of the welds decrease with increasing nanoparticle contents. The best weld quality is obtained at low weld pressure without nanoparticles. The fracture surfaces and microstructure of the welds showed that the reduced weld quality is caused by the orientation of nanofillers parallel to the weld plane, the destruction of interphase between fillers and matrix, and the reduction of molten‐film thickness by incorporation of nanoparticles. POLYM. ENG. SCI., 55:243–250, 2015. © 2014 Society of Plastics Engineers     

Strength and Microstructure of Solvent Welded Joints of Polycarbonate

The relationship of joint strength of solvent welded joints of polycarbonate to their microstructure is investigated. We used three solvents - butanone, acetone, and cyclohexanone - to test the effect of solubility parameters, and a mixture of cyclohexanone with ethanol to test the effect of a cosolvent; the effect of variation of welding temperature-on both the joint strength and the microstructure is also investigated. Three fracture modes in shear, tensile and tear tests are analyzed. Polycarbonate treated with butanone has maximum joint strength. Cyclohexanone at 78 vol% in ethanol produces the maximum joint strength of polycarbonate. The joint strength of polycarbonate joints welded with cyclohexanone increases with the temperature at which the weld is made. Comparing microstructure with joint strength, tongues, equiaxed dimples and elongated dimples are responsible for the maximum shear, tensile and tear strength, respectively.     

Solvent screening for non‐aqueous extraction of Alberta oil sands

Non‐aqueous extraction of bitumen from oil sands has the potential to reduce fresh water demand of the extraction process and eliminate tailings ponds. In this study, different light hydrocarbon solvents, including aromatics, cycloalkanes, biologically derived solvents and mixtures of solvents were compared for extraction of bitumen from Alberta oil sands at room temperature and ambient pressure. The solvents are compared based on bitumen recovery, the amount of residual solvent in the extracted oil sands tailings and the content of fine solids in the extracted bitumen. The extraction experiments were carried out in a multistage process with agitation in rotary mixers and vibration sieving. The oil sands tailings were dried under ambient conditions, and their residual solvent contents were measured by a purge and trap system followed by gas chromatography. The elemental compositions of the extraction tailings were measured to calculate bitumen recovery. Supernatants from the extraction tests were centrifuged to separate and measure the contents of fine solid particles. Except for limonene and isoprene, the tested solvents showed good bitumen recoveries of around 95%. The solvent drying rates and residual solvent contents in the extracted oil sands tailings correlated to solvent vapour pressure. The contents of fine solids in the extracted bitumen (supernatant) were below 2.9% for all solvents except n‐heptane‐rich ones. Based on these findings, cyclohexane is the best candidate solvent for bitumen extraction, with 94.4% bitumen recovery, 5 mg of residual solvent per kilogram of extraction tailings and 1.4 wt% fine solids in the recovered bitumen. © 2012 Canadian Society for Chemical Engineering     

磺化金属酞菁的溶剂效应

文章测试了5种磺化金属酞菁在7种不同极性溶剂中的吸收光谱,用N icol理论研究了金属酞菁染料的溶剂效应。实验和理论结果表明,此类化合物最大吸收峰的波数与函数f(n,ε)存在良好的线性关系,线性相关系数都在0.93以上;而Bayliss函数项(n2-1)/(2n2+1)决定了最大吸收波长(λm ax)的位移变化,λm ax总体上随着溶剂折射率的增大而蓝移,随着溶剂极性的增强而红移。基于此结果,提出了通过选择合适的溶剂调节酞菁染料吸收峰的有效方法,从而使酞菁染料更好地应用于激光防护。     

Comparison of vibration and hot‐tool thermoplastic weld morphologies

Because of very different heating rates in hot‐tool and vibration welding, and the higher weld pressures used in vibration welding inducing more squeeze flow, the weld zones in these two processes see very different flows and cooling rates, resulting in different morphologies. The weld morphologies of bisphenol‐A polycarbonate (PC) and poly(butylene terephthalate) (PBT) for these two processes are discussed in relation to these differences. The thickness of the heat‐affected zone (HAZ) in hot‐tool welds increases with the melt time; this zone is thicker than in vibration welds. The HAZ thickness in hot‐tool welds increases from the center toward the edges. The HAZ thickness is more uniform in vibration welds. Hot‐tool welds of PC have large numbers of bubbles around the central plane; the bubble size increases from the center to the edges. PC vibration welds do not have bubbles except near the edges. Both hot‐tool and vibration welds of PBT do not have bubbles. The morphology of the HAZ in PBT is very different in hot‐tool and vibration welds. In hot‐tool welds, the resolidified material consists of a sandwich structure in which two thin layers with very small crystallites surround a thicker central layer in which the spherulites are almost as large as in the original molded material. In vibration welds, the HAZ has large crystallinity gradients across the weld zone as well as squeeze‐flow induced distortion of the small spherulites.     

纤维素溶解体系的研究进展

综述了纤维素无机溶剂及有机溶剂的研究进展,分析比较了各溶剂体系的优缺点。其中有机溶剂中离子液体和N-甲基氧化吗啉的溶解能力最强,无机溶剂中碱/尿素或硫脲/水体系的溶解能力最强。但纤维素在各个溶解体系中都有一定程度的降解。     

Comparison of Various Solvent Media Efficiency in the Grinding of a Frit Containing Zirconium Oxide

In the present work thermal and chemical properties of a glass-ceramic frit containing zirconium oxide are evaluated after milling in various polar and nonpolar solvents. Particle-size distribution is one of the main variables investigated to evaluate the efficiency of several solvents. Milling in various solvents does not affect the thermal properties of the glass while the presence of polar groups in the solvent molecule increases the cation release from the glass.     

聚合物-溶剂体系中能量对溶剂扩散的影响

The Vrentas-Duda free-volume theory has been extensively used to correlate or predict the solvent diffusion coefficient of a polymer/solvent system.The energy term in the free volume diffusion equation is difficult to estimate,so the energy term was usually neglected in previous predictive versions of the free volume diffusion coefficient equation.Recent studies show that the energy effect is very important even above the glass transition temperature of the system. In this paper, a new evaluation method of the energy term is proposed,that is the diffusion energy at different solvent concentrations is assumed to be a linear function of the solvent diffusion energy in pure solvents and that in polymers under the condition that the solvent in infinite dilution.By taking consideration of the influence of energy on the solvent diffustion,the prediction of solvent diffusion coefficient was preformed for three polymer/solvent systems over a wide range of concentrations and temperatures.The results show an improvement on the predictive capability of the free volume diffusion theory.     

Solvent selection for extractive distillation using molecular simulation

This study examines a search for a new solvent for extractive distillation using molecular simulation, and the performance of the proposed extractive distillation processes using the solvents is compared to conventional processes. Unlike other solvent search procedures, the proposed solvent finding technique relies on a chemical structure similarity between the solvent and the extracted material without depending on a solvent database. Two new processes of benzene, toluene, and xylenes separation from naphtha reformate and propene/propane separation are compiled with the newly developed solvents for the performance examination. The simulation of the proposed extractive distillation processes demonstrates a significant performance improvement in energy saving and investment cost over conventional processes.     

The vibration welding of poly(methyl methacrylate) to itself and to polycarbonate,poly(butylene terephthalate), and modified poly(phenylene oxide)

The weldability of poly(methyl methacrylate) (PMMA) to itself and to polycarbonate (PC), poly(butylene terephthalate) (PBT), and modified poly(phenylene oxide) (M-PPO) is assessed through 120 and 250 Hz vibration welds. Weld strengths equal to those of the base resin have been demonstrated in welds of PMMA and M-PPO to themselves. In welds of PMMA to PC and to M-PPO, weld strengths equal to those of PC and M-PPO, respectively, have been demonstrated. PMMA does not weld well to PBT; the highest weld strength obtained was 21% of the strength of PBT resin.     

Strength of glass-filled modified polyphenylene oxide vibration-welded butt joints

The strengths of glass-filled modified polyphenylene oxide (GF-MPPO) welds relative to the strengths of GF-MPPO are shown to depend on specimen thickness. (Modified polyphenylene oxide is a blend of poly (2,6-dimethyl-1,4-phenylene ether) and high-impact polystyrene.) Relative strengths on the order of 70 and 87 percent can be achieved in 6.1 and 3.18-mm-thick specimens, respectively. Welds of GF-MPPO to modified polyphenylene oxide (MPPO) can easily attain the strength of MPPO, the weaker of the two materials. In contrast to MPPO, in which weld strength decreases with increased weld pressure, the strengths of GF-MPPO to GF-MPPO welds and GF-MPPO to MPPO welds, are not affected by weld pressure.     

润滑油基础油络合脱氮的溶剂选择

采用Klopman所给出的溶剂化能公式,计算了润滑油基础油络合脱氮中不同精制溶剂所产生的溶剂化能的大小。计算结果表明,在同一溶剂中,过渡金属离子所带的电荷越多,产生的溶剂化效应越大;当不同溶剂与同种金属离子相互作用时,溶剂的介电常数降低,对金属离子的溶剂化效应也相对减弱,有利于络合物的生成,亦即络合物有较大的稳定性。除了考虑溶剂化效应之外,还要求溶剂具有适当的选择性和一定的溶解能力。当用于工业化生产时,还需要考虑溶剂的价格是否适中。综合溶剂化效应、选择性、溶解能力、价格和实际的碱氮脱除率5个方面来看。糠醛是润滑油基础油络合脱氮的最佳精制溶剂。     

Regeneration of Mixed Solvent by Ion Exchange Resin: Selective Removal of Chloride and Sulfate

Abstract

The selective extraction of sulfate and chloride ions from mixed solvent solutions was investigated. The mixed solvents consisted of water and 50 to 100%‐w (salt‐free solvent) ethylene glycol. The extraction was measured for mixed solvent solutions containing only sulfate and chloride, and mixed solvent solutions saturated with trona (sodium sesquicarbonate, Na₂CO₃ · NaHCO₃ · 2H₂O(s). Three anion exchange resins, Dowex 1X8‐50, Dowex 21K‐Cl, and Dowex MSA‐1, were investigated for their chemical and physical resistance to the mixed solvent carbonate/bicarbonate solutions, for their swelling behavior in the different mixed solvents, and for their extraction efficiency for chloride and sulfate.

The loading of the ion exchangers was fitted to a Langmuir‐type sorption model. While the extraction from trona‐free mixed solvents was well reproduced, the loading of the ion exchangers with chloride and sulfate from trona‐saturated mixed solvent solutions did not fit the sorption model. It appears, rather, that under these conditions chloride and sulfate are “salted out” of the bulk solution and driven into the ion exchangers.     

The vibration welding of poly(phenylene oxide)/poly(phenylene sulfide) blends

The weldability of three blends of poly(phenylene oxide) and poly(phenylene sulfide), each with a different level or type of impact modifier, is assessed through 120 and 240 Hz vibration welds. The type of impact modifier is shown to have a large effect on the strength and ductility of welds. Weld strength in these blends is shown to be sensitive to the weld frequency; higher weld strengths are attained at the higher weld frequency. In these three blends, maximum relative weld strengths of about 70%, 85%, and 87% have been demonstrated at a weld frequency of 240 Hz. The highest weld strength in each of these three blends is achieved at different weld pressures.     

选择性溶剂萃取生产低凝柴油的溶剂筛选和溶剂选择性的表征

酮类、酯类、氯代烃类溶剂分别对减一线油和常三线油进行了选择性萃取生产低凝柴油的实验。溶剂乙酸乙酯的选择性好,可降低减一线油和常三线油冷滤点分别为18°C和16°C,同时对柴油燃烧性能的影响较小,是选择性萃取生产低凝柴油的最佳溶剂。比较了各溶剂的脱蜡率、脱出的各碳数正构烷烃的质量分布和脱蜡油的冷滤点,引入了由高碳数正构烷烃脱出量、脱蜡率和冷滤点降低值三个因子组成的综合评价参数。该参数能表征本工艺要求的选择性,并直观地指导对两种油样均优的萃取溶剂的选择。