Understanding the foamability and mechanical properties of foamed polypropylene blends by using extensional rheology

In this article, the influence of the rheological behavior of miscible blends of a linear and a high melt strength, branched, polypropylene (HMS PP), on the cellular structure and mechanical properties of cellular materials, with a fixed relative density, has been investigated. The rheological properties of the PP melts were investigated in steady and oscillatory shear flow and in uniaxial elongation in order to calculate the strain hardening coefficient. While the linear PP does not exhibit strain hardening, the blends of the linear and the HMS PP show pronounced strain hardening, increasing with the concentration of HMS PP. Related to the cellular structure, in general, the amount of open cells, the cell size, and the width of the cell size distribution increase with the amount of linear PP in the blends. Also mechanical properties are conditioned by the extensional rheological behavior of PP blends. Cellular materials with the best mechanical properties are those that have been fabricated using large amounts of HMS PP. The results demonstrate the importance of the extensional rheological behavior of the base polymers for a better understanding and steering of the cellular structure and properties of the cellular materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42430.     

Corrosion and corrosion inhibition of nickel in HClO4 solutions using the EQCM technique

Application of the electrochemical quartz crystal microbalance (EQCM) to the study of metal corrosion and its inhibition is rather recent. Among the advantages of this technique are its very high sensitivity and the possibility of simultaneous mass variations and voltammogram recording. These characteristics suggest the use of the EQCM for research in very low corrosion rate conditions. This paper reports the results of EQCM measurements on the corrosion inhibition rates of Ni in 0.1m HClO4, in the absence and presence of different inhibitors in free corrosion conditions, for following inhibitors: acridine (A), benzyl quinolinium chloride (BQCl), dodecyl quinolinium bromide (DDQBr), tributylbenzyl ammonium iodide (TBNI) and potassium iodide (KI). The corrosion rate was reduced considerably by KI and TBNI. DDQBr showed a good inhibitive efficiency, while BQCl had only a small effect, and A stimulated corrosion of the Ni. Voltammograms at different scanning rates and the mass variation in the same solutions were recorded. Comparison of the current density and the mass changes provided the basis for a qualitative interpretation of the passivation of Ni and the mechanism of action of the different inhibitors.     

Corrosion and corrosion inhibition of nickel in HClO4 solutions using the EQCM technique

Application of the electrochemical quartz crystal microbalance (EQCM) to the study of metal corrosion and its inhibition is rather recent. Among the advantages of this technique are its very high sensitivity and the possibility of simultaneous mass variations and voltammogram recording. These characteristics suggest the use of the EQCM for research in very low corrosion rate conditions. This paper reports the results of EQCM measurements on the corrosion inhibition rates of Ni in 0.1m HClO4, in the absence and presence of different inhibitors in free corrosion conditions, for following inhibitors: acridine (A), benzyl quinolinium chloride (BQCl), dodecyl quinolinium bromide (DDQBr), tributylbenzyl ammonium iodide (TBNI) and potassium iodide (KI). The corrosion rate was reduced considerably by KI and TBNI. DDQBr showed a good inhibitive efficiency, while BQCl had only a small effect, and A stimulated corrosion of the Ni. Voltammograms at different scanning rates and the mass variation in the same solutions were recorded. Comparison of the current density and the mass changes provided the basis for a qualitative interpretation of the passivation of Ni and the mechanism of action of the different inhibitors.     

Improving foamability of polypropylene by grafting modification

Polypropylene (PP) foam has been considered as a potential substitute for other thermoplastics foams in industrial applications. However, the key concern is the weak melt strength of PP, which leads to a high content of open‐cell structure in PP foams; and, thus, unsatisfactory for a number of applications. In this work, PP was modified by grafting with unsaturated linear polyester (ULP) in a twin‐screw extruder in attempt to improve the melt strength of PP. The grafting reaction on PP and the modified PP were characterized using FT‐IR, DSC, and TGA. The improved foamability was verified by SEM observation. In addition, the rheological behavior of modified PP was investigated using a Hakke rheometer. The results indicated that the melt strength of grafted PP was significantly enhanced, facilitating the foam formation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4114–4123, 2006     

面激光诱导荧光技术用于快速液液微观混合研究

建立了面激光诱导荧光技术研究液液微观混合过程的实验方法,在无干扰流场条件下,研究了毫米尺度流道内、错流接触的两股液膜的时空混合行为,以可视化的手段揭示了液液微观混合过程的二维瞬态浓度场,发现了液膜快速错流接触后形成的有序波形涡结构,涡的尺度大小为1～2 mm,涡的发展过程是影响两股流体混合的主要因素.同时建立了混合过程的定量表征方法,用混合液膜中组分的离析度（intensity of segregation, IOS）定量描述了混合过程所达到的程度,获得了不同液膜流速下液液混合过程IOS值随着液体流动方向的变化趋势图,并分析了两股液膜之间的速率比以及混合液膜的Reynolds数对混合过程的影响.     

The effect of recycling on LDPE foamability: Elongational rheology

The purpose of this work was to investigate changes in the elongational rheology of low density polyethylene (LDPE) when recycled. Both foamed and unfoamed LDPE were submitted up to 10 generations in a closed loop using constant extrusion conditions and azodicarbonamide as a chemical blowing agent. For both foamed and unfoamed polymers, decreasing elongational properties in terms of strain hardening was observed, indicating progressive loss of foamability with the number of time the polymer is recycled. It was also found that the elongational properties of the foamed polymer decreased more rapidly than its unfoamed counterpart. It is believed that higher mechanical degradation of polymer may be the result of higher deformation rates (biaxial) associated with foaming and the accumulation of blowing agent residues limiting polymer chain mobility and entanglement. POLYM. ENG. SCI., 48:11–18, 2008. © 2007 Society of Plastics Engineers     

用热分析技术研究煤的热解特性

用热分析技术研究了自洗蒙古煤和乌煤在氮气中的热解特性,探讨了升温速率和煤样粒径对热解过程的影响,根据煤热解产物释放特性指数r的大小来确定两种煤的热解性能。结果表明:同一升温速率下,自洗蒙古煤的热解特性要好于乌煤;同一种煤,升温速率越高,r值越大,热解特性越好。应用不同升温速率下的热解曲线计算出两种煤热解过程的动力学参数。用等转化率法求得热解过程的活化能;用主曲线法确定失重过程的最可几机理函数。     

微型反应器-HPLC催化合成水杨酸甲酯的研究

选择水杨酸甲酯的催化合成反应为基础反应体系，以固体超强酸为催化剂，建立微型催化反应器与高效液相色谱的联用新技术，并对液固相催化酯化反应进行微反催化合成研究。使用ZrO₂-SiO₂/SO_^2-4催化剂制成微型催化反应器进行试验，建立微反-HPLC联用实验装置，考察了水杨酸的加入量以及反应温度对转化率的影响。并通过X-射线衍射、红外光谱和电子透镜等技术，对反应前后催化剂的晶相、酸性特征峰以及催化剂的形态形貌进行了表征。     

Study of pulsing flow in a trickle bed using the electrodiffusion technique

Absract An electrochemical technique is employed for measuring local, instantaneous liquid-solid mass transfer coefficients in downward cocurrent gas-liquid flow through a packed bed under pulsing flow conditions. The technique involves specially designed electrodes of the same dimensions as the packing material. Also microelectrodes on the surface of a particle are tested for flow diagnostics in the microscale. The feasibility of the method is examined. Interpretation of measurements from various electrodes provides information on the pattern of mass transfer and liquid distribution in the packing. This paper was presented at the International Workshop on Electrodiffusion Diagnostics of Flows held in Dourdan, France, May 1993.     

Study on combustion mechanism of asphalt binder by using TG-FTIR technique

The combustion mechanism of asphalt binder was investigated by using thermogravimetric analyzer coupled with Fourier transform infrared spectrometer (TG-FTIR) in a mixed gas environment of 21% oxygen and 79% nitrogen. The results show that the combustion process of asphalt binder consists of three main consecutive stages at a low heating rate. The combustion reaction becomes more and more intense from the 1st to 3rd stage. The release of volatiles occurs mainly at 300-570 °C, and the gaseous products in each stage are different. The main products in the 1st stage are CO₂, CO, H₂O, hydrocarbons, formaldehyde, tetrahydrofuran, formic acid, aromatic compounds, etc. In the next stage, the combustion products mentioned above keep on increasing, but some new volatiles such as alcohols, phenols, styrene, etc. are present. In the last stage, the CH and CO bonds continue to fracture and aromatization reaction occurs, and the release amount of CO₂, CO, and H₂O reaches the maximum. But the content of other products decreases or even disappears due to burning. Among the above volatiles, CO₂ is the dominant gaseous product in the whole combustion process. The concentration of CO₂ and CO keeps increasing, and reaches the maximum intensity at about 520 °C. The evolution of H₂O, CH₄, and formic acid exhibits the trend of increase first, and then decrease. Over 570 °C, there are few products released at the end of the combustion process. Asphalt binder combustion process includes two modes of complete and incomplete combustion, and the latter may be main combustion mode of asphalt binder.     

熔融纺丝法研究LDPE的拉伸流变性能

采用熔融纺丝法研究了低密度聚乙烯(LDPE)熔体的拉伸流变性能。LDPE熔体强度随温度升高而下降;适当降低拉伸黏度可提高熔体的可拉伸性;随拉伸应变速率升高拉伸应力上升,而拉伸黏度下降;拉伸应力和拉伸黏度都随温度的升高呈下降趋势;提高挤出速率可得到较低的拉伸应力和拉伸黏度。     

超声辅助提取落叶松树皮原花青素的工艺研究

对落叶松树皮中原花青素的超声波辅助提取工艺进行了研究,考察了提取温度、料液比、超声时间、溶剂浓度等4个因素对原花青素提取的影响。在单因素试验和正交试验的基础上,优选出超声波辅助提取落叶松树皮原花青素的最佳工艺条件为:以60%的乙醇溶液为溶剂,在50℃、料液比1∶25(g/mL)的条件下,用200 W的超声功率作用辅助提取60 min,原花青素的提取率可以达到1.0512%。     

Device processing using the trilevel technique

Three front runners for the next generation of devices for fine line lithography are photo, electron, and X-ray lithography. Each of these techniques has both advantages and disadvantages when considered for direct wafer processing. This paper discusses the problems encountered using each of these techniques and how a trilevel technique can be applied to make each of these techniques more viable.     

The effect of some foam boosters on the foamability and foam stability of anionic systems

The foaming properties of anionic surfactant solutions containing a nonionic surfactant, fatty acid N-methyl-ethanolamide (NMEA), were investigated. Foamability, which is the foam-generating power at the initial stage of foaming, was measured by a laboratory-built foam-testing apparatus, and also by the conventional Ross-Miles test NMEA synergistically increased the foamability of anionic surfactant solutions, particularly when small amounts of NMEA were added. Shorter hydrocarbon chain lengths of NMEA, such as N-octanoyl-N-methylethanol (NMEA-08) and N-decanoyl-N-methylethanol (NMEA-10), showed better performance in the laboratory-built foam tester. The results of the Ross-Miles evaluation, however, were completely opposite. Compared with commercial nonionic boosters, such as fatty acid monoethanolamide, fatty acid diethanolamide, and lauramidopropyldimethylbetaine (LPB), NMEA was the most effective for increasing foamability of the solution at the initial stage. The most popular amphoteric foam booster, LPB, did not increase foamability but likely generated the initial foam volume on the Ross-Miles test as a result of foam film stabilization. From these results, a foam-boosting mechanism of NMEA different from that of LPB is suggested.     

Enhanced foamability of isotactic polypropylene/polypropylene-grafted-nanosilica nanocomposites in supercritical carbon dioxide

Polypropylene-grafted nanosilica (PP-g-SiO₂) was prepared by us as a new modified nanosilica with long polymer chains and high grafting density. It was found that the addition of PP-g-SiO₂ resulted in remarkable strain-hardening behavior of PP. Herein, the foaming behavior of isotactic polypropylene (iPP)/PP-g-SiO₂ nanocomposites was investigated by using supercritical carbon dioxide (scCO₂) as a blowing agent. The results demonstrated that the incorporation of PP-g-SiO₂ could obviously enhance the foamability of iPP. In particular, the uniform cell distribution and smaller cell size could be obtained by 1 wt% particle loading, and 5 wt% particle content showed a wider foaming temperature range and higher cell density. The noticeable enhancement in the foamability of iPP was attributed to the reinforced melt strength, high melt elasticity and the increased heterogeneous nucleation caused by well dispersed and long polypropylene chains grafted SiO₂. These findings provide new insights to improve the foaming ability of iPP with incorporation of modified nanoparticles.     

Preparation of long‐chain branching polypropylene and investigation on its foamability

In this work, zinc N,N‐dimethyldithiocarbamate (ZDMC) was used to mediate the melt modification of polypropylene (PP) with 1,6‐hexanediol diacrylate (HDDA) in an internal mixer in the presence of dicumyl peroxide (DCP). Fourier transformed infrared spectroscopy analysis revealed that HDDA was directly grafted onto PP backbone. The dependence of torque on processing time indicated that the presence of ZDMC restrained the degradation of PP, and the end‐torque value increased with the addition of ZDMC. Dynamic rheological measurement indicated that the modified PP possessed higher G′ and lower tan δ at low frequency, displaying an increase in η* and disappearance of Newtonian plateau in η*–ω plot, as well as larger radius of semicircle in Cole–Cole plot. All the rheological characterizations, together with the decreased gel content with the increase of ZDMC, confirmed the formation of long‐chain branching. Subsequently, the foamability of the modified samples was investigated by one‐step compression–molding process. The cellular structure and morphology of the obtained foams were observed by scanning electron microscopy, and the results showed that the addition of ZDMC decreased the cell size, increased the cell density, and brought about well‐defined closed cell structure. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Gas separation using the membrane rectification technique

The membrane rectification technique offers a multitude of possibilities for adapting the technique to special separating processes. It was confirmed experimentally that the membrane rectification technique with dephlegmation operates more efficiently than a simple enriching column, at least in the region investigated. Furthermore, industrial processing measures for improving the separation efficiency in the stripping column section of a membrane reactification plant were discussed. The use of stripping gas for this purpose was shown to be very effective. An investigation of the influence of backmixing on the separation efficiency of membrane rectification plants showed that in particular in the stripping section it can cause the separation efficiency to be reduced by up to 50%. However, by ensuring that the gas velocity is maintained above a certain minimum value it is possible to completely suppress the backmixing phenomenon in counter-flow permeators.     

Measuring the amount of crystallinity in solutions using DSC

The amount of solid that forms in a solution at temperatures below the cloud point, is an important quantity in the design of crystallisation processes. A new method using differential scanning calorimetry (DSC) to measure the fraction of crystallised solution, α ' is proposed. A very good agreement is obtained between the data measured by the new calorimetric method and using alternative techniques. A simple graphic version of the calculation procedure is also presented. It is shown to produce quick and fair estimates for the solid fraction by a simple analysis of a plot of enthalpy variation with temperature.