聚乙烯挤出发泡的发泡特性研究

本文作者用Ｈａａｋｅ流变仪发泡材料实验附件，研究了聚乙烯化学发泡物料在用于连续挤出发泡时的发泡特性。实验比较了不同发泡剂含量、不同聚乙烯在相同条件下的发泡特性曲线，确定了适合于连续挤出发泡的最佳特性曲线。结果证实。用发泡特性曲线来指导连续挤出发泡配方设计是可行的。     

Experimental Investigation of the Mechanism of Foaming Agent Concentration Affecting Foam Stability

With the aim of determining the effect of foaming agent concentration (FAC) on foam stability, the half‐life of a selection of typical foaming agents was investigated at different concentrations using the FoamScan^® instrument. The surface tension of the bulk solution after foaming was tested using a surface tension meter. The FAC had a significant effect on foam stability at concentrations <1%, and a weak relationship at concentrations >1%. A significant turning point in the plot of foam stability versus FAC indicated maximum foam stability. The concentration at this point was defined as the optimal stability concentration, which is a guide in foam application. The micelles were thermodynamically unstable at low concentrations and degraded into surfactant solution, but were extremely stable at high surfactant concentrations that did not affect the stability of the foam. A turning point was also observed in the plot of surface tension versus FAC, beyond which the surface tension remained constant; the concentration at this point was defined as the no spherical micelle concentration. The influence of FAC on foam stability is explained in terms of mean bubble diameter (d_mb) and bubble size distribution.     

Study of Foaming Properties and Effect of the Isomeric Distribution of Some Anionic Surfactants

Using different reaction conditions of photosulfochlorination of n-dodecane, two samples of anionic surfactants of sulfonate type are obtained. Their micellar behavior has been already reported and the relationship between their isomeric distribution and their chemical structures and micellar behaviors have been more thoroughly explored. In this investigation, we screened the foaming properties (foaming power and foam stability) by a standardized method very similar to the Ross–Miles foaming tests to identify which surfactants are suitable for applications requiring high foaming, or, alternatively, low foaming. The results obtained for the synthesized surfactants are compared to those obtained for an industrial sample of secondary alkanesulfonate (Hostapur 60) and to those of a commercial sample of sodium dodecylsulfate used as reference for anionic surfactants. The foam formation and foam stability of aqueous solutions of the two samples of dodecanesulfonate are compared as a function of their isomeric distribution. These compounds show good foaming power characterized in most cases by metastable or dry foams. The highest foaming power is obtained for the sample rich in primary isomers which also produces foam with a relatively high stability. For the sample rich in secondary isomers we observe under fixed conditions a comparable initial foam height but the foam stability turns out to be low. This property is interesting for applications requiring low foaming properties such as dishwashing liquid for machines. The best results are observed near and above the critical micellar concentrations and at 25 °C for both the samples.

Effect of Temperature on Foaming Ability and Foam Stability of Typical Surfactants Used for Foaming Agent

Foam has extensive applications in a wide range of industrial fields. Some surfactants are used as foaming agents in the preparation of foam. The performance of the foaming agent directly affects the application of the foam. In this paper, experiments were designed and conducted to reveal the influence of temperature on foaming performance of 10 typical anionic, cationic, nonionic, and amphiprotic surfactants. They were exposed to different temperature conditions to measure the foaming capacity (FC), foaming expansion (FE), and foam’s half-life. FC and FE represent foaming ability (FA), and half-life represents foam stability (FS). The results show that the FC increased at elevated foaming temperature, while FS decreased with rising temperature. Anionic surfactants are less affected by temperature and have better FA and longer FS. It seems that 20–30 °C is an ideal foaming temperature. This study lays an important foundation for the efficient preparation and utilization of foam in industrial fields.     

The Corrosion Inhibition Performance and Mechanism of Rhamnolipid for X65 Steel in CO2-Saturated Oilfield-Produced Water

The corrosion inhibition effect and mechanism of rhamnolipid (RL) were studied for X65 steel in oilfield-produced water saturated with CO₂ using the weight loss method, electrochemical measurements, surface analysis, surface-enhanced Raman spectroscopy (SERS), and quantum chemical calculations. The results prove that RL is an excellent inhibitor against CO₂ corrosion and predominantly inhibits the anodic corrosion reaction of X65 steel. The inhibition performance of RL is connected with surface activity and molecular structure. RL adsorbs on the metal surface by the reactivity centers to form a protective film, and the film has good inhibition ability for X65 steel for up to 168 h.     

High-Performance Production of Biosurfactant Rhamnolipid with Nitrogen Feeding

Nitrate is one of the most important factors for fermentative production of rhamnolipid, while it has not yet been conclusively demonstrated that nitrogen limitation or abundance is beneficial for improvement of rhamnolipid production. This study clarified that high concentration of NaNO₃ is conducive for high-performance production of rhamnolipid. An optimum rhamnolipid yield was achieved by 43.3 g L⁻¹ with an initial concentration of NaNO₃ equal to 10 g L⁻¹ during the regular fed-batch fermentation process by Pseudomonas aeruginosa ATCC 9027. Additionally, this rhamnolipid production was further improved to 61.2 g L⁻¹, which was two folds higher than that value obtained during batch fermentation, when the NaNO₃ concentration was maintained about 5 g L⁻¹. Furthermore, specific volume productivity of rhamnolipid was improved by over 30% in the presence of NaNO₃ at concentration ranging from 5 to 6 g L⁻¹ during sequential fed-batch fermentation, resulting a high value of 0.4 and 0.59 g L⁻¹ h⁻¹ within one batch of sequential fed-batch fermentation for a period of 17 days by P. aeruginosa ATCC 9027 and PAO1, respectively. It seems that sustaining high-concentration NaNO₃ during fed-batch fermentation is advantageous for high-performance production of rhamnolipid.     

高抗冲聚苯乙烯挤出发泡研究

采用自由挤出发泡工艺研究了两种高抗冲聚苯乙烯(HIPS)低发泡的成型配方，讨论了发泡剂DDL、SBS和硬脂酸钙[Ca(St)2]的用量对发泡制品的影响，利用SEM电镜和生物显微镜观察了制品的泡孔结构。结果表明，发泡剂用量为0．5份，SBS用量为10份和Ca(St)2用量为3份时，制品的泡孔比较均匀，机械性能良好。两种HIPS做发泡制品时效果基本一致。     

超临界二氧化碳发泡聚苯硫醚研究

采用超临界二氧化碳间歇批处理成型方法成功制备了PPS泡沫材料,同时对所得发泡制品的形态、结晶性能和动态力学性能进行分析,发现在CO2浸泡过程中PPS发生了压力诱导结晶.在温度为80℃,压力为20 MPa情况下,在CO2中浸泡2h的PPS样本可以发泡,而浸泡时间4h和8h的PPS由于结晶度较高不能发泡,为进一步探究该工艺成型发泡PPS奠定了理论基础.     

聚丙烯及聚苯乙烯发泡体系熔体密度的研究

通过高压毛细管流变仪测量聚丙烯发泡体系的PVT关系,得到一定压力和温度下聚丙烯发泡体系的熔体密度,用于分析发泡体系的毛细管流变特性。与聚苯乙烯和高冲击强度聚苯乙烯发泡体系的熔体密度进行了对比,研究并分析了温度、压力、发泡剂及成核剂含量对发泡体系熔体密度的影响。结果表明:发泡体系的熔体密度均随压力的增大而提高,随温度的升高而降低;在发泡气体的临界压力处,发泡体系的熔体密度产生突变;高压下,发泡剂与成核剂含量对熔体密度的影响很小。     

成核剂CaCO_3对聚丙烯开孔发泡性能影响的研究

将高熔体强度聚丙烯(HMSPP)、线型低密度聚乙烯(LLDPE)、成核剂CaCO3共混后在自制超临界CO2动态发泡模拟机上发泡制备了聚丙烯开孔泡沫材料,研究了CaCO3的粒径和含量对聚丙烯开孔发泡性能的影响。结果表明:2 500目CaCO3在HMSPP/LLDPE共混体系中的分散效果比5 000目CaCO3的好。添加2 500目和5 000目CaCO3后,发泡样品的发泡倍率减小,泡孔密度增大,泡孔直径减小,泡孔形貌变得规则,泡孔直径分布变窄,泡孔均匀性增加。添加3%的2 500目和5 000目CaCO3时发泡性能最好。在共混体系中添加成核剂CaCO3能够提高发泡样品的开孔性能。     

聚丙烯共混发泡材料研究进展

综述了聚丙烯(PP)发泡材料的特点及常用发泡方法,重点介绍了PP与无机矿物粉体、聚乙烯、橡胶、玻璃纤维、木纤维等共混制备发泡材料的研究进展,指出了PP发泡材料的发展方向。     

马来松香酯聚氨酯硬泡发泡工艺研究

本文研究了以不同封闭剂封闭的胺类催化剂在马来松香酯聚氨酯硬泡发泡过程的行为特性，开发了一种显著改善发泡流动性并加快固化反应的高性能催化剂。     

Modeling of Rhamnolipid Biosurfactant Production: Estimation of Kinetic Parameters by Genetic Algorithm

Studies about kinetics and modeling of production parameters for biosurfactants are essential to the development of efficient processes from an economic point of view. In this sense, this work evaluated the performance of four nonstructured models to explain the experimental data for biomass growth, substrate consumption, and rhamnolipid production using glycerol as carbon source and a Pseudomonas aeruginosa strain. The kinetic parameters of each model were estimated using a global search method known as genetic algorithm and numerical discretization of differential equations by the Runge–Kutta 4th order method. The main result of this study showed that the Monod model best represented the experimental data, with μ_max values of 0.06 h⁻¹, K_S of 50.8 g L⁻¹, Y_X/S of 0.43 g g⁻¹, and Y_P/X equal to 0.017 g g⁻¹.     

阴离子型发泡剂在泡沫粉煤灰水泥中的应用研究

选用α-烯烃磺酸钠（AOS）、脂肪醇聚氧乙烯醚硫酸钠（AES）和十二烷基苯磺酸钠(LAE)3种阴离子表面活性剂,并实验研究了复合发泡剂的用量对粉煤灰泡沫水泥石的抗压强度及导热系数的影响。结果表明：AOS的泡沫性能指标优于AES和LAS,自制稳泡剂将使发泡剂发泡能力略有下降,但泡沫稳定性有明显提高。选用含量为0.8%的 AOS 溶液并添加0.3%稳泡剂的复合发泡剂制备泡沫水泥,复合发泡剂用量达到3.5%时,泡沫水泥石的导热系数已降至0.12 W/(m·K),其抗压强度为1.6 MPa。     

聚二甲基硅氧烷对聚丙烯发泡成型的影响

以超临界CO2为发泡剂,以马来酸酐接枝聚丙烯(PP-g-MAH)为相容剂,在连续挤出发泡过程中研究了聚二甲基硅氧(烷PDMS)对无规共聚聚丙烯(R-PP)发泡性能的影响。结果表明:当CO2用量为5%时,少量PDMS和PP-g-MAH的加入能提高R-PP发泡样品的膨胀率;与纯R-PP相比,R-PP/PP-g-MAH/PDMS共混物在各个温度下发泡样品的泡孔密度要明显高于纯PP发泡样品的泡孔密度。     

PE泡沫绝缘料模压发泡工艺的考察

研究了模塑温度、模塑压力、模塑时间、固化过程中的冷却速率及方式、模具条件以及原料的预处理等因素对PE泡沫绝缘料模压发泡质量的影响,结果表明,预处理可减少泡孔直径在150μm以下,模塑温度和模塑时间是影响的最大因素。确定了实验室内测试其发泡性能的合理方法,对表观密度为0.6g/cm^3的PE泡沫,YP028为最佳工艺条件,并可有效地预测该绝缘料经高速加工制成通信电缆后的发泡性能。     

Screening of Surfactant Foaming Properties Using the Gas-Sparging Method: Design of an Optimal Protocol

Foaming properties of five model surfactants, namely, sodium laureth sulfate (SLES), sodium dodecylsulfate (SDS), polyoxyethylene 23 lauryl ether (Brij L23), polysorbate 20 (Tween 20), and polysorbate 80 (Tween 80), have been compared as a function of experimental conditions using the gas-sparging method. The influence of surfactant concentration relative to the critical micelle concentration (CMC) and three process parameters—frit porosity, gas flow rate, and preset volume of foam (or bubbling time)—was studied by means of a 2^4–1 factorial design. Three foaming properties were considered: foam capacity, foam stability, and maximal foam density. At the CMC, SLES, SDS, Tween 20, and Brij L23 were indistinguishable, all having very high foaming capacity and stability, regardless of process conditions. At 0.1 CMC, differences among them were highlighted especially at the lowest frit porosity coupled to the highest gas flow rate. Those conditions are thus recommended when a rapid screening of surfactant foaming performances is needed.     

Rhamnolipid Effects on Water Imbibition,Germination, and Initial Root and Shoot Growth of Soybeans

Rhamnolipid is a nontoxic and biodegradable bioproduct that offers sustainable solutions in agricultural, pharmaceutical, cosmetic, and refinery applications. Its imminent uses in agriculture warrant thorough investigations of rhamnolipid interactions with plants. In this work, the effects of rhamnolipid on soybeans during imbibition and germination under different conditions were studied. Seed coat was determined to serve as the main barrier that regulates water imbibition, and rhamnolipid at 2 g L⁻¹ was found to increase the imbibition rate to 16.1 (% dry bean weight)/h from 12.6% h⁻¹ at 0 g L⁻¹ rhamnolipid in intact soybeans for 0.5–5 h, when the soybean weight increased almost linearly due to the constant permeation rate through hydrated seed coat. Rhamnolipid, however, did not transport freely into beans; only about 50% of the rhamnolipid carried in the volume of water imbibed was absorbed by beans. Two different studies showed that absorbed rhamnolipid, from up to 1.5 g L⁻¹ solutions, did not affect the germination percentages in wet cloths and soil pots. However, an additional study with constant (7-day) exposure of germinating beans to more concentrated rhamnolipid solutions indicated a slight decrease of germination percentage, down to ~85% at 20 g L⁻¹ rhamnolipid. Rhamnolipid had far more pronounced effects on root development. At high concentrations (5–20 g L⁻¹), rhamnolipid severely stunted the root growth, causing reduced root and shoot weights and visible browning and damages of roots; however, low (0.5–1 g L⁻¹) concentrations of rhamnolipid stimulated higher lateral root development while reducing the primary root extension, causing no change in the overall root or shoot weight. The findings indicated complex rhamnolipid interactions with soybeans and warranted further study while developing agricultural applications of rhamnolipid.     

Optimization and Characterization of Biosurfactant Rhamnolipid Production by Pseudomonas aeruginosa Isolated from an Artificially Contaminated Soil

Biosurfactants are surfactants biologically produced by microorganisms, presenting several advantages when compared to synthetic surfactants. Pseudomonas aeruginosa is known for producing rhamnolipids, considered one of the most interesting types of biosurfactants due to their high yields, when compared to other types. In this work, the production of rhamnolipid from P. aeruginosa was optimized. At first, the Plackett–Burman design was used to select most significant variables affecting the biosurfactant production yield among nine variables—carbon–nitrogen ratio, carbon concentration, nitrogen source, pH, cultivation time, potassium and magnesium concentrations, agitation, and temperature. Then, using main variables, a central point experimental design aiming to optimize rhamnolipid production was performed. The maximum biosurfactant concentration obtained was 0.877 mg L⁻¹. The rhamnolipid also displayed a great emulsification rate, reaching approximately 67%, and the ability to reduce water surface tension from 72.02 to 35.26 mN m⁻¹ at a critical micelle concentration (CMC) of 127 mg L⁻¹, in addition to presenting a good stability when exposed to wide pH and salinity ranges. The results suggest that rhamnolipids are promising substitutes for synthetic surfactants, especially due to lower impacts on the environment.     

复合改性新型苯乙烯-丁二烯弹性体TVA发泡材料的研究

为研制高性能的新型苯乙烯-丁二烯弹性体(TVA)发泡鞋底材料,以偶氮二甲酰胺(AC)作为发泡剂,过氧化二异丙苯(DCP)作为交联剂,加入乙烯-醋酸乙烯共聚物(EVA)和二元乙丙橡胶(EPR)对TVA进行改性,用化学模压发泡法成型了TVA发泡材料.实验结果表明,改性剂EVA和EPR的加入,可以使得发泡材料的撕裂强度,耐压缩强度以及耐磨性等性能得到提升;高压毛细管流变分析发现,加入EVA可以提高材料的流动性,而加入EPR则会降低其流动性.考虑到各方面的影响因素,最终确定TVA/EVA/EPR三元共混体系的最佳配方,所制得的TVA发泡材料性能优异,具有较大的实际应用价值.