Melt processing of ethylene–vinyl acetate/banana starch/Cloisite 20A organoclay nanocomposite films: structural,thermal and composting behavior

This work shows the preparation of ethylene vinyl acetate copolymer/banana starch/Cloisite 20A organoclay (EVA/starch/C20A) nanocomposites by melt processing. Wide angle X-ray diffraction (WAXD), field emission scanning electron microscopy (FE-SEM), differential scanning calorimetry and thermogravimetric analysis were used to characterize the obtained nanocomposites. Mechanical properties were also determined. In addition, the performance of the nanocomposite films under composting was preliminarily studied; it was conducted using the soil burial test method. Despite knowing that the starch is difficult to process by extrusion, nanocomposite films with high homogeneity were obtained. In this case, C20A organoclay acts as an effective surfactant to make the starch natural polymer compatible with the EVA synthetic polymer. The good compatibility between EVA, starch and C20A clay was also deduced by the formation of intercalated and intercalated-exfoliated structures determined by WAXD and FE-SEM. Physical evidence of the damage in EVA/starch/C20A nanocomposite films after the composting test was observed. It is worth noting that despite the absence of starch, the EVA/C20A nanocomposite film, used as a control, also showed surface damage. This behavior is related to the organic modifier linked to clay C20A, which contains molecules derived from fatty acids that can be used as a food source for microorganisms.

     

Formation of Triterpenoids throughout <Emphasis Type="Italic">Olea europaea</Emphasis> Fruit Ontogeny

Drupes were handpicked from olive (Olea europaea L.) trees, cv chemlali, at 13 distinct stages of fruit development, referred to as weeks after flowering (WAF), and analyzed for their free and esterified sterols and triterpenoids content. These two classes of compounds are synthesized via the acetate/mevalonate pathway and share common precursors up to oxidosqualene (OS). Cyclization of OS in either cycloartenol or beta-amyrin constitutes a branch point between primary (sterol pathway) and secondary (triterpenoid pathway) metabolisms. At the onset of fruit development, i.e., between 12 and 18 WAF, drupes were found to contain high amounts of alpha- and beta-amyrins as well as more-oxygenated compounds such as triterpenic diols (erythrodiol and uvaol) and acids (oleanolic, ursolic and maslinic acids). Concomitantly, sterol precursors were barely detectable. From 21 WAF, when the olive fruit reached its final size and began to turn from green to purple, alpha- and beta-amyrins were no longer present, while 4,4-dimethyl- and 4alpha-methylsterols started to be formed, indicating a redirection of the carbon flux from the triterpenoid pathway towards the sterol pathway. Between 21 and 30 WAF, sterol end products, mainly represented by sitosterol, progressively accumulated and triterpenic diols were replaced by triterpenic acids, essentially maslinic acid. Interestingly, the developing olive fruit was found to accumulate significant amounts of parkeol as an ester conjugate. Whatever the stage of development, triterpenoids represent the major triterpenic compounds of the olive fruit.     

Microcellular polymeric foams based on 1‐vinyl‐2‐pyrrolidone and butyl‐acrylate with tuned thermal conductivity

Microcellular polymers have been produced by ScCO₂ foaming, based on 1‐vinyl‐2‐pyrrolidone (VP) and butyl‐acrylate (BA). Three different copolymers were prepared, varying the compositions of VP and BA, following a simple radical polymerization process using an UV initiator. The samples a good foaming behavior and also excellent flexibility and handle ability, with expansion ratios between 1.53 and 1.72, and cell sizes in the microcellular range (below 5 µm). However, it was observed that the gas distribution and, consequently, the cellular structure inside the polymer foams was highly dependent on the VP and BA proportions, leading to very different thermal conductivity values, even for similar volume gas fraction values. These results were related to the copolymer nanostructuration, which seems to have an influence in the final pore structure, thus opening the possibility of designing microcellular foams with similar macroscopic characteristics but different thermal conductivity values. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45872.     

Surface grafting of carbon fibers with artificial silver‐nanoparticle‐decorated graphene oxide for high‐speed electrical actuation of shape‐memory polymers

Poor heat conduction in the interface between the carbon fiber and polymer matrix is a problem in the actuation of shape‐memory polymer (SMP) composites by Joule heating. In this study, we investigated the effectiveness of grafting silver‐nanoparticle‐decorated graphene oxide (GO) onto carbon fibers to improve the electrothermal properties and Joule‐heating‐activated shape recovery of SMP composites. Self‐assembled GO was grafted onto carbon fibers to enhance the bonding of the carbon fibers with the polymeric matrix via van der Waal's forces and covalent crosslinking, respectively. Silver nanoparticles were further self‐assembled and deposited to decorate the GO assembly, which was used to decrease the thermal dissimilarity and facilitate heat transfer from the carbon fiber to the polymer matrix. The carbon fiber was incorporated with SMP to achieve the shape recovery induced by Joule heating. We found that the silver‐nanoparticle‐decorated GO helped us achieve a more uniform temperature distribution in the SMP composites compared to those without decoration. Furthermore, the shape‐recovery behavior and temperature profile during the Joule heating of the SMP composites were characterized and compared. A unique synergistic effect of the carbon fibers and silver‐nanoparticle‐decorated GO was achieved to enhance the heat transfer and a higher speed of actuation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41673.     

ICP-MS测定饮用水中汞

采用盐酸作为样品基体,应用ICP-MS对饮用水中汞进行检测。本方法的检出限为0.0038 ng/mL,对1.0和0.050ng/mL的标准溶液进行7次测定,相对标准偏差分别为0.7%和1.4%。样品加标回收率在92.0%～110.0%之间。     

GK-Ⅵ型裂解炉对流段改造

中国石油辽阳石化分公司烯烃厂裂解装置有3台GK-Ⅵ型裂解炉,在运行过程中,由于裂解炉对流段结垢造成烟气阻力增大,引风机负荷逐渐提高至最大,导致裂解炉加工能力降低,燃料气消耗增加,热效率降低,烟气热损失增大,能耗增加。2011年7月对GK-Ⅵ型裂解炉对流段进行改造。改造后,解决了裂解炉运行中存在的问题,提高了裂解炉的热效率,降低了装置能耗。     

Potassium persulfate-mediated preparation of conducting polypyrrole/polyacrylonitrile composite fibers: Humidity and temperature-sensing properties

Conducting polypyrrole (PPy)/polyacrylonitrile (PAN) composite fibers were prepared by the polymerization of pyrrole in the presence of PAN fibers with potassium persulfate in an acidic aqueous solution. We obtained composite fibers containing concentrations of PPy as high as 1.14% and having surface resistivities as low as 0.6 kΩ/cm² by changing the polymerization parameters, including the temperature and concentrations of pyrrole and oxidant. The tensile strength of 10.02 N/m² and breaking elongation of 32.68% for the pure PAN fiber increased up to 10.45 N/m² and 33.23%, respectively, for the composite fiber containing 0.13% PPy. The change in the resistivity of the PPy/PAN composite fiber during heating–cooling cycles in the temperature range of +5 to 120°C was examined. Scanning electron microscopy and optical microscopy images of the composite fibers showed that the PPy coating was restricted to the surfaces of the PAN fibers. Surface resistivity measurements, Fourier transform infrared spectroscopy, and thermogravimetric analysis techniques were also used to characterize the composite fibers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

高分子絮凝剂处理高浓度化妆品原料生产废水研究

化妆品原料生产过程中产生的废水水质成分复杂、有机物含量高、难降解,利用混凝工艺处理该废水能够减缓生化处理单元的负担,提高污水处理效率。为揭示无机高分子混凝剂混凝过程中污染物的去除机制和污泥性质的变化,考察了不同的絮凝剂聚合氯化铝(PAC)、聚合硫酸铁(PFS)、聚合氯化铝铁(PAFC)和助凝剂聚丙烯酰胺(PAM)投加浓度对污染物去除率和污泥性质的影响。采用傅里叶变换红外光谱(FTIR)、X射线能谱(EDX)、扫描电镜(SEM)、热重分析仪(TGA)分析污泥絮体官能团、表面形貌、元素组成和热稳定性的变化,采用三维荧光光谱(3D-EEM)和超滤技术分析出水中有机物分子量的分布规律和有机物成分的变化,优化最佳混凝工艺运行条件。结果表明:进水中的天然有机物(NOM)荧光强度高,有机物分子量主要分布在>100×10³和<3×10³区间,其所占比例分别为22.89%和50.57%。当进水COD为6700～7500 mg/L时,在助凝剂PAM投加浓度为0.03 g/L,PAC、PFS和PAFC投加浓度分别为2.8 g/L、2.8 g/L和3.0...     

纳米微珠二氧化硅用量对空气弹簧用天然橡胶胶料性能的影响

将纳米微珠二氧化硅添加至空气弹簧用天然橡胶（NR）胶料中,研究纳米二氧化硅用量对NR胶料的加工性能和物理性能以及空气弹簧耐疲劳性能的影响。结果表明：随着纳米微珠二氧化硅用量的增大,NR胶料的硫化特性和门尼粘度未发生明显变化,NR硫化胶的邵尔A型硬度先减小后增大,300%定伸应力无明显变化,拉伸强度和拉断伸长率呈减小趋势;当纳米微珠二氧化硅用量为10～15份时,NR硫化胶的耐屈挠性能较佳;在空气弹簧用NR胶料中加入10份纳米微珠二氧化硅能够有效地提高空气弹簧的耐常温疲劳性能和耐高温疲劳性能。