Interfacial effects on the melt state behavior of polyethylene-EPDM-calcium carbonate composites

Dynamic mechanical spectra of various composites of high density polyethylene (PE), ethylene propylene diene rubber (EPDM), and calcium carbonate were obtained at 190°C with a parallel plate instrument. Interfacial effects were found to have a significant influence on the dynamic mechanical behavior of these composites.Composites of calcium carbonate in PE displayed prominent particle—particle interaction effects. This resulted in a greatly enhanced dynamic shear modulusG _d due to the filler addition. Treatment of the calcium carbonate with gamma-aminopropyltriethoxysilane (-APS) or gamma-methacryloxypropyltrimethoxysilane (-MPS) significantly reduced the particle—particle interactions. Solution deposition of EPDM or EPDM grafted with maleic anhydride (EPDM-MA) on the calcium carbonate, before incorporation into a PE composite, also had a significant effect on the composite properties. Comparison of data from composites treated with EPDM vs. EPDM-MA suggested the presence of an interaction between the calcium carbonate surface and the maleic anhydride modification. This conclusion was further supported by solid state proton NMR relaxation model experiments which showed significant immobilization of the EPDM-MA chains on the filler surface. The treatment of calcium carbonate with-APS or-MPS before incorporation into multicomponent polyethylene-rubber-filler composites also had a significant influence on the dynamic mechanical properties of the resultant composites. There is evidence for a reaction between-APS and EPDM-MA during processing on the roll mill.     

煤矿雷管点火剂设计中的模糊数学方法

以煤矿雷管电点火剂为例，对组成材料的综合性能进行了评价。在工程应用中，引入模糊概念对点火剂进行了设计尝试。研究结果表明:模糊数学方法应用在煤矿工业雷管点火剂设计中是可行的。     

Cultural differences and collective action: A social network perspective

This study investigates how cultural differences on the individualism–collectivism (I–C) dimension of social networks influence the outcomes of collective action. Evidence shows that I–C values are indicators of how people construct their social networks and use strong/weak ties as a behavioral reference. Specifically, when compared with individualists, collectivists tend to hold larger strong‐tie networks and endow strong ties with greater interpersonal influence. Results obtained from agent‐based modeling indicate that individualistic cultures are more effective at propagating collective action when one of the two following conditions is met: (1) people have a strong motivation to participate and (2) the connectivity of the social system is low. In contrast, spread of collective action in collectivistic cultures is more effective when motivation is not strong and the connectivity of the social system is high. These findings call for a serious consideration of the role of culture in collective action. © 2014 Wiley Periodicals, Inc. Complexity 20: 68–77, 2015     

Highly sensitive multianalyte immunochromatographic test strip for rapid chemiluminescent detection of ractopamine and salbutamol

A novel immunochromatographic assay (ICA) was proposed for rapid and multiple assay of β₂-agonists, by utilizing ractopamine (RAC) and salbutamol (SAL) as the models. Owing to the introduction of chemiluminescent (CL) approach, the proposed protocol shows much higher sensitivity. In this work, the described ICA was based on a competitive format, and horseradish peroxidase-tagged antibodies were used as highly sensitive CL probes. Quantitative analysis of β₂-agonists was achieved by recording the CL signals of the probes captured on the two test zones of the nitrocellulose membrane. Under the optimum conditions, RAC and SAL could be detected within the linear ranges of 0.50–40 and 0.10–50 ng mL⁻¹, with the detection limits of 0.20 and 0.040 ng mL⁻¹ (S/N = 3), respectively. The whole process for multianalyte immunoassay of RAC and SAL can be completed within 20 min. Furthermore, the test strip was validated with spiked swine urine samples and the results showed that this method was reliable in measuring β₂-agonists in swine urine. This CL-based multianalyte test strip shows a series of advantages such as high sensitivity, ideal selectivity, simple manipulation, high assay efficiency and low cost. Thus, it opens up new pathway for rapid screening and field analysis, and shows a promising prospect in food safety.     

Flow Mechanism of Partially Cross-Linked Polyacrylamide in Porous Media

Partially cross-linked polyacrylamides (PCPAM) were prepared, and their rheological property, gel content, swelling property, and suspension property in saline solution were analyzed in laboratory. The goal of the research was to study the flow mechanism of PCPAM as a novel oil displacement agent in porous media. The migration behaviors of PCPAM were studied by single and series connection of double-tube sandpacked core flow experiments. The results showed that there was a critical pressure existing in the migration of PCPAM particles in porous media, and the migration was a dynamic process of plugging and flooding at the same time. When the pressure reached the critical pressure, the PCPAM particles would deform to pass through the pore throat and go ahead. Besides, the profile control experiments were conducted using a parallel connection of double-tube sandpacked core models, and the results revealed that PCPAM could generate “fluid diversion” and enlarge the swept volume of the lower permeable core. Moreover, micro-visualization displacement experiments were also carried out and proved that PCPAM could plug the high permeable pore throat to enlarge the swept volume, leading to an enhancement in oil recovery.     

Effects of the chain length of crosslinking agent and dye-doped amount on the electro-optical properties of polymer-dispersed liquid crystal films prepared by nucleophile-initiated thiol-ene click reaction

ABSTRACT

A series of crosslinking agents with different chain lengths were used to explore their effect on electro-optical properties of dye-doped polymer dispersed liquid crystals (PDLCs) film prepared by nucleophile-initiated thiol-ene click reaction. The influences of dye contents and temperatures on electro-optical properties were also investigated. It was found that the increase in chain length of crosslinking agent leads to the increase in driving voltage and the decrease in memory effect. The decrease in reaction temperature causes a decrease in driving voltage and an increase in transmittance. Particularly, the dye content could be optimised to obtain promising materials with minimum driving voltage and high contrast ratio for display applications.     

氟硅烷偶联剂在α-铁表面疏水性能模拟研究

利用分子动力学研究了十三氟辛基三甲氧基硅烷(PFOTMS)、十三氟辛基三乙氧基硅烷(PFOTES)、十七氟癸基三甲氧基硅烷(HFTMS)在α铁(111)与(110)晶面上的吸附及疏水行为,分析了径向分布函数、结合能、相对浓度等参量,探讨了三种氟硅烷偶联剂与金属铁表面的作用机理,并对其对铁表面的改性进行了分析。羟基化处理后,相比(110)表面,三种氟硅烷偶联剂与(111)晶面的吸附更为牢固,并且PFOTMS与羟基铁表面吸附最牢固。径向分布函数表明,三种氟硅烷偶联剂均易与羟基铁表面形成氢键,覆盖铁表面形成稳固的结合。氟硅烷偶联剂大大提高了铁表面的疏水性并阻止了铁表面与外界直接接触,在(111)表面上,PFOTMS疏水性最好,在(110)表面上,三种氟硅烷偶联剂疏水性能差别不大。     

CuO Nanostructures Based Electrochemical Sensor for Simultaneous Determination of Hydroquinone and Ascorbic Acid

A simple, sensitive and reliable electrochemical sensor has been developed based on CuO nanostructures modified glassy carbon electrode for simultaneous determination of hydroquinone (HQ) and ascorbic acid (AA). The CuO nano material was synthesized by aqueous chemical growth method using different sources of OH. The characterization of nano material was performed by Fourier transform infrared spectroscopy, X‐ray diffraction, field emission scanning electron microscopy and energy dispersive X‐ray spectroscopy. The glassy carbon electrode was modified by CuO nano material using drop cast method and studied by cyclic voltammetry. The CuO/GCE exhibited excellent electrocatalytic activity towards the oxidations of HQ and AA in borate buffer solution (pH 8.0) and the corresponding electrochemical signals have appeared as two well resolved oxidation peaks with significant peak potential differences of (0.21V vs. Ag/AgCl). Differential pulse voltammetry was used for simultaneous determination of HQ and AA using the CuO/GCE. At the optimum conditions, for simultaneous determination by synchronous change of the analyte concentrations, the linear response ranges were between 0.0003–0.355 mM for HQ and 0.0001–0.30 mM for AA respectively. Furthermore, CuO/GCE was successfully applied for the independent determination of AA in fruit juices as well as for the simultaneous determination of HQ and AA in cosmetic samples.     

Effect of charring agents on solvent‐free fireproof coatings

The choice of charring agent is one of the major issues for solvent‐free fireproof coatings. The effects of processing method and charring agent on the thermal insulation and fire resistance of the coatings were investigated in simulated fire scenarios. Dipentaerythritol (DPER), triazine agent (CFA), and pentaerythritol phosphate (PEPA) were compared as charring agent, and the thermal, combustion, fire resistance, and charring behaviors in different fire scenario were characterized for the fireproof coatings. Compared with high‐speed dispersing equipment, kneading processing equipment is favorable for improving the thermal stability and fire resistance of the coatings, because the stronger shearing force has promoted mixing and dispersion of the ingredients in solvent‐free fireproof coatings. As for charring agents, it is found that the fireproof coatings containing CFA or PEPA show better thermal and flame‐retardant performances. More residue was observed under nitrogen atmosphere in thermogravimetric analysis, less heat and smoke were released in cone calorimetry test. However, during the high temperature fire resistance test, their char layers were prone to delaminate while DPER‐containing coatings produced intact and stronger char layer with better heat insulation. For practical applications, the coating formulations need to be optimized to achieve both fire resistance and flame retardancy.     

Great improvement of low‐temperature impact resistance of isotactic polypropylene/ethylene propylene diene monomer rubber blends by traces of carbon nanotubes and β‐nucleating agents

In this work, a considerable low‐temperature toughness enhancement of isotactic polypropylene (iPP) was achieved by adding 30 wt% ethylene propylene diene monomer rubber (EPDM) as well as traces of β‐nucleating agent (β‐NAs) and carbon nanotubes (CNTs). The impact strength of the iPP/30 wt% EPDM blend with 0.1 wt% β‐NAs reached 6.57 kJ/m² at ?20°C, over 2.5 times of pure iPP. A slightly improved impact strength was further found in the β‐nucleated iPP/30 wt% EPDM at the presence of 0.05 wt% CNTs. The presence of traces of CNTs, β‐NAs, and EPDM displayed synergistic low‐temperature toughness reinforcement effect on the iPP blends. The underlying toughening mechanism was attributed to the formation of a great amount of voids and plastic deformation of iPP matrix affected by CNTs, β‐NAs, and EPDM. Our work provided a feasible strategy to significantly increase the low‐temperature toughness of iPP.