Characterization of Filler-rubber Interaction,Filler Network Structure,and Their Effects on Viscoelasticity for Styrene-butadiene Rubber Filled with Different Fillers

For styrene-butadiene rubber (SBR) compounds filled with the same volume fraction of carbon black (CB), precipitated silica and carbon–silica dual phase filler (CSDPF), filler-rubber interactions were investigated thru bound rubber content (BRC) of the compounds and solid-state ¹H low-field nuclear magnetic resonance (NMR) spectroscopy. The results indicated that the BRC of the compound was highly related to the amount of surface area for interaction between filler and rubber, while the solid-state ¹H low-field NMR spectroscopy was an effective method to evaluate the intensity of filler-rubber interaction. The silica-filled compound showed the highest BRC, whereas the CB-filled compound had the strongest filler-rubber interfacial interaction, verified by NMR transverse relaxation. The strain sweep measurements of the compounds were conducted thru a rubber process analyzer; the results showed that the CSDPF-filled compound presented the lowest Payne effect, which is mainly related to the weakened filler network structure in polymer matrix. The temperature sweep measurement, tested by dynamic mechanical thermal analysis, indicated that the glass transition temperature did not change when SBR was filled with different fillers, whereas the storage modulus in rubbery state and the tanδ peak height were greatly affected by the filler network structure of composites.     

Use of flow microcalorimetry and dynamic mechanical thermal analysis for probing interphase structure in poly(styrene-b-butadiene-b-styrene)/magnesium hydroxide composites

Interactions between magnesium hydroxide (Mg(OH)₂ particles (both untreated and treated with 16-methyl heptadecanoic acid (isostearic acid)) and low molar mass poly(styrene) (PS) and poly(butadiene) (PB) have been studied by flow microcalorimetry (FMC) and have been related to the interphase structure in poly(styrene-b-butadiene-b-styrene) (SBS)/Mg(OH)₂ composites using dynamic mechanical thermal analysis (DMTA). The FMC studies revealed that both polymers adsorbed strongly onto an untreated magnesium hydroxide surface though the PB showed greater irreversible adsorption from the heptane carrier fluid. Diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) studies on filler samples removed from the FMC cell after the adsorption-desorption cycle confirmed strong polymer filler interaction. Adsorption of the low molar mass samples of PS and PB onto a pre-adsorbed monolayer of isostearic acid on Mg(OH)₂ resulted in a very significant reduction in polymer adsorption activity due to blockage of adsorption sites. DMTA studies revealed that strong adsorption of PS and PB blocks of SBS onto untreated filler in composites containing 60% w/w Mg(OH)₂ gave rise to phase mixing that led to an 18 °C reduction in the T _g of the PS phase relative to that in the unfilled matrix. However, in equivalent composites based on isostearic acid treated filler a smaller reduction (10 °C) was observed, therefore reflecting reduced filler-matrix interaction and reduced phase mixing.     

Effect of Dispersion of Carbon Black on Electrical and Thermal Properties of Poly(Ethylene Terephthalate)/Carbon Black Composites

A type of grafted carbon black (GCB), prepared with a low molecular weight antioxidant compound by in-situ reaction, was dispersed in poly(ethylene terephthalate) (PET) by a melt-blending process. Dispersion of fillers, volume resistivity, and thermal properties were investigated using scanning electron microscopy, a high-resistance meter, differential scanning calorimetry, and thermogravimetric analysis, respectively. The results show that, compared with carbon black (CB) particles, GCB particles dispersed better in the PET matrix, whereas the conductivity percolation threshold of PET/GCB was higher than that of PET/CB. The addition of GCB or CB elevated the cold crystallization temperature of PET, reflecting the effectiveness of carbon fillers as nucleating agents. But carbon fillers decreased the crystallization enthalpy of PET during both heating and cooling process. Both CB and GCB elevated the starting temperature of thermal degradation of PET and increased the amount of residues for the composites over that of neat PET.     

Electron and probe microscopy investigation of the surface of elastomers modified with antifriction fillers

The surface of frost-resistant elastomers (rubbers) based on nitrile-butadiene rubber and propylene- oxide rubber (pure and modified with fillers: ultrafine PTFE and carbon black) is investigated. Tribological tests show that the addition of carbon black produced the greatest effect: the friction coefficient decreases to 0.2 and remains virtually constant during cooling. Surface and subsurface defects are detected by SEM. These defects can affect the processes in the zone of friction and destruction of the sliding surface of rubber. It is demonstrated that the modification of propylene-oxide rubber results in surface smoothing; the effect is the most pronounced in the samples modified with carbon black. The potential to use scanning probe microscopy for local investigation of the surface of rubber is assessed. A conclusion is made about the adhesive properties of surfaces based on the obtained force–distance curves. The investigation of vibration parameters of a probe in contact with the surface provides an opportunity to estimate the surface elasticity. It is shown that the addition of carbon black results in an increase in hardness of the rubber samples and a drastic reduction in adhesion. At the same time, the introduction of ultrafine PTFE leads to a slight enhancement of the adhesion and hardness. It is concluded that carbon black is the best modifying additive for the studied elastomers.     

Effects of the Synergy of Hardness and Resilience on the Akron Abrasion Properties of SBR Vulcanizates

The hardness (H) and resilience (R) of rubber vulcanizates were combined together in this paper, named as hardness–resilience product (H⁴R), and its relationship with the Akron abrasion loss was investigated using various styrene-butadiene rubber (SBR) vulcanizates possessing specific hardness and resilience characteristics as samples. For the unfilled SBR vulcanizates with different chain microstructure, possessing high elastic resilience and low hardness, the results showed that their Akron abrasion loss had a good linear relationship with the log(H⁴100R). This linear relationship also occurred when these SBRs were filled with 50 phr carbon black. For two particular types of SBR, after being filled with different fractions of carbon black and aged for different times, all their Akron abrasion losses (including unaged, aged for 24 h, and aged for 48 h) also had a good linear relationship with the log(H⁴100R). However, this linear relationship weakened for one of the SBRs after being aged for 48 h. In the high H⁴R region (the carbon black fractions being 60 and 70 phr), the data obviously deviated from the fitting curve due to the high hardness of the aged vulcanizates. However, after being filled with 50 phr of various kinds of carbon blacks, the relationships between abrasion loss and log(H⁴100R) were also approximately linear, with the correlation coefficient of the fitting curves being 0.99966 and 0.99878, respectively, for the two types of SBR.     

The NMR-MOUSE: quality control of elastomers.

New applications of the NMR-MOUSE (mobile universal surface explorer) to non-destructive quality control of elastomers are reported. One example concern the thermal aging of fast clutches which was probed by measurements of 1H transverse relaxation time. Novel methodological developments show that 1H double-quantum filtered NMR signals can be generated in the inhomogeneous fields of the NMR-MOUSE for characterization of residual dipolar couplings. This technique was applied to characterize reference natural rubber samples with different crosslink density and carbon black and silica fillers.     

Insights into the Reinforcement of Butyl Rubber by Carbon Black and Silica with the Aid of Their Dynamic Properties

Carbon black (N234) and silica (Vulksail N) with a silane coupling agent Si-69 were chosen as reinforcing fillers in butyl rubber (IIR). The rheological behavior of the IIR compounds and the dynamic mechanical properties of IIR vulcanizates were investigated with a rubber processing analyzer and dynamic mechanical analysis (DMA) to examine the filler dispersion in the rubber matrix and the interaction between filler and matrix. The data indicated that the N234 filled IIR compounds had more filler networks than those filled with silica. Filler networks first appeared at 30 phr N234 and 45 phr silica with silane coupling agent Si-69. The interaction between N234 and IIR was far stronger than that between silica and IIR. However, the silica Vulksail N filled IIR had better wet-grip and lower rolling resistance compared to the carbon black-filled IIR should IIR be chosen as a substitute of styrene-butadiene rubber (SBR) in tire tread. The reinforcing factor, R, R (related to the difference in tan d peak height at T_g for the filled and nonfilled rubbers), also demonstrated that the N234-IIR interaction was stronger than for the silica. IIR with 30 phr N234 exhibited the largest tensile strength, 20.1 MPa, for those vulcanizates examined. The tensile and tear strengths of N234 filled IIR were higher than those of IIR with similar amounts of silica. Thus, it was concluded that N234 is a more active reinforcing filler in IIR than silica (Vulksail N) even with a silane coupling agent (Si-69).     

Some new developments in rubber reinforcement

The reinforcement of natural rubber provided by in-situ generated silica is compared with that obtained with anisotropic particles such as nanofibers of sepiolite. In addition, the effect of a dual loading is also investigated. Compared with networks filled with a single type of filler (sepiolite or in-situ generated silica), the samples containing two types of fillers display high modulus but less extensibility.     

Conductance noise investigations with four arbitrarily shaped and placed electrodes

A general relation is derived for the spectral noise density of the voltage between two arbitrarily shaped and placed sensor electrodes on a conductor, when a constant current or voltage is applied to another pair of arbitrarily shaped and placed driver electrodes. The general relation is based on the sensitivity calculation in linear electrical networks. The relation is elaborated for conductivity fluctuations due to 1/f noise by using empirical 1/f noise relations. The influence of spot radii of the sensor electrodes on the noise is demonstrated. The theoretical results for 2 and 3-dimensional conductors are in agreement with our experimental results for carbon resistance sheets and on silicon and germanium in the resistivity range of 1Ωcm to 400Ωcm. The possibility of using the four-point probe for measuring the fluctuations in the resistivity has been demonstrated.     

Nanostructured carbons for solid phase extraction

Nanostructured carbons have been obtained by the template method using zeolite NaY and silica gels (SG60, Fluka and ZK, POCh) as structure directing agents. Texture and porous structure of carbons were characterized by TEM, XRD and nitrogen adsorption. Surface chemistry was investigated by the potentiometric titration method. It has been shown that all carbons show developed and uniform porous structure with mean size in the micropore range (1.1 nm) for zeolite derived carbon and in the mesopore range (3.4 and 4.8 nm) for silica gel derived carbons. The BET surface area of silica gel derived carbons is in the range 1230-1280 m²/g whereas zeolite derived carbon possesses very high BET surface area, 3000 m²/g. Potentiometric titration showed that carbons obtained by the template method contain significant amount of acid surface groups (carboxylic, lactone/enol and phenolic) with the total amount 1.1-1.5 mmol/g. To study adsorption-desorption properties of nanostructured carbons towards phenol and chlorophenols the solid phase extraction method was used. High recoveries of chlorophenols were obtained (80-93%) at the breakthrough volumes 1700-3000 mL. The recoveries are much higher than that obtained with commercially available carbon ACC (Supelco).     

Preconcentration of Trace Cu(II) in Water Samples with Nano-Sized ZnO and Determination by GFAASSCIEI北大核心CSCD

The content of copper in natural water is very low, and direct determination is difficult. Therefore, it is very meaningful for the combination of efficient separation-enrichment technology and highly sensitive detection. Based on the high adsorption capacity of Cu(II) onto nano-sized ZnO, a novel method by using nano-sized ZnO as adsorbent and graphite furnace atomic absorption spectrometry as determination means was in this work. The adsorption behaviors of Cu(II) on nano-sized ZnO was studied. Effects of acidity, adsorption equilibrium time, adsorbent dosage and coexisting ions on adsorption rates were investigated. The results showed that the adsorption efficiency was above 95% in a pH range from 3.0 to 7.0. Compared with other adsorbents for trace element enrichment such as activated carbon, nano-sized TiO2 powder, the most prominent advantage is nanosized ZnO precipitate with the concentrated element can directly dissolved in HCl solution without any filtration and desorption process can directly analyzed by graphite furnace atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry. Compared with colloid nano materials, nano-sized ZnO is the true solution after dissolving have small matrix effect and viscosity more suitable for graphite furnace atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry detection. The proposed method possesses low detection limit (0.13 mu g.L-1) and good precision (RSD=2.2%). The recoveries for the analysis of environmental samples were in a rang of 91.6%-92.6% and the analysis results of certified materials were compellent by using the proposed method.     

XPS and SIMS investigation on the role of nitrogen in Si nanocrystals formation

Since the demonstration of optical gain in silicon nanocrystals, in the last few years several papers appeared in the literature reporting gain measurements in silicon nanocrystals embedded in a silica matrix produced by different techniques. However, it is still unclear which are the structural, physical and chemical factors that contribute to enhance photoluminescence and gain in this type of samples. In particular, the presence and the role of nitrogen in the SiO₂ matrix are in fact supposed to be essential factors in understanding the gain mechanism.In fact it is possible to obtain similar samples with very different nitrogen content in the silica matrix changing one of the precursor gases used in the deposition process, thus evidencing the structural and chemical differences introduced by the presence of nitrogen. In this paper SIMS and XPS analysis of two series of similar samples, but with a very different nitrogen content, will be presented and compared. The data collected at different annealing temperatures, together with ellipsometric measurements, give important information on the role played by the nitrogen present in the matrix in the process of silicon nanocrystal formation. Moreover, we demonstrate that the annealing process causes always some oxidation of the sample surface and that nitrogen is incorporated in the material from the annealing atmosphere in nitrogen free samples.     

Polypropene nanocomposites by metallocene/MAO catalysts

In our experiments, monospheres (balls of silica, diameter 200–250 nm), carbon fibers (diameter 200 nm, length 0.5–3 mm) and carbon nanotubes (diameter 15–25 nm, length 50 μm) were used as fillers. Before polymerization, the fillers were separated by ultrasound and then treated by methylaluminoxane (MAO). The MAO reacts partially with the OH-groups of the silica and the formation of methane. Catalytically active centers are formed after adding the zirconocenes or other transition metal complexes. The thickness of the polyolefins can be controlled by the pressure of ethene or propene and by the polymerization time. By this method, highly filled nanocomposite polypropenes can be obtained with a silica content of up to 60 wt%. Such combined materials are stiff and hard. Every particle is surrounded by a thin film of polyolefin with a thickness of 30 to 100 nm. Carbon fibers and carbon nanotubes can be covered also within isotactic or syndiotactic polypropene. Because of the hydrophobic character of the carbon surface, the polymer is drawing on the fiber. This leads to a reinforced combined polymer with special properties.     

Carbon nanotube synthesis on oxidized porous silicon

Carbon nanotubes were grown on thermally oxidized porous silicon by catalytic chemical vapor deposition from the mixture of ferrocene and xylene precursor. The growth rate of carbon nanotubes showed dependence on the oxidation extent of porous silicon. On pristine porous silicon surfaces, only poor nanotube growth was observed, whilst samples oxidized in air at 200, 400, 600 and 800 °C prior to the deposition process proved to be suitable substrates for carbon nanotube synthesis. Networks of carbon tubes with diameter of ∼40 and ∼10 nm observed on the surfaces of samples were investigated by electron microscopy and by energy dispersive X-ray analysis.     

多孔硅/DR1复合膜三阶非线性光学性质的研究

采用物理吸附方法制备出多孔硅和偶氮化合物染料分散红（DR1）的复合薄膜.用单光束扫描法研究了多孔硅/ DR1复合膜的三阶非线性光学性质，测量了在1064 nm处多孔硅/DR1复合膜的双光子吸收系数和非线性折射率.实验结果表明，同多孔硅相比，多孔硅/DR1复合膜三阶非线性光学效应明显得到了增强.     

纳米氧化锌富集分离-石墨炉原子吸收光谱法测定水中痕量铜

天然水体中铜含量很低,直接测定较为困难。利用纳米氧化锌对Cu(Ⅱ)良好的吸附性能,建立了纳米氧化锌富集分离,石墨炉原子吸收光谱法测定水样中痕量铜的新方法。研究了纳米氧化锌对Cu(Ⅱ)的吸附行为,优化了吸附条件。实验结果表明：pH 3～7时,纳米氧化锌粉末对Cu(Ⅱ) 吸附率达95%以上,且吸附速度快。与文献报道的用于痕量元素富集的活性炭、粉体纳米二氧化钛等吸附剂比较,纳米氧化锌最突出的优点是富集后不需要脱附,用酸溶解后即可用石墨炉原子吸收光谱、电感耦合等离子体发射光谱测定溶液中被富集元素的含量,因此方法简单、快速;与富集后不需脱附,用酸溶解后又成为均匀胶体溶液的胶体纳米材料比较,纳米氧化锌溶解后是真溶液,黏度小,基体效应小,更加适用于石墨炉原子吸收光谱、电感耦合等离子体发射光谱检测。该方法简单快速,检出限低(0.13 μg·L-1),精密度好, 相对标准偏差(RSD)为2.2%,用于实际水样中痕量Cu(Ⅱ) 检测,其回收率为91.6%～92.6%;用于国家水质环境标准样品铜的测定,结果吻合。     

Alkoxysilane-Functionalized Silica Fillers — Preparation and Characterization

A number of new silica fillers have been obtained in the emulsion system and changes in their surface properties appearing as a result of modification with the following alkoxysilanes have been evaluated: [3-(phenylamino)propyl]trimethoxysilane (PhAPS), (3-glycidoxypropyl)trimethoxysilane (GPS), N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS), 3-mercaptopropyltrimethoxysilane (McPS) and octyltriethoxysilane (OS). Functionalization of SiO₂ surface has been made with different amounts of the modifiers. The fillers have been characterized by determination of their dispersion, adsorption abilities, morphological and chemical properties (effectiveness of modification and hydrophobization determined by wetting and sedimentation methods). The silica-based fillers obtained have been made of spherical shaped particles characterized by high size uniformity (low polydispersity index) of the mean diameter within the range 440–520 nm. The fillers show limited hydrophilic properties as confirmed by the wettability and sedimentation tests in water.     

Ignition of fuel/air mixtures by radiatively heated particles

The current work examines the ignition of fuel/air mixtures by particles which have been heated up rapidly by intense electromagnetic radiation from an infrared laser source. Experiments have been conducted at relatively large beam sizes, where ignition times are a function of the irradiance. Particles in the form of fine powders were placed into a chamber filled with ignitable butane/air mixtures. Possible ignition is shown for a range of carbon based materials including different carbon blacks, graphite, the C₆₀ fullerene and diamond powder, as well as for non-reactive powders such as silicon carbide, iron-, copper- and silicon oxides. The irradiance was varied independently and results are shown to become independent of the size of the irradiated area if a sufficiently large area is illuminated. The particle size was found to have a significant impact on the time to ignition. Specifically, finer particles lead to shorter ignition times due to the higher surface area to volume ratio which reduces both particle and gas heating times. Ignition could be achieved across the whole flammability range of butane/air using carbon black and silicon carbide particles, although, near the rich flammability no ignition could be obtained with carbon black.     

Reinforcement effects of multiwall carbon nanotubes in elastomeric matrices: Comparison with other types of fillers

Mechanical and electrical properties of composites based on butyl rubber and multiwall carbon nanotubes (MWNTs) are investigated. Gradual increases in elastic moduli are observed with the filler content. It was found that the degree of strain affects the electrical resistivity. Finally, the level of reinforcement imparted to a rubbery matrix by carbon nanotubes is compared with that provided by other types of fillers such as carbon black, clay fibers or layered silicates.     

N-邻羟基苯基马来酰胺酸-改性活性炭对Cu(Ⅲ)的吸附性能

研究了新型吸附剂N-邻羟基苯基马来酰胺酸-活性炭(AC-HPMA)对样品中Cu(Ⅱ)的固相萃取并用电感耦合等离子体-原子发射光谱法(ICP-AES)测定。优化了pH值、吸附剂(AC-HPMA)的用量、流速等条件以达到定量吸附(≥95%),同时考察了共存离子的影响和洗脱剂的洗脱条件。本法测定Cu(Ⅱ)的检出限为0.27μg.L-1,将其应用于茯苓、黄河水、青海湖水中的Cu(Ⅱ)含量的测定,加标回收率在96.3%—99.0%之间;用于测定标准物质中铜离子的含量,结果与标准物参照值一致。