Pure Blends Research Articles

Curaua fiber reinforced high-density polyethylene composites: effect of impact modifier and fiber loading

Short fibers are used in thermoplastic composites to increase their tensile and flexural resistance; however, it often decreases impact resistance. Composites with short vegetal fibers are not an exception to this behavior. The purpose of this work is to produce a vegetal fiber reinforced composite with improved tensile and impact resistance in relation to the polymer matrix. We used poly(ethylene-co-vinyl acetate), EVA, to recover the impact resistance of high density polyethylene, HDPE, reinforced with Curaua fibers, CF. Blends and composites were processed in a corotating twin screw extruder. The pure polymers, blends and composites were characterized by differential scanning calorimetry, thermogravimetry, infrared spectroscopy, scanning electron microscopy, tensile mechanical properties and Izod impact resistance. EVA used as impact modifier in the HDPE matrix exhibited a co-continuous phase and in the composites the fibers were homogeneously dispersed. The best combination of mechanical properties, tensile, flexural and impact, were obtained for the formulations of composites with 20 wt. % of CF and 20 to 40 wt. % of EVA. The composite prepared with 20 wt. % EVA and containing 30 wt. % of CF showed impact resistance comparable to pure HDPE and improved tensile and flexural mechanical properties.

Titanate nanotubes for reinforcement of a poly(ethylene oxide)/chitosan polymer matrix

Soft polyethylene oxide (PEO)/chitosan mixtures, reinforced with hard titanate nanotubes (TiNTs) by co-precipitation from aqueous solution, have been used to produce compact coatings by the ‘drop-cast’ method, using water soluble PEO polymer and stable, aqueous colloidal solutions of TiNTs. The effects of the nanotube concentration and their length on the hardness and modulus of the prepared composite have been studied using nanoindentation and nanoscratch techniques. The uniformity of TiNT dispersion within the polymer matrix has been studied using transmission electron microscopy (TEM). A remarkable increase in hardness and reduced Young’s modulus of the composites, compared to pure polymer blends, has been observed at a TiNT concentration of 25 wt %. The short (up to 30 min) ultrasound treatment of aqueous solutions containing polymers and a colloidal TiNT mixture prior to drop casting has resulted in some improvements in both hardness and reduced Young’s modulus of dry composite films, probably due to a better dispersion of ceramic nanotubes within the matrix. However, further (more than 1 h) treatment of the mixture with ultrasound resulted in a deterioration of the mechanical properties of the composite accompanied by a shortening of the nanotubes, as observed by the TEM.

Modelling of evaporative losses in n-alcohol/diesel fuel blends

Alcohol/diesel fuel blends allow reducing the formation of soot in diesel engines. However, its use in a large scale framework still faces the challenge of high evaporative losses under storage conditions which is hindered by the high volatility of the alcohols. Since the design of the most adequate fuelling system for each blend requires detailed knowledge about the evaporation losses from the liquid phase, in this work a method for calculating the evaporation of pure n-alcohols (from C1 to C5 carbon atoms) and blends of these alcohols with ultra-low sulphur diesel (ULSD) was proposed. Alcohols vapour pressure was determined with the Antoine equation, while the diffusion coefficient of alcohols in air was calculated as a function of carbon number and temperature. The coefficients of activity were obtained by the combination of continuous thermodynamic (gamma distribution function) and a modified UNIFAC-Dortmund-Continuous method. The evaporation losses model is based on Fick’s law and exhibited good agreement with experimental data for all alcohols and blends at 20% content of all alcohols and at 20–60% contents of n-butanol with diesel fuel. The evaporation was found to decrease approximately with an inversely proportional rate with respect to the increase in the carbon chain length of the alcohol. The paradox of faster evaporative losses from blends with lower alcohol content is explained.

Composition of fatty acids and triglycerides in goat cheeses and study of the triglyceride composition of goat milk and cow milk blends

The composition of fatty acids and triglycerides in the fat of Uruguayan goat cheeses was determined. Additionally, in the present study, triglyceride composition was determined in terms of partition number (PN) for fats from pure goat milk, pure cow milk and blends thereof (90:10, 80:20, and 50:50 blends of goat milk:cow milk). All Uruguayan goat cheeses showed high levels of conjugated linoleic acid and trans-vaccenic acid, well above those reported in cheeses from other countries. This is advantage in terms of nutritional quality. In fats from goat milk in Uruguayan cheeses, the highest average percentages of triglycerides correspond to PN=36 (13.2%) and PN=42 (13.6%). The results demonstrate that the triglyceride profile changes when cow milk is added to goat milk. When the amount of cow milk added to goat milk increases, triglycerides with PN values of 38, 40, and 42 tend to decrease, while triglycerides with PN values of 46, 48, and 50 tend to increase. These results suggest that the triglyceride profile could be used to determine whether a given goat cheese was adulterated with cow milk, which is cheaper. This was detected in the case of three Uruguayan goat cheeses that were analysed.

Improvement of emission characteristics and thermal efficiency in diesel engines by fueling gasoline/diesel/PODEn blends

PODEn (polyoxymethylene dimethyl ethers) stand for the mixtures of ethers with the chemical formula CH3O(CH2O)nCH3, which have high cetane number and nearly 50% oxygen content. Gasoline/Diesel (GD) blends reduce the soot emissions of diesel engines with the penalty of combustion efficiency. In order to reduce emissions and improve thermal efficiency of diesel engines, blends of GDP (gasoline/diesel/PODEn) were proposed and studied in this work. Experiments were carried out in a diesel engine fueled with pure diesel, GD blends, and GDP blends. The results show that both GD blends and GDP blends have single-stage premixed heat release. GDP blends have shorter ignition delay, lower max pressure rise rate and COVIMEP (coefficient of variation of indicated mean effective pressure) than GD blends. GD blends have lower soot emissions than diesel fuel, while GDP blends have lowest soot emissions and exhibit best NOx-soot trade-off. GDP blends also have higher combustion efficiency and thermal efficiency than GD blends, even slightly higher than diesel fuel.

Effect of Octane on Performance, Energy Consumption and Emissions of Two Euro 4 Passenger Cars

The combustion performance of gasoline engines has traditionally been measured using Research Octane Number (RON) and Motor Octane Number (MON) which describe antiknock performance under different conditions. Recent literature suggests that MON is less important than RON in modern cars and a relaxation in the MON specification could improve vehicle performance, while also helping refiners in the production of gasoline. At the same time, for the same octane number change, increasing RON appears to provide more benefit to engine power and acceleration than reducing MON. It has also been suggested that there could be fuel efficiency benefits (on a tank to wheels basis) for specially adapted engines, for example, operating at higher compression ratio, on very high RON (100+). Other workers have advocated the use of an octane index (OI) which incorporates both RON and MON to give an indication of octane quality.The objective of this study was to investigate the effect of RON and MON on the power and acceleration performance of modern gasoline vehicles under full throttle acceleration conditions. Tests were carried out using two Euro 4 vehicles. Fuels covering RON levels from 95 to 103 and sensitivities (RON minus MON) of up to 15 were blended. Both pure hydrocarbon and blends containing ethanol or ETBE were included so that specific effects of oxygenates could be identified. The results confirmed the findings of other studies that MON is not a good predictor of vehicle performance and in fact high MON levels increase acceleration time under full throttle conditions. In addition to performance testing, emissions testing was also carried out. Carbon balance was used to calculate energy consumption during the acceleration tests and NEDC tests.

Performance analyses of a spark-ignition engine firing with gasoline–butanol blends at partial load operation

Biofuels seem to represent one of the most promising means for the limitation of the greenhouse gas emissions coming from traditional energy systems.In this paper, the performance of a “downsized” spark-ignition engine, fueled by gasoline and bio-butanol blends (20% and 40% butanol mass percentage), has been analyzed.In the first phase of this activity, the experimental tests have been carried out at operating points ranging from low to medium engine speed and load.The first investigations were aimed to assess the main differences among the different fuels in terms of output torque, thermal efficiency, combustion duration and optimal spark timing. In order to study the engine behavior in a wide range of fuel mixtures, these parameters have been evaluated for equivalence ratio values ranging from 1.25 to 0.83.The results obtained in this step show that both the engine torque and thermal efficiency slightly decrease (meanly about 4%) when the blend alcohol content increases. However, butanol increases the burning rate of lean mixtures and an interesting result is that the spark advance does not require adjustments when fueling changes from neat gasoline to bio-butanol/gasoline blends.Later, the pollutant emissions and the CO2 emissions, for both rich and lean mixtures of pure gasoline and gasoline bio-butanol blends, have been measured. In general, firing with alcohol blends, NOx and CO emissions remain quite the same, HC emissions slightly decrease while the CO2 emissions slightly increase.At the end, in order to reproduce the real world urban driving cycle, stoichiometric mixtures have been analyzed. In these conditions, the engine thermal efficiency, at given speed and torque, has been evaluated for each kind of fueling. The results obtained in these operating points have shown that the alcohol blend fueling performs an efficiency penalty less than 2 percent.

Recycling of blends made of polypropylene and an iron-based oxygen scavenger – Influence of multiple extrusions on the polymer stability and the oxygen absorption capacity

An often used oxygen scavenger is a blend of iron powder and additives dispersed in a polymer carrier matrix. It is applied as an additive for separate layers of multilayer film structures which are produced by coextrusion. Not much is known about the influence of multiple extrusions, for example during recycling processes, of these materials on polymer properties, film properties and process stability. Therefore the aim of this study was to assess these issues. The focus was on polypropylene because it is a common blend partner for iron-based oxygen scavenger additives. Pure polypropylene and blends of polypropylene with approximately 20 wt.-% iron-based oxygen scavenger additive (SHELFPLUS® O2 2710) were extruded up to ten times at two temperature profiles (T1: 160–230 °C; T2: 210–300 °C). Polymer degradation was evaluated by different means of measurement: MFR, DSC, colorimetry, IR-spectroscopy and oxygen absorption. The results indicate that polypropylene and polypropylene with dispersed oxygen scavenger degrade by the impact of extrusion which can be seen by increased MFR and crystallinity and color changes. Furthermore the iron particles did undergo changes regarding color and oxygen scavenging capacity. The absorption capacity at 23 °C was reduced by one third from 39 to 48 mg oxygen per one gram scavenger additive after one extrusion to 26–35 mg oxygen per one gram scavenger additive after 9 and 10 extrusion cycles, respectively. Overall the iron based oxygen scavenger has a lower impact on degradation than the temperature and the number of extrusions.

Reactive extrusion effects on rheological and mechanical properties of poly(lactic acid)/poly[(butylene succinate)‐co‐adipate]/epoxy chain extender blends and clay nanocomposites

ABSTRACTPoly(lactic acid) (PLA), a biosource, biodegradable polymer, is not suitable for some important polymer processing operations, such as film blowing and blow molding, due to its low melt strength. Moreover, while it has high tensile modulus and strength in the solid state, it exhibits low ductility. The present work is an extension of our earlier effort to improve the processability and mechanical properties of PLA by blending with poly[(butylene succinate)‐co‐adipate)] (PBSA), a biodegradable polymer with lower glass transition temperature. We evaluate the influences of incorporation of an epoxy chain extender and nanoclay on the properties of the blend. Since earlier work was conducted in a batch mixer, the influence of melt processing in the twin screw extruder and the differences between products obtained in the extruder and the batch mixer are evaluated and explained. Based on earlier work, the following PLA/PBSA blend ratios of 90:10, 80:20 and 70:30 were selected. All the samples were prepared in the twin‐screw extruder at two different screw speeds (50 and 150 rpm), to evaluate the effects of residence time and shear rates. The morphology and structure of the blends were examined using field emission scanning electron microscopy. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) were used to evaluate the levels of intercalation and exfoliation in the nanocomposites. The chain extension reaction was evaluated using nuclear magnetic resonance (NMR) spectroscopy and other techniques. Rheological properties (dynamic oscillatory shear and elongational viscosity measurements) and mechanical characteristics of the pure components, blends, and nanocomposites were studied and discussed in light of the composition and morphology of the blends and the nanocomposites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42664.

The Investigation of Thermodynamics and Combustion Properties of Alcohol-Gasoline Blends in an SI Engine

In this study, the thermodynamic properties, energy release, combustion, and emission variations in a spark ignition (SI) engine fueled with alcohol-gasoline blends and gasoline has been investigated. Test results showed that the net indicated work area of alcohol-gasoline blends was wider than pure gasoline blends and also; this situation affected positively the brake mean effective pressure and engine power output. The mass burn ratio of alcohol–gasoline blends was higher than those of pure gasoline. The exhaust emission level decreased with the increase of ethanol content in the fuel blend, but similar results was not observed with methanol–gasoline blends.

Combustion related characterisation of Miscanthus peat blends applying novel fuel characterisation tools

Abstract A continuously increasing demand for energy from biomass encourages utilisation of new biomass fuels which usually cause ash related problems in conventional wood combustion systems. One approach to make these biomass fuels applicable in such systems is to prepare blends with other fuels such as peat, which positively influence the behaviour of ash-forming elements. Usually the application of fuel blends has been evaluated experimentally, but in this study novel and advanced fuel characterisation tools (developed for fixed bed/grate combustion systems) are applied to Miscanthus/peat blends. In a first step the pure fuels and the Miscanthus/peat blends were chemically analysed. Fuel indexes provide primary information on ash-melting behaviour and a first estimation of the K release, indications of aerosol emissions, risk of high-temperature chlorine corrosion and the NO x emission potential. Thermodynamic equilibrium calculations were used for a qualitative and semi-quantitative prediction of the release of volatile and semi-volatile elements (K, Na, S, Cl, Zn, Pb) and the ash-melting behaviour. To quantitatively determine the release behaviour of ash-forming elements, lab-scale reactor experiments for the pure fuels and blends were conducted and a comparison with the theoretical calculations was performed. This work shows that the new approach of applying novel and advanced fuel characterisation tools to characterise Miscanthus/peat blends works well and meaningful blends can be recommended. The advantage of this characterisation method is that the influence of varying peat compositions (since the composition of peat strongly depends on its origin) can be considered. Additionally this approach helps to significantly reduce time-consuming and expensive testing programs.

70]PCBM and Incompletely Separated Grades of Methanofullerenes Produce Bulk Heterojunctions with Increased Robustness for Ultra-Flexible and Stretchable Electronics

An organic solar cell based on a bulk heterojunction (BHJ) of a polymer and a methanofullerene ([60]PCBM or [70]PCBM) exhibits a complex morphology that controls both its photovoltaic and mechanical compliance (robustness, flexibility, and stretchability). Methanofullerenes are excellent electron acceptors; however, they have relatively high cost and production energy (in the purest samples) compared to other small-molecule semiconductors. Moreover, [60]PCBM and [70]PCBM—typical of van der Waals solids—can be stiff and brittle. Stiffness and brittleness may lower the yield of working modules in roll-to-roll manufacturing, shorten the lifetime against mechanical failure in outdoor conditions, and jeopardize wearable and portable applications that demand stretchability or extreme flexibility. This paper tests the hypothesis that “technical grade” PCBM (incompletely separated but otherwise pure blends containing ≥ 90% [60]PCBM or [70]PCBM) could lower the cost of manufacturing organic solar cells while simul...

Electrospun cellulose nitrate and polycaprolactone blended nanofibers

Pure cellulose nitrate (CN) and blends of CN and polycaprolactone were electrospun to form nonwoven mats. Polymers were dissolved in a mixed solvent system of tetrahydrofuran and N,N-dimethylformamide. The concentrations were varied to obtain sub-micron and nanoscale fiber mats. Fiber mats were analyzed using scanning electron microscopy, contact angle analysis, Fourier transform infrared spectroscopy and thermal gravimetric analysis. The fiber morphology, surface chemistry and contact angle data show that these electrospun materials are suitable for applications including biosensing, biomedical and tissue engineering.

Determinação da capacidade antioxidante de produtos naturais in vitro pelo método do DPPH•: estudo de revisão

Os antioxidantes podem ser de grande benefício para a melhoria da qualidade de vida, já que eles têm a capacidade de proteger um organismo dos danos causados pelos radicais livres, prevenindo ou adiando o início de várias doenças. Uma das técnicas atualmente utilizada para detectar a presença de compostos antioxidantes, é um método baseado na eliminação do radical livre estável 1,1-difenil-2-picrilhidrazil (DPPH•). Este método é considerado fácil, preciso, rápido, simples, e econômico, sendo adequado para a determinação da capacidade antioxidante de substâncias puras e misturas. O objetivo deste artigo de revisão é fornecer informações sobre esse método. A pesquisa foi realizada usando o termo radical DPPH•, capacidade antioxidante-DPPH• e método DPPH• em periódicos, tais como: Pubmed, Wiley Online Library, ACS Publications, SpringerLink e ScinceDirect até janeiro de 2014.

Study on the structure, melting, and nonisothermal crystallization behaviors of isotactic polypropylene with nematic liquid crystalline polymer as a new β-nucleating agent

Wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) were used to evaluate the effect of nematic liquid crystalline polymer as a new β-nucleating agent (LCP-NA) on the structure, melting, and nonisothermal crystallization behaviors of isotactic polypropylene (iPP). A high content of β-crystal could be obtained by the combined effect of the optimum LCP-NA content and crystallization temperature and time. The relative content of β-crystal increased with increasing LCP-NA content, reached a maximum value of 59% when LCP-NA content was 1.0 wt % at 130°C for 1h, and then decreased with a further increase of LCP-NA content. Avrami, Jeziorny, Ozawa, and Mo methods were applied to describe the crystallization process. Jeziorny and Mo methods showed a good agreement in describing the nonisothermal crystallization behaviors of pure iPP and iPP blends with 1.0 wt % LCP-NA, but Ozawa method could not better describe these behaviors. The addition of LCP-NA could effectively increase the crystallization temperature and the crystallization rate, and induce heterogeneous nucleation with the nonisothermal tridimensional growth of the spherulite. Kissinger’s method indicated that the iPP blends with 1.0 wt % LCP-NA needed a higher energy for crystallization per mole than pure iPP.

Collagenase H is Crucial for Isolation of Rat Pancreatic Islets

The role(s) of collagenase G (ColG) and collagenase H (ColH) during pancreatic islet isolation remains controversial, possibly due to the enzyme blends used in the previous studies. We herein examined the role of ColG and ColH using highly pure enzyme blends of recombinant collagenase of each subtype. Rat pancreases were digested using thermolysin, together with ColG, ColH, or ColG/ColH (n = 9, respectively). No tryptic-like activity was detected in any components of the enzyme blends. The efficiency of the collagenase subtypes was evaluated by islet yield and function. Immunohistochemical analysis, in vitro collagen digestion assay, and mass spectrometry were also performed to examine the target matrix components of the crucial collagenase subtype. The islet yield was highest in the ColG/ColH group (4,101 ± 460 islet equivalents). A substantial number of functional islets (2,811 ± 581 islet equivalents) was obtained in the ColH group, whereas no islets were retrieved in the ColG group. Mass spectrometry demonstrated that ColH reacts with collagen I and III. In the immunohistochemical analysis, both collagen I and III were located in exocrine tissues, although collagen III expression was more pronounced. The collagen digestion assay showed that collagen III was more effectively digested by ColH than by ColG. The present study reveals that ColH is crucial, while ColG plays only a supporting role, in rat islet isolation. In addition, collagen III appears to be one of the key targets of ColH.

The influence of TiO2 and ZnO powder mixtures on photocatalytic activity and rheological behavior of cement pastes

The photocatalytic activity of titania nano/microparticles (nT and mT) and zinc oxide microparticles (mZ) as well as the rheological behavior of cement pastes with the addition of those particles were evaluated applying design of experiments (DoE). Such additives ranged from 0 to 1.2wt.% in the cement paste, while the water/cement ratio (0.45) and superplasticizer (0.45wt.%) remained invariable. Thus, pure blends and binary or ternary mixtures were studied. Pure blends containing nT or mT and ternary mixtures 0.67mT:0.17nT:0.17mZ reached the best and comparable performances in terms of photocatalytic activity. The rheological parameters (plastic viscosity and yield stress) values changed along time in distinct levels described by a quadratic model. Samples with nT became less fluid, and the yield stress was the main rheological parameter affected. The kinetics of hydration was not significantly affected by additions up to 120min testing, but showed noticeable distinctions for longer periods: mZ (delayed) and nT (shortened), while mT required about the same time to reach the maximum exothermic peak than reference paste.

Dynamics of polypropylene chains in their binary blends of different stereochemical sequences studied by Monte Carlo simulations

The conformational and dynamic properties of polypropylene (PP) for both pure melts and blends with different chain tacticity were investigated by Monte Carlo simulation of isotactic (iPP), atactic (aPP) and syndiotactic (sPP) polypropylenes. The simulation of coarse-grained PP models was performed on a high coordination lattice incorporating short- and long-range intramolecular interactions from the rotational isomeric state (RIS) model and Lennard-Jones (LJ) potential function of propane pairs, respectively. The dynamics of chains in binary PP/PP mixture were investigated with the composition of C150H302 with different chain taciticity. The diffusion rates of PP with different stereochemistry are generally in the order as: iPP > aPP ≫ sPP. For PP/PP blends with 50:50 wt% binary mixtures, immiscibility was observed when sPP was introduced into the mixtures. The diffusion rate of iPP and aPP became slower after mixing, while sPP diffuses significantly faster in the binary mixtures. The mobility of PP chains depends on both intramolecular (molecular size and chain stiffness) and intermolecular (chain packing) interactions. The effect of intramolecular contribution is greater than that of intermolecular contribution for iPP and aPP chains in binary mixtures. For sPP chain, intermolecular interaction has greater influence on the dynamics than intramolecular contribution.

Impact of low temperature combustion attaining strategies on diesel engine emissions for diesel and biodiesels: A review

Simultaneous reduction of particulate matter (PM) and nitrogen oxides (NOx) emissions from diesel exhaust is the key to current research activities. Although various technologies have been introduced to reduce emissions from diesel engines, the in-cylinder reduction techniques of PM and NOx like low temperature combustion (LTC) will continue to be an important field in research and development of modern diesel engines. Furthermore, increasing prices and question over the availability of diesel fuel derived from crude oil have introduced a growing interest. Hence it is most likely that future diesel engines will be operated on pure biodiesel and/or blends of biodiesel and crude oil-based diesel. Being a significant technology to reduce emissions, LTC deserves a critical analysis of emission characteristics for both diesel and biodiesel.This paper critically investigates both petroleum diesel and biodiesel emissions from the view point of LTC attaining strategies. Due to a number of differences of physical and chemical properties, petroleum diesel and biodiesel emission characteristics differ a bit under LTC strategies. LTC strategies decrease NOx and PM simultaneously but increase HC and CO emissions. Recent attempts to attain LTC by biodiesel have created a hope for reduced HC and CO emissions. Decreased performance issue during LTC is also being taken care of by latest ideas. However, this paper highlights the emissions separately and analyzes the effects of significant factors thoroughly under LTC regime.

Predicting the kinematic viscosity of FAMEs and biodiesel: Empirical models

Three correlations are proposed to predict the kinematic viscosity of fatty acid methyl esters (FAMEs) in a wide temperature range. One correlation is derived for saturated species from C6:0 to C24:0 while two complementary correlations are used for unsaturated species, from C14:1 to C22:1, including C18:2 and C18:3. The correlation for saturated FAMEs was derived from 247 viscosity experimental points taken from the literature, giving an average absolute deviation (AAD) of 1.33%. In the case of unsaturated species, 154 experimental data points reported in the literature were considered, obtaining an AAD of 2.88%. The predictive capacity of the proposed correlations was tested by calculating the viscosity of 31 pure biodiesels (193data points) and four binary biodiesel blends (150data points) whose compositions and viscosities at different temperatures were gathered from the literature. A global AAD of 5.33% was obtained for pure biodiesels while the global AAD for biodiesel blends was 7.58%. These results were compared to the AADs obtained for other different six models previously reported in the literature and applied to the same data bank. The comparison showed that the lowest AADs for both data sets (pure biodiesel and biodiesel blends) were obtained with the correlations of this work.