Progress Report on Natural Fiber Reinforced Composites

This century has witnessed remarkable achievements in green technology in material science through the development of natural fiber reinforced composites. The development of high‐performance engineering products made from natural resources is increasing worldwide day by day. There is increasing interest in materials demonstrating efficient use of renewable resources. Nowadays, more than ever, companies are faced with opportunities and choices in material innovations. Due to the challenges of petroleum‐based products and the need to find renewable solutions, more and more companies are looking at natural fiber composite materials. The primary driving forces for new bio‐composite materials are the cost of natural fibers (currently priced at one‐third of the cost of glass fiber or less), weight reduction (these fibers are half the weight of glass fiber), recycling (natural fiber composites are easier to recycle) and the desire for green products. This Review provides an overview of natural fiber reinfocred composites focusing on natural fiber types and sources, processing methods, modification of fibers, matrices (petrochemical and renewable), and their mechanical performance. It also focuses on future research, recent developments and applications and concludes with key issues that need to be resolved. This article critically summarizes the essential findings of the mostly readily utilized reinforced natural fibers in polymeric composite materials and their performance from 2000 to 2013.     

A composite model for an intermeshing counter‐rotating twin‐screw extruder and its experimental verification

A composite simulation model of solids conveying, melting and melt flow in a closely intermeshing counter‐rotating twin‐screw extruder has been developed. The model is based on combining new melt conveying models with melting and solids conveying models, and the die is included into considerations. A general approach is applied using fully three‐dimensional non‐Newtonian FEM modeling for melt conveying to develop screw pumping characteristics which are implemented into the composite model. Several screw configurations are considered including non‐classical elements. Computations are made for axial fill factor, pressure, temperature, and melting profiles. The results are validated experimentally. POLYM. ENG. SCI., 55:2838–2848, 2015. © 2015 Society of Plastics Engineers     

Designing of low-power data oriented adders

The paper presents an idea of designing of low-power adders addressed to specific data processing. Mainly, the idea consists in proper choosing of 1-bit full adder cells for given probability of summed data, to obtain reduction in consumed power. Additionally different structures of the cells can be used, in one design, if it leads to reduction of power dissipation. To proper choice of structures of 1-bit full adders theirs energy characteristic versus summed data is needed. So, at the beginning we present results of assessment of a few 1-bit adder cells selected from literature and designed in UMC180 CMOS technology. The extended model of power consumption, taking into consideration input vector changes, was used, giving more accurate values than traditional model based on switching activity only. Thanks to the use of this model, obtained results allow detailed analysis of 1-bit adders on account of the using them in designing of low-power multi-bit adders summing specific data. Based on the results of analyses and given characteristic of summed data, appropriate full adder cells can be chosen to the final design of low-power data oriented adder. In specific case, cells which are made in different techniques can be used in multi-bit adder. A few examples are shown at the end of the paper.     

Computational spectroscopy and DFT investigations into nitrogen and oxygen bond breaking and bond making processes in model deNOx and deN2O reactions

Molecular DFT modeling combined with computational spectroscopy (EPR and IR) were applied for analysis of the NO bond breaking and NN and OO bond making in the context of deNO_x and deN₂O reactions. Interaction of NO, N₂O and NO₂ with cationic (transition metals) and anionic (surface O²⁻ ions) centers was explored at the molecular level. The elementary events such as reactant coordination, charge and spin redistributions, which are principal molecular constraints for efficient decomposition of the nitrogen oxides (N₂O and NO) were discussed. Particular attention was paid to dynamics of the NO bond cleavage in N₂O molecule through electron and oxygen atom transfer routes, evaluation of preferable coordination modes of NO, discrimination between inner- and outer-sphere mechanism of NN bond formation, and the influence of spin and electronic redistribution on the reaction course (spin catalysis). Owing to their simplicity and well known surface chemistry, model systems selected for studies of such processes include MoO_x/SiO₂, MgO and ZSM-5 zeolite exchanged with various transition metal ions (TMI) of different electron configuration and spin multiplicity: Mo⁵⁺ (d¹, ²D) Fe³⁺, Mn²⁺, Cr⁺ (d⁵, ⁶S), Fe²⁺ (d⁶, ⁵D), Co²⁺ (d⁷, ⁴F), Ni²⁺ (d⁸, ³F), Cu²⁺ (d⁹, ²D) and Cu⁺, Zn²⁺ (d¹⁰, ¹S).     

Modeling the elastomeric properties of stereoregular polypropylenes in nanocomposites with spherical fillers

The elastomeric properties of networks of stereoregular polypropylenes (PP) filled with spherical nanoparticles have been modeled in an attempt to obtain better insights into elastomer reinforcement. The polymers were either isotactic or syndiotactic PP in the amorphous state, and the simulations were based on rotational isomeric state (RIS) theory combined with the largest eigenvalue method for deriving conditional bond probabilities. Monte Carlo simulations gave distributions of the end-to-end distance of these chains in the presence of the particles, and these were used in the Mark-Curro theoretical approach to calculate values of the normalized stress, and the reduced stress (shear modulus) under uniaxial stretching. The simulations were calculated for PP chains having 100-200 skeletal bonds, for several temperatures from 481 to 650 K, and for varying filler particle sizes (up to 100 Å). The presence of the filler nanoparticles was found to influence chain conformations, frequently leading to significant chain extensions, which significantly affect the elastomeric properties of the nanocomposites.     

Large-scale synthesis and characterization of carbon spheres prepared by direct pyrolysis of hydrocarbons

Large-scale production of pure carbon spheres, with diameters from 50 nm to 1 μm, has been achieved via direct pyrolysis of a wide range of hydrocarbons, including styrene, toluene, benzene, hexane, cyclohexane and ethene, in the absence of catalyst. Specific systematic studies using styrene as the feedstock indicate that the sizes of the resulting of carbon nanospheres can be controlled quite well by adjusting the experimental conditions. The resulting materials have been fully characterized using SEM, TEM, AFM, HRTEM, EDX, elemental analysis, density measurement, XPS, FTIR, XRD, Raman, and TGA. The results show that the spheres, which are 99% carbon, consist of concentric incompletely closed graphitic shells. The dangling bonds on the edges of the shells result in high chemical reactivity.     

Long chain polyunsaturated fatty acids in smoked Atlantic mackerel and Baltic sprats

Atlantic mackerel and Baltic sprats are rich sources of n − 3 long chain polyunsaturated fatty acids (LC PUFA). Literature data point to an influence of the properties of the raw material, storage conditions, and processing parameters of hot- and cold-smoking on the stability of these acids. The effects of industrial smoking in an automatic smokehouse in controlled, mild conditions at core temperature below 60 °C, as well as of cold storage, on the fatty acids (FA) in mackerel and sprats have been investigated. The FA were determined by gas chromatography (GC) according to the AOCS Ce 1b-89 method, in lipids extracted from the meat of several batches of defrosted and smoked fish early after smoking and during storage at 2 °C for up to 2 weeks. The contents of eicosapentaenoic acid C20:5 n − 3 (EPA) and docosahexaenoic acid C22:6 n − 3 (DHA) in different assortments of smoked mackerel meat were from 50 to 55 and from 67 to 100 mg/g of lipids, respectively while, in hot-smoked sprats, they were from 48 to 68 and from 73 to 128 mg/g of lipids. The results show that the variability of the FA composition of the frozen raw material was larger than the changes induced by smoking or by storage within the period of high quality life of the smoked product.     

Effects of milling conditions on hydrogen storage properties of graphite

Two milling modes (shearing and impact) were applied to investigate the hydrogen storage properties of graphite. It was found that the shearing mode leads to 0.613 wt.% hydrogen absorbed in graphite, while impact mode leads to 2.718 wt.%. X-ray diffraction was used to investigate the structure of the as-milled and subsequent annealed samples. Differential scanning calorimetry was used to study thermally induced transformations in the as-milled samples. Infrared spectrometry was carried out to investigate the interaction between carbon and hydrogen atoms. Results are compared and discussed in conjunction with Laser desorption time-of-flight mass spectrometry results obtained earlier.     

CdS Nanoplates Modification as a Platform for Synthesis of Blue-Emitting Nanoparticles

In this paper, the study of surface modification of two-dimensional (2D), non-luminescent CdS nanoplates (NPLs) by thiol-containing ligands is presented. We show that a process of twophase transfers with appropriate ligand exchange transforms non-luminescent NPLs into spherical CdS nanoparticles (NPs) exhibiting a blue photoluminescence with exceptionally high quantum yield ~90%. In the process, transfer from inorganic solvent to water is performed, with appropriately selected ligand molecules and pH values (forward phase transfer), which produces NPs with modified size and shape. Then, in reverse phase transfer, NPs are transferred back to toluene due to surface modification by combined Cd (OL)₂ and Cd (Ac)₂. As a result, spherical NPs are formed (average diameter between 4 and 6 nm) with PL QY as high as 90%. This is unique for core only CdS NPs without inorganic shell.