Polymer science

In recent days, Polymer is very useful and important material for its unique properties and applications. A Polymer is a large molecule or macromolecule which is composed of several repeating subunits, called monomer. Polymers are classified depending on several parameters like chemical structure, polymeric structure, arrangement of monomer, tacticity etc. It has several applications in the field of industry, science and medical. Several properties of polymers can be tuned by embedding different materials with it. Among them graphene and carbon nanotube are most desirable material. Graphene is the latest discovery belonging to the group of carbon allotropes and a versatile material in nanotechnogy due to its unique electronic, optical and mechanical properties. It is a two dimensional material, a Single layer of graphite. It has several properties such as conductive, flexible, highly strong and transparent. On the other side, carbon nanotube is most valuable material in several applications for its unique electronic, mechanical and optical properties. Like graphene and graphite, it is also a carbon based material. Due to its high surface to volume ratio, even a low content of nanotube in polymer matrix can change the interphase or interface region which changes their properties significantly. The electromagnetism and microwave absorption properties of several material can be modified by incorporation of desired value of carbon nanotube with that material. Dielectric properties of several polymer materials also can be modified by embedding carbon nanotube with it. It is also acted as a filler material for introducing Piezoelectricity in some Polymer material. Here properties of polymer, graphene and carbon nanotube has been discussed in brief. Synthesis and applications of these three materials are also the key focus of this paper.

In this paper, a study on the batch processing and characterization of microcellular foamed high-density polyethylene (HDPE/iPP) blends is reported. A microcellular plastic is a foamed polymer with a cell density greater than 109 cells/cm3 and fully grown cells smaller than 10 µm. Recent studies have shown that the morphology and crystallinity of semicrystalline polymers have a great influence on the solubility and diffusivity of the blowing agent and on the cellular structure of the resulting foam in microcellular batch processing. In this research, blends of HDPE and iPP were used to produce materials with variety of crystalline and phase morphologies to enhance the subsequent microcellular foaming. It was possible to produce much finer and more uniform foams with the blends than with neat HDPE and iPP. Moreover, the mechanical properties and in particular the impact strength of the blends were significantly improved by foaming.
(citation # 293)

Standard fused filament fabrication (FFF)-based 3-D printers fabricate parts from thermopolymers, such as polylactic acid (PLA). A new range of metal based PLA composites are available providing a novel range of potential engineering materials for such 3-D printers. Currently, limited material data, specifically thermal property characterization is available on these composites. As a result, the application of these materials into functional engineered systems is not possible. This study aims to fill the knowledge gap by quantifying the thermal properties of copperFill, bronzeFill, magnetic iron PLA, and stainless steel PLA composites and provide insight into the technical considerations of FFF composite 3-D printing. Specifically, in this study the correlation of the composite microstructure and printing parameters are explored and the results of thermal conductivity analysis as a function of printed matrix properties are provided. Considering the relative deviation from the filament raw bulk analysis, the results show the printing operation significantly impacts the resultant component density. Experimentally collected thermal conductivity values, however, do not correlate to the theoretical models in the literature and more rigorous quantitative exercises are required to determine true percent porosity to accurately model the effect of air pore volume fraction on thermal conductivity. Despite this limitation, the thermal conductivity values provided can be used to engineer thermal conductivity into 3-D printed parts with these PLA-based composites. Finally, several high-value applications of such 3-D printed materials that look metallic, but have low thermal conductivity are reviewed.

In order to assist researchers explore the full potential of distributed recycling of post-consumer polymer waste, this article describes a recyclebot, which is a waste plastic extruder capable of making commercial quality 3-D printing filament. The device design takes advantage of both the open source hardware methodology and the paradigm developed by the open source self-replicating rapid prototyper (RepRap) 3-D printer community. Specifically, this paper describes the design, fabrication and operation of a RepRapable Recyclebot, which refers to the Recyclebot's ability to provide the filament needed to largely replicate the parts for the Recyclebot on any type of RepRap 3-D printer. The device costs less than $700 in mate rials and can be fabricated in about 24 h. Filament is produced at 0.4 kg/h using 0.24 kWh/kg with a diameter ±4.6%. Thus, filament can be manufactured from commercial pellets for <22% of commercial filament costs. In addition, it can fabricate recycled waste plastic into filament for 2.5 cents/kg, which is <1000X commercial filament costs. The system can fabricate filament from polymers with extrusion temperatures <250 °C and is thus capable of manufacturing custom filament over a wide range of thermopolymers and composites for material science studies of new materials and recyclability studies, as well as research on novel applications of fused filament based 3-D printing.

In this study, the thermal, dynamic-mechanical and tribological behavior of nanocomposites of a photocurable epoxy-acrylate resin and multiwalled carbon nanotubes (MWCNT) are investigated. A route consisting of a combination of sonication, mechanical and magnetic stirring is used to disperse 0.25-0.75 wt. (%) MWCNT into the resin. Two photocuring cycles using 12 hours and 24 hours of UV-A radiation are studied. The storage modulus, the loss modulus and the tan delta are obtained by dynamic mechanical analysis. Thermal stability is investigated by thermogravimetry, morphology by transmission electronic microscopy (TEM) and tribological performance using a pin-on-disk apparatus. The results indicate an increase in stiffness and higher ability to dissipate energy, as well as a shift in the glass transition temperature for the nanocomposites. The addition of nanofillers also decreased friction coefficient and wear rate of the nanocomposites but did not change the observed wear mechanisms.

The response of a H-PDLC device is improved by means of a two-step method. First, component optimization-initiator system, crosslinker, and cosolvent-enables the diffraction efficiency of the hologram to be maximized. Second, the use of N-methyl-2pyrrolidone in combination with N-vinyl-2-pyrrolidone prevents the overmodulation in photopolymers containing ethyl eosin.

Boron doped and undoped Poly(vinyl) alcohol/Zirconium-yttrium acetate (PVA/Zr-Y) nanofibers were prepared by electrospinning using PVA as a precursor. The effect of boron doping was investigated in terms of solution properties, morphological changes and thermal properties. The effect of boron doping on calcined yttria stabilized zirconia (YSZ) fibers were evaluated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy analysis. XRD
analysis revealed varying amounts of monoclinic and tetragonal zirconia present in the undoped fibers calcined at 800oC. The average crystallite sizes of the undoped YSZ were increased from 9.28 to 22.79 nm with calcining temperature increasing from 250 to 800 °C. The crystallite size was enhanced with boron doping. The systematic evolution of morphological features in the spun and the processed fibers were employed by scanning electron microscopy.

We approach the problem of coil−globule transition dynamics numerically by Brownian dynamics simulations. This method allows us to study the behavior of polymer chains of varying stiffness and the effects of bending stiffness on chain morphology during the process of coil− globule collapse, imitating globule formation in poor solvent conditions. We record and analyze a three-stage process of globule formation for flexible chains: (1) nucleation, (2) coalescence of nuclei, and (3) collapsed globule formation. Stiffer chains undergo similar formation stages; however, the "raindrops" formed by these chains are elongated (unlike spherical structures formed by flexible chains) and exhibit regular packing of chains into antiparallel hairpin structures. In order to assess the transition dynamics quantitatively, polymer chain configurations were analyzed by generating contact maps and contact frequency histograms for all given configurations. These clusters are initial-configuration-dependent, and their growth and intercluster contacts have direct analogy with the process of raindrop coalescence.

Advanced modulation formats can enable >40 Gb/s data rates in waveguide-based optical interconnects without the need for high-specification optoelectronic components. Record 56Gb/s PAM-4 data transmission is demonstrated over a 1 m-long multimode polymer waveguide.

In this study, the mechanical and chemical properties of a series of sulfonated poly(styrene-isobutylene-styrene) (SIBS) block copolymers were evaluated using a combination of nanoindentation, dynamic mechanical analysis (DMA), elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR), water absorption, and small angle X-ray scattering studies (SAXS). The materials properties were characterized as a function of the sulfonation percent in the block copolymers, as well as a result of the counterion substitution with Mg 21 , Ca 21 , and Ba 21 . Nanoindentation studies revealed that the elastic modulus (E) and hardness (H) increase with sulfonation up to a certain level, at which point, the effect of water content further hinders any mechanical reinforcement. The incorporation of counter-ions increases E and H, but the results are dependent upon the size of the counter-ion. DMA results showed that the polymer maintained the glass transition temperature (T g ) of the polyisobutylene (PIB) segment (260 C) regardless of the sulfonation level or counter-ion substituted. However, both the shoulder of the PIB T g (230 C), which was probably caused by a Rouse-type motion, as well as the T g of polystyrene (105 C) disappeared upon sulfonation. Counter-ion substitution increased the storage modulus of the rubbery plateau, which is indicative of a stronger and more thermally stable crosslinked complex formation. Additional unique relaxations were observed with the counter-ions, and could be attributed to the stretching/rotation of the SAO bond and the interaction of the cations with the oxygen in the sulfonic group. FTIR results also revealed a unique shifting of the asymmetric SAO band when counter-ions were added.

This study was conducted to detect and estimate some toxic metals present in branded (BS) and non branded
(NS) condiments and spices widely used in Punjab, Pakistan. Flame atomic absorption spectroscopy was applied
to determine the concentration of Cadmium (Cd), Copper (Cu), Nickel (Ni), Lead (Pb) and Zinc (Zn) in the
studied samples where as the UV/Vis spectroscopy was used for evaluating the antioxidant potential of samples
via 1, 1- diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay. On comparing the standards set by
FAO/WHO, concentration of Cd and Ni was found higher in many of the samples. Minimum risk level (MRL) was
also calculated by assessing the daily intake of samples and t test was applied using SPSS 13.0. Higher metal
concentration in studied samples correlates with the metal pollution in soil, air and water, while higher
antioxidant potential of NS substantiates the medicinal importance of condiments and spices.

The cationic polymerization of N-tert-butyl aziridine (TBA) can be conducted in such a way that the rate of termination is much slower than the rate of propagation, thus permitting preparation of a corresponding polymer which is "temporarily living." Reactions of N-methyl-N-tert -butyl aziridinium triflate (which is the model for the active species of the living polymer) with different nucleophiles show that, a t room temperature, the aziridinium ring reacts almost instantaneously with nucleophiles to form the corresponding ring-opened product. Analogous reactions with the aziridinium end group of living poly-TBA lead to polymers with varying end groups such as hydroxy, ester, primary, secondary or tertiary amino, halogen, and others. End group analysis by means of 360-MHz 'H-NMR nuclear magnetic resonance spectroscopy showed that the concentration of the end groups was in all cases equal to the concentration of the methyl head group, originating from the initiation reaction, if the terminating nucleophile was added five minutes after initiation (at 15OC). Under these conditions the polymerization is quantitative for initiator concentrations down to 0.01 mol L-1.

Numerous non-ionic thermally responsive homopolymers phase separate from their aqueous solutions upon heating. Far fewer neutral homopolymers are known to phase separate upon cooling. A systematic compilation of the polymers reported to exhibit thermoresponsive behaviour is presented in this review, including N-substituted poly[(meth)acrylamide]s, poly(N-vinylamide)s, poly(oxazoline)s, protein-related polymers, poly(ether)s, polymers based on amphiphilic balance, and elastin-like synthetic polymers. Basic properties of aqueous solutions of these polymers are briefly described.

High-density polyethylene filaments prepared by a solid-state deformation in an Instron capillary rheometer show unusually high crystal orientation, chain extension, axial modulus, and ultimate tensile strength. The Young's modulus and ultimate tensile strength have been determined from stress-strain curves. Gripping of this high modulus polyethylene has been a problem heretofore, but the measurement of ultimate tensile strength has now been made feasible by a special gripping procedure. Tensile moduli show an increase with sample preparation temperature and pressure. Values as high as 6.7 X 1 0 ' ' dyne/cm2 are obtained from samples extruded a t 134°C and 2400 atm and tested a t a strain rate of 3.3 X 10-4 sec-1. The effect of strain rate and frequency on modulus has also been evaluated by a combination of stressstrain data and dynamic tension plus sonic measurements over nine decades of time.

In this research the variation of mechanical and rheological properties of the composite as a function of different processing parameters and ethylene propylene diene monomer (EPDM) rubber content was studied. The optimum amount of dicumyl peroxide (DCP) to achieve the highest percentage of grafting of maleic anhydride to EPDM was obtained by Fourier transform infrared (FTIR) spectroscopy. In general, immiscibility between nylon 66 and EPDM, and their high interfacial tension makes their blending difficult. Maleic anhydride was grafted to EPDM to reduce interfacial tension between two phases. Also the blends were prepared at highest possible speed of mixing (screw speed in extrusion) and lowest temperature to reach a well mixed sample which can be seen in scanning electron microscopy (SEM) images and impact strength results. Dynamic mechanical thermal analysis (DMTA) tests were conducted to evaluate the miscibility of the components and to measure the glass transition temperature of...

Biocompatible poly(vinyl alcohol)/poly (vinylpyrrolidone) iodine/poly(ethylene glycol) fibers containing (hydroxypropyl)methyl cellulose (HPMC) and aloe vera were successfully prepared by electrospinning their aqueous solution. Aloe vera which is known to be effective in the treatment of various wounds was added to the polymer solution. HPMC was added to the system as the water retention agent. The hybrid fiber mats were subjected to detailed analysis using a differential scanning calorimeter, a scanning electron microscope (SEM), and a Fourier transform infrared spectrometer. Images obtained from the SEM showed that the polymer fibers were linear, homogenous, and contained no beading. The fiber diameters ranged between 100 and 900 nm. It was seen that the electrospun mats obtained could potentially be used as a material for dressing wounds. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The annealing effect was studied on PMMA/PET immiscible polymer blends. Composite ratios of 0/100,25/75, 50/50, 70/30, 80/20 and 100/0 wt % of PMMA/PET were prepared by novel injection molding methods. Morphological interactions of these blends were investigated through thermal analysis using DMA and DSC. The samples were subject to testing in their as molded form and after annealing. Thermal analysis revealed crystallite growth effect on the storage modulus and increased Tg for annealed samples.

This work deals with design and development of false ceiling board from polyvinyl-acetate (PVAc) composite reinforced with false banana fibres and filled with sawdust. The aim was to develop a light weight and good strength performance false ceiling board using raw materials that are fully biodegradable including sawdust, thus solving the problem of its disposal. The false banana fibres were characterized for its tensile strength, elongation, and moisture content since these parameters affect the composite properties. Hand lay-up method combined with compression molding followed by curing was utilised in the manufacture of the false ceiling composites. The optimum proportions of the raw materials were identified using central composite design software, and the results were 40% sawdust, 40% binder (PVAc), and 20% fibres. The mechanical properties of the developed composite board were evaluated in terms of its tensile strength, flexural strength, and compressive strength. In addition,...

We investigate the viscosity dependence on
concentration and molecular weight of semiflexible polyelectrolyte
sodium carboxymethylcellulose (NaCMC) in aqueous salt-free and
NaCl solutions. Combining new measurements and extensive
literature data, we establish relevant power laws and crossovers
over a wide range of degree of polymerization (N) as well as
polymer (c) and salt (cs) concentrations. In salt-free solution, the
overlap concentration shows the expected c* ∝ N−2 dependence,
and the entanglement crossover scales as ce ∝ N−0.6±0.3, in strong
disagreement with scaling theory for which ce ∝ c* is expected, but
matching the behavior found for flexible polyelectrolytes. A second crossover, to a steep concentration dependence for specific viscosity (ηsp ∝ c3.5±0.2), commonly assigned to the concentrated regime, is shown to follow c** ∝ N−0.6±0.2 (with c**/ce ≃ 6) which thus suggests instead a dynamic crossover, possibly related to entanglement. The scaling of c* and ce in 0.01 and 0.1 M NaCl shows neutral polymer in good solvent behavior, characteristic of highly screened polyelectrolyte solutions. This unified scaling picture enables the estimation of viscosity of ubiquitous NaCMC solutions as a function of N, c, and cs and establishes the behavior expected for a range of semiflexible polyelectrolyte solutions.

Spatial confinement in nanoporous media affects the structure, thermodynamics and mobility of molecular soft matter often markedly. This article reviews thermodynamic equilibrium phenomena, such as physisorption, capillary condensation, crystallisation, self-diffusion, and structural phase transitions as well as selected aspects of the emerging field of spatially confined, non-equilibrium physics, i.e. the rheology of liquids, capillarity-driven flow phenomena, and imbibition front broadening in nanoporous materials. The observations in the nanoscale systems are related to the corresponding bulk phenomenologies. The complexity of the confined molecular species is varied from simple building blocks, like noble gas atoms, normal alkanes and alcohols to liquid crystals, polymers, ionic liquids, proteins and water. Mostly, experiments with mesoporous solids of alumina, gold, carbon, silica, and silicon with pore diameters ranging from a few up to 50 nm are presented. The observed peculiarities of nanopore-confined condensed matter are also discussed with regard to applications.
A particular emphasis is put on texture formation upon crystallisation in nanoporous media, a topic both of high fundamental interest and of increasing nanotechnological importance, e.g. for the synthesis of organic/inorganic hybrid materials by melt infiltration, the usage of nanoporous solids in crystal nucleation or in template-assisted electrochemical deposition of nano structures.

The aim of this work was to characterize the lipids extracted from pangus fish (P. pangasius) available in the local market in Bangladesh. The pangus fish (P. pangasius) was collected from the local market of Dhaka. Lipids were isolated from both the fresh as well as cooked fish by solvent extraction method. The physical characteristics of lipid of (P. pangasius) were analyzed and also found that the percent of lipid content of fresh pangus fish (pangasius pangasius) was 9.126% and lipid content of cooked panagus fish (pangasius pangasius) was 6.334% and specific gravity of the lipid was 0.87 at 25°C. Furthermore, the chemical characteristics of lipid of (pangasius pangasius) were analyzed and also found that the saponification value, the saponification equivalent, the ester value, the iodine value, the peroxide value and the acid value of pangus fish were 179.88, 311.87, 177.95, 53.93, 43.63 and 1.93 respectively. Besides this, the percent of free fatty acid was 0.97%. However, The Pangus fishes are also played an important role in our daily dietary routine. The lipids from pangus contain polyunsaturated fatty acids (PUFA), which play important roles in cardiovascular system or reduce the risk of heart attract. The daily consumption of fish oils (omega-3 polyunsaturated fatty acids) can significantly lower blood pressure in people suffering from hypertension. The benefit of the fish oils is comparable to that obtainable by sodium reduction and weight loss. Fish consumption also helps to prevent prostate cancer. So, its very important to isolate and characterize the lipid of pangus fish (P. pangasius).

The study is aimed at assessing how the date palm wood fibers (DPWF) can be used for the removal of heavy metals from water. The study involved examination of the radical polymerization and graft polymerization parameters such as reaction period, reaction time, monomer volume, amount of the catalyst, and concentration of initiator to obtain the maximum yield of graft polymerization. Fiber and copolymer were characterized using SEM and FT-IR spectroscopy to ensure the completion of polymerization. Hydroxylamine hydrochloride was used for treating the grafted copolymers for the preparation of polyamidoxime chelating resin, which was then examined for removing the heavy metal ions. Different resin dosages, contact time, and initial concentrations were used, and the batch technique experiment was utilized. The study also applied the Langmuir and Freundlich isotherm model, and Langmuir was found to be better. The absorption ability was found to be better for polyamidoxime resin for metal...

Neutral or charged polymers that are densely end-grafted to surfaces form brushlike structures and are highly stretched under good-solvent conditions. We discuss and compare relevant results from scaling models, self-consistent-field methods and MD simulation techniques and concentrate on the conceptual simple case of planar substrates. For neutral polymers the main quantity of interest is the brush height and the polymer density profile, which can be well predicted from self-consistent calculations and simulations. Charged polymers (polyelectrolytes) are of practical importance since they are soluble in water. Counterion degrees of freedom determine the brush behavior in a decisive way and lead to a strong and non-linear swelling of the brush.

“Wear of Polymers and Composites” is basically prepared to be used by senior and graduate students of tribology; yet, the author hops the current work be of interest to a larger pool of readership. The book, therefore, introduces fundamentals of polymer tribology and sliding mechanics. It establishes a link between the load parameters and wear response, and shows how they are important in determining the mechanism of fatigue wear. Furthermore, a new approach to explore the effect of surface defects on the wear behaviour of polymers is introduced. On the other hand, it discusses the tribological characteristics of externally and internally lubricated polymers. Wear of composite materials is also carefully discussed in the light of many publications. Different methods for polymer wear evaluation are described in terms of tribometers configurations, controlled and measured parameters including procedures recommended in testing wear of polymeric materials. Fundamentals and capabilities of different well-known methods used in predicting wear of polymers are presented. In particular, an intelligent algorithm, in the form of Artificial Neural Network has been introduced to map the relationship between wear rate, applied loads, sliding conditions, and number of surface cracks.
Overall, the book extends a summary of valuable pioneer and up-to-date publications established by a number of research workers in the field of polymer tribology. At the end of each chapter, relevant important references are presented in order to build a useful index for future needs.  Hopefully, this book provides a comprehensive discussion and fair knowledge of the present understanding of wear of polymers and their composites.

In many applications, polymer materials undergo a large variety of mechanical loading conditions, wherein the influences of temperature and strain rate are of prime importance. Mahieux and Reifsnider [Mahieux CA, Reifsnider KL. Polymer 2001;42:3281. [19]] have proposed a statistical model to describe the stiffness variation of polymers over a wide range of temperatures. However, this model does not consider any frequency/strain rate dependence of the stiffness modulus. Starting from this consideration, we propose here to transform this latter model into a robust physically based model for the prediction of the stiffness modulus for a wide range of temperatures and frequencies/strain rates. This new formulation has been successfully validated for two amorphous polymers, polymethylmethacrylate (PMMA) and polycarbonate (PC), using dynamic mechanical analysis and uniaxial compression testing. Good agreement has been found between theory and experiment for the non-linear behavior of the initial Young's modulus, at the very high strain rates.

Besides piloted ignition, autoignition is also an important aspect to real fire development as combustible materials may be ignited without independent flame. Fire behaviors of non-charring and charring polymers were then investigated in a cone calorimeter under autoignition conditions. Fire risk of non-charring polymers are higher than those of charring polymers because of high heat release, and the increase of heat release rate is much obvious with a higher heat flux or thickness. Charring polymers seem to have a higher CO yield, while non-charring polymers have a higher CO2 yield. Ignition methods have influences to combustion efficiency of non-charring polymers as effective heat of combustion under autoignition are observed lower than those reference data under piloted ignition conditions. Its influences to charring polymers are not obvious. Both CO and CO2 yields under flaming combustion are higher than those under non-flaming combustion, but mass percent of carbon seem to has limited effect. Experimental data in this study can provide a guidance to fire risk evaluation of non-charring and charring polymers.

Amination of vinylbenzyl chloride-divinylbenzene (VBC-DVB) copolymers is an effective method for preparation of ionexchange resins. Conventionally, the starting polymer is produced by chloromethylation of a styrene-divinylbenzene copolymer that utilizes chloromethyl methyl ether, a known carcinogen. An alterative approach is to copolymerize vinylbenzyl chloride with divinylbenzene to generate the necessary VBC-DVB. This method provides precise control over the density of the ionexchange groups. The regiochemistry of the vinylbenzyl chloride methods was realized using solvent-ion exchange groups. In this investigation, an improved solvent system was found for the preparation of anion exchange resins by the vinylbenzyl chloride route. The effectiveness of amination of the intermediate VBC-DVB polymers with a variety of trimethylamine reagents was investigated, and ethanolic trimethylamine produced the highest degree of amination. These resulting ion-exchange polymers were characterized by a variety of techniques such as analytical titrations, nitrogen analysis, Fourier transform infrared spectroscopy and thermal gravimetric analysis. Testing of these copolymers for breakthrough was performed. The results indicate that these anion exchangers have a meaningful increase in thermal stability over commercial anionic exchange beads.

We present results of the molecular dynamics simulations of salt solutions of polyelectrolyte chains with number of monomers N = 300. Polyelectrolyte solutions are modeled as an ensemble of beadÀspring chains of charged Lennard-Jones particles with explicit counterions and salt ions. Our simulations show that in dilute and semidilute polyelectrolyte solutions the electrostatic induced chain persistence length scales with the solution ionic strength as I À1/2 . This dependence of the chain persistence length is due to counterion condensation on the polymer backbone. In dilute polyelectrolyte solutions the chain size decreases with increasing the salt concentration as R µ I À1/5 . This is in agreement with the scaling of the chain persistence length on the solution ionic strength, l p µ I À1/2 . In semidilute solution regime at low salt concentrations the chain size decreases with increasing polymer concentration, R µ c p À1/4 , while at high salt concentrations we observed a weaker dependence of the chain size on the solution ionic strength, R µ I À1/8 . Our simulations also confirmed that the peak position in the polymer scattering function scales with the polymer concentration in dilute polyelectrolyte solutions as c p 1/3 . In semidilute polyelectrolyte solutions at low salt concentrations the location of the peak in the scattering function shifts toward the large values of q* µ c p 1/2 while at high salt concentrations the peak location depends on the solution ionic strength as I À1/4 . Analysis of the simulation data throughout the studied salt and polymer concentration ranges shows that there exist general scaling relations between multiple quantities X(I) in salt solutions and corresponding quantities X(I 0 ) in salt-free solutions, X(I) = X(I 0 )(I/I 0 ) β . The exponent β = À1/2 for chain persistence length l p , β = 1/4 for solution correlation length ξ, and β = À1/5 and β = À1/8 for chain size R in dilute and semidilute solution regimes, respectively.

Nanocrystalline aromatic polyimide films were prepared by imidization processes from Poly (amic acid) (PAA) of poly (pyromellitic dianhydride-co-4,4'-oxydianiline) (PM). The crystal structure, particle size, chemical structure, morphology, thermal stability, weight loss and optical properties were studied by using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microscope (SEM), thermogravimetry / differential thermal analysis (TG/DTA) and UV-2300 spectrophotometer respectively. The results revealed the preparation of fully crystalline polyimide with new values of high thermal stability, high energy band gap, high optical and electrical conductivity and low dielectric value. The obtained results suggested the suitability of the prepared polyimide for microelectronic applications.

The natural fiber / polylactic acid (PLLA) composites were prepared with Alfa-Alfa fibers as reinforcement and PLLA as matrix. The composite materials were obtained through the simple mechanical compounding of PLLA matrix with various fibers contents up to 40 wt %, followed by drying, kneading and hot pressing into sheets and were characterized by TGA, DSC, FTIR spectroscopy, SEM and water uptake. Composites prepared from several percentages of PLLA and Alfa-Alfa fibers represent a new category of environmentally safe materials for applications to explore to reduce the raw materials cost of PLLA due to Alfa-Alfa fibers is an abundance local plant in Algeria, the increasing utilization of renewable resources will be one of the strong drivers for sustainable products.

In this research, the dependence of glass transition temperature (Tg) and melting point (Tm) on the specific cohesive energy was studied for various non-& low polar and polar polymers. It was found that the studied thermo-physical features of polymers correlate much better with the volume cohesive energy (Ev) than with the molar cohesive energy (Em). When using polymers belonging to a certain group, only non-& low polar or only polar, a linear dependence Tg = f(Ev) was obtained with relative small deviation. However, when studying this dependence for all studied polymers of different groups, the linear correlation is highly disturbed. This disturbance can be explained by the fact that the concept of cohesive energy was developed only for non-& low polar polymers. In order to adapt this theory to polar polymers, it is necessary to introduce a special correction to eliminate the contribution associated with polar interactions and hydrogen bonds to the cohesive energy. After calculating the corrected volume cohesive energy (Ev,c) the linear regression equations, Tx = aEv,c + b, with high correlation coefficients were derived for all polymers of different classes,  where Tx is Tg or Tm; and a, b are coefficients.  The relationship between Tm and Tg was also obtained.

This article is the first of a series devoted to various aspects of exchange reactions in molten bis-phenol-A polycarbonate-poly(buty1ene terephthalate) mixtures. The statistical aspects of exchange reactions between two polycondensates of different chemical structure are ...

Archaeologists have defined past civilizations by the materials that predominated in their societies. The evolution of the use of these materials—stone, bronze, and iron—enabled significant and concurrent changes in the cultures that mastered them. The ability to develop, shape, and use these substances has been one of the measures of a civilization’s capabilities, so much so that we now identify them as the Stone Age, Bronze Age, and Iron Age. Historians have also associated the comings and goings of other, more recent, periods with the prevalence of particular types of materials. Brooke Hindle identified America’s pre-Civil War period as its “Wooden Age,” and he characterized the society as one that was “pervasively conditioned by wood.”  This dependence slowly subsided after 1850 and was replaced in part by metals and the corresponding products of industrialization. 

There was one common characteristic that defined these former ages. The materials in question all came from nature. However, at the dawning of the twentieth century, scientists and engineers began to master a new class of materials called polymers. Although some of these occurred in nature (like spider silk or natural rubber), other polymers were made in laboratories and factories and had properties superior to those existing in the natural world. Over the past century, the ability to create and manipulate natural and synthetic polymers has resulted in a revolutionary transformation of our own material culture. One hundred years ago, the artifacts of everyday life were made of wood, stone, textiles, glass, or metal. This is no longer the case, as polymers now often replace these substances and enhance the quality of the products made with them. The result is that the emergence of polymers has become one of the most significant scientific and engineering achievements in the past century. The father of polymer education, Herman Mark, suggested in 1982 that society was “coming to an age in polymer science.”  In 1976, an author in Chemical Week simply christened this the “polymer age.” 

Although it is often difficult and arbitrary to pinpoint dates of when “ages” like this begin or end, it might be argued that the Polymer Age had its beginnings in the late 1970s. While the earliest polymer discoveries took place in the 1920s, it was not until a half century later that the consumption of synthetic polymer materials overtook metals in the United States.  In 1973, the United States produced the same amount of synthetic polymers as it did steel—15.5 million cubic meters.  In 1976, the United States consumed more plastics than metal on a per volume basis for the first time, and plastics became the most consumed synthetic material in the country.  The rapidity with which polymers became so prevalent is an astonishing story.  In the 1930s, the United States produced virtually no polymers. Forty years later, it produced twenty-three million metric tons. In 1900, only a handful of chemists concerned themselves with materials that would later be known as “polymers,” and none knew what they truly were. Today, half of all chemists work with them in one form or another.  Statistics like these are strong indicators that a new material age has begun.

Cultural indicators also point to a sea change since the 1970s in how we value polymer or plastic products. Consider how the idea of plastics was interpreted by Hollywood and pop music stars in the 1960s. In the 1967 film The Graduate, Benjamin Braddock (played by Dustin Hoffman) was told by one of his father’s colleagues that the future lay in one word—“plastics.” To Braddock, this suggestion conveyed a sense of conformity, selling-out, boredom, and cheap imitation. The audience of the 1960s easily understood how the mere suggestion of “plastics” symbolized the dull life Braddock would eagerly try to escape. It reminded viewers of a similar song released that same year by pop duo Sonny and Cher, who sang about the “plastic man.” Their lyrics warned about a man not to be trusted, like someone selling cars on television. He was working day and night, not disclosing he was recruiting everyone for his commercial desires. They sang, “He’s doing everyone he can . . . Plastic Man.” The Beatles Rubber Soul album, released in the mid 1960s, further exemplified the negative connotation of another polymer term.

Significantly, an important cultural shift has occurred since then. By the 1970s, the image of plastics began to lose its substandard connotations and instead conveyed the belief that polymers represented a new and potentially better way of life.  Symbolizing this phenomenon was an unlikely musician who recognized the emergence of polymers as a new dominant material reality. From 1976 to 1979, legendary punk rock singer Marion Elliot adopted the pseudonym “Poly Styrene” to make a statement about the significance of the changes she saw happening around her.  She created a character who idealized the glamour of plastic and echoed a youth movement that would eventually come to embrace a new polymer world. She chose the name Poly Styrene for this persona as she herself became infatuated with “plastic” society. One of her songs, a top-thirty hit in London, was called “The Day the World Turned Day-Glo;” in its lyrics she observed that polymers were over taking society.

This song paralleled the dawn of a new material era—a Polymer Age.

While it is now nearly impossible to go about a normal day without interacting in significant ways with polymers, they have ironically become something of a unseen substance. As Steve Love, Akron journalist and coauthor of Wheels of Fortune, wrote, “Polymers have an identity problem. They are, comparatively speaking, invisible . . . .” 

This invisibility needs to change.

After the process of vulcanization was established in 1839, natural rubber quickly became one of the vital material components of society. The dependence upon it grew so great that during World War II, when the United States realized that it could be easily cut off from the world’s sources of natural rubber, its entire military operation nearly ground to a halt. Without rubber, the greatest military nation in the world would be quickly rendered powerless. The quest to develop synthetic rubber during World War II led in part to the predominance of the synthetic polymer materials that surround us almost invisibly. We are living in the midst of a Polymer Age, and few of us realize it, or even know what this means. As Jeffrey L. Meikle argued in his book American Plastic, “most people ignored . . . that the United States entered the ‘Plastics Age’ in 1979 when the annual volume of plastic exceeded that of steel.”  We can no longer ignore its presence in our lives, and the history of its emergence requires telling.

With some notable exceptions, there is a disproportionate relationship between the significance of polymers and the number of historical, scientific, and popular discussions that analyze their development.

Compared to the number of scholarly studies on other scientific and technological developments like computers, automobiles, and electricity, historians have also been surprisingly quiet on the subject of polymers.  The retrospective studies that do exist were largely written by former polymer practitioners. These “insider” stories include memoirs, review articles, and autobiographies. Ffor the most part, biographical treatments have far superseded the institutional perspective of the history of polymers.

There is no question that institutions have been essential to the emergence of the Polymer Age, and their historical neglect is an oversight that requires attention. An institutional perspective can help us understand the intellectual and social foundations from which polymer science and engineering developed. Much as an individual’s biography yields important insights into a particular historical context, so, too, does an institutional focus reveal key perspectives. The Polymer Age arose through an international network of researchers working within large academic, industrial, and governmental organizations that over time developed the scientific and engineering skills to create and commercialize polymers. Among these institutions are academic programs (including the University of Akron, the University of Massachusetts-Amherst, Case Western Reserve University, California Institute of Technology, the University of Southern Mississippi, and Brooklyn Polytechnic), industrial organizations (including IG Farben, DuPont, Dow Chemical, Goodyear, Bridgestone/Firestone, B. F. Goodrich, and General Tire), and various government agencies and scientific societies like the Rubber Division of the American Chemical Society.

It is beyond the scope of this book to present a sweeping account of the entire network of institutions responsible for the emergence of the Polymer Age over the past century. Instead, this book examines the story within the framework of one academic institution that has played the longest, and arguably the most influential, role in creating and shaping the Polymer Age—the University of Akron. This university has played a signal role in the emergence of the Polymer Age starting in 1909 when Charles Knight offered the world’s first complete course in rubber chemistry, marking the birth of a new academic discipline. This course has now evolved into an entire college—the College of Polymer Science and Polymer Engineering—which has been ranked for the last ten years as one of the top two academic institutions in the United States in the field.  An examination of the near century in between the foundation of the course and the flourishing of the college, demonstrates how these long polymer chains became chains of opportunity for an academic discipline, an economic region, and a university.

Radiation and chemical cross-linking of medical grade ultrahigh molecular weight polyethylene (UHMWPE) has recently been utilized in an effort to improve wear performance of total joint replacement components. However, reductions in mechanical properties with cross-linking are cause for concern regarding the use of cross-linked UHMWPE for high-stress applications such as in total knee replacement prostheses. In this study, the fracture behavior of radiation cross-linked UHMWPE was compared to that of uncross-linked UHMWPE. The Rice and Sorensen model that utilizes mechanical parameters obtained from uniaxial tensile and compact tension tests was used to calculate the steady state J-integral fracture toughness, J ss , for radiation cross-linked UHMWPE. J ss decreased monotonically with increase in radiation dose. UHMWPE exhibited tough, ductile tearing behavior with stable crack growth when it was cross-linked using a gamma radiation dose of 0-50 kGy. However, in cross-linked UHMWPE irradiated to a dose of 100 and 200 kGy, unstable fracture occurred spontaneously upon attaining the initial crack driving force, J 1c . This indicates that a high degree of cross-linking is less desirable for high-stress applications in orthopaedic implants. However, a substantial increase in J 1c , even at a low degree of cross-linking, suggests that a low degree of cross-linking may be beneficial for resistance to delamination and catastrophic failure, both of which require an initiation step for the fracture to propagate in the material. This mechanical test should, however, be considered along with fatigue tests and joint simulator testing before determination of an appropriate amount of cross-linking for total joint replacement prostheses that experience high stresses.

Corn fibers and luffa peels were evaluated for removing toxic heavy metal ions and dissolved organic dyes from water. Fresh peels were pretreated to remove all soluble components before using them for extraction studies. Presence of eOH and eCO 2 H functional groups on the surface of the peels and rough morphologies were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy investigations, respectively. Corn fibers and luffa peels showed maximum extraction effi-ciencies within the pH range of 4e10 and adsorption reached a steady state within 2e3 h. Prewashed corn fibers and luffa peals extracted 159 mg g À1 and 90 mg g À1 of alcian blue, 70 mg g À1 and 124 mg g À1 of methylene blue, 50 mg g À1 and 108 mg g À1 of neutral red as well as 35 mg g À1 and 40 mg g À1 of coomassie brilliant blue from water, respectively. Both materials did not show significant extraction affinity towards heavy metal ions such as Pb 2þ (1 mg g À1), Ni 2þ (4 mg g À1 for corn fiber and 12 mg g À1 for luffa peels), and chromate (3 mg g À1 for corn fibers and 6 mg g À1 for luffa peels) ions from water. The Langmuir and Freundlich isotherms were used to understand the adsorption process on the surface of the adsorbents. Langmuir isotherm model yielded the best fit for the data obtained in the study, indicating a monolayer adsorption of pollutants on the adsorbent surface. Both adsorbents can be regenerated at acidic pH and could be reused for up to five cycles without significant loss of efficiency. Our experimental results suggest that both natural materials are effective towards removing dissolved dyes from water.

Chloro penta amine cobalt(III) cloride [Co(NH3)5Cl]Cl2was prepared and then characterized by Fourier transform infrared spectroscopy and X-ray diffraction. The obtained results indicated the formation of orthorhombic [Co(NH3)5Cl]Cl2nanoparticles of ≈28.75 nm size. Polymeric films based on polyvinyl acetate (PVAc) doped with chloro penta amine cobalt(III) cloride [Co(NH3)5Cl]Cl2in different weight percent ratios were prepared using the solvent cast technique. The complexation of the additive with the polymer was confirmed by FTIR and SEM studies. The XRD pattern revealed that the amorphousicity of PVAc polymer matrix increased with raising the [Co(NH3)5Cl]Cl2content. Parameters such as extinction coefficient, refractive index, real and imaginary parts, and optical conductivity were studied by using the absorbance and measurements from computerized UV-visible spectrophotometer in the spectral range 190–800 nm. This study showed that the optical properties of PVAc were affected by the ...