Volume 31, Issue 2-3 - Special Issue International Conference on Polymer Processing and Characterization, Kottyam, Kerala, India, January 15–17, 2010

Polystyrene (PS) based composites respectively with cenosphere (CS) and calcium aluminosilicate (CAS) as fillers were studied using the positron lifetime technique to reveal the correlation between free volume, a microstructural property, and mechanical properties of the composites (tensile strength and tensile modulus). The thermal stability of the composites was determined using differential scanning calorimetry. The results showed that addition of CAS filler lead to a significant improvement in the mechanical properties of the composite, whereas addition of CS resulted in improvement in tensile modulus only. Both PS/CAS and PS/CS composites showed enhancement in thermal stability compared with that of the pure PS matrix. The positron results showed that the average free volume size for the PS/CAS composite (at 40 phr CAS) was reduced significantly compared with that of the pure PS. These results are understood in terms of the influence of silica content, filler-matrix interaction, and particle size.

In the fields of organic electronics and biotechnology, applications for organic polymer thin films fabricated using low-temperature non-equilibrium plasma techniques are gaining significant attention because of the physical and chemical stability of thin films and the low cost of production. Polymer thin films were fabricated from non-synthetic terpinen-4-ol using radiofrequency polymerization (13.56 MHz) on low loss dielectric substrates and their permittivity properties were ascertained to determine potential applications for these organic films. Real and imaginary parts of permittivity as a function of frequency were measured using the variable angle spectroscopic ellipsometer. The real part of permittivity (k) was found to be between 2.34 and 2.65 in the wavelength region of 400–1100 nm, indicating a potential low-k material. These permittivity values were confirmed at microwave frequencies. Dielectric properties of polyterpenol films were measured by means of split post dielectric resonators (SPDRs) operating at frequencies of 10 GHz and 20 GHz. Permittivity increased for samples deposited at higher RF energy – from 2.65 (25 W) to 2.83 (75 W) measured by a 20-GHz SPDR and from 2.32 (25 W) to 2.53 (100 W) obtained using a 10-GHz SPDR. The error in permittivity measurement was predominantly attributed to the uncertainty in film thickness measurement.

In this paper, we report on the computation of the induced forces in crosslinked polymer blends, with immersed small colloidal particles (nanoparticles) or confined to two parallel plates (film). We assume that the particles or the walls prefer to be attracted by one polymer, close to the spinodal temperature where a microphase separation takes place. This is the so-called “critical adsorption”. As an assumption, the particle diameter or the film thickness is considered to be small enough in comparison with the size of microdomains (“mesh size”). The critical fluctuations of the crosslinked mixture induce a pair potential between particles located in the non-preferred phase or between the confining walls. The purpose is to recall how this Casimir pair potential can be determined, as a function of the interparticle distance or the walls separation. To achieve calculations, use is made of an extended de Gennes model that takes into account the colloid-polymer and polymer-wall interactions. Finally, the obtained results are compared to those relatively to uncrosslinked polymer blends in the same geometries, and the main conclusion is that the induced force is reduced by the presence of permanent crosslinks.

In this article, poly(vinyl chloride) (PVC)/acrylonitrile butadiene rubber (NBR)/clay nanocomposites were melt-mixed using the computerized Brabender plasticorder. During preparation of the nanocomposites self-crosslinking (crosslinking without aid of any crosslinking agent) occurs and affects all properties of a sample. The extent of crosslinking reaction depends on the processing temperature, rotor speed and mixing temperature and it increased with increasing each of mixing parameters. The mechanism of the self-crosslinking reaction was examined by the Fourier transform infrared spectroscopy test. The morphology of the materials was characterized using X-ray diffraction and scanning electron microscope. The swelling test and tensile test were applied to distinguish the effects of self-crosslinking phenomena on physical properties of NBR/PVC nanocomposites. Dynamic mechanical thermal analysis tests of nanocomposites were also performed to study the physical properties, such as glass transition temperature ( T g ). The results showed that the crosslinking reaction made a material more strong with high modulus and tensile strength. Thus, it can be deduced that crosslinks convert the NBR/PVC nanocomposites to stiffer materials that are less penetrable by the solvent. The results drawn from the loss tangent (tan δ ) curves of nanocomposite samples can be used as further evidence for the above conclusions.

In this work, an effective method of characterizing the adhesion at the interface of partially miscible and immiscible binary polymer is used. Three polymer blends namely PS/PMMA, PP/NBR and PVC/SAN were irradiated with e-beam and microwaves, in order to bring about interfacial modification, and were characterized in terms of free volume measured by Positron Lifetime technique. The changes in free volume parameters upon e-beam and microwave irradiation on the two systems clearly shows improved interaction between the blend constituents as a result of cross-linking through hydrogen bond formation. However, the extent of interfacial modification brought in at different weight compositions is not forthcoming. Therefore, the hydrodynamic interaction parameter α, which accounts for friction at the interface between the dissimilar chains of the blend constituents, is evaluated from the very same free volume data. Since α represents the strength of hydrodynamic interaction, it could be taken as an indicator of the adhesion strength at the interface. Present results showed that both e-beam and microwave irradiations can be used to stabilize the interfaces in binary polymer blends as evidenced by hydrodynamic interaction.

A new method of characterizing the adhesion at the interface of partially miscible and immiscible binary polymer blends based on free volume concept is described here. The efficacy of the method is tested in four binary polymer blend systems namely PS/PMMA, PVC/EVA, PP/NBR and PVC/SAN. The usefulness of hydrodynamic interaction is exploited which is derived from free volume data to understand the changes at the interface. We understand that if the adhesion at the interface is good it exhibits large negative values for hydrodynamic interaction parameter α, a measure of excess friction at the interface. The thermal properties (indicated by T g ) also improve for this condition. To show that the method is sensitive to the changes at the interface, we modified the interface through microwave and e-beam irradiation and found from α characterization, that blends with polar groups exhibit interface stabilization for microwave irradiation while e-beam is good for blends with no polar or weak polar groups.

A novel, efficient methodology for the synthesis of phthalonitrile derivatives was investigated, using ionic liquid (IL) and microwave media as well as both simultaneously. Phthalonitrile monomers containing imide linkages were prepared from the reaction between aromatic dianhydrides, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BPTA), pyromellitic dianhydride (PMDA), 4,4′-(hexafluroisopropylidene) diphthalic anhydride (6FDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BTDA) and the end-capping agent 4-(3-aminophenoxy)phthalonitrile through the imidization reaction. The use of the IL1-butyl-3-methyl imidazoliumchloride as a solvent significantly increased the rate and yield of the reaction. The use of microwave irradiation and reaction parameters significantly shortened the reaction time while enhancing the purity. The polymerization of the prepared phthalonitrile monomers was carried out with 3 wt% of aromatic diamine 4,4′-oxydianiline (ODA) curing agent under microwave irradiation. It is shown that condensation was successfully carried out using the recyclable IL medium under microwave irradiation.

Polymer and surfactant complexation was investigated in systems containing anionic biopolymers and cationic surfactants by various classical and modern methods. Differently charged carrageenans (one, two or three sulfate groups per monomeric unit) and dodecylammonium chloride (DDACl) were used as model systems. Formation of various soluble and insoluble complexes (from nano- to microdimensions) and gelation strongly depends on carrageenan and DDACl concentrations, their molar ratio and linear charge density on carrageenan chains. The main factors governing complexation include electrostatic and hydrophobic interactions as well as conformation of carrageenan chains. With increasing carrageenan concentration, the intramacromolecular complexes change to intermacromolecular, which subsequently reorganize into better ordered structures, giant vesicles, and precipitated stoichiometric compounds, dodecylammonium carrageenates. Structural analysis of the new compounds revealed the formation of a lamellar structure with the polar sublayer containing carrageenan chains and the non-polar sublayer consisting of disordered dodecylammonium chains electrostatically attached to the carrageenan backbone. At gelling carrageenan concentration, progressive addition of DDACl caused gradual transitions from the structure of carrageenan gel alone to lamellar ordering of collapsed gel balanced by intermolecular forces within the gel network, i.e., by hydrogen bonding, electrostatic, hydrophobic and van der Waals forces.

The aim of this work was to study the effect of two solvents such as N , N ′-dimethylformamide (DMF) and dimethylacetamide (DMAc) used in the production of polysulfone (PSf) and polyurethane (PU) blend ultrafiltration membranes, influence permeability and selectivity. PSf/PU membranes were prepared by the phase inversion method using polymer concentrations of 100/0, 20/80 and 0/100 wt%. Permeation performance of the prepared membranes was evaluated in terms of pure water flux, water content and hydraulic resistance. It was found that the membrane composed of 20/80 wt% of PSf/PU in the presence of DMAc showed a water flux of 60.5 l m -2 h -1 under transmembrane pressure of 345 kPa, and the water flux of 23.5 l m -2 h -1 for 20/80 wt% of PSf/PU in the presence of DMF. With increasing the polarity of DMAc in the casting solution, an increase in porous layer thickness was observed, and then a good water flux of membranes can be obtained. It was found that the polar solvent caused the rapidly demixing of casting solution in coagulation bath and formed porous asymmetric membranes with defective skin layer. The permeation rates of proteins were measured with different molecular weights of the proteins.

Polymers have attractive properties when compared with inorganic materials: they are lightweight, inexpensive, pliable, and easily processed and manufactured. They can be configured into complex shapes and their properties can be tailored according to demand. With the rapid advances in materials used in science and technology, various substances embedded with intelligence at the molecular level are being developed. A type of electroactive polymer known as electrostrictive has shown considerable promise for a variety of applications, such as actuation with a strain thickness of 15% for an electric field of 10 V/μm. Polyurethane-based nanocomposite films were prepared by incorporating a carbon black nanopowder (C) into the polymer matrix. Electric field-induced strain measurements revealed that a loading of 1 vt% C (volume percentage of carbon black nanopowder) increased the strain level by a factor of 2.5 at a moderate field strength (10 V/μm). Moreover, another application for this material concerned the harvesting of mechanical energy, which constitutes an attractive alternative to the strict reliance on traditional batteries with limited lifetimes. For instance, an effective conversion from the mechanical-to-electric domains of 2.3 μW/cm 3 , under a transverse vibration level of 0.25% at 100 Hz, has been demonstrated for nylon. The final results indicated that the dielectric constant was a crucial parameter for energy harvesting.

Nanocomposites of phenoxy resin with various functionalized multi-walled carbon nanotubes (CNTs) were investigated to assess and compare the effect of functionalization on dynamic mechanical properties. Non-functionalized and various functionalized CNTs containing -COOH, -OH, and -NH 2 groups were utilized for preparing phenoxy/CNT nanocomposites through a melt mixing process. Dynamic mechanical properties of nanocomposites, storage modulus ( E ′), and loss tangent (tanδ) data in temperature range of 20–120°C were collected. Transmission electron microscopy and optical microscopy were also used to gain an insight into the CNTs dispersion state within phenoxy matrix. The functionalized CNTs had no adverse effect on storage modulus of phenoxy. The morphological investigation revealed the highest degree of agglomeration and the shortest tube lengths for the CNT-COOH within phenoxy matrix.

A thermodynamic study of phase separation induced by the polymerization process was carried out in a variant epoxy/amine system modified with polystyrene (PS) by means of a model based on the Flory-Huggins theory in which the polydispersity of components was taken into account. Modification of the epoxy/amine system was to continually change its molecular structure from a linear polymer to a highly crosslinked polymer using a monoamine and a diamine mixed in different proportions. The cloud-point curves during polymerization for five epoxy/monoamine-diamine systems with PS blends were experimentally measured. Application of the thermodynamic model led to obtaining the corresponding phase diagrams. All studied blends showed an upper critical solution temperature behavior and an increase in miscibility was observed by increasing the monoamine/diamine ratio. The polydispersity of components caused a molecular fractionation leading to a difference in the conversion of separate phases.

Hybrid materials, which consist of organic-inorganic materials, are of profound interest owing to their unexpected synergistically derived properties. Aluminum oxide (Al 2 O 3 ) nanoparticles/polymer composites have been produced using a one-system polymer synthesis. The linear polymer, poly(methyl methacrylate) (PMMA, M W =15,000 g/mol) is applied for the stabilization of Al 2 O 3 nanoparticles. Fourier transfer infrared analysis data and scanning electron microscopy image reveal that the core shell structure of the Al 2 O 3 /PMMA nanocomposite has been synthesized. The ratio of concentration of the capping polymer material to the concentration of the Al 2 O 3 precursor could control the size of Al 2 O 3 nanoparticles. With specific concentration of the reductant, the core-shell nanostructure could be fluctuated in order.

An investigation on the behavior of four new non-crimp fabric (NCF) composite materials developed by using the thermoplastic resin polyetheretherketone (PEEK) was performed with the aim to assess their potential for producing structural airframe parts of the required quality at reduced cost. In this framework, the mechanical behavior as well as the hot forming behavior of the materials developed was experimentally investigated. In addition, the draping behavior of the NCFs was experimentally evaluated to assess their suitability for being exploited in composite component manufacturing technologies involving direct lay-up processes. To better understand the behavior observed, both C-scan ultrasonic and optical microscopy analyses were performed. Furthermore, a complete series of tests was also carried out for the thermoplastic composite APC-2/AS4 to obtain a reference for comparison. The results of the test have shown that the mechanical properties of thermoplastic NCFs compare well with the respective properties of the reference material. Furthermore, the promising results of the hot forming tests support the expectation of using thermoplastic NCF composites in aircraft structural parts. Finally, the improved drapeability of the NCF material allows for a direct lay-up in a curved form tool. In conclusion, the developed thermoplastic NCF composites show a clear potential to compete with the established aeronautical prepreg material APC-2/AS4.

The linear electromagnetic response of polymer composite with nanocarbon inclusions was modeled for a random multi-component system with particles and clusters of different shape and size. The results of the generalized effective medium Maxwell-Garnett theory below the percolation threshold demonstrate good coincidence with the experimental data for onion-like carbon-based polyurethane composites collected in a quasi-static regime (at 129 Hz) in a broad temperature range.

TiO 2 filled bio-based composites were prepared from epoxidized soy bean oil and Diglycidyl ether of bisphenol-A, in which the nano TiO 2 particles were dispersed using ultra sonication method. Composites prepared with 1, 3, 5 and 7 weight percent level (wt%) of TiO 2 particles were characterized for their thermal properties such as glass transition temperature and degradation stability. Thermo gravimetric analysis (TGA) showed that thermal stability of the composites increases up to 5 wt% addition of TiO 2 ; thereafter it follows a decreasing trend, since the increased amount of nano sized particles makes it difficult for dispersion. The glass transition temperature of the composites was improved considerably. Dynamic mechanical analysis (DMA) further confirms the restricted chain mobility of the composites upon reinforcement. The significant improvements in mechanical properties such as tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength were achieved on reinforcement. The wide angle X-ray diffraction (WAXD) studies show that the nanoparticles are exfoliated in the soy based epoxy matrix system. The morphological behavior of composites studied using scanning electron microscopy (SEM) reveals the compatibility between the matrix and nanoparticles. The results showed that adding nano sized TiO 2 particles can improve the properties of thermal, mechanical, compatibility and water resistance of these renewable resource based epoxy matrices suitable for engineering applications.

This paper focuses on the comparative evaluation of the glass transition temperature (T g ), storage modulus and thermal conductivity of trans-polyisoprene (TPI) and CdS-TPI nanocomposite. The CdS nanoparticles synthesized by chemical route are dispersed into TPI using ultrasonic vibrations. Particle size of nanocrystals is obtained from X-ray diffraction and found to be 1.84 nm. Thermo-mechanical properties (T g and storage modulus) are measured by dynamic mechanical analyzer (DMA), while thermal conductivity is a measured using the transient plane source (TPS) technique. It is observed that glass transition temperature and thermal conductivity are higher while storage modulus and mechanical properties are lower for CdS-TPI nanocomposites than for pure TPI. This has been explained on the basis of structural changes occurring due to introduction of CdS as filler into the TPI.

Polymer/clay nanocomposites were prepared by the single screw extruder with an attached die to an ultrasound of variable amplitude. The structure and morphology of nanocomposites were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Mechanical properties such as Young’s modulus, elongation, breaking stress, toughness, yield stress and yield stain of ultrasonically treated nanocomposites were changed significantly in comparison to untreated nanocomposites. From rheology data, it was found that the complex viscosities of nanocomposites were increased with clay loading and decreased after ultrasonic treatment. It was found that both clay and ultrasonic intensity played a vitalrole in the dispersion of clay in the polymer matrix. From the differential scanning calorimeter (DSC) results it was found that the addition of clay in the nylon 6 matrix leads to a decrease of crystallization and this property increased ultrasonic amplitude. The oxygen permeability of PA6/clay nanocomposites was measured and it was found that a substantial reduction in oxygen permeability was observed by increasing clay loading.

The interaction of two cationic dyes, namely crystal violet (CV), with anionic polyelectrolytes, namely sodium carrageenate (NaCar) and sodium heparinate (NaHep), has been investigated by spectrophotometric method. The polymers induced metachromasy in the dye resulting in the shift of the absorption maxima of the dyes towards shorter wavelengths. The stability of the complexes formed between crystal violet and sodium carrageenate was found to be greater than that formed between crystal violet and sodium heparinate. This fact was further confirmed by reversal studies using alcohols, urea surfactants and electrolytes. The interaction parameters revealed that binding between crystal violet and sodium carrageenate was mainly due to electrostatic interaction while that between crystal violet and sodium heparinate is found to involve both electrostatic and hydrophobic forces.

The synthesis of copolymers from different feed ratios of N-(p-bromophenyl)-2- methacrylamide (PBPMA) and glycidyl methacrylate (GMA) was achieved by using free radical solution polymerization technique and characterized using FT-IR, 1 H and 13 C NMR spectroscopy. The thermal stability of the synthesized copolymers was studied using thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The molecular weight of the copolymer is determined by gel permeation chromatography (GPC). The corrosion performances of low nickel stainless steel specimens dip coated with different composition of copolymers were investigated in 0.5 M H 2 SO 4 using potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) techniques. The polarization and impedance measurements showed different corrosion protection efficiency with change in composition of the copolymers. It was found that the corrosion protection properties are owing to the barrier effect of the polymer layer covered on the low nickel stainless steel surfaces. However, it is observed that the mole ratio of PBPMA and GMA plays a major role in the protective nature of the copolymer.

A technique for preparing flexible composites by dispersing high T c yttrium based superconductor filler in a polyethylene matrix with transition temperature of about 90 K has been developed. Susceptibility measurements demonstrated a high degree of field exclusion, indicating that the superconducting behavior is preserved in the yttrium barium copper oxide (YBa 2 Cu 3 O 7-× ) filler material. It is found that all the composites showed the diamagnetic transition at around 90 K, which is the same as that of the pure YBCO sample. The single transition for both the parent YBCO material and the composite samples indicates the dominant presence of isolated superconducting grains within such samples. A large drop in resistivity with increasing filler content is observed for all the ceramic-polymer systems investigated in this study. At low percentages of the filler, the composite behaves as an insulator with very low conductivity. No dc zero resistance transition is observed. The absence of zero resistance in these composites was presumably due to the absence of appropriate contacts between the superconducting grains and the lack of a conductive path necessary for a zero resistance transition to occur.

Conducting polymers (CPs) provide a class of processible, film forming semiconductors and metals. Electrical and optical properties of CPs, similar to those of metals and semiconductors, and the attractive properties associated with conventional polymers such as ease of synthesis and processing, has given these polymers a wide range of applications in the microelectronics industry, in biological field and also as humidity, chemical and mechanical sensors. The principal interest in the use of polymers lies in the scope for low cost manufacturing. Organic polymers offer several advantages over analogous inorganic semiconductors, the most important of which are the processability and the large surface film technology together with the possibility of tuning the polymer properties through a chemical design of the constituent units. In contrast, problems of environmental stability and the inability to process these into useful devices constitute the main drawbacks of organic materials. To set a material suitable for applications in various technological fields one has to improve the processability, mechanical strength and environmental stability of the polyheterocycles: one method adopted to do this is synthesizing the composites of conducting polymers within a matrix of insulating polymers. In this paper, the science of conducting polymers will be discussed. A review from literature on selected applications of organic devices based on conducting polythiophene and its composites will be discussed with a view to targeting the areas of future research in this topic.

Extrudate swell is simulated using an Arbitrary Lagrangian Eulerian (ALE) technique based finite element formulation and the same has been validated by comparing the results with reported numerical and experimental studies. In the present work we compare our ALE simulations with our own experimental data on the extrudate swell of commercial grade low density polyethylene (LDPE) resin. The resins were characterized for their rheological behavior in both shear and uniaxial extension. The polymers were extruded from a capillary under isothermal conditions and the extrudates were observed on-line using a video camera. ALE simulations were performed using molecular constitutive model like eXtended Pom–Pom (XPP) for branched (LDPE). The simulated extrudate swell was a good match with the experimental data. It was found that the swell values of LPDE through planar die are higher than the axisymmetric die.

The immiscible blend of polyphenyleneoxide (PPO) and polyamide (PA) is used in several applications exposed to high temperature. The complexity of numerical modeling of such materials is dependent on their thermorheological behavior with significant simplification possibilities, if the material is found to follow the time temperature superposition (TTS) principle and show thermorheological simplicity (TRS). Hence as a precursor to selecting accurate constitutive modeling approach, the paper investigates the applicability of the TTS principle and the nature of thermorheological behavior to the blend. Dynamic mechanical analysis (DMA)frequency scans were performed in the range of 0.1–100 rad/s from 0°C to 210°C at 10°C intervals. Temperature dependency was observed on the Cole-Cole plot pointing to the thermorheological complexity and the need for vertical shift factors. 2-D minimization algorithm was used to shift the isotherms horizontally and vertically to obtain master curves. Except, in the vicinity of glass transition temperature T g , the isotherms overlap to form a master curve, but further analysis considering various conditions indicate that in a strict sense TTS is not applicable to the blend when both storage G ′ and loss modulus G ″ are considered. However, a continuous master curve of storage modulus spanning 31 decades of time is obtained using horizontal shifting alone when loss modulus is neglected. Further testing is required to ascertain if relaxation modulus can be approximated with storage modulus alone before taking recourse to characterization methods developed for thermorheologically complex (TRC) materials.

In this study, nine ternary blends of polypropylene (PP)/poly [styrene-b-(ethylene-co butylene)-b-styrene] tri-block copolymer (SEBS)/polycarbonate (PC) were produced at different processing conditions through twin screw extruder. Accordingly, die temperature, screw speed, and blending sequences were altered based on L9 Taguchi experimental design as indications of processing variables. Consequently, the impact strength of each produced sample is considered as the responding variable. Analyzing two important aspects, namely main and interactive effects by using Taguchi analysis, was the especial point of view in our contribution; as a result, not only was the PP/SEBS/PC ternary system studied for the first time, but the SEBS-g-MAH compatibilizer also showed sufficient effects on morphology development. It was observed that the impact strength of PP/SEBS/PC ternary blends is not affected by die temperature significantly, whereas screw speed and blending sequence have had effective impacts. Besides, the optimum processing condition, which is proportional to the highest value of impact strength, is recommended through the mentioned ternary blends. These results are also confirmed while applying image analysis on morphology micrographs.

Different parameters, namely polymerization temperature, polymerization time, monomer/initiator ratio, nature of the initiator, amount of water or other impurities etc. are very significant for polymerization reactions either in bulk or solution. Monomer to initiator ratio has a very significant role in polymerization reactions and a value ranging from 50 to 5000 that has been reported by different researchers. Recrystallization of the monomer removes the meso compounds from the monomer, which absorbs the moisture and effects polymerization reaction. So, it is necessary to recrystallize the monomer with any anhydrous solvent like dry toluene, ethyl acetate etc. Prolonged reaction time cannot increase the polymer yield; it generally causes the decrease of molecular weight and broadening of molecular weight distribution of formed polymers. This is probably due to the transesterification side reaction in polymerization, intensifying at prolonged time periods. Several groups like hydroxyl and carboxylic acid affect the polymerization rate.

The modeling of ring-opening polymerization of lactide to poly(lactic acid) (PLA) has been carried out. Carothers first synthesized PLA in 1932. Since then, hundreds of research papers and patents have appeared in the literature. However, there is a lack of data concerning the rate constants for initiation, propagation and termination steps of PLA polymerization, except some data about the apparent rate constant. This work investigates, theoretically, the individual rate constants using a simple numerical technique. The progress of lactide polymerization can be modeled by assuming a ring opening reaction mechanism comprising chain initiation, chain propagation, and chain termination. The simulator developed, based on the solutionof differential equations corresponding to the above-mentioned kinetic scheme, Generates a detailed molecular weight distribution that can be used to estimate average molecular weights (or average degree of polymerization) vs. polymerization time curves. These simulated curves, on matching with the reported experimental data (for different catalysts), yield the absolute values of rate constants. The values have been determined for zinc lactate. Rate constants could be determined by using the molecular weight and the polydispersity vs. polymerization data. This methodology offers greater opportunity for capturing high, non-equilibrium polymer yield through appropriately timed termination of the polymerization reaction.

Structural variation and its effect on the properties of aromatic polyurethanes (PUs) with different chain structures have been reported. Polarized optical microscopic studies of aromatic PUs demonstrate the development of micro clusters with increasing hard segment content (HSC). Higher crystallinity has also been proven from differential scanning calorimeter (DSC) and X-ray diffraction (XRD) studies. A globular pattern has been observed through atomic force microscopy (AFM) and the pattern depends on the type of diisocyanate used to prepare the PU. The difference in surface morphology is evident for two different PUs. The tensile modulus increases systematically with increasing HSC while toughness decreases, due to the presence of bigger crystallites in higher HSC polymer. Both the modulus and toughness vary on the type of diisocyanate present in PUs.

Sudan enjoys abundant solar, wind, hydro, and biomass resources. Like many tropical countries, Sudan has ample biomass resources that can be efficiently exploited in a manner that is both profitable and sustainable. Fuel-wood farming offers cost-effective and environmentally friendly energy solutions for Sudan, with the added benefit of providing sustainable livelihoods in rural areas. Biogas from biomass appears to have potential as an alternative energy in Sudan, which is potentially rich in biomass resources. This is an overview of some salient points and perspectives of biomass technology in Sudan. The current literature is reviewed regarding the ecological, social, cultural and economic impacts of biomass technology. This article provides an overview of biomass energy activities and highlights future plans concerning optimum technical and economical utilization of biomass energy available in Sudan.

We have analyzed the thermal conductivity and the tensile modulus of composite materials within the framework of the Halpin-Tsai and Lewis-Nielsen models. The parameter linking thermal conductivity and tensile modulus together is the shape factor of the (nano)filler. Model analysis based on experimental data shows that particle aggregation into a weak mechanical network may be required to achieve good correlation between thermal conductivity and the Young’s modulus when analyzing the data within the framework of a single model and requiring the same value of the shape factor. We believe this approach will make quantitative analysis of nanocomposite thermal properties possible.

The development of new polymeric systems with high ionic conductivity is one of the main objectives in the field of polymer materials with application point of view. In the present work, Ag + ion conducting solvent free composite polymer electrolyte thin films have been prepared using polyvinyl alcohol (PVA) as host polymer and polyethylene glycol (PEG) as plasticizer by standard solution cast technique. The structural characteristics of the prepared films have been obtained from X-ray diffraction (XRD) patterns. Maximum room temperature ionic conductivity of order of 10 -5 S cm-1 is obtained using complex admittance ( B-G ) spectroscopy. The temperature dependent conductivity shows two distinct regions of Arrhenius type thermally activated behavior before and after glass transition temperature. Dielectric constant, ε ′ and dielectric loss, ε ″ of the samples increases with temperature which is similar in behavior as that of conductivity. The activation energy for ion conduction has been calculated from temperature dependent conductivity curve and its minimum value is found to be 0.30 eV for PVA-PEG-20% AgI polymer electrolyte sample. High value of transference number shows that samples are ionic in nature which is confirmed by Wagner’s polarization technique.

In this paper, the mechanical characteristics of Kevlar multi-filament-polypropylene (KV M/F-PP) hybrid yarns and its composites have been studied. The hybrid yarns have been prepared by the principle of friction spun method in a DREF-3 (Dr Ernst Fehrer A.G. the name of the inventor 1973) Machine. The system uses Kevlar-29 (poly paraphenylene terephthalamide) multifilament (KV M/F) and polypropylene (PP) of 38 mm staple length fibres as core and sheath materials, respectively. The tensile properties of selected reinforcing materials and hybrid yarns are tested before preparing the composite samples. The weight percentages of KV M/F were kept as 0%, 15%, 20%, 25% and 30% corresponding to the percentages of matrix. DREF-3 hybrid yarns are characterized by very homogeneous component distributed over the yarn cross-section. The hybrid yarn is used for thermoplastic composites in compression molding, where Kevlar multifilaments take place in core as reinforcing materials and sheath or wrapped PP fibres as matrix. The prepared composite samples have been studied using specific standards to evaluate the void volume fraction and the tensile behavior in the standard conditions. The composite having 30% of Kevlar shows the highest tensile strength with a high void percentage, however, the elongation to break is a minimum due to lower weight percentage of low elastic modulus polypropylene matrix as compare to other samples.

This paper focuses on the study of novel blends based on poly(3-hydroxybutyrate) (PHB) and polymers with different hydrophilicity [polyethylene (PELD) and polyamide resin (PA548)]. Polymer blends were produced from five ratios of PHB/PELD in an effort to regulate the resistance to hydrolysis or (bio)degradation through the control of water permeability. The relation between the water transport and morphology (TEM data) shows the impact of polymer component ratio on the regulating water flux in hydrophobic matrix. To elucidate the role of hydrophilicity of the second component in the PHB blends, we studied the PHB/PA blends where PA is the polyamide resin composed of statistical copolymer of hexamethyleneadipinate and ε-caprolactam in ratio 1:1. The complex of techniques including DCS and Fourier Transform Infrared (FTIR)-imaging (on the scale of temperature) indicates an interaction between PHB and PA in the temperature ranges of crystallization and melting. The general approach based on Flory-Huggins equation is presented as a way to choose pairs of compatible or partly compatible polymers. Blending PHB with PA could be a simple and effective method to design new matrices for drug delivery, while the same procedure applied to PHB-PELD system with better resistance again, hydrolysis and lower cost than parental PHB could be used as novel bioerodible packaging materials.

Polythiophene (PTh) – polyvinyl acetate (PVAc) composite films were prepared by chemical oxidative polymerization with ZnCl 2 as oxidant, in methanol solvent at room temperature. In this study DC conductivity as a function of temperature was measured. An attempt has been made to investigate the effect of temperature and concentration of ZnCl 2 oxidant on the conductivity of polythiophene and polyvinyl acetate composite films. For fixed wt% of PVAc, the DC electrical conductivity initially increases with the molar concentration of ZnCl 2 which increases the rate of polymerization and then decreases with further increase in concentration of ZnCl 2 due to reduced segmental motion of the polymer. The Fourier transforms infrared (FTIR) spectra reveal that the structure remains the same throughout the series. The small shift in the observed peak frequencies is due to composition change of ZnCl 2 , but the overall trend of the IR spectra is the same. From the finger print region it is observed that the terminal branching is completely absent. The ionic transference number is calculated from the polarization current versus time plot. Ionic contribution is found to be dominant. The thermo gravimetry (TG) curves of the samples show single step degradation.

This paper presents the adaptation of a conventional injection moulding process to manufacture microfluidic components in thermoplastic polymers using alternative, exchangeable microstructured silicon-based mould inserts. The mould inserts consist of thick silicon wafers with microfeatures patterned in SU-8 epoxy photo-resist. This process allows changing the mould inserts according to the design, very easily and cost-effectively. The SU-8/Si mould inserts were robust enough to manufacture small series for laboratory purpose. More than a hundred replicas in thin polypropylene (PP) were produced successfully for a biochip designed for protein crystallisation and analysis.

Polymer properties are often engineered in desired directions by additives or by irradiations or by both. However, in space and certain other applications, energetic particles or γ-rays may damage the polymeric parts in undesired directions, needing prior radiation damage studies for necessary precautions. Case studies of three completely different polymer-additive composites follow: (1) shielding e lectro m agnetic i nterference (EMI) by different composites of a polymeric binder, (2) electrical, thermal, mechanical (Young’s Modulus, Y) and positron lifetime (PL) characterizations of solid polymer electrolytes (SPEs), and (3) determination of total free volume and hole size by pressure-volume-temperature (P-V-T) and positron lifetime techniques, respectively, in two types of polymers. One type consists of complexes of poly-(ethylene oxide), PEO, with a suitable salt, PEO-salt SPEs. The other type consists of silica-filled and pure varieties of poly(dimethyl siloxane), PDMS. Melting point and glass transition temperature of these polymers have been determined from PL techniques as well as from differential scanning calorimetry (DSC). Electrical contact problem has been addressed by measuring impedance as a function of pressure, p, and then extracting p=0 values of impedance and Young’s Modulus. These illustrative measurements have been carried out for better characterization of the polymers. DSC thermogram showed that radiation induced changes of melting point of PEO-salt samples are in opposite directions for 160 MeV Ne 6 + ion and 1.25 MeV γ-ray irradiations. This interesting feature hints at different mechanisms of radiation damage in two cases.

Sheet moulding compound (SMC) is a combination of glass fibers and filled polyester resin. It is processed by a compression moulding process and finds extensive applications in structural, automotive, electrical and electronic industries. The compression moulding process is characterized by the flow behavior of SMC under heat and pressure in the press mould. This paper is focused on the prediction of ideal processibility conditions of SMC. The qualitative aspect of a properly thickened (matured) moulding compound could be seen from its tack-free nature, which was quantitatively calibrated in terms of penetration depth, measured by a specially constructed softness indicator. The weight (wt)% of calcium carbonate (CaCO 3 ) as filler, magnesium oxide (MgO) as thickener, graphite (C) and zinc stearate [Zn (C 18 H 35 O 2 ) 2 ] (ZnSt) as lubricants along with the maturation time (T m ) were selected as process variables. Taguchi’s scheme of experimental design was adapted to perform the experiments. It was found that the higher levels of MgO and CaCO 3 were favorable for a good penetration depth as well as a reduced maturation time. We have also found that a penetration depth of at least 5 mm was required for achieving good processability conditions of SMC. An optimization study was under taken to find the right blend of additives and fillers, at their minimal weights and in the least possible maturation time, to achieve the desired processability. This study is particularly useful in a production run to make moulded parts from SMC.