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This study aimed to improve the dispersion state of single-walled carbon nanotubes (SWCNTs) in a cyclo-olefin polymer (COP) matrix by introducing extensional flow during the compounding through a twin-screw extruder (TSE). A modified mixing element with multiple holes, called a fixed blister disc (XBD), was developed. To describe the mixing performance of XBD, the flow state was characterized via numerical simulation and acquisition of process data such as pressure drop ([DELTA]P) at XBD and specific mechanical energy (SME), while the operational conditions of TSE were varied. The dispersion state of SWCNTs was evaluated from the viewpoint of the melt viscoelastic property, surface resistivity of extruded samples and mechanical properties of injection molded samples. Furthermore, the dispersion morphology was observed via optical microscopy and scanning electron microscopy. As a result, the mixing performance of XBD was improved by increasing the ratio of throughputs Q to screw speed [N.sub.s] (Q/[N.sub.s]) since [DELTA]P, which is related to extensional stress, was increased. However, the trade-off relationship between [DELTA]P and SME was confirmed versus Q/[N.sub.s]. Although the dispersion state at the submicron level was markedly improved with higher SME inputs, higher [DELTA]P reduced the largest agglomerate size and improved dispersion uniformity. Consequently, the mechanical properties were improved significantly. KEYWORDS dispersive mixing, extensional flow, nanocomposite, single-walled carbon nanotube, twinscrew extrusion, 1 | INTRODUCTION The introduction of extensional flow during compounding in a corotating twin-screw extruder (TSE) to improve the dispersion of nanofillers into a polymer matrix has been studied at [...]

Extending the fused filament fabrication process to highly filled thermoplastics in metallic powder used in metal injection molding is a promising method to produce small series. However, the lack of adhesion between deposited filaments can cause ruptures during the fabrication or debinding process. We designed a simple device to measure the shear strength required to tear off a filament deposited on a substrate. This device makes it possible to quickly determine the processing window for a good welding of filaments. We developed a 2D thermal simulation using the finite difference method while integrating the enthalpy of fusion and crystallization kinetics of the material. We then fitted it to the thermal measurements at depths of 0.45 and 0.75 mm under the substrate surface using small-diameter thermocouples. Simulation results highlight the key role of the thermal contact resistance between the filament and the substrate in the evolution of the interface temperature. This provides essential information to explain the process window that can be determined experimentally. The characteristic time of macromolecule diffusion was determined by rheological measurements and was found to be too small to play a role in filament bonding for the simulated cooling rates for the studied material. The methodology introduced in this work was used to improve highly filled polymers interlayer adhesion, but it can be used to improve other filled or unfilled polymers. KEYWORDS feedstock material, fused deposition modeling, fused filament fabrication, highly filled thermoplastic, process window, thermal simulation, thermoplastic welding, 1 | INTRODUCTION Metal injection molding (MIM) is a process for molding highly filled polymers with metallic powder in the same way as thermoplastic injection molding with the aim to [...]

For or product manufacturers and processors, plasma surface treatments create competitive advantages and transform parts into specialized, engineered components with many times the application value of untreated versions. Plasma is [...]

Gas-assisted sheet extrusion is a promising and environment-friendly method used in polymer processing. Insufficient gas intake due to the adherence of the polymer melt to the inlet gap is a disadvantage of the method. Therefore, in this study an improved die assembly with parallel gas intake was designed. As the melt is prone to falling at the die exit during the horizontal extrusion process, different thickness settings are used for the up and down gas layers (0.25 and 0.75 mm, respectively) to avoid this. For the improved die assembly, the gas inlet pressure may be varied systematically to study the mechanism of stable sheet extrusion. When the gas inlet pressure is 0.1 MPa, the melt can be extruded smoothly, and the extruded sheet surface is transparent and flat. However, when the optimum pressure is exceeded, the extruded sheet becomes twisted or even broken. KEYWORDS down gas layer, gas inlet pressure, gas-assisted extrusion (GAE), improved die assembly, numerical simulation, 1 | INTRODUCTION Plastic sheets are used extensively in the production of thermoforming products, packaging products, circuit board partitions, handicrafts, and other industries. [1-5] However, owing to the viscoelasticity [6-8] [...]

Traditional micropellet and powder-based polymer processing techniques, such as powder bed fusion, compression molding, and rotational molding have shown an increased demand in polymer processing. These processes require powders and micropellets with a small particle size, narrow size distribution and defined geometry for a variety of polymer resins. Therefore, micropelletization technologies, where particles in the size range of 50-1,000 [micro]m are generated, have been attracting growing attention over the past decade. A new technique, presented here, yields micropellets with a controlled morphology and narrow particle size distribution. In this process, a polymer melt is extruded through a capillary and is subsequently stretched with a hot airstream until flow instabilities or melt fracture cause it to break up into particles. Small changes in process conditions result in different size distributions and particle shapes, such as lenticular pellets, fibers, and strand segments. This work shows how processing parameters and different polymer materials influence the produced micropellets. Depending on the processed polymer resin and process conditions, spherical particles with sizes ranging from 50 to 1,000 [micro]m can be produced using the novel extrusion technique. Comprehensive design of experiment and data analysis was used to establish a more detailed understanding of the micropelletization process. POLYM. ENG. SCI., 58:2264-2275, 2018., INTRODUCTIONMicropellets and powders are used for a variety of polymer processing applications, such as rotomolding, compression molding, and sintering processes [1-3]. When compared with conventional molding pellets, which are usually [...]

Author(s): Ian D. Robertson [sup.1] [sup.2] , Mostafa Yourdkhani [sup.1] , Polette J. Centellas [sup.1] [sup.3] , Jia En Aw [sup.1] [sup.3] , Douglas G. Ivanoff [sup.1] [sup.4] , Elyas [...], Thermoset polymers and composite materials are integral to today's aerospace, automotive, marine and energy industries and will be vital to the next generation of lightweight, energy-efficient structures in these enterprises, owing to their excellent specific stiffness and strength, thermal stability and chemical resistance.sup.1-5. The manufacture of high-performance thermoset components requires the monomer to be cured at high temperatures (around 180 °C) for several hours, under a combined external pressure and internal vacuum.sup.6. Curing is generally accomplished using large autoclaves or ovens that scale in size with the component. Hence this traditional curing approach is slow, requires a large amount of energy and involves substantial capital investment.sup.6,7. Frontal polymerization is a promising alternative curing strategy, in which a self-propagating exothermic reaction wave transforms liquid monomers to fully cured polymers. We report here the frontal polymerization of a high-performance thermoset polymer that allows the rapid fabrication of parts with microscale features, three-dimensional printed structures and carbon-fibre-reinforced polymer composites. Precise control of the polymerization kinetics at both ambient and elevated temperatures allows stable monomer solutions to transform into fully cured polymers within seconds, reducing energy requirements and cure times by several orders of magnitude compared with conventional oven or autoclave curing approaches. The resulting polymer and composite parts possess similar mechanical properties to those cured conventionally. This curing strategy greatly improves the efficiency of manufacturing of high-performance polymers and composites, and is widely applicable to many industries.Frontal polymerization of dicyclopentadiene is used to generate thermoset polymers and composite materials with much lower energy requirements and cure times than are needed in conventional oven or autoclave curing approaches.

The study of the interactions among metals, minerals, and humic substances is essential in understanding the migration of inorganic pollutants in the geosphere. A considerable amount of organic matter in the environment is associated with clay minerals. To understand the role of organic matter in the environment and its association with clay minerals, a hybrid day-based material (H CM), montmorillonite (STx-1)--melanoidin, was prepared from L-tyrosine and L-glutamic acid by the Maillard reaction. The HCM was characterized by elemental analysis, nuclear magnetic resonance, x-ray photoelectron spectroscopy (XPS), scanning transmission x-ray microscopy (STXM), and thermal analysis. The presence of organic materials on the surface was confirmed by XPS and STXM. The STXM results showed the presence of organic spots on the surface of the STx-1 and the characterization of the functional groups present in those spots. Thermal analysis confirmed the existence of organic materials in the montmorillonite interlayer, indicating the formation of a composite of melanoidin and montmorillonite. '[he melanoidin appeared to be located partially between the layers of montmorillonite and partially at the surface, forming a structure that resembles the way a cork sits on the top of a champagne bottle. Abbreviations: DTA, differential thermal analysis; GHD, glutamine hybrid material naelanoidin fraction; GHS, glutamine hybrid material solid fraction; HCM, hybrid clay-based material; NMR, nuclear magnetic resonance; STx-1, sodium-montmorillonite; STXM, scanning transmission x-ray microscopy; THD, tyrosine hybrid material melanoidin fraction; THS, tyrosine hybrid material solid fraction; XPS, x-ray photoelectron spectroscopy. doi: 10.2136/sssaj2009.0454

We describe the synthesis and characterization of metal-chelating polymers with a degree of polymerization of 67 and 79, high diethylenetriaminepentaacetic acid (DTPA) functionality, [M.sub.w]/[M.sub.n], [less than or equal to] 1.17, and a maleimide as an orthogonal functional group for conjugation to antibodies. The polymeric disulfide form of the [DP.sub.n] = 79 DTPA polymer was analyzed by thermogravimetric analysis to determine moisture and sodium-ion content and by isothermal titration calorimetry (ITC) to determine the [Gd.sup.3+] binding capacity. These results showed each chain binds 68 [+ or -] 7 [Gd.sup.3-] per chain. Secondary goat antimouse IgG was covalently labeled with the maleimide form of the DTPA polymer ([DP.sub.n] = 79) carrying [sup.159]Tb. Conventional ICPMS analysis of this conjugate showed each antibody carded an average of 161 [+ or -] 4 [sup.159]Tb atoms. This result was combined with the ITC result to show there are an average of 2.4 [+ or -] 0.3 polymer chains attached to each antibody. Eleven monoclonal primary antibodies were labeled with different lanthanide isotopes using the same labeling methodology. Single cell analysis of whole umbilical cord blood stained with a mixture of 11 metal-tagged antibodies was performed by mass cytometry. 10.1021/ac101901x

Treatment of bone defects generally requires a fixation device. Biodegradable implants can often prevent second operations in contrast to metallic implants that are surgically removed after healing. In this study, we investigate the preparation of a bone fixation device with additional bioactivity by adding nanoparticulate amorphous tricalcium phosphate (ATCP) to improve bonding to bone. Medically approved poly(lactide-co-glycolide) (PLGA) and spherical (ATCP) nanopar-ticles were blended directly or through a two-step approach, where ATCP was first dispersed in PLGA by solvent casting, extruded and hot pressed producing blocks and bone screws. The latter route yielded good particle dispersion while blending alone led to inhomo-geneous mixtures. Samples were immersed in simulated body fluid and showed rapid formation of surface hydroxy apatite layers (examined by X-ray diffraction and scanning electron microscopy) already after 3 days, thus confirming very high bioactivity. Polymer degradation during processing and upon simulated implantation conditions was followed by gel permeation chromatography. The elevated temperature during extrusion was the strongest single factor contributing to PLGA degradation. Screws could be machined out of extruded cylinders and demonstrated the ability to process PLGA/ATCP 90/10 composites with regular workshop tools. These properties suggest the use of such composites as improved, bioactive, and degrad-able bone fixation systems particularly in oral and maxillofacial surgery. POLYM. ENG. SCI., 50:952-960, 2010. [C] 2009 Society of Plastics Engineers, INTRODUCTION Biomedical composites are used in temporal or permanent implant materials and they have gained significant clinical interest due to their ability to integrate into the body (l-3). The advantage [...]

Many industrial processes involve the transportation of a continuous web of material over a series of rollers to obtain a finished product. The manufacture of polymer film is one such web transport process, which utilizes a series of rotating elements that act to manipulate the film. This paper develops a dynamic mathematical model of the 'forward draw' in a polymer film production process. The model is capable of being implemented in real-time for control purposes, yet includes significant physical phenomena such as material damping. Experimental results from a pilot production plant are used to validate the model under steady-state and transient conditions. The model is then used as a basis for a feed-forward control scheme, which reduces speed variations in the forward draw by a factor of 8 and therefore improves considerably the film quality. [DOI: 10.1115/1.4000712] Keywords: web production process, web system modeling, forward draw, speed estimation, large-scale systems, feed-forward control

In the present study a more complete numerical solution approach using parallel computing technology is provided for the three-dimensional modeling of mold insert polymer injection molding process by considering the effects of phase-change and compressibility for non-Newtonian fluid flow conditions. A volume of fluid (VOF) method coupled with a finite volume approach is used to simulate the mold-filling stage of the injection molding process. The variations in viscosity and density in the polymer melt flow are successfully resolved in the present VOF method to more accurately represent the rheological behavior of the polymer melt flow during the mold filling. A comprehensive high-resolution differencing scheme (compressive interface capturing scheme for arbitrary meshes or CICSAM) is successfully utilized to capture moving interfaces and the pressure-implicit with splitting operators pressure-velocity coupling algorithm is employed to enable a higher degree of approximate relation between corrections for pressure and velocity. The capabilities of the proposed numerical methodology in modeling real molding flow conditions are verified through quantitative and qualitative comparisons with other simulation programs and the data obtained from the experimental study conducted. The present numerical results are also compared with each other for a polypropylene female threaded adaptor pipe fitting model with a metallic insert for varying governing process conditions/parameters to assess the modeling constraints and enhancements of the present numerical procedure and the effects of these conditions to optimize the polymer melt flow for mold insert polymer injection molding process. The numerical results suggest that the present numerical solution approach can be used with a confidence for further studies of optimization of design of mold insert polymer injection molding processes. [DOI: 10.11151/1.4000620] Keywords: injection molding, polymer, metallic insert, finite volume method, mold filling, three-dimensional modeling

The simulation of injection molding involves the filling of cavities and runners in complicated shapes. The 3D elements in large numbers are generally required to satisfy the precise simulation of real processes. It results in the computation in large scales, so that the efficiency of computation becomes very important. On the basis of previous explicit software realized by the authors, the new algorithm avoids the global solution for pressure fields to improve its efficiency. Another feature of the new algorithm is the use of same order interpolation elements instead of MINI elements, which simplifies significantly the software procedures. Except for the operations at element level, neither global solution nor the construction of global matrix is required in simulation. A special feedback regulation strategy is used to meet the incompressibility in filled domain at each time step. In case of the mold filling problems, this method provides a fast way to simulate the filling processes. The computational cost is about linearly proportional to the degree of freedom number. Comparison of velocity field obtained by the previous algorithm using MINI element and analytical theoretical solution proves that the feedback regulation strategy in the new algorithm can satisfy well incompressibility. Moreover, comparison with the results of filling process and temperature field obtained by the previous algorithm proves the validity of the new algorithm. POLYM. ENG. SCI., 49:1243-1252, 2009. [C]2009 Society of Plastics Engineers, INTRODUCTION Injection molding is a widely used technology in manufacture. For the process simulation of polymer injection molding of limited thickness models (1), (2), Hele-Shaw model is generally adopted. The [...]

Poly(2-hexadecylsuccinic acid-sebacic acid) (P(HSA-SA)) copolymers have been prepared by melt polycondensation. The copolymers were characterized by FT-IR, (1) HNMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). In vitro studies showed that all our prepared copolymers are degradable in phosphate buffer at 37 [degrees]C. The release profiles of hydrophilic model drug, ciprofloxcin hydrochloride, from the copolymers, follow first order release kinetics. All the preliminary results suggested that the copolymer might be potentially used as drug delivery devices. Key words: Polyanhydrides, melt polycondensation, in vitro degradation, drug released, INTRODUCTION Polyanhydrides have been considered to be useful biomaterials as carriers of drugs to various organs of the human body such as brain, bone, blood vessels and eyes. They can [...]

Dynamically vulcanized PP/EPDM blends were treated by high-intensity ultrasonic waves during extrusion. These blends were compared with unvulcanized PP/EPDM blends that were treated by ultrasound during extrusion and then dynamically vulcanized. Die pressure and power consumption were measured. The effects of different gap sizes, ratio of components, and number of ultrasonic horns were investigated. The rheological properties, morphology and mechanical properties of the blends with and without ultrasonic treatment were compared. The results obtained indicated that ultrasonic treatment induced thermo-mechanical degradation, causing enhanced molecular transport and chemical reactions at the interfaces, thus leading to in-situ compatibilization, which is evident by the morphological and mechanical property studies. Processing conditions were established for enhanced in-situ compatibilization of the PP/EPDM blends that were either originally dynamically vulcanized and then ultrasonically treated or first treated and then dynamically vulcanized. Polym. Eng. Sci. 44:2019-2028, 2004. [c] 2004 Society of Plastics Engineers., INTRODUCTION Preparation of novel polymer blends is a research area of considerable interest. Most polymer pairs in blends are thermodynamically incompatible; the incompatible blends often give poor mechanical properties due [...]

Pressure measurements in flows of highly viscous and elastic fluids are of practical importance in polymer processing and rheology systems. Special problems arise during such pressure measurements. High fluid viscosity results in excessive dynamic response time (rise time) of the pressure measuring systems. This is true for systems that consist of manometers as well as pressure transducers attached to the base of a small hole at the wall. We model the dynamic response and examine related disturbing effects. These systematic errors in pressure measurements include hole-pressure effects, instabilities in cavity flow, and the time lag of the disturbance wave. We consider static and dynamic flow systems of a polymer solution (PIB/C14/PB Boger fluid) to study these problems and show that instantaneous pressure measurements in these systems can effectively be performed.

Surface-confined living radical polymerization is shown to be a controlled means of covalently bonding both linear and cross-linked polymer films on silica. CuCl/bipyridine initiates radical formation through atom transfer with a self-assembled monolayer of benzyl chloride, onto which polymer then grows. The polymerization is intrinsically confined to the surface, avoiding problems associated with polymer formed in the solution. The surface-confined polymerization scheme is generally applicable to radical polymerization of vinyl monomers and was studied here for the case of acrylamide. Infrared spectroscopy shows that the film growth is controllable, and atomic force microscopy reveals that smooth films are prepared. The surface-confinement polymerization scheme was tested for both linear and cross-linked polyacrylamide. Capillary electrophoresis of strongly basic proteins confirms that the coated capillaries provide the high efficiency expected for polyacrylamide. The cross-linked coating exhibits higher reproducibility with respect to migration time than does the linear coating. Surface-confined living radical polymerization prepares linear and cross-linked polymer films without danger of clogging narrow capillaries and will ultimately facilitate cross-laboratory comparisons by enabling control of film thickness.

This paper reviews recent studies on the mechanism of corona treatment of polyolefin films, specifically the chemical and physical changes of this process and the self-adhesion mechanism. Corona discharge of polymeric films introduces polar groups into the surfaces, which increases the surface energy and, as a consequence, improves substrate wettability and adhesion. The main chemical mechanism of corona treatment is oxidation. In addition, corona treatment can crosslink surface regions and increase the film cohesive strength., INTRODUCTION For polyolefin films, surface treatments are usually necessary to improve surface wetting and adhesion characteristics in different application situations such as adhesive bonding, printing, extrusion coatings, metallized polyolefins, composites, [...]

The coextrusion of two polymers in a square channel is presented in this paper. Fluids are fed into the channel through different passages with a plane separating them partway through the channel. Downstream of the separation plane, the streams merge forming an interface between them, which is normally distorted before reaching the exit of the channel. These results show that the degree of distortion depends upon factors in addition to the ratio of the viscosity of the two fluids. The ratio of the flow rates in addition to the shape and location of the separation plane are also important., INTRODUCTION Multilayer polymer sheets or films are normally produced by the coextrusion of two or more polymers from flat dies. This is accomplished by using either of two possible die [...]

When polymer blends are prepared from a mixture of pellets, the melting order of the components is important in determining the mechanism of morphology development. Here, we show that an inversion of phase continuity occurs during processing when a minor phase component has a softening or melting transition temperature which is lower than the softening temperature of the major phase component. Three 80:20 concentration systems were studied: polyarylate/rubber, polyamide 6,6/polystyrene, and polystyrene/ethylene propylene rubber. Initially, the minor phase was the continuous phase and coated the major phase in all three systems. As the major phase melted, a switching of phase continuity occurred, and in the final blend state, the major phase was the continuous phase. An increase in power input was required during the switching of the dispersed and matrix phases. The compounding process was studied through continuous video monitoring, torque-temperature analysis, and microscopy of quenched samples. A continuity inversion mechanism is proposed. It is found that the initial morphology of the blend consists of sheets of the major phase inside the minor phase. These sheets break up into irregularly shaped particles, which then coalesce around the minor phase. The effects of compatibilization (using reactive polymers or adding a premade diblock) on the rheology and morphology of the blend are also investigated. Interfacial reaction is seen to delay and intensify the Inversion of phase continuity, whereas addition of pre-made diblock does not have any significant effect. The torque increases due to interaction of the major phase domains and due to reactive stabilization of the interface against coalescence, and the contributions of each to the torque can be decoupled., INTRODUCTION AND BACKGROUND Blending polymers has proved to be the most efficient way to satisfy new requirements for material properties (1, 2). Thermal and mechanical behavior can be enhanced via [...]

A model is presented for free expansion polymer foam processing that includes simultaneous nucleation and bubble growth. The nucleation model includes dissolved gas, small critical cluster size, elastic, and non-ideal solution effects. An influence volume approach, which couples nucleation and bubble growth, is used to account for the limited supply of dissolved gas. The resulting set of equations are solved using a combination of numerical techniques. A parametric study is conducted to examine the effects of key process variables on bubble growth, nucleation, and final bubble size distribution., INTRODUCTION With the ever-mounting environmental pressures, the polymer foam industry is in crisis because existing process technologies are based largely on the use of chlorofluorocarbons (CFCs) and volatile organics (VOCs) [...]

Polymer insulators for electric apparatus and high-voltage overhead lines are promising for replacing porcelain and glass insulators. The possibility of this application is shown by radiation-chemical technology for the manufacture of rod-shaped polymer insulators. An ethylene and vinyl acetate copolymer (EVA) was used as the basis for polymer insulators. The composition also contains aluminium hydroxide as a filler and N,N′-m-phenylene dimaleimide as a sensitizer. The investigation of [Gamma]-radiation-induced crosslinking of this composition made it possible to establish the following optimum conditions of radiation processing of insulators: the absorbed dose of up to 200 kGy at a dose rate of 10 kGy/h in air. By forming a three-dimensional network in the polymer bulk by radiation, the service properties of the insulators are improved: Shape and heat stability is >200 ° C and the stability to tracking and erosion >200 h. Differential scanning calorimetry (DSC) and a method of stress relaxation were used in evaluation. In the Saint Petersburg region (Russia), several types of high-voltage (10-110 kV) polymer insulators are manufactured with the application of such radiation-chemical technology., INTRODUCTION Rod-shaped polymer insulators are increasingly used in power engineering, in place of traditional high-voltage porcelain and glass insulators, for electric apparatus and overhead power transmission lines (1-3) see Fig. [...]