Search

Understanding the solvent-induced stresses in polymeric materials is of profound importance for drug release and soft robotics. This work presents an alternative method to obtain an analytical solution of solvent-induced stress in an elastic slab using the Moutier theorem under the framework of equilibrium thermodynamics and the elastic solution available in the literature. Using the analytical solution and the temporal evolution of the mass of organic solvents in polymeric slabs, we analyze the spatiotemporal evolution of the solvent-induced stress in the polymeric slabs and reveal the effects of the solvent transport on the stress evolution. The approach presented in this work provides a simple method to solve the decoupling problem involving diffusion and solvent-induced stresses. KEYWORDS elastic slab, Moutier theorem, solvent-induced stress, 1 | INTRODUCTION Solvent transport in glassy polymers has been studied for several decades. In addition to diffusion named Case I transport, Case II and anomalous transport are often observed [...]

BY JACK RULANDER, PROTOLABS Creating consistency in injection molded parts requires a detailed, scientific process Scientific, decoupled and intelligent molding are commonly used terms in the plastics industry to describe [...]

In this study, to make gas-assisted extrusion (GAE) can be better applied to conventional horizontal extrusion forming process, the thickness difference between up and down gas layer was simulated for the first time by GAE of molten high-density polyethylene sheet. In order to ascertain the effects of the thickness difference of up and down gas layers on sheet extrusion molding, a method based on the model of two-phase (gas and melt) flow was put forward, and an outer-layer GAE isothermal numerical simulation made by POLYFLOW was explored and researched. The numerical results analysis indicated that when the thickness of down gas layer is increased, the velocities, pressure drop and shear rate of the melt increase. Compared with the simplified-GAE simulation, GAE simulation method can well reflect the flow characteristics, the physical field distribution, and the morphology changes of melt extrudates. The experimental results show that with the increase of the thickness of the down gas layer, the melt falling can be obviously improved during extrusion. Thus, in the actual use of GAE for sheet production, not only the thickness difference between up and down gas layers should be reasonably controlled, but also other factors, such as melt inlet volume flow rate, gas pressure and temperature should be controlled accordingly. Finally, GAE forming technology can give full play to its advantages. KEYWORDS extrusion, numerical simulation, polymer, thickness difference of up and down gas layers, twophase flow, 1 | INTRODUCTION In polymer processing and production, due to the inherent characteristics of polymer melt itself, the traditional extrusion method is prone to extrudate swell, [1-3] melt fracture [4,5] [...]

Biodiesel is considered one of the best alternative fuel sources in the transportation industry, but rt has shown aggressive characteristics on materials that are used in fuel storage and delivery systems in vehicles. In this study, the effect of biodiesel (B100) on the properties of two polyamide-6-based semicrystalline polymers was studied and compared with that of diesel and a 20/80 blend of biodiesel and diesel (B20). Experiments were conducted using room temperature immersion tests in the three fuels for 720 h followed by postimmersion thermal and mechanical tests. In all three fuels, the polymers exhibited non-Fickian weight increase during immersion and did not achieve equilibrium level of absorption in 720 h. The glass transition temperature ([T.sub.g]), yield and tensile strengths, storage modulus, and peak tan [delta] decreased after immersion, while the degree of crystallinity and loss modulus increased. Fourier transform infrared spectroscopy study showed that no chemical changes occurred due to immersion. It is concluded that all three fuels absorbed into the polymers acted as plasticizers which caused the observed changes in the properties of the two polymers investigated in this research., INTRODUCTION Polymers are used in many fuel container and fuel delivery applications where they are exposed to or immersed in fuels that can cause degradation in their physical and mechanical [...]

CONDUCTIVE ALUMINUM COMING SOON Researchers at Pacific Northwest National Laboratory (PNNL), Richland, Wash., are working on ways to increase the conductivity of aluminum and make it economically competitive with copper. [...]

Creep response, stress relaxation behavior, and melt rheological study of the shape memory polymer blend based on EOC-EPDM has been studied in details. In this study, especially the effect of the crosslinks formation in presence of electron beam on the creep response, melt rheological study and stress relaxation behavior has been reported. With increase of electron beam dose, creep response becomes lower and the creep compliance value also comes down. Higher resistance creep response of the radiation crosslinked blends indicates the superior shape recovery behavior of the blends. Stress relaxation behavior of the crosslinked blend also shows the lower decay of stress value with time for higher radiation crosslinked blend. The lower relaxation ratio of the highly radiation crosslinked blend also supports the superior shape recovery behavior of the crosslinked blend. Apart from, melt rheological study shows the higher storage modulus value and higher complex viscosity of the radiation crosslinked blend which also supports the formation of higher crosslinked network structure. Tension set value also clearly indicates the better shape recovery behavior of the crosslinked blend. POLYM. ENG. SCI., 58:876-885, 2018. [C] 2017 Society of Plastics Engineers, INTRODUCTION Among the existing polymers, blending of polymers is a smart and economical strategy for the development of new and improved polymeric materials that are difficult to obtain by direct [...]

Many applications in wireless communication, microelectronics, and microwave power engineering rely on dielectrics with particular dielectric properties. This article proposes an original approach that can be used for producing materials with required complex permittivity. The technique is based on an inverted power-law mixing rule model computing volume fractions in which three or more prime materials should be taken to get in the resulting homogeneous mixture the required dielectric properties. Functionality of the approach is demonstrated by production of composites from a polymer matrix (polymethyl methacrylate) and two inorganic fillers (silicon and alumina). The composites are made by mechanically mixing the powders and axially hot-pressing and cooling the mixture. Complex permittivity of the samples is measured by a split-post resonator method. Experimental data on dielectric properties of the samples help calibrate the technique; for the used powders, the Looyenga power-law model is found to be most adequate. In the produced samples, the target values of dielectric constant are reached with a higher precision than the ones of the loss factor; however, analysis of the production process and error propagation in the computations suggest that deviations of the resultant complex permittivity fall in the anticipated ranges. Features and issues of both computational and production parts of the technique are finally discussed., INTRODUCTION Numerous scientific and industrial applications in wireless communications, telemetry, biomedical engineering, material processing and process control include propagation/interaction of electromagnetic fields through/with the media. Dielectric properties of those media [...]

Antibacterial effects of electrosynthesized polymethylolacrylamide films to Staphylococcus aureus and marine biological organisms have been detected. The maximal effect of bacteria growth suppression is observed for freshly prepared samples during 7-14 days. Biocide influence of the films maintained up to 45 days. The toxicity depends on the polymer composition, method of its pretreatment, and duration of exposure to a biological object. It was shown that the antiseptic properties were imparted to the polymer material by formaldehyde as both sorbed by the polymer and included into the polymer chain. It is established that the polymer waste could be utilized by microbial destruction. The toxicological effect of the polymethylolacrylamide films could be applied both in medicine (antiseptic materials and implants) and for protection of equipment against biopollution and biocorrosion and for partial sterilization of organic solutions during baromembrane filtration., INTRODUCTION Extensive application of polymer materials in various fields of science and technology provides for a demand for deep understanding of their properties, which would determine the possibilities of polymers [...]

Author(s): Yunqing Zhu [1, 3]; Charles Romain [2, 3]; Charlotte K. Williams (corresponding author) [1] Modern life relies on polymers, from the materials that are used to make clothing, houses, [...], Renewable resources are used increasingly in the production of polymers. In particular, monomers such as carbon dioxide, terpenes, vegetable oils and carbohydrates can be used as feedstocks for the manufacture of a variety of sustainable materials and products, including elastomers, plastics, hydrogels, flexible electronics, resins, engineering polymers and composites. Efficient catalysis is required to produce monomers, to facilitate selective polymerizations and to enable recycling or upcycling of waste materials. There are opportunities to use such sustainable polymers in both high-value areas and in basic applications such as packaging. Life-cycle assessment can be used to quantify the environmental benefits of sustainable polymers.

The objective of this study is to evaluate the long-term aging effect on the rheological properties of the modified PG 76-22/PG 76-16 binders produced from ground tire rubber (GTR) with various polymers after a long-term aging process. The tests included the investigation of G*sinδ, phase angle, amplitude sweep, frequency sweep, creep and creep recovery and stress relaxation in terms of three base binders and five polymers. The test results indicated that both base binder and polymer type affect the fatigue resistance, creep and creep recovery, viscoelastic property, and relaxation characteristic of each modified binder. In addition, terminally blended GTR binder has better fatigue resistance than laboratory blended GTR binder after a long-term aging procedure in this study. It seems that binders modified with polyphosphoric acid combined with 7% GTR exhibit more elastic properties and better rheological properties than other modified binders regardless of binder sources. Key words: long-term aging, ground tire rubber, polymer, rheological properties, fatigue resistance factor, creep, creep recovery, amplitude and frequency sweep, relaxation. L'objectif de cette etude est d'evaluer l'effet du vieillissement a long terme sur les proprietes rheologiques des liants modifies PG 76-22/PG 76-16 fabriques a partir de caoutchouc de pneus morceles (CPM) avec differents polymeres, et ce, apres un processus de vieillissement a long terme. Les essais comprennent l'etude de G*sinδ, de l'angle de phase, du balayage de l'amplitude, du balayage des frequences, du fluage et de la recuperation au fluage et de la relaxation de contrainte en ce qui a trait a trois liants de base et a cinq polymeres. Les resultats des essais indiquent que tant le genre de liant de base que le genre de polymere a un effet sur la resistance a la fatigue, le fluage et la recuperation au fluage, la propriete viscoelastique et la caracteristique de relaxation de chaque liant modifie. De plus, le liant CPM melange en fin de phase resiste mieux a la fatigue que le liant CPM melange en laboratoire a la suite de la procedure de vieillissement a long terme dans le cadre de cette etude. Il semble que les liants modifies a l'aide d'acide polyphosphorique ajoutee a 7% CPM montrent des proprietes plus elastiques et de meilleures proprietes rheologiques que d'autres liants modifies independamment des sources des liants. [Traduit par la Redaction] Mots-cles: vieillissement a long terme, caoutchouc de pneus morceles, polymere, proprietes rheologiques, facteur de resistance a la fatigue, fluage, recuperation au fluage, balayage de l'amplitude et des frequences, relaxation., Introduction Several asphalt pavement distresses, such as fatigue cracking, thermal cracking, and raveling etc, may be attributed to the variation of viscoelastic properties of asphalt mixtures with time, among which [...]

Ion-exchange membranes are used in a wide range of applications for separations, energy conversion and energy storage systems, where selective barrier properties are essential for high performance in membrane-integrated systems. [...], The regulation of water content in polymeric membranes is important in a number of applications, such as reverse electrodialysis and proton-exchange fuel-cell membranes. External thermal and water management systems add both mass and size to systems, and so intrinsic mechanisms of retaining water and maintaining ionic transport (1-3) in such membranes are particularly important for applications where small system size is important. For example, in proton-exchange membrane fuel cells, where water retention in the membrane is crucial for efficient transport of hydrated ions (1,4-7), by operating the cells at higher temperatures without external humidification, the membrane is self-humidified with water generated by electrochemical reactions (5,8). Here we report an alternative solution that does not rely on external regulation of water supply or high temperatures. Water content in hydrocarbon polymer membranes is regulated through nanometre-scale cracks ('nanocracks') in a hydrophobic surface coating. These cracks work as nanoscale valves to retard water desorption and to maintain ion conductivity in the membrane on dehumidification. Hydrocarbon fuel-cell membranes with surface nanocrack coatings operated at intermediate temperatures show improved electrochemical performance, and coated reverse-electrodialysis membranes show enhanced ionic selectivity with low bulk resistance.

MAKING ULTRATHIN POLYMERS Researchers from Sweden's Linkoping University, Sweden, and Germany's Technical University of Munich and the Deutsches Museum, along with other international collaborators, created a new method to manufacture [...]