Effect Of Polymer Content Research Articles

Bioinspired Printable Tough Adhesives with In Situ Benignly Triggered Mechanical Enhancements

AbstractAdhesives can intimately connect humans to machines, seamlessly bond diverse tissues in the human body, and manage various diseases. However, the precise spatial control of wet and tough adhesion of biocompatible hydrogels on biological tissues remains a major challenge. Inspired by the bioglue secreted by sandcastle worms, the design of printable tough adhesives (PTAs) is proposed, a supramolecular hydrogel that can be printed into defined structures, in situ mechanically reinforced into a tough matrix with physiologically relevant benign triggers, and strongly adhere to diverse substrates. With carefully selected polymer components and ratios, it is discovered that the 3D printed PTAs can achieve a marked increase in toughness, tensile strength, and stiffness after being immersed in water/saline solution or attached to biological tissues. To assess the robust toughening mechanism triggered by the supramolecular interactions, the effects of polymer content and pH on the mechanical performance of PTAs and the kinetics of their triggered reinforcement are thoroughly investigated. The potential of PTAs is further demonstrated for manufacturing tough connective tissue mimetics, controlling patterned bioadhesion, and designing programmable 4D soft robotics. The bioinspired, printable, benignly triggerable, and adhesive supramolecular PTAs are expected to find broad applications in engineering and medicine.

Property transitions of neat and styrene–butadiene-styrene (SBS)-modified asphalt binders from small, medium to large-amplitude oscillatory shears

ABSTRACT Tests on asphalt binder are typically performed in its linear viscoelastic (LVE) range. In this research, the rheological properties of neat and styrene–butadiene-styrene (SBS)-modified asphalt binders were examined from 0.01% to 1000% at a high usage temperature, and focus was placed on their non-linear viscoelastic (NLVE) behaviours. Experimental variations and binder property changes in small, medium and large-amplitude oscillatory shears were revealed. Besides strain amplitude, the effects of polymer content, short-term aging and test frequency on NLVE behaviours were also analysed based on three quantitative methods. Additionally, polymers in asphalt binders were examined by using confocal fluorescence microscopy. The NLVE behaviours were found to be affected by shear strain amplitude, polymer content, shear frequency, and the interactions of such factors, but to a less extent by short-term aging. Besides polymer content, the size and morphology of polymer phase likely affect the property variations of modified asphalt binders. Large amplitude oscillatory shear (LAOS) test and morphology analysis help identify the threshold polymer content in producing high-quality polymer-modified asphalt binders.

Mechanical Properties Improvement of Polyvinyl Acetate Polymer-Treated Sand with Plant Fiber Reinforcement

Abstract Sand as a building material is pretty common in engineering constructions such as slopes and foundation pits. The great instability is generally generated because of the lack of cohesion inside and such instability is more serious during rains or when subjected to excessive external loads. This paper is aimed to study a combination of polyvinyl acetate polymer and sisal fiber as reinforcement materials. The focus of this study is to determine the effects of polymer content, fiber content, and dry sand density on the improvement in mechanical behavior of reinforced poorly graded sand. A series of direct shear, unconfined compression, and tensile tests on the reinforced sand have been conducted. The results suggest that the reinforcement effect increases with dry sand density up to 1.55 g/cm3 and then levels off. For fixed dry sand density, the strength of the improved sand enhances with the augment of polymer and plant fiber contents. At maximum contents, the reinforced sand can have 480 kPa of shear tensile strength, 1,276 kPa of unconfined compressive strength, and 240 kPa of tensile strength. The reinforcement mechanisms are revealed by Scanning Electron Microscope images. Polymer forms firm the polymer–soil matrices that enhance the fiber–sand interactions to mobilize tensile stresses. The combined use of polymer and fiber is preferred in engineering practices because of its zero negative impacts on the environment.

The Effect of Polymer Content of Quenchant on Microstructural and Mechanical Characteristics of AA-7075 Plates Before Age Hardening

In the heat treatment of AA 7075, residual stress, in some cases, increases the mechanical properties of the parts, such as resistance to fatigue, and in most cases, distorts the parts. This research tried to investigate the effects of residual stress on microstructure after the solutionizing process. After homogenizing, 7075 Al alloy samples with 6 and 20 mm thicknesses were solutionized at 485 °C for 30 and 90 minutes, respectively. Then samples were quenched in 10, 30, and 50% Polyalkylene Glycol (PAG) solutions with water. Afterward, the hole drilling method was used to measure post-quench residual stress. The results showed that the hardness number dropped in 6-mm samples as the tensile residual stress increased. This stemmed from the decrease in the quench rate due to the rise in the amount of PAG. However, this trend in 20-mm samples was upward and then dropped as the PAG amount increased from 30% to 50%. The results also demonstrated that in the 6-mm sample, tensile residual stress has an inverse proportion to the hardness. As the quench rate decreased, and subsequently, the tensile residual stress raised, 6-mm samples' grain size decreased, while grains in 20-mm samples were hardly distinguishable. A decrease in 6-mm samples' grain size could be the effect of more nucleation during the recrystallization under the elastic force's influence, and consequently, raise in overall stored energy created by tensile residual stress. Therefore, in the quenched AA 7075, the tensile residual stress can contribute to the recrystallization phenomenon. This effect is created by the rise in the system's overall stored energy due to the lattice's elastic force.

Hardness of chemically densified Yellow birch in relation to wood density, polymer content and polymer properties

Abstract Density of wood can be increased by filling its porous structure with polymers. Such densification processes aim to increase hardness of wood and are particularly interesting for flooring applications. This study aims to evaluate efficiency of different polymers for chemical densification based on the polymer properties. Yellow birch (Betula alleghaniensis Britt.) was chemically densified with seven monomer mixtures through acrylate monomer impregnation and electron beam in-situ polymerization. Chemical retention and polymer content of densified woods were recorded. Hardness of treated and untreated Yellow birch was measured and compared to hardness of Jatoba (Hymenaea courbaril L.). All densified woods showed higher or comparable hardness to Jatoba. Hardness of densified wood was analyzed in relation to initial density of wood and polymer content of the material using multivariable linear mixed models. Efficiency of polymers for chemical densification was evaluated through effect of polymer content on hardness with interaction coefficients. Polymer films corresponding to monomer impregnating mixtures were prepared through low energy electron beam and characterized by their glass transition temperature, micro hardness, indentation modulus and crosslinking density. Polymers showed statistically significantly different efficiencies and were separated in two main groups. Overall, polymer efficiency increased with increasing glass transition temperature of polyacrylates.

Effect of polymer content and temperature on mechanical properties of lightweight polymer concrete

This study investigates the mechanical properties of lightweight polymer concrete (LWPC) containing four different polymer ratios (10%, 12%, 14%, and 16%) tested at three different temperatures (−15 °C, +5 °C, and +25 °C) using destructive and non-destructive tests. In addition, a series of expressions are suggested to predict the splitting-tensile, flexural and impact strength of LWPC based on the main parameters and compressive strength. The analysis of variance (ANOVA) method was also used to determine relative contributions of the experimental parameters. The results of the destructive tests show that increasing the polymer ratio caused an increase in the compressive, splitting-tensile, and impact strengths, and energy absorption of LWPC. With decreasing the temperature from +25 °C to −15 °C, the compressive, splitting-tensile, flexural strengths, and elastic modulus (EM) increased, whereas the energy absorption, impact energy, and ductility decreased. The findings of this research provide beneficial information toward understanding the behavior of LWPC and its safe use in engineering applications where a material of high strength-to-weight ratio is required.

Sisal Fiber-Polymer–Treated Sand Mechanical Properties in Triaxial Test

ABSTRACT Natural sisal fiber is an environment-friendly and efficient material for soil reinforcement. Many studies have reported that the shear strength of soil has been improved by the addition of fiber. However, the mechanical properties of sand can be more effectively improved by the incorporation of water-based polymer and sisal fiber. An extensive laboratory testing program was conducted to determine the effect of water-based polyurethane and sisal fiber reinforcement on sand. Laboratory tests included sieve analysis, X-ray diffraction, conventional triaxial compression, and scanning electron microscopy (SEM) tests. The effects of polymer content (PC), fiber content (FC), fiber length (FL), and sample dry density (ρ) are thoroughly investigated. The results indicate that the increases of PC, FC, and ρ all improve the mechanical properties of sand. For FL, this improvement in shear strength was maintained to FLs of up to 18 mm. Beyond 18 mm, the shear strength decreased with further increase in FL. The mixing of polymer and fiber changes the failure mode from shear faulting to ductile flow. This indicates that the ductility of sand is improved. From the SEM images we found that sisal fibers, binding with colloidal materials formed by polymer, fill the sand voids and join the sand particles. This demonstrates that mixing of fiber and polymer can enhance the bonding of sand particles.

Preparation of new nanocomposite poly(GDMA)/mesoporous silica and its adsorption behavior towards cationic dye

In this work, a new nanocomposite based on crosslinked Glycerol Dimethacrylate (GDMA) and the mesoporous silica MCM-41 was prepared. The GDMA is first synthesized by the ring opening of glycidyl methacrylate (GMA) using methacrylic anhydride (MA) and promoted by a new solvent-free green catalysis process at room temperature. The nanocomposites are further obtained by in-situ polymerization of the GDMA in the channels of the mesoporous silica and then tested for the removal of methylene blue (MB) dye. Effect of polymer content, adsorbent mass, contact time and initial dye concentration were studied and discussed in terms of affinity and adsorption efficiency. The results showed that the poly(GDMA) was well immobilized in the internal and external surface of the mesoporous silica MCM-41. The adsorption efficiency of MB dye increased with increasing poly(GDMA) content in which the nanocomposite (NC-3) exhibited the best adsorption capacity of MB dye. The adsorption of MB dye by nanocomposite NC-3 followed Langmuir adsorption isotherm models and pseudo-second-order kinetics. The maximum adsorbed amount of MB dye on nanocomposite NC-3 is 111.11 mg/g.

Strength and Solidification Mechanism of Silt Solidified by Polyurethane

To determine the mechanism and strength characteristics of solidification of silt by a permeable polyurethane grouting material, the effects of polymer content, soil moisture, and immersion time on the unconfined compressive strength (UCS) of the silt have been studied. The results showed that the permeable polymer grouting material can significantly improve the performance of silt: (1) A higher amount of polymer produced a greater strength in the solidified soil. (2) The strength of the solidified soil increased as the immersion time was increased. (3) Moisture in the soil was not conducive to improving the strength of the solidified soil. The X‐ray diffraction (XRD) and energy‐dispersive spectroscopy (EDS) have proven that polyurethane does not react with the silt, but they could improve the strength of the silt through physical action. Mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were performed to find that polymers can reduce soil porosity, and the addition of polyurethane improved the strength of the silt mainly through adhesion, wrapping, filling, and bridging.

Shear stress limit, rheological properties and compressive strength of cement-based grout modified with polymers

Grouting is a comprehensive technology used in the construction projects due to the rapid development of sub-surface urban infrastructures, the main reasons for grouting soils are strengthened the cohesion-less soils and increasing the shear stress (pure shear) of the grouted soils. Providing high flowability with high viscosity for the cement-based grout in the liquid stage (slurry) and high compressive strength of the cement-based grout in the hardened stage are significant challenges. In this study, the impact of two types of water reducer [polycarboxylate (PCE)] polymer on the rheological properties with the ultimate shear strength and compressive strength of cement-based grout with water-cement ratios (w/c) of 0.6 and 1.0 at two different temperatures 25 °C and 50 °C were studied. XRD and TGA were used to analysis the cement, polymers, and cement modified with polymers. The behavior of cement-based grout in the liquid phase (slurry) and hardened phase modified with different percentages of polymer up to 0.16% (by dry weight of cement) were investigated. The compressive strength of cement-based grout modified with polymer was tested from the young age up to 28 days of curing. Vipulanandan rheological model was used to predict the shear stress-shear strain behavior of cement-based grout slurry and compared to the Herschel–Bulkley (HB) model. The rheological and the compressive strength are increased with increasing the of PCE content. The polymer modification increased the yield stress, apparent viscosity and plastic viscosity of the cement grout by 19–136%, 32–319% and 58–367%, respectively based on the types of polymer, polymer content, w/c, and temperature. The compressive strength of the cement-based grout increased by 94–786% based on the types of polymer, polymer content, w/c and curing time. Increasing the temperature of cement-based grout slurry to 50 °C increased the maximum shear stresses by 110% and 107%, respectively. Effects of polymer content, w/c, curing time and the temperature of the plastic and hardened properties of cement-grout were modeled using a multiple nonlinear regression analysis.

Viscosity, yield stress and compressive strength of cement-based grout modified with polymers

In this study, two types of polycarboxylate (PCE) polymer (DBC-21 and VK-98) were used as additives in the cement-based grout. The water-cement ratio (w/c) was fixed to 0.6 and 1.0 ​at temperature of 25° Celsius and 50° Celsius. Experimentalists were conducted to study the chemical composition of the cement-based grout, the mass loss, the rheology behavior, and the compressive strength. Numerical studies were performed to understand the shear strength, rheological properties and compressive strength by taking advantages of numerical models. The results show that the 0.16% PCE polymer additive leads to low cement weight loss at 800° Celsius, drastic increase of apparent and plastic viscosity, and significant improvement of compressive strength. Effects of polymer content, w/c, curing period and the temperature on the rheological properties and compressive strength (CS) of cement-based grout were investigated using a multiple nonlinear regression analysis.

Toward a General Methodology for Modeling Diffusive-Controlled Reactions in Free Radical Polymerization

A mathematical model for describing the bulk free-radical polymerization of methyl-methacrylate was developed. This model includes a novel methodology for describing the diffusive step of the kinetic rate coefficients, which is based on geometric considerations and application of the Einstein diffusion Equation. The effect of polymer content and temperature on the Rp behavior is discussed in terms of the evolution of the interdependent parameters defining the Rp. The applicability of Smoluchowski equation and the importance of the translational diffusion of short radicals in the rate of termination reaction are questioned in this context. Similitudes and differences between the model results and experimental data are discussed including minima in the Rp curves at low conversions.

The Effect of Polymer Content on the Non-Newtonian Behavior of Acetaminophen Suspension

Acetaminophen is used as an analgesic and antipyretic agent. The aim of the study was evaluation of the effect of different polymers on rheological behavior of acetaminophen suspension. In order to achieve controlled flocculation, sodium chloride was added. Then structural vehicles such as carboxymethyl cellulose (CMC), polyvinyl pyrrolidone (PVP), tragacanth, and magnesium aluminum silicate (Veegum) were evaluated individually and in combination. Physical stability parameters such as sedimentation volume (F), redispersibility (n), and growth of crystals of the suspensions were determined. Also, the rheological properties of formulations were studied. The results of this study showed that the combination of suspending agents had the most physical stability and pseudoplastic behavior with some degree of thixotropy. Viscosity of suspensions was increased by adding NaCl 0.02%. Presence of PVP is necessary for improving rheological behavior of suspensions by NaCl. This may be related to the cross-linking between the carbonyl group in the PVP segment and Na+ ions.

Influence of the Polymer Content in the Preparation of Polymeric Membranes

This work aims to evaluate the effect of polymer content in the preparation of membranes obtained from polyamide 6/national clay nanocomposites. The polymeric membranes were produced varying the polymer content at 20 and 22% and using the technique of precipitation by immersion, which consists of three main steps: preparation a homogeneous polymer solution, scattering the solution on a surface forming a film of determined thickness and finally formation of polymeric structure of membrane by separation phases the system. The obtained results by scanning electron microscopy (SEM) indicated that the content of polymer changes the pore formation, the distribution and density, thereby obtaining membranes with different pore sizes, and it was possible to observe that the higher the polymer content, the lower will the pore diameter and more thicker will be the selective membrane layer.

Resource Utilization of Electronic Waste Plastic

In the paper, electronic waste plastic and petroleum asphalt were used to synthesize plastic asphalt. The effect of polymer content, shearing rate and time on properties of plastic asphalt has been studied. The results show that softening point and ductility of plastic asphalt can reach optimal values at condition of polymer content 6%, shearing rate 3 kr/min, shearing time 40 min and initiator of potassium persulfate.

Experimental investigation on the properties of polymer modified SCC

This paper presents an experimental investigation on the properties of polymer modified self compacting concrete SCC. This concrete is considered as a modification of polymer concrete. Polymer modified self compacting concrete achieves the advantages of both self compacting concrete and polymer modified concrete. Polymer modified SCC may be used successfully in repair of concrete elements or construct new concrete elements especially when concrete subjected to sever conditions. There is no further information about properties of polymer modified SCC. This research aims to study the interactions between main self compacting concrete components (filler and high dose of chemical admixtures) and main components of polymer modified concrete which is polymer itself. The effect of polymer content, polymer type, filler type and base of chemical admixtures were studied. Cube compressive strength, tensile strength, dynamic modulus of elasticity, bond strength between concrete and steel reinforcement, bond strength between self compacting concrete and old concrete, thermogravimetric and X-ray diffraction analysis were used to evaluate the effect of studied parameters. From this work, styrene butadiene rubber and polyvinyl acetate can be used to produce polymer modified self compacting concrete. Also, polymer self compacting concrete has good mechanical properties especially tensile strength and bond strength. Finally, the use of polymer decreases the degree of hydration of cement.

In-situ monitoring of polysulfone membrane formation via immersion precipitation using an ultrasonic through-transmission technique

An ultrasonic through-transmission technique as a non-invasive technique was developed to monitor the formation process of asymmetric polysulfone (PSF) membrane via immersion precipitation. The effect of polymer content in the casting solution in water/1-methyl-2-pyrrolidinone (NMP)/PSF and ethanol (EtOH)/NMP/PSF systems on the membrane morphology were investigated. Results showed that the systematic movement of ultrasonic signals in the arrival time observed during the membrane formation is associated with the changes of sound velocity in the media. The shift of ultrasonic signals in the arrival time decreased with an increase in the PSF concentration in both water and EtOH coagulations. The arrival time of ultrasonic signals kept stable at the initial time of membrane formation and then gradually shifted with the membrane formation when using water as a coagulation agent. It is relevant to the formation of the dense skin layer and finger-like macrovoids as well as the out-diffusion of NMP from the bottom surface of the casting solution. The systematic shift of ultrasonic signals forward along transmission direction of the sound wave in time-domain with the membrane formation time using EtOH as a coagulation agent is correlated with the formation of the porous surface and sponge-like structure. It is the reason because the double diffusion between EtOH and NMP leaded to liquid–liquid phase separation and the shrinkage in the lateral layer, mainly dominated by the penetration of EtOH from the coagulation to the casting solution. The SEM and AFM observation of membrane morphology corroborated ultrasonic measurements.

Development of Alginate/Chitosan Microparticles for Dust Mite Allerge

Purpose : To develop chitosan/alginate microparticles for the mucosal delivery of allergen from dust mite (Dermatophagoides pteronyssinus). Methods : Chitosan/alginate microparticles were prepared by ionotropic gelation. The effects of polymer content, crosslinking agent, and preparation method on the physicochemical characteristics of the microparticles as well as their in vitro cytotoxicity were investigated. Results: The microparticles were small (1 - 17 µm) and spherical in shape. The highest allergen content (0.30 ± 0.07 mg/g) was obtained with 2.5 % initial allergen loading in chitosan- triphosphate (CS-TPP) microparticles. Sustained allergen release (approx. 50 % over 24 h) was observed from alginate-coated chitosan microparticles. Allergen incorporation method and initial drug-loading could be varied to obtain optimum particle size with high allergen-loading and sustained release. The cytotoxicity of various microparticle formulations did not differ significantly (p > 0.05 ), as cell viability values were close to 100 %. Conclusion: This study indicates that alginate and alginate-coated chitosan microparticles are safe and can be further developed for mucosal allergen delivery.

Investigation of the heat capacity of poly (vinyl methyl ether)/water mixtures using the stepscan method

The heat capacity of poly(vinyl methyl ether) (PVME)/water mixtures was measured over a wide range of temperatures using the stepscan method. The results showed that water exists in different states in the mixtures. The Cp values of dry PVME and PVME/water mixtures with a low water content were obtained by the stepscan method, and the Cp of bound water in the mixtures was approximated. The results showed that the Cp of bound water in the mixtures with a low water content is higher than that of mixtures with glassy water and ice, and it shows no dependence on water content in the glassy state. Because of the larger conformational contribution to Cp, the heat capacity of water in the mixtures in the liquid state increases with water content. Because there is a weak interaction between PVME and water molecules, the structure of water in mixtures is different from that of glassy water. The Cp value of unfreezable bound water in the mixtures was calculated without considering the effect of polymer content, and the interaction between PVME and water was obtained; these calculations explained the phase separation observed at high temperature. The Cp calculation value (♦) of unfreezable bound water in PVME/water mixtures at low temperature. ◊: the experimental Cp of glassy water;21 □: the Cp of cubic ice.30

Preparation of PVDF-HFP Microporous Membranes via the Thermally Induced Phase Separation Process

The thermally induced phase separation (TIPS) process was employed to prepare poly (vinylidene fluoride-co-hexafluoropropylene; PVDF-HFP) microporous membranes using sulfolane as the diluent. The phase diagram of the PVDF-HFP/sulfolane system was drawn and analyzed. The effects of polymer content in casting solution and cooling rate on the cross-sectional morphology, crystallinity, crystal structure, and porous structure of the resulting membranes were investigated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and a mercury porosimeter, respectively. The mechanical properties of the membranes were evaluated by tensile tests. It was found that a solid-liquid phase separation occurred in the PVDF-HFP/sulfolane system. Spherulites and “net-shaped” structures coexisted in the obtained membranes. Polymer content and cooling rates had some influences on the crystallinity, porous structure, and mechanical properties of the membranes, but no influence on the polymer crystal structure of the membranes.