Polymers and Polymer Composites

Alternating polymer flooding has achieved great attractions recently in oil industry, however, the research of pressure analysis in alternating polymer flooding reservoir is rare. This work presents a numerical pressure analysis method of three-zone composite model for formation evaluation. A new numerical pressure analysis model (three-zone composite model) is established by considering diffusion, convection, shear, and inaccessible pore volume, which is based on the rheology experiments. Based on this model, the type curves are then developed and sensitivity analysis is further conducted. The type curves have seven regimes in three-zone composite model. The characteristic is the obvious upturn of pressure derivative curve in transient regime between low concentration and high concentration polymer solution. Formation parameters can be interpreted by history matching and formation evaluation can be conducted based on this model. As an important part of formation evaluation, formation damage as a result of adsorption of polymers in porous media is evaluated by comparing the interpreted permeability with the original value before polymer flooding. The field test data proves that this proposed method can accurately evaluate reservoir characteristics in alternating polymer flooding reservoirs, which emphasizes the potential application of this method in petroleum industry.

Graphene oxide (GO) was served as mechanical strengthening to prepare GO/Polyvinyl Alcohol(PVA) composite film. This was accomplished in order to explore the influence of contents of GO on the tensile strength and failure strain of GO/PVA composite film. The results showed that as the GO content increased, the tensile strength of the composite film became greater rapidly at first, and then decreased gradually. When the GO content was 20%, the film had its maximum tensile strength (59.6 MPa). This is over 500% of the tensile strength of pure PVA film. The failure strain of GO/PVA composite film decreased rapidly as the GO content increased. The enhancement mechanism of the composite can be explained by the existence of multi-hydrogen bonds between the hydroxyl (-OH) groups of PVA and oxygen-containing functional groups of GO.

The oyster shell powder/natural rubber composites were successfully prepared by blending the modified oyster shell powder with natural rubber (NR). The oyster shell powder with a particle size of 209 nm were well distributed within the rubber matrix. The characteristic Fourier transform infrared spectroscopy (FTIR) absorption bands of both oyster shell powder and natural rubber were observed in the FTIR spectra of NR/oyster shell powder composites. The C-O absorption bands in carbonates of composites exhibit a shift from 1425 cm⁻¹ to 1446 cm⁻¹ which suggests the bonds formed among oyster shell powder, earth coupling agent and NR. The tensile strength and stress at 500% elongation increased with rising of the earth coupling agent. Composites with 1.5 parts per hundred rubber (phr) coupling agent achieved the highest mechanical properties, where an increase of 13.4% in tensile strength was found. The tensile strength and tear strength increased along with an increment of oyster shell powder. When the content of oyster shell powder attained 25–30 phr, the composites exhibited the best mechanical properties. In particular, the tensile strength and tear strength increased by 27.9% and 17.2% when compared with those of the control samples. Furthermore, the addition of the oyster shell powder leads to the improvement of thermal stability which is evidenced by an increase of 8 °C in the initial degradation temperature. The improvement of the mechanical properties and thermal stability of the composites have demonstrated that the oyster shell powder can be used as potential fillers for natural rubber.

In this paper, a continuous glass fiber-reinforced polypropylene prepreg was prepared by fiber treatment with a silane coupling agent and MAH-g-PP resin. Continuous glass fiber-reinforced polypropylene sheets were made from prepreg and PP mats by hot-pressing; they displayed exceptional performance. This paper studies the effects of maleic anhydride grafting on the polypropylene crystallinity and MAH-g-PP content in the prepreg, and the mechanical properties of the composites. The results showed that modifying PP with maleic anhydride decreased the tacticity of the polypropylene molecular chain, which reduced the crystallinity and melting point. An excellent interface formed between the polypropylene and fiber after the glass fiber was treated with a silane coupling agent and MAH-g-PP resin. The mechanical properties of the polymer materials displayed more favorable properties as MAH-g-PP content increased; the ideal MAH-g-PP content was 50%.

A numerical simulation procedure is presented to investigate the heat transfer and temperature distribution and then predict the curing uniformity of fiber/resin composite laminates during the hot molding process. By means of a coupled thermochemical simulation of the composite material curing process, the effects of curing temperature and heating rate on curing uniformity are investigated. Compared with the curing process with lower temperature and heating rate, the curing process with higher temperature and heating rate can cure the composites much faster but generate more uneven temperature distribution. By comparatively analyzing the influencing factors of curing non-uniformity, the curing characteristics of composites are revealed distinctly, which is helpful to understand the curing mechanism and design optimal curing cycle according to specific requirements.

In this study we modified nanoparticles to prepare Si₃N₄/PMMA nanocomposites. Surface modification of nano-Si₃N₄ powder was carried out by using a suitable modification agent (NDZ-102) for improving nanoparticles dispersion stability. The surface properties of Si₃N₄ nanoparticles were systematically investigated by Fourier transform infrared spectroscopy, thermogravimetric analysis, size distributions analyzer, surface free energy measurement and transmission electron microscopy (TEM). We concluded that 11% of NDZ-102 is the appropriate dosage of the coupling agent used to modify the surface of Si₃N₄ nanoparticles. Based on TGA and the spectra of FTIR, our results indicate that the coupling agent molecules are linked to the nanoparticles by chemical bonds, and that the surface of nanoparticles were coated by an organic layer. On the basis of the surface free energy experiments, it can be seen that there is an obvious improvement in the nanoparticles hydrophobicity after modification. Particle size tests and TEM reveal that the average diameter of the modified nano-Si₃N₄ is less than 100 nm and the nanoparticles have good dispersion in the solvent. It has also been found that the dynamic mechanical property of polymethyl methacrylate nanocomposite shows regular changes with an increasing powder content.

This study investigated the friction performance of polyimide-matrix composites with various silica powder contents of different sizes. The friction tests were performed on a pin-on-disk tester at various velocities, ranging from 30 to 160 km/h. The experimental results indicate a silica powder size of 0.25±0.05 mm, a sample of 4 wt.% SiO₂ demonstrated a high friction coefficient and better wear performance as compared to a sample without silica. The influence of silica content and powder size on the friction coefficient is directly related to the friction velocity. At low friction velocity (30–90 km/h), the friction coefficient increases as the SiO₂ content increases, but decreases with increasing SiO₂ particle size. At high friction velocity (90–160 km/h), the content and particle size of SiO₂ have little influence on the friction coefficient. Experimental results indicate that large SiO₂ particles can effectively hinder the motion of third body, which is advantageous to the formation of a compact third body and to the protection of the friction surface.

The recent core technologies developed in automobile and aerospace industries can be classified into two types, namely, advancement technology for safety and convenience and mechanical technology for eco-friendly and lightweight systems. Research in the field of composite materials has attracted significant attention. Carbon-fiber-reinforced plastics (CFRP) show high specific stiffness and specific strength compared with metallic materials. They exhibit mechanical properties with high damping characteristics and are lightweight. However, according to the direction of a laminate or its stacking sequence, the structural characteristics of CFRPs vary. It is hard to predict fracture under tensile and bending forces in CRFPs, when compared to metals. Threaded fasteners with easy assembly and disassembly are used widely in several fields. However, to maintain clamping force, proper torque force should be applied. As the size of the components decreases, the clamping force also decreases because the contact area between the component and other components decreases. In this study, CFRP specimens were subjected to tensile tests via a universal testing machine to estimate their mechanical properties with respect to the stacking angles of the laminates. The reverse screw torque and screw torque at each stacking angle were determined using a torque tester after tapping holes on the CFRP specimens. It was expected that both the epoxy attached to the screw surface and stacking direction of CFRP laminates affect the screw torque force of the composite material. In the case of woven composite specimens, there was no difference observed even when torque was applied to prevent loosening of the specimens with or without coating. The average results for the woven composite specimens were better than that for the other specimens.

Drug-loaded hydrophilic polymeric composite (HPC) is one of the most promising biomaterials for resolving the long-standing challenge of the development of oral solid formulations for insoluble drugs. With polyvinylpyrrolidone K10 (PVP) as polymeric carrier and sodium dodecyl sulfonate (SDS) as a surface active agent, a new type of HPC was fabricated for enhancing the dissolution of quercetin using an electrospraying process. A solvent mixture consisting of acetic acid, acetone and ethanol were exploited to prepare the co-dissolving solution of quercetin, PVP, and SDS for creating HPC. Both the sprayed nanoparticles and casting film fabricated using a thermal solvent evaporation process were amorphous composites, as demonstrated by the XRD results. ATR-FTIR spectra verified that the drug and the pharmaceutical carriers had good compatibility. In vitro dissolution experiments showed that the sprayed HPC could provide an over ten-fold faster dissolution rate than the casting film. Electrospraying is a facile method for developing new kinds of HPCs for insoluble drugs.

To reinforce the use of kenaf-derived cellulose as a compatible plastic filler, the cellulose (C) was thermally grafted with various concentrations (5, 8, and 11 wt.%) of hydrolysed 3-aminopropyltriethoxysilane (APS). The silane-grafted cellulose (SGC) were named as SGC5, SGC8 and SGC11. C (30 wt.%) and all of the SGC were respectively melt-compounded into poly(lactic acid) (PLA) before being hot-pressed into ∼0.3 mm sheets, which is the approximate thickness of clamshell packaging. The intermolecular interaction between SGC and PLA, which was absent with C, was confirmed via Fourier Transform Infrared Spectroscopy (FTIR). PLA filled with SGC5 or SGC8 showed significant improvement in thermal, tensile, physical, and barrier properties compared with the PLA/C composite. In contrast, adverse effects were observed with the PLA/SGC11 composite. 8 wt.% of APS was concluded as the critical concentration to be thermally-grafted onto the kenaf-derived cellulose as PLA/SGC8 composite showed optimum reinforcement in tensile strength (52 MPa), crystallizability (16% crystallinity), water resistance (5.3%) and dimensional stability (3.3%), and significantly shifted oxygen barrier from medium-low range to medium range (3.2 ×10⁻¹⁷ m³ m/m² s Pa). Overall, the variation in the properties of these biocomposites may extend PLA's range in food packaging applications.

The repair of damaged structures is a complicated problem in the construction industry and it is no uniform standard for evaluating the effectiveness of repair materials. Two different redispersible polymer powders, ethylene vinyl acetate (EVA) and polyvinyl acetate-vinyl carboxylate (VA/VeoVa), were added in the repair mortars with two water-cement ratios and three polymer-cement ratios. The effectiveness of repair materials was evaluated according to the physical, mechanical properties and micrographs. Testing program includes setting time, drying shrinkage, thermal expansion, compressive strength, tensile strength, flexural strength, bond strength, X-ray diffraction analysis, scanning electron microscopy observation.

Test results show that the specimens with VA/VeoVa and w/c of 0.5 have highest compressive strength, tensile strength, flexural strength and bond strength. The specimen with EVA also has higher strength than control one at the age of 28 days. The drying shrinkage deformation of VA/VeoVa specimen is close to the control one. The specimens with VA/VeoVa have lower thermal expansion than EVA specimen when the water-cement ratio is 0.5 and there is no difference between EVA and VA/VeoVa specimens for the water-cement ratio of 0.6. The micrographs show that adding polymer powder can reduce the pore and improve the durability.

This paper analyzes the miscibility state of EUG blended with CR, BR, SBR, NR and NBR via Molecular Dynamics (MD) simulations performed using Blends and the Flory-Huggins interaction parameter, phase diagrams, and mixing energy. The results showed that EUG can be miscible with CR, BR, SBR, NR, and NBR above 350K, and the simulation predictions and experimental results were mainly the same.

The surface modification effects of triethoxysilane (KH-550), methacryloxy propyl tri-methoxy silane (KH-570), and maleic anhydride grafted polypropylene (MAPP) on sawdust (SD), wheat straw (WS) and cellulose (CE) were studied by a tensile test, as well as surface morphology observation on reinforced composites. The results revealed that MAPP was the most effective coupling agent, and SD composites performed better than WS and CE. The tensile test results indicated that the optimum conditions for coupling agents were 1 wt.% for silane coupling agents and 5 wt.% for MAPP. SEM studies confirmed the tensile test results, proving that adhesion was improved with the employment of MAPP. MAPP-treated composite samples presented a prevailed fiber broken pattern which resulted in strong fiber-matrix interface bonding, whereas silane treatments did not provide an obvious enhancement in adhesion between the fiber and the matrix.

A series of damage tests and axially repeated compressive tests with high strain rates were conducted to investigate the behavior of aramid fiber reinforced polymer (AFRP) wrapped concrete under repeated impacts. The relation between damage condition and variables such as impact number and polymer thickness were examined. The tests were performed using a 100 mm diameter Split Hopkinson Pressure Bar (SHPB) apparatus and a nonmetal supersonic test meter. Various AFRP layers were applied to produce varied confinement ratios. The experimental results indicated that the AFRP-wrapped concrete exhibited excellent performance in resisting repeated impacts. Also, the specimens maintained their shapes and bearing capacity after multiple impacts with a mean strain rate of 50 s⁻¹. No distinct decline was observed from the history of peak stress and impact toughness in AFRP-wrapped concrete. Moreover, additional AFRP layers significantly decreased the impact damage on the core concrete, as reflected by the different strain rate histories in damage progression.

In this study, we present a novel approach to graft a large number of poly(glycidyl methacrylate) (PGMA) chains onto the carbon fiber (CF) surface through reversible addition-fragmentation chain transfer (RAFT) polymerization. Characterization results of FT-IR, XPS and TGA demonstrated that PGMA was covalently combined with carbon fibers. The CF/epoxy composites were obtained by addition of pristine CF and CF functionalized with poly(glycidyl methacrylate) (CF-PGMA) into epoxy resin. Experiment results revealed that the grafting of PGMA chains on the CF surface could increase significantly roughness and number of active groups of CF, which enhanced interface and mechanical properties of the composites. The compression strength, tensile strength, flexural strength and interfacial shear strength (IFSS) of CF-PGMA/epoxy composites are enhanced by at least 63.1%, 37.9% 55.6% and 122.5%, respectively, compared to pristine carbon fiber/epoxy composites. This enhancement indicates that surface modification of the carbon fibers by RAFT technique is a potential method to preparing CF-reinforced polymer matrix composites with excellent mechanical properties.