Low Initial Viscosity Research Articles

Containment strategy for subsurface H2 storage based on time-dependent soft solids

We propose an innovative containment strategy based on time-dependent soft solids, namely 2 wt% Laponite suspensions, to reinforce natural subsurface seals and engineer flow barriers, with an eye toward making H2 subsurface storage scalable and geographically agnostic. This suspension can be injected at its initial low viscosity and elasticity into a porous medium, allowing for easy pumping and targeted delivery. Once inside the target zone, it matures into a soft solid with much higher viscosity and elasticity, acting as a potential flow barrier. We discuss the rheological properties of the suspensions and demonstrate that hydrogen does not adversely affect their microstructure, but rather increases the suspensions’ viscosity and elasticity. Moreover, the suspensions enhance the rock samples’ compressive strength, while hydrogen exposure increases their stiffness and ductility. The ability of rock samples saturated with the suspensions to contain higher injected gas pressures is enhanced by aging at higher temperatures.

The Advances in Phospholipids-Based Phase Separation Gels for the Sustained Release of Peptides, Proteins, and Chemotherapeutics.

Implantable drug delivery systems formed upon injection offer a host of advantages, including localized drug administration, sustained release, minimized side effects, and enhanced patient compliance. Among the various techniques utilized for the development of in situ forming drug implants, solvent-induced phase inversion emerges as a particularly promising approach. However, synthetic polymer-based implants have been associated with undesirable effects arising from polymer degradation. In response to this challenge, a novel category of drug delivery systems, known as phospholipids-based phase separation gels (PPSGs), has emerged. These gels, characterized by their low initial viscosity, exhibit injectability and undergo rapid transformation into in situ implants when exposed to an aqueous environment. A typical PPSG formulation comprises biodegradable components, such as phospholipids, pharmaceutical oil, and a minimal amount of ethanol. The minimized organic solvents in the composition show good biocompatibility. And the relatively simple composition holds promise for industrial-scale manufacturing. This comprehensive review provides an overview of the principles and advancements in PPSG systems, with specific emphasis on their suitability as drug delivery systems for a wide range of active pharmaceutical ingredients (APIs), spanning from small molecules to peptides and proteins. Additionally, we explore the critical parameters and underlying principles governing the formulation of PPSG-based drug delivery strategies, offering valuable insights on optimization strategies.

Experimental Evaluation of Performance of a Low-Initial-Viscosity Gel Flooding System.

In order to effectively adjust reservoir heterogeneity and further exploit the remaining oil, a new type of low-viscosity gel was prepared by adding a regulating agent, retarder, and reinforcing agent on the basis of a polymer + Cr3+ crosslinking system. The new gel has the advantages of low initial viscosity, a slow gel formation rate, and high strength after gel formation. The effectiveness of the gel was verified through three-layer core displacement experiments, and the injection scheme was optimized by changing the slug combination of the polymer and the gel. The results showed that the gel can effectively block the high-permeability layer and adjust reservoir heterogeneity. An injection of 0.1 pore volume (PV) low-initial-viscosity gel can improve oil recovery by 5.10%. By changing the slug combination of the gel and polymer, oil recovery was further increased by 3.12% when using an injection of 0.07 PV low-initial-viscosity gel +0.2 PV high-concentration polymer +0.05 PV low-initial-viscosity gel +0.5 PV high-concentration polymer.

Novel Environmentally Responsive Polyvinyl Polyamine Hydrogels Capable of Phase Transformation with Temperature for Applications in Reservoir Profile Control.

Hydrogel has been widely used in reservoir regulation for enhancing oil recovery, however, this process can experience negative influences on the properties and effects of the hydrogels. Therefore, developing novel hydrogels with excellent environmental responsiveness would improve the formation adaptability of hydrogels. In this study, novel polyvinyl polyamine hydrogels were synthesized by a ring-opening addition reaction between polyvinyl polyamines and polyethylene glycol glycidyl ether. The results of atomic force microscopy and transmission electron microscopy showed that the polyvinyl polyamine gel had a porous and irregular bulk structure and was endowed with water storage. With the temperature rising from 30 °C to 60 °C, the transmittance of diethylenetriamine hydrogel decreased from 84.3% to 18.8%, indicating that a phase transition had occurred. After the polyvinyl polyamine hydrogel with low initial viscosity was injected into the formation in the liquid phase, the increase of the reservoir temperature caused it to turn into an elastomer, thereby migrating to the depth of the reservoir and achieving effective plugging. Polyvinyl polyamine hydrogel could improve the profile of heterogeneous layers significantly by forcing subsequent fluids into the low permeability zone in the form of elastomers in the medium temperature reservoirs of 40-60 °C. The novel environmentally responsive polyvinyl polyamine hydrogels, capable of phase transformation with temperature, exhibited superior performance in recovering residual oil, which was beneficial for applications in reservoir profile control and oilfield development.

Synergistic dopa-reinforced fluid hydrosol as highly efficient coal dust suppressant

A highly efficient coal dust suppressant with low initial viscosity and high adhesion-solidification properties was fabricated by reinforcing a polyacrylic acid hydrosol with dopa and glutathione (DG) redox system. The synthesis mechanism and dust suppression properties of the dust suppressant were investigated by ultraviolet–visible spectroscopy, high-performance liquid chromatography, and nuclear magnetic resonance spectroscopy experiments combined with density functional theory calculations. The polyacrylic acid hydrosol was synthesized by free radical polymerization with an optimal concentration ratio of 0.36 % ammonium persulfate to 9 % acrylic acid; the DG redox system presented a catechol-quinone dynamic equilibrium, and the dopa polymer reinforcing adhesion was synthesized by the reverse dismutation and polymerization of dopa and dopaquinone. Results revealed that the dust suppressant system formed a multiple hydrogen bonding cross-linking network, dominated by strong double hydrogen bonding interaction formed between the carboxyl groups of dopa polymer and polyacrylic acid, and synergized by hydrogen bonds between the carboxyl groups of glutathione and PAA, and between the hydroxyl and carboxyl groups of dopa and dopaquinone. Moreover, the − OH and − COOH groups in the dust suppressant system were more tightly bonded after dehydration and can form a mesh film to effectively adhere and solidify coal dust, and the coal crust film did not raise dust at 20.526 ± 0.083 m/s wind speed.

Assessment of the enhancement potential of salicylic acid on physicochemical, mechanical, barrier, and biodegradability features of potato starch films

Filmogenic suspensions based on starch (S) and salicylic acid/starch (SA-S) were prepared and used to produce casted films (TPS and SA-TPS). An extensive characterization was conducted on both suspensions and casted films to assess their properties. Results evidenced that after storage for 120 days at 4 °C and 25 °C, the mold and yeast counts were significantly lower in the SA-S than in the S suspensions. Moreover, SA-S had a much lower initial viscosity than S. In reference to the films produced, salicylic acid caused a significant increase in film crystallinity, as well as a 2.3-fold increase in stress at break and a 3.8-fold increase in Young's modulus over the control films. Additionally, compared to TPS, the SA-TPS films exhibited a 46% decrease in water vapor permeability. All films showed a high biodegradation extent (≥85%) upon 75 days of home composting. These findings suggest that the salicylic acid addition at low concentrations (2 mM) can be a cost-effective approach for the development of highly stable starch filmogenic suspensions and also biobased films with distinguishing properties.

Evaluation of properties and aging resistance of epoxy asphalt composite modified by ultraviolet absorber

AbstractThis research investigated the effect of ultraviolet absorber (UV‐531) on the properties of epoxy asphalt (EA) binders. EA binders were modified by adding UV‐531 absorber at contents of 0, 0.3, 0.6, 0.9, and 1.2 wt%, and composites were then subjected to ultraviolet (UV)‐based aging, including UV, oxygen, and heat treatment. Laboratory tests were conducted to assess UV absorption, viscosity, mechanical parameters, contact angle, microstructure, and chemical functional groups of absorber‐modified EA composites before and after aging. The results showed that the addition of UV‐531 resulted in enhanced UV absorption capacity, lower initial viscosity, and longer allowable application time for EA composites. The UV‐531 absorber has good compatibility with EA binders and does not weaken the performance of EA binders. From anti‐aging perspective, UV‐531 absorber effectively delayed the degradation of the physical, mechanical, and chemical structures of EA composites. The breakage of alkyl and ester groups of EA composites containing absorber was significantly reduced under aging conditions. Overall, the presence of UV‐531 retarded severe performance deterioration in EA composite. Considering aging improvement and economic cost, it is recommended to use a content of 0.9 wt% UV‐531 absorber as an anti‐aging agent for EA composites.

In situ gelation of thiolated poly(aspartic acid) derivatives through oxidant-free disulfide formation for ophthalmic drug delivery

Efficient topical treatment of ocular diseases requires a prolonged residence time of drug formulations. An in situ gelling, mucoadhesive system can provide improved residence time while keeps the installation of the formulation easy and accurate due to its low initial viscosity. We synthesized a two-component, biocompatible water-based liquid formulation showing in situ gelation upon mixing. S-protected, preactivated derivatives of thiolated poly(aspartic acid) (PASP-SS-MNA) were synthesized by coupling the free thiol groups of thiolated poly(aspartic acid) (PASP-SH) with 6-mercaptonicotinic acid (MNA). The amount of protecting groups was 242, 341, and 530 µmol/g depending on the degree of thiolation of PASP. The chemical interaction between PASP-SS-MNA and mucin was proven, indicating the mucoadhesive properties. Disulfide cross-linked hydrogels were formed in situ without an oxidizing agent by mixing the aqueous solutions of PASP-SS-MNA and PASP-SH. The gelation time was controlled between 1 and 6 min, while the storage modulus was as high as 4–16 kPa depending on the composition. Swelling experiments showed that hydrogels with no residual thiol groups are stable in phosphate-buffered saline at pH = 7.4. In contrast, the presence of free thiol groups leads to the dissolution of the hydrogel with a rate depending on the excess of thiol groups. The biological safety of the polymers and MNA was confirmed on Madin-Darby Canine Kidney cell line. Furthermore, a prolonged release of ofloxacin was observed at pH = 7.4 compared to a conventional liquid formulation, supporting the potential of the developed biopolymers in ophthalmic drug delivery.

Gas channeling control with an in-situ smart surfactant gel during water-alternating-CO2 enhanced oil recovery

Undesirable gas channeling always occurs along the high-permeability layers in heterogeneous oil reservoirs during water-alternating-CO2 (WAG) flooding, and conventional polymer gels used for blocking the “channeling” paths usually suffer from either low injectivity or poor gelation control. Herein, we for the first time developed an in-situ high-pressure CO2-triggered gel system based on a smart surfactant, N-erucamidopropyl-N,N-dimethylamine (UC22AMPM), which was introduced into the aqueous slugs to control gas channeling in WAG processes. The water-like, low-viscosity UC22AMPM brine solution can be thickened by high-pressure CO2 owing to the formation of wormlike micelles (WLMs), as well as their growth and shear-induced structure buildup under shear flow. The thickening power can be further potentiated by the generation of denser WLMs resulting from either surfactant concentration augmentation or a certain range of heating, and can be impaired via pressurization above the critical pressure of CO2 because of its soaring solvent power. Core flooding tests using heterogeneous cores demonstrated that gas channeling was alleviated by plugging of high-capacity channels due to the in-situ gelation of UC22AMPM slugs upon their reaction with the pre- or post-injected CO2 slugs under shear flow, thereupon driving chase fluids into unrecovered low-permeability areas and producing an 8.0% higher oil recovery factor than the conventional WAG mode. This smart surfactant enabled high injectivity and satisfactory gelation control, attributable to low initial viscosity and the combined properties of one component and CO2-triggered gelation, respectively. This work could provide a guide towards designing gels for reducing CO2 spillover and reinforcing the CO2 sequestration effect during CO2 enhanced oil recovery processes.

Design of a Polymer Composition for the Conformance Control in Heterogeneous Reservoirs

The article is devoted to the issue of a low sweep efficiency in the heterogeneous terrigenous reservoirs containing remaining oil. Water plugging operations that redirect the injection fluid flows into unswept zones, are one approach to enhancing the oil recovery in these reservoirs. The commonly used chemical reagents in these treatments are acrylate polymer solutions. The polymer solutions must reach the target water-saturated zones and form a strong gel barrier there. Furthermore, the polymer compositions should have a low initial viscosity to provide a good injectivity and penetration ability. Therefore, the methods of adjusting the gelation time are necessary. There are numerous studies in modern scientific society devoted to the study of water-plugging polymer compositions. However, aspects, such as the effect of the hydrogen index on gelation, have received insufficient attention. In this paper, we describe the features of the developed polymer composition, based on a hydrolyzed polymer of acrylonitrile with a controlled gelation time for the chemically enhanced oil recovery. The component composition and the concentration levels were selected, based on the alterations in the hydrogen index of the polymer solution. It was scientifically proven that by adhering to a neutral hydrogen index, it is possible to improve the properties of the polymer composition. Moreover, using a model of a heterogeneous reservoir, it was confirmed that the proposed polymer composition achieves selective plugging. As a result of the polymer gel treatment, the water cut decreased by 4% and the displacement coefficient of oil increased by 20%, in comparison with the effect of the original composition without a gel-time modifier.

Long-term compressive strength and hydraulic property of nanosilica-improved sand in different soaking environments

Traditional grouting materials (such as cements, sodium silicates and organic polymers etc.) have some limitations in improving soil, the rheological property of cement-based slurries is inferior to chemical grouting materials, sodium silicates have non-negligible shrinkage, organic polymers are often toxic. As a new kind of grouting materials, nanosilica has nano-scale particles, low initial viscosity, good penetration, and environment friendly characteristics. Literature showed that nanosilica could effectively increase the compressive strength and reduce the pore volume of sand. But the long-term mechanical and hydraulic properties of nanosilica-improved sand (NIS) in different soaking environments were rarely studied. In this study, different soaking environments (dry air, pure water, seawater, and acidic water) were adopted to simulate various practical engineering environments, with a soaking time of up to 365 days. The long-term compressive strength, hydraulic property, and microscopic structure were monitored. The results showed that the performance of NIS in pure water was better than in other environments. The compressive strength of NIS in pure water reached 283 KPa, and the erosion resistance time of NIS in pure water reached 350 hours. The maximum compressive strengths of NIS in acid water, seawater and air were 270 KPa, 253 KPa and 250 KPa, respectively. The maximum erosion resistance times of NIS in acid water, seawater and air were 263 hours, 205 hours and 261 hours, respectively. According to the microscopic results, the improved sand transformed from loose particles to agglomerates, and finally, to cemented aggregates. The NIS showed obvious roughening and shrinkage in dry air, while remained relatively complete in other three saturated environments. The results may provide reference for practical application of nanosilica-improved sand. • Nanosilica can improve the mechanical and hydraulic properties of sand. • The long-term performance of NIS can be basically maintained at a stable level. • The performance via environments is ranked as follows: Water, Sea, Acidic, Air. • The early strength of NIS increased with the concentration of catalyst. • NIS transformed from loose particles to agglomerates, and to cemented aggregates.

Performance Evaluation and Structure Optimization of Low-Emission Mixed Epoxy Asphalt Pavement

Epoxy asphalt concrete (EAC) has excellent properties such as high strength, outstanding thermal stability, and great fatigue resistance, and is considered to be a long-life pavement material. Meanwhile, the low initial viscosity of the epoxy components provides the possibility to reduce the mixing temperature of SBS-modified asphalt. The purpose of this study is to verify the feasibility of low-emission mixing of SBS-modified epoxy asphalt and to compare the mechanical responses in several typical structures with EAC, in order to perform structure optimization for practical applications of EAC. In this paper, the Brookfield rotational viscosity test was conducted to investigate the feasibility of mixing SBS-modified epoxy asphalt at a reduced temperature. Subsequently, the dynamic modulus tests were carried out on EAC to obtain the Prony series in order to provide viscoelastic parameters for the finite element model. Six feasible pavement structures with EAC were proposed, and a finite element method (FEM) model was developed to analyze and compare the mechanical responses with the conventional pavement structure. Additionally, the design life was predicted and compared to comprehensively evaluate the performance of EAC structures. Finally, life cycle assessment (LCA) on carbon emissions was developed to explore the emission reduction effect of the epoxy asphalt pavement. The results indicate that the addition of epoxy components could reduce the mixing temperature of SBS-modified asphalt by 30 °C. The proper use of EAC can significantly improve the mechanical condition of the pavement and improve its performance and service life. It is recommended to choose S5 (with EAC applied in the middle-lower layer) as the optimal pavement structure, whose allowable load repetitions to limit fatigue cracking were more than 1.7 times that of conventional pavements and it has favorable rutting resistance as well. The LCA results show that in a 25-year life cycle, the carbon emissions of epoxy asphalt pavements could be reduced by 29.8% in comparison to conventional pavements.

Effect of varying cell densities on the rheological properties of the bioink

The rheological characterization of any biopolymer solution is crucial for evaluating the overall printability or injectability of the hydrogel. However, the effect of cells in the cell-laden hydrogel's rheological profile is often ignored. As a result, there is a significant difference in the predicted and experimental outcome in the structural stability of the construct as well as on the cell viability, proliferation, and differentiation potential of the embedded cells. Our present study has addressed the effect of different cell densities (0.1 million cells/ml, 0.5 million cells/ml, 1 million cells/ml and 2 million cells/ml) of TVA-BMSCs on the flow property, modulus behaviour, gelation kinetics and printability of our proprietary silk fibroin-gelatin (5SF-6G) bioink. The cell-laden hydrogels demonstrated a characteristic shear thinning behaviour (low initial viscosity), low storage modulus and increased gelation time when compared to the acellular 5SF-6G hydrogel. The printability analysis also portrayed a square pore geometry with low spreading ratio in 1 million cells/ml encapsulated 5SF-6G hydrogel comparable to the acellular hydrogel. We postulated that incorporation of cells in the bioink interfered with the gelation mechanism of the mushroom tyrosinase in the 5SF-6G bioink by masking the active sites. Additionally, the mechanistic crosstalk between the cell-surface integrins with the cell-attachment motifs of the biomaterial alters the cellular biomechanics of the cell that in-turn profoundly impacts the rheological properties of the polymer blend. Therefore, cell density of 1 million cells/ml was considered the best fit for extrusion-based 3D bioprinting owing to its optimum rheological traits and printability index akin the acellular hydrogel.

Study on the Compatibility between Combined Control of Channel Plugging and Foam Flooding and Heterogeneous Reservoirs—Taking Bohai Z Oilfield as an Example

With the oilfield developed to a later stage and its heterogeneity gradually becoming more serious, the adaptability of conventional profile control technologies for the reservoir becomes worse and worse. Therefore, the fitness of compatibility between combined patterns of profile control and target reservoir becomes an important factor for the efficient development of the oil field. Due to the importance of compatibility between the profile control and reservoir property, research on the remaining oil recovery with combined patterns of profile control and foam flooding were carried out. The experimental results showed that the combined profile control is highly consistent with the target reservoir. With a little lower initial viscosity (28.3–40.9 mPa·s), the channel plugging system is easy to inject. Due to the addition of a polymer, the reinforced foam is not easy to defoam when transporting in the pore throats of the core sample, and its spontaneous adaptability makes it match with the porous media of the formation automatically, which effectively prolongs the transporting distance for the foam in the deep part of the core sample. The segment plug with a gel-type profile control agent injected at the front stage is of great significance to the non-homogeneous reservoir, so it is necessary to inject a sufficient gel-type profile control agent into the high permeability layer to make it produce a seal. When the permeability differential was equal to 10, the maximum increase of oil recovery degree was 29.69%, and the development effect became worse after increasing or decreasing the permeability differential.

One-pot synthesis of multifunctional silicone elastomer: Ring-opening copolymerization of D4 and Dual-D4Vi

Herein, a Dual-D4Vi monomer is designed for one-pot synthesis of multifunctional silicone elastomer. Dual-D4Vi plays dual roles in silicone elastomer. It functions both as monomer and as cross-linker, and thus can copolymerize with octamethyl cyclotetrasiloxane (D4) for one-pot synthesis of multifunctional silicone elastomer. This is different from the conventional multi-step preparation process which needs polymerization and vulcanization. Dual-D4Vi is synthesized by a simple hydrosilylation reaction with high yield and characterized by FTIR, NMR and LC/MS spectrometry. And this method can be used for both laboratory research and large-scale preparation. Notably, the mixture of the prepolymer before heat-curing was water-like with the viscosity as low as 10 mPa·s, endowing this type of material system with wide applicability in gap filling, 3D printing, optoelectronic device packaging and roll-to-plate hot embossing. Moreover, the very low initial viscosity and good flow behavior also allows substantially adjustable filler type and content. Additionally, the polymerization rate is fast. The viscosity can reach 100 Pa·s within 20 s. And the polymerization is controllable by adjusting the reaction temperature and catalyst dosage.

Cost-efficient and recyclable epoxy vitrimer composite with low initial viscosity based on exchangeable disulfide crosslinks

Epoxy (EP) vitrimer with excellent processing and recyclability is of great potential for industrial application. In this study, we prepared an EP vitrimer based on the low viscosity homogenous mixture of diglycidyl ether of bisphenol A (DGEBA) and a liquid hardener dimethyl 3,3′-dithiodipropionate (DTDP) catalyzed by 2,4,6-tris (dimethylaminomethyl) phenol (DMP30). The optimal curing condition was determined to be 110 °C × 12 h for the original EP vitrimer. Owing to the exchangeable disulfide crosslinks, rapid stress relaxation was found for the vitrimer with a relaxation time of 1.9 s at 160 °C. Moreover, the prepared EP vitrimer possessed excellent self-healing ability and recyclability, with recovery ratio of at least 94.1% during 3 times recycling. The self-healing ability, recyclability and processing performance remain excellent for the vitrimer even after incorporating 30 wt% boron nitride (BN), which can be recycled using DMF as a solvent.

Soybean-Oil-Based CO2-Switchable Surfactants with Multiple Heads.

Oligomeric surfactants display the novel properties of low surface activity, low critical micellar concentration and enhanced viscosity, but no CO2 switchable oligomeric surfactants have been developed so far. The introduction of CO2 can convert tertiary amine reversibly to quaternary ammonium salt, which causes switchable surface activity. In this study, epoxidized soybean oil was selected as a raw material to synthesize a CO2-responsive oligomeric surfactant. After addition and removal of CO2, the conductivity analyzing proves that the oligomeric surfactant had a good response to CO2 stimulation. The viscosity of the oligomeric surfactant solution increased obviously after sparging CO2, but returned to its initial low viscosity in the absence of CO2. This work is expected to open a new window for the study of bio-based CO2-stimulated oligomeric surfactants.

A strong magnesium oxychloride cement wood adhesive via organic–inorganic hybrid

Developing high performance and non-toxic adhesives to replace the petroleum-based adhesives are highly desirable for wood industry. The use of magnesium oxychloride cement (MOC) inorganic adhesive is beneficial for the protection of human health and conservation of fossil resources. However, the low initial viscosity and poor water resistance have limited their application in plywood fabrication. In this study, polyacrylamide (PAM) and sodium polyacrylate (PAAS) were added to the adhesive as organic agents to construct wood-based composites by the organic–inorganic hybrid strategy. The MOC would be solidified by a cold-pressing method, forming a formaldehyde-free wood adhesive with high bonding performance. The addition of PAM efficiently improved the stability and processability of MOC, while PAAS improved the water resistance of MOC by inducing Mg2+ chelation and transforming the phase 5 structure. This adhesive exhibited a 53.5% increase in wet shear strength in contrast with the unmodified MOC adhesive. In addition, the MOC adhesive bonded wood-based composites showed high flame-retardant properties.

High density bromide-based nanocomposite gel for temporary plugging in fractured reservoirs with multi-pressure systems

The coexistence of blowout and lost circulation in multi-pressure fractured reservoirs has always been a huge challenge to the oil industry. Although the use of high-density kill fluids can ensure the safety of well control, the problem of lost circulation in low pressure layer is still troublesome. Gel is widely used as a temporary plugging system, but the conventional gel plugging system will float when used in combination with high-density kill fluid, resulting in failure of temporary plugging. In this paper, a novel high-density bromide-based nanocomposite gel (HDGEL) was developed, the gel formation mechanism was explored, and its performance was evaluated in the laboratory. The gel is weighted by sodium bromide (NaBr), and cross-linked by covalent bonds, density 1.2–1.5 g/cm 3 adjustable, and its temperature resistance can reach 160 °C. Rheological tests show that the gel solution has low initial viscosity and easy to pump. The gelation time can be adjusted from 8 to 12 h, which can be directly broken by the drill or regular jetting nozzle and then flowed back. It can be used in combination with high-density kill fluid to ensure temporary plugging effect. In the fractures with tip sizes (0.014 cm), the maximum bearing pressure of HDGEL is 17.52 MPa, and the regained-permeability recovery can reach 86.81% without the use of gel breaker. This paper introduces a new gel system for multi-pressure reservoirs that can be used in combination with high-density kill fluid and makes recommendations for its engineering application. • High-density bromide-based nanocomposite gel (HDGEL) was developed. • HDGEL will not float in high density well killing fluid. • HDGEL combined with high density well killing fluid can work in multi-pressure reservoir. • HDGEL performs high pressure bearing performance and low damage to the fractured core.

Experimental studies for the additive manufacturing of continuous fiber reinforced composites using UV-curing thermosets

The economical production of lightweight structures with tailor-made properties and load-adapted geometry is limited using conventional technologies. Additive manufacturing processes offer a high potential to meet these requirements, where the established solutions are based primarily on thermoplastics matrix systems. From a process-technological point of view, thermoplastics enable simplified processing, but only a limited range of applications for high-performance components. These limitations are due to their comparatively low heat resistance, low melting temperatures and limited adhesion to embedded reinforcing fibers. In contrast, thermosets show high potential for realization of high- performance lightweight structures with adaptable properties. The present work employs a UV-curing thermoset resin for the impregnation of a continuous filament strand for 3D printing. The main challenge is to reconcile the crosslinking reaction of the thermoset and the process velocity during impregnation and cure. The liquid polymer must provide low initial viscosity to impregnate the filaments and a sufficiently high cure rate and dimensional stability after discharge from the print head to ensure sufficient bonding strength to the substrate. To demonstrate feasibility, a prototypic print head with UV-LED activation was designed and implemented. With a robot-guided printing platform, the 3D-deposition of continuous fiber-reinforcements without additional supporting structures can be realized. To derive initial process parameters, reaction and thermos-mechanical properties are determined by rheometer measurements. Impregnation and cure behavior of the glass fiber reinforced resin is investigated. The presented results provide a reliable process window and a straightforward process monitoring method for further enhancement of the conceived 3D printing process.