Experimental investigation of vibration pretreatment-microwave curing process for carbon fiber reinforced resin matrix composites

The vibration pretreatment-microwave curing process is an efficient,low energy consumption,and high-quality out-of-autoclave curing process for carbon fiber resin matrix composites.This study aims to investigate the impact of vibration pretreatment temperature on the fiber weight content,microscopic morphology and mechanical properties of the composite laminates by using optical digital microscopy,universal tensile testing machine and thermo-gravimetric analyzer.Additionally,the combined mode of Bragg fiber grating sensor and temperature measurement fiber was employed to explore the effect of vibration pretreatment on the strain process during microwave curing.The study results revealed that the change in vibration pretreatment temperature had a slight impact on the fiber weight content when the vibration acceleration remained constant.The metallographic and interlaminar strength of the specimen formed at a vibration pretreatment temperature of 80℃ demonstrated a porosity of 0.414% and a 10.69% decrease in interlaminar shear strength compared to autoclave curing.Moreover,the introduction of the vibration energy field during the microwave curing process led to a significant reduction in residual strain in both the 0°and 90°fiber directions,when the laminate was cooled to 60℃.

Curing kinetics and plugging mechanism of high strength curable resin plugging material

Lost circulation, a recurring peril during drilling operations, entails substantial loss of drilling fluid and dire consequences upon its infiltration into the formation. As drilling depth escalates, the formation temperature and pressure intensify, imposing exacting demands on plug materials. In this study, a kind of controllable curing resin with dense cross-network structure was prepared by the method of solution stepwise ring-opening polymerization. The resin plugging material investigated in this study is a continuous phase material that offers effortless injection, robust filling capabilities, exceptional retention, and underground curing or crosslinking with high strength. Its versatility is not constrained by fracture-cavity lose channels, making it suitable for fulfilling the essential needs of various fracture-cavity combinations when plugging fracture-cavity carbonate rocks. Notably, the curing duration can be fine-tuned within the span of 3-7 h, catering to the plugging of drilling fluid losing of diverse fracture dimensions. Experimental scrutiny encompassed the rheological properties and curing behavior of the resin plugging system, unraveling the intricacies of the curing process and establishing a cogent kinetic model. The experimental results show that the urea-formaldehyde resin plugging material has a tight chain or network structure. When the concentration of the urea-formaldehyde resin plugging system solution remains below 30%, the viscosity clocks in at a meager 10 mPa·s. Optimum curing transpires at 60℃, showcasing impressive resilience to saline conditions. Remarkably, when immersed in a composite saltwater environment containing 50000 mg/L NaCl and 100000 mg/L CaCl_(2), the urea-formaldehyde resin consolidates into an even more compact network structure, culminating in an outstanding compressive strength of 41.5 MPa. Through resolving the correlation between conversion and the apparent activation energy of the non-isothermal DSC curing reaction parameters, the study attests to the fulfillment of the kinetic equation for the urea-formaldehyde resin plugging system. This discerning analysis illuminates the nuanced shifts in the microscopic reaction mechanism of the urea-formaldehyde resin plugging system. Furthermore, the pressure bearing plugging capacity of the resin plugging system for fractures of different sizes is also studied. It is found that the resin plugging system can effectively resident in parallel and wedge-shaped fractures of different sizes, and form high-strength consolidation under certain temperature conditions. The maximum plugging pressure of resin plugging system for parallel fractures with outlet size 3 mm can reach 9.92 MPa, and the maximum plugging pressure for wedge-shaped fractures with outlet size 5 mm can reach 9.90 MPa. Consequently, the exploration and application of urea-formaldehyde resin plugging material precipitate a paradigm shift, proffering novel concepts and methodologies in resolving the practical quandaries afflicting drilling fluid plugging.

Effect of low curing temperature on the anticorrosion performance of composite coatings reinforced with modified Fe_(3)O_(4)

In this manuscript,the neat epoxy(EP)and functionalized Fe_(3)O_(4)(G-Fe_(3)O_(4))reinforced epoxy(G-Fe_(3)O_(4)/EP)coatings were cured under different temperatures,and the effect of the low curing temperature on the anticorrosion performance was investigated.The experimental results show that the epoxy-amine ring-open addition reaction mainly exists in the curing process,and the activation energies of the reaction for the two coatings are 55.84 and 53.29 kJ/mol,respectively.For the coatings cured at the low temperature,almost no pores could be detected on the fracture surface,but the presentence of the rough regions reflects the poor curing state.As compared with the samples cured at the high temperature,the anticorrosion performance of the coatings with the low curing temperature is worse,and the decrease rate of the anticorrosion performance is slower,because of the poor curing state and low adhesion obtained at the low temperature.

Fabrication and Properties of a New Reactive Diluent for Cationic UV Curing

The reactive diluent prepared by siloxane modified Trimethylene oxide can improve the performance of the UV curing system.Therefore,1,7-bis[(3-ethyl-3-methoxyoxacylobutane)propyl]octadecylosiloxane(BEMOPOMTS)was synthesized from diethyl carbonate,trimethylopropanes,allyl bromide,and 1,1,3,3,5,5,7,7-octadecylosiloxane as the main raw materials.BEMOPOMTS can be used as reactive diluents in the field of cationic UV curing.It has good thermal stability,and the addition of BEMOPOMTS significantly improves the tensile strength and elongation at break of epoxy resin.Compared with the pure epoxy resin,adding 20%BEMOPOMTS increased the elastic modulus by 25%to 677 MPa.

A strength model for cement-stabilized mud subjected to various curing temperatures and its early-stage quality control

The influence of curing temperature on the strength development of cement-stabilized mud has been well documented in terms of strength-increase rate and ultimate strength.However,the strength development model is not mature for the extremely early stages.In addition,there is a lack of studies on quality control methods based on early-stage strength development.This paper presents a strength model for cement-stabilized mud to address these gaps,considering various curing temperatures and early-stage behaviors.In this study,a series of laboratory experiments was conducted on two types of muds treated with Portland blast furnace cement and ordinary Portland cement under four different temperatures.The results indicate that elevated temperatures expedite strength development and lead to higher long-term strength.The proposed model,which combines a three-step conversion process and a hyperbolic model at the reference temperature,enables accurate estimate of the strength development for cement-treated mud with any proportions cured under various temperatures.With this model,a practical early quality control method is introduced for applying cement-stabilized mud in field projects.The back-analysis parameters obtained from a 36-h investigation at temperature of 60C demonstrated a sufficient accuracy in predicting strength levels in practical applications.

Fluorinated semi-interpenetrating polymer networks for enhancing the mechanical performance and storage stability of polymer-bonded explosives by controlling curing and phase separation rates

Herein, the effect of fluoropolymer binders on the properties of polymer-bonded explosives(PBXs) was comprehensively investigated. To this end, fluorinated semi-interpenetrating polymer networks(semiIPNs) were prepared using different catalyst amounts(denoted as F23-CLF-30-D). The involved curing and phase separation processes were monitored using Fourier-transform infrared spectroscopy, differential scanning calorimetry, a haze meter and a rheometer. Curing rate constant and activation energy were calculated using a theoretical model and numerical method, respectively. Results revealed that owing to its co-continuous micro-phase separation structure, the F23-CLF-30-D3 semi-IPN exhibited considerably higher tensile strength and elongation at break than pure fluororubber F2314 and the F23-CLF-30-D0 semi-IPN because the phase separation and curing rates matched in the initial stage of curing.An arc Brazilian test revealed that F23-CLF-30-D-based composites used as mock materials for PBXs exhibited excellent mechanical performance and storage stability. Thus, the matched curing and phase separation rates play a crucial role during the fabrication of high-performance semi-IPNs;these factors can be feasibly controlled using an appropriate catalyst amount.

Alkali Tolerance of Concrete Internal Curing Agent Based on Sodium Carboxymethyl Starch

Internal curing agents (ICA) based on super absorbent polymer have poor alkali tolerance and reduce the early strength of concrete.An alkali tolerate internal curing agent (CAA-ICA) was designed and prepared by using sodium carboxymethyl starch (CMS) with high hydrophilicity,acrylic acid (AA) containing anionic carboxylic group and acrylamide (AM) containing non-ionic amide group as the main raw materials.The results show that the ratio of CAA-ICA alkali absorption solution is higher than that existing ICA,which solves the low water absorption ratio of the ICA in alkali environment.The water absorption ratio of CAA-ICA in saturated Ca(OH)_(2) solution is 95.8 g·g^(-1),and the alkali tolerance coefficient is 3.4.The application of CAA-ICA in cement-based materials can increase the internal relative humidity and miniaturize the pore structure.The compressive strength of mortar increases up to 12.95%at 28 d,which provids a solution to overcome the reduction of the early strength.

Study on Effects of Curing Process on Characteristics of Marinated Beef Products

[Objectives]This study was conducted to compare the effects of different curing processes on the characteristics of marinated beef.[Methods]Marinated beef was obtained by two curing processes:static curing and injection and vacuum tumbling curing.The effects of the two curing processes on the production rate,curing absorption rate,water content,soluble protein content,amino acid nitrogen content,texture characteristics and microstructure of the product were compared.[Results]Compared with static curing,the production rate of marinated beef increased by 10%,the curing absorption rate increased by 28%,the texture and microstructure were improved,and the water content increased,while the soluble protein content decreased.As a result,the sensory score was higher.There was no significant difference in the content of amino acid nitrogen,but it decreased compared with raw meat.To sum up,injection and vacuum tumbling curing is more conducive to the processing of marinated beef.[Conclusions]This study provides a theoretical basis for the industrial production of marinated beef,and lays a foundation for in-depth exploration of injection and vacuum tumbling curing technique of marinated beef.

Synthesis of Ionic and Non-Ionic Modified Waterborne Polyurethane Curing Agent

By using HDI and TMP as the main raw materials,polyethylene glycol 400(PEG400)is used as a non-ionic hydrophilic modifier,and sodium hydroxyethyl sulfonate is used as an ionic hydrophilic modifier to synthesize a dual hydrophilic modified polyurethane curing agent.Research revealed that introducing PEG400 for hydrophilic chain segments and sodium hydroxyethyl sulfonate for hydrophilic ionic groups in the polyurethane curing agent component leads to a uniform distribution of hydrophilic components,significantly enhancing compatibility with the aqueous polyol component,and results in excellent film performance.The synthesis process and film were characterized using Fourier transform infrared spectroscopy and high-resolution scanning electron microscopy in the study.

Advancements and Applications of Polyurethane Curing Technology in Railway Track Bed Construction in China

This paper examines the application of polyurethane curing technology in the construction of railway track beds,with a specific focus on its implementation in China’s rapidly developing railway infrastructure.The study begins by identifying the limitations of traditional ballasted track beds,especially under the demands of high-speed and heavyload railways.It then methodically analyzes the advantages of polyurethane-cured track beds,highlighting their improved mechanical properties,including enhanced stability and durability.The paper further explores the benefits of transitioning to prefabricated polyurethane track beds,emphasizing significant cost reductions,better construction quality,and enhanced maintainability.Through a detailed review of experimental data and practical applications,the paper demonstrates the efficacy of polyurethane track beds in various railway settings.A critical part of the research involves optimizing the structural parameters of polyurethane track beds to achieve the best balance of mechanical and damping properties.The conclusion of the paper underscores the potential of polyurethane curing technology as a transformative approach to railway track bed construction,offering a solution to the challenges posed by traditional methods and aligning with the evolving needs of modern railways.

Securing the Sea Lanes

Some people,mainly in the West,were taken by surprise when six Chinese warships were seen near the Red Sea in October 2023 amid the conflict in Gaza.Some Western media and politicians tried to frame China’s mission as an escalatory move in the Middle East.

Securing Sustenance

National food security is the backbone of any economy,and achieving food security is essential for the prosperity of a nation.During my study in China at the Institute of South-South Cooperation and Development,Peking University,from September 2022 to July 2023,I leant how China has managed to achieve food security despite its large population of around 1.4 billion and numerous other challenges by means of strategic planning,e"ective policy execution,technological advancement and global collaboration.

Application of Polyurethane Curing Barn in Flue-cured Tobacco Production

[ Objective] This study aimed to investigate the curing performance of polyurethane curing barn and reduce the cost of tobacco leaf flue-curing. [ Meth- odl The temperature control effect, curing effect and curing cost of polyurethane curing barn and traditional bulk curing barn were analyzed and compared. [ Re- suit] The results showed that there were no significant differences in curing performance between two types of curing barns. Horizontal temperature differences in- creased slightly as the temperature rose. Specifically, horizontal temperature differences between each layer ranged from 0.2 ~C to 0.5 ~. Both two types of curing barns exhibited uniform air distribution. Polyurethane curing barn exhibited stable vertical temperature differences. Both two types of curing barns presented good curing effects with slight differences. Polyurethane curing barn exhibited higher economic benefits, lower coal cost, lower electricity cost, lower labor cost and lon- ger service life than traditional bulk curing barn, but its construction cost was higher. [ Conclusion] Polyurethane curing barn exhibits better curing performance with ~ood application prospects.

Effects of Tobacco Curing on Accumulation of Chemical Components and Aroma Components in Tobaccos

[Objective]The aim was to explore effects of curing technique parameters on chemical components and aromatic material accumulation to formulate a suitable curing technique and for and to achieve tobacco scalding, drying and giving aromat- ic flavor. [Method] With tobacco variety KRK 26 as test materials, the test involved parameters of three curing-techniques in down, middle and upper parts of flue-cured tobaccos in an oven to measure chemical components and aromatic substances in tobaccos. [Result] The effects of curing techniques on total sugar and reducing sug- ar differed upon temperature and humidity. The contents of chemical components, such as total alkaloid, total N and the ratio of sugar/ alkali by moderate temperature and high humidity technique were of significant differences with those by moderate temperature and moderate humidity technique and with low temperature and low hu- midity technique; the chemical components by moderate temperature and moderate humidity were of insignificant differences with the treatment by low temperature and low humidity technique. Total amount of aroma components by different curing tech- niques from high to low was the treatment by low temperature and low humidity technique （461.72 μg/g）, the treatment by moderate temperature and moderate hu- midity technique （450.06μg/g） and the treatment by moderate temperature and high humidity technique （385.12μg/g）, suggesting the content of aromatic substances is high at low temperature and low humidity. [Conclusion] Moderate temperature and high humidity curing technique has significant effects on total alkaloid, total N and the ratio of sugar/ alkali of tobaccos and different curing techniques also affect the total amount of aromatic substances of flue-cured tobaccos.

Curing of the Bacillus subtilis Plasmid Using Sodium Dodecyl Sulfate

Curing of Bacillus subtilis plasmid using sodium dodecyl sulfate (SDS)was studied in order to obtain a host strain. An overnight culture of Bacillus subtilis 24/pMX45 was used to inoculate fresh LB containing SDS (0-0.008%). No growth of 24/pMX45 was observed when LB contained an SDS concentration of 0.006% or greater, and the sublethal concentration (w/v) of SDS was 0.005% with a killing rate of 99%. Samples were diluted and plated on LB agar, individual colonies were randomly picked to a selective agar medium by tooth to screen for loss of plasmid-encoded erythomycin resistance. CsCl-EtBr gradient centrifugation and plasmid DNA profile demonstrated that plasmid-cured derivative A7 has completely lost its plasmid. A7 had a shorter lag, and its cell concentration was consistently higher than that of the 24/pMX45. Elimination of the plasmid was first observed after 24/pMX45 had been treated with SDS for 8 h. The percent elimination then continued to increase until about 22 h, after which the fraction of cured cell in the population remained constant. Plasmid cured cell numbers were measured in a separate control culture of 24/pMX45 untreated by SDS. No spontaneous loss of pMX45 was observed after 24/pMX45 were incubated for 24 h and 48 h with shaking at 37 ℃.These results suggested that SDS can be used as curing agent to eliminate the plasmid of Bacillus subtilis.

Effects of Three Major Tobacco Curing Techniques on Raw Tobaccos

[Objective] The aim was to compare effects of three curing techniques （Chinese tobacco curing-method for improving tobacco quality and fragrance, Chi-nese （three-phase） tobacco curing technique, and Zimbabwe tobacco curing tech-nique） on quality of tobacco and to select optimal curing method. [Method] In Peng-shui county in Chongqing, tobacco variety K326 was chosen as test materials to conduct tobacco curing tests as per three techniques to analyze key components of raw tobacco, grade quality and evaluation quality. [Result] The content of starch in tobacco was reduced by Chinese tobacco curing-method for improving tobacco quality and fragrance, and the ratio of middle and high quality grade tobaccos improved by 1.8%-7.95%; average price increased by 1.64-3.21 yuan/kg; evaluation grade grew by 1.5-4.4. The technique is proved in enhancing tobacco fragrance quality and quantity as wel as improving and adjusting fragrance, taste and flavor. [Conclusion] Chinese （three-phase） tobacco curing technique improves tobacco quality and provides references for production demonstration areas of tobacco curing.

Effect of Different Flue-curing Techniques on the Taste and Aroma Substances of Tobacco Leaves

[Objective]This study aimed to optimize the conditions for curing tobacco leaf, so as to improve its flavor and quality. [Method] Leaves of Yuanyan 87 were col ected and cured by three different techniques （moderate-intensity conditions throughout the curing course; high-intensity conditions at leaf yel owing and wilting stages, moderate-intensity conditions at leaf drying and vein drying stages; high-in-tensity conditions throughout the curing course）, and then the contents of 48 aroma substances and taste indices of the finished tobacco leaves were measured. [Result] The contents of 28 aroma substances in the tobacco leaves cured under high-inten-sity conditions throughout the course were higher and the taste indices of these to-bacco leaves were better, compared with those flue-cured by the other two tech-niques. The contents of the other 20 aroma substances were not significantly af-fected by the curing techniques. The second best technique was high-intensity con-ditions at leaf yel owing and wilting stages and moderate-intensity conditions at leaf drying and vein drying stages. Curing tobacco leaves at moderate-intensity condi-tions throughout the course was the worst one. [Conclusion] Compared with the oth-er two methods, the contents of aroma substances and taste indices of the tobacco leaves cured under high-intensive conditions throughout the course were the best.

Curing mechanism of alkaline phenolic resin with organic ester

To study the curing mechanism of alkaline phenolic resin with organic ester, three esters were chosen to react with three systems - alkaline phenolic resin, potassium hydroxide aqueous solution containing phenol, and potassium hydroxide aqueous solution. The variations of pH, heat release and gel pH during the reactions were monitored and measured. Infrared spectroscopy （IR） and thermal gravity analysis （TG） techniques were used to characterize the curing reaction. It was found that organic ester is only partial y hydrolyzed and resin can be cured through organic ester hydrolysis process as wel as the reaction with redundant organic ester. The sequential curing mechanism of alkaline phenolic resin cured by organic ester was identified as fol ows： a portion of organic ester is firstly hydrolyzed owing to the effect of the strong alkaline; the gel is then formed after the pH decreases to about 10.8-10.88, meanwhile, the redundant organic ester （i.e. non-hydrolysis ester） starts the curing reaction with the resin. It has also been found that the curing rate depends on the hydrolysis velocity of organic ester. The faster the hydrolysis speed of the ester, the faster the curing rate of the resin.

COMPARISON OF THE E44 EPOXY RESINS IN DIFFERENT CONTENTS OF CURING AGENT BY MICROWAVE AND THERMAL CURING METHODS

This paper discusses the fundamental principle of microwave heating, and based on the advantages of microwave heating, use maleic anhydride as curing agent. The technology of microwave curing E44 epoxy resins is investigated, the mechanical properties of cured epoxy resin samples in different contents of curing agent by microwave and thermal curing methods are measured respectively, and then some experimental results for which are obtained. At last, this paper analyses why microwave curing can improve mechanical property of epoxy resin.

A unique method for curing composite materials by introducing vibration treatment into the hybrid heating process

Carbon fiber reinforced plastics provide many excellent properties and are widely used in the aerospace industry.However,the existing composites autoclave process still faces difficulties such as high-energy consumption,uneven distribution of temperature field,complications of pressure transmission,and high cost,which limit their application in manufacturing of large complex composites components.In this study,the vibration treatment was introduced into the composites microwave curing process innovatively.On the basis of giving full play to the uniform heating characteristics of the microwave,the problems of a large number of internal defects and poor molding quality caused by the insufficient curing pressure have been solved.The results showed that the samples cured by the improved microwave process without external pressure had a few internal voids,excellent interface bonding conditions,and lower residual stress.Their properties were almost consistent with the samples prepared by the standard autoclave process,which provided a new method for the high-performance,efficient,safe,and low-cost manufacturing of large complex composites components.