EPS System Research Articles

Fast curing unidirectional carbon epoxy prepregs based on a semi-latent hardener: The influence of ambient aging on the prepregs Tg0, processing behavior and thus derived interlaminar performance of the composite

The aging behavior of a fast-curing epoxy resin (EP) was examined over three months in unidirectional carbon fiber prepregs for the first time. The semi-latent, 120 °C curing one-pot formulation was developed based on industry-grade diglycidyl ether of bisphenol A (DGEBA) resins without the necessity of B-staging, to fully monitor the property change by aging without any post-processing influence. To extend the shelf-life compared to standard wet EP systems, the latent dicyandiamide (DICY) and a semi-latent urea-based catalyst were used, leading to full conversion within 15 min. The conversion was monitored by increasing Tg0 and rheology. High quality unidirectional carbon prepregs were manufactured and then investigated over three months regarding tackiness and resin flow. In parallel, laminates were autoclave-manufactured to evaluate the aging influence on the interlaminar properties. Thus, a correlation between decreasing gel-time, interlaminar adhesion and resulting multiple crack growth was observed via GIC and interlaminar shear strength (ILSS) testing. The investigations show a clear influence of the consolidation quality of the prepregs based on ILSS values and GIC values. A decrease of 19% in ILSS and combined with an erroneous increase of 63% of the GIC due to multiple delamination was observed in the worst case.

Perceived Security and Trust in Electronic Payment Systems: How They Affect the Decision to Use EPS During the COVID-19 Pandemic

Research aims: This study is intended to determine the influence of perceived security and trust on the decision to use digital payment systems during the COVID-19 pandemic.Design/Methodology/Approach: The type of data used in this study was primary data, which was collected using an online survey. Sample used in this study determined by purposive sampling method. The information collected was handled and analyzed using SEM-PLS.Research findings: This study shows the results that the presence of technical protection explicitly affects the perception of security and trust significantly. In addition, security also greatly affects an individual's confidence in the use of digital payment systems. However, of the various findings made in this study, trust is the only one that influences the choice in using EPS.Theoretical contribution/Originality: During this pandemic Covid-19, limited studies talk about consumers’ perceptions instead of technical protection of digital payment in detail. Meanwhile, consumers' security is the thing that needs to be studied further to create a comprehensive study result.Practitioner/Policy implication: Results of this study give some implications for the EPS providers to complete and develop a secure EPS system for users, especially in this pandemic era when the EPS users increase and people’s mobility is restricted in some areas.Research limitation/Implication: The implication of this research is to emphasize the importance of one's knowledge regarding risks when using an electronic payment system. It is because the use of EPS in the pandemic era is unavoidable. Therefore, not only providers must improve their security systems, but users must also be aware of the EPS risks and security. Nevertheless, the limitation of this study is that it only used samples in Indonesia; maybe the results will be different when applied in other countries with better EPS security systems.

Pseudo-elevation of conduction system pacing threshold through parallel connection of an intracardiac electrogram recording system.

Parallel connection of an electrophysiology recording system (EP system) to equipment for conduction system pacing (CSP) has been widely used for fine monitoring of intracardiac electrograms and pacing evaluation. We experienced a case showing unexpected pacing threshold exacerbation under specific conditions when the EP system was connected in parallel. We evaluated the underlying mechanism using an ex vivo model. An ex vivo pacing and intracardiac electrogram monitoring model was generated using an oscilloscope, pacing system analyzer (PSA), EP system, and simulated heart. The discrepancy between expected output at the PSA and the actual measured output value at the simulated heart was measured under various conditions and using various combinations of pacing equipment. Parallel connection of the EP system was associated with reduced electrical output from the PSA as recorded at the simulated heart. The unexpected adverse effects were particularly noticeable when using an RMC-5000 EP system with the pacing function on. The trouble is completely resolved by simply turning off the pacing function of the system. There is a possibility that the EP system might increase the pacing threshold in CSP when the PSA and EP system is are deployed in parallel. The issue may provoke pseudo failure of CSP due to the high pacing threshold. When the RMC-5000 is used for conduction system pacing in parallel with a PSA for the pacing test, the pacing function of RMC-5000 should be turned off.

Non-aromatic Si, P, N-containing hyperbranched flame retardant on reducing fire hazards of epoxy resin with desirable mechanical properties and lower curing temperature

Plastic combustion has adverse impacts on air quality and human health. In this work, a novel non-aromatic Si, P, N-containing hyperbranched flame retardant (HPNSi) was synthesized and proposed to epoxy resin. The modified epoxy exhibits not only reduced fire hazards and less smoke production in favor of eco-friendly, but also remarkable mechanical properties and lower curing temperature for facile processability. With 6 wt% incorporation, the peak heat release and total smoke production were reduced by 29.6% and 20.7%, respectively, and the time to ignition (TTI) increased as well as the fire growth rate (FIGRA) dropped off, which is of vital significance for saving lives in a fire. Meanwhile, the impact strength and flexural strength greatly enhanced by 72.9% and 22.0%, while its curing temperature was lower than that of controlled EP system. Interestingly, we also found that the solid carbon particles on the char surface apparently reduced from SEM image. The blending of its unique non-aromatic hyperbranched structure containing Si, P, N with epoxy architecture was responsible for the desirable integrated enhancement. The broad possibilities in the field of flame-retardant plastic with reduced fire hazards and excellent integrated performance enable the novel hyperbranched flame retardant a bright future for application.

Study on decomposition and calculation method of EPS assist characteristic curve

Steering feel is closely related to the matching of the EPS assist characteristic curve, however, due to the lack of theoretical basis for the design of the EPS assist characteristic curve, the steering feel can only be changed indirectly by adjusting the magnitude of assist, which is very difficult. To control steering feel directly and reduce the difficulty of adjustment, this paper proposes a decomposition and calculation method of the EPS assist characteristic curve. At first, the mechanism of the EPS assist characteristic curve is revealed. It is found that the process of designing and adjusting the EPS assist characteristic curve is a process of changing the corresponding relationship between the steering wheel torque and the steering motion intensity based on considering vehicle dynamic characteristics. On this basis, the driver’s desired steering motion intensity and the pinion angle position are taken as intermediate variables, the EPS assist characteristic curve is decomposed into three parts: driving style, steady-state inverse characteristics of chassis dynamics, and steady-state inverse characteristics of steering system dynamics. According to the designed driving style and the calibrated steady-state inverse characteristics of chassis dynamics and steering system dynamics, the EPS assist characteristic curve can be directly calculated. The test results show that the EPS system adopting assist characteristic curve calculated can realize the designed driving style and provide consistent and controllable steering feel on the premise of meeting the requirements of steering portability and road feel.

Insights into the synergistic mechanism of reactive aliphatic soft chains and nano‐silica on toughening epoxy resins with improved mechanical properties and low viscosity

AbstractToughening epoxy resin (EP) without sacrificing strength, modulus, and processing performance is always a harsh task. Here, a series of epoxy systems containing soft butyl glycidyl ether (BGE) and rigid nano‐silica (nano‐SiO2) were prepared. Micro‐phase separation structures derived from the self‐assembly effect of BGE can be observed in atomic force microscopy images by controlling the total amount of BGE and nano‐SiO2 at 2 wt% for the EPC:Si‐m:n (m + n = 4) systems. Due to the synergistic effect of self‐assembly effect of BGE and the rigid effect of well dispersed nano‐SiO2, EPC:Si‐2:2 system exhibited improvement of tensile strength of 59.3% (92.63 MPa), tensile modulus of 24.8% (3.52 GPa), elongation at break of 78.6% (4.84%), and glass transition temperature of 2.4% (138.4°C) compared with Pure EP system. Besides, due to the low loading of nano‐SiO2 (≤2 wt%) and the dilution effect of BGE, the viscosity of all the toughening systems is lower than 600 mPa·s, which can provide this toughening system with superior processing performance for large production of composites by automotive manufacturing methods such as vacuum assistant resin infusion technology.

Effects of graphene oxide size on curing kinetics of epoxy resin.

To study the effects of graphene oxide (GO) size on the curing kinetics of epoxy resin (EP), two kinds of GO were selected and characterized by Fourier transform infrared spectrometry (FT-IR), FT-Raman spectrometry (FTIR-Raman), thermo gravimetric analysis (TGA), dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The results showed that the two kinds of GO had similar chemical structures but different sizes—the average particle size of GO-A was 190.1 nm and that of GO-B was 1510 nm, and GO-A has more oxidizing groups on its surface. The two kinds of GO were separately added to EP, and the curing kinetics of GO/EP composites and neat EP were investigated through differential scanning calorimetry (DSC). It can be seen that the addition of GO promoted the curing process of the EP system, and GO-A had a more significant catalytic effect. Furthermore, the curing activation energy (Ea) was calculated by Kissinger model, and the change of Ea in the whole curing reaction process was studied by Ozawa method to further understand the curing mechanism. It showed that the apparent Ea of EP system increases with the increase of the conversion rate, and Ea of EP-A is obviously lower in the early curing stage. However, as the curing reaction proceeds, Ea of EP-B is a little lower than that of EP-A in the later curing stage. But EP-A has the lowest Ea combined with the whole process from Kissinger method. To sum up, it can be concluded that the curing process of EP can be promoted by adding GO and the smaller size (190.1 nm) of GO had a greater effect and lower Ea than the GO with particle size of 1510 nm. And the related mechanisms were discussed and analyzed.

A qualitative approach to investigate emergency preparedness state for the built environment in the UAE

PurposeEmergency preparedness (EP) is one of the crucial phases of the disaster management cycle for the built environment. The body of knowledge, therefore, reports on different preparedness standards adopted by developed countries such as the United Kingdom (UK), the United States of America (USA), Canada, Japan and Australia. Other countries, however, such as the United Arab Emirates (UAE) (in the absence of its preparedness framework), have long adapted the UK preparedness standards. This has called for this study to investigate the state of EP practices in the UAE to identify the limitations and challenges it has been facing during its preparedness phase when adopting the UK preparedness standards.Design/methodology/approachQualitative methods of data collection and documentation with the content analysis were adopted to identify the barriers faced by the preparedness phase of emergency management (EM) in the UAE. A Pilot study was therefore conducted to validate eight key elements of the EP phase identified from the literature. The state of EP phase and the extent to which the eight key elements of EP elements were practiced and the barriers in their implementation in the UAE were explored through interviews at federal (National Crisis and Emergency Management Authority) and local levels (local team of crisis and emergency management).FindingsThe study identified eight key elements of the EP phase and the associated barriers related to their implementation in the UAE. The barriers were ranked based on their severity by interviewing experts at both federal and local levels.Practical implicationsThis paper addresses the need to investigate the state of the EP phase, its key elements and the barriers faced during its implementation in the UAE.Originality/valueDue to the absence of any EP frameworks or systems in the UAE, this paper aims to validate the EP elements identified by adopting a qualitative approach.

P15 Using prescribing nudges to reduce medication errors: paracetamol on paediatric intensive care

AimParacetamol is widely available and its safety profile is relatively good. However, the risk associated with a paracetamol overdose is much greater in a neonate than that associated with an adult.In 2018, 8% of paediatric medication errors related to the use of paracetamol, including three 10x overdoses. These irregular but serious risks are difficult to manage over time due to degradation of heightened awareness. The aim of this project was to improve the prescribing quality of IV paracetamol on PICU and prevent recurrence of a 10-fold overdose by the implementation of multi-level changes.MethodElectronic prescribing (EP) has been in use on our unit since 2016. Small changes (prescribing nudges) in the configuration of the EP system can be used to improve prescribing quality. Forced functions, automation and standardisation have been found to be more effective in this than more traditional education and training methods.1 2The changes implemented in January 2019 were as follows:Forced function: All paracetamol prescriptions for patients under 1 year of age were capped at 180 mg (change from 1000 mg). The prescriber could not enter a number greater than 180 mg.Automation: All oral paracetamol prescriptions were changed to automatically prescribe 15 mg/kg 6 hourly regardless of age (previously 2 different options requiring the prescriber to input dose and frequency according to formulary directions).Standardisation/simplification: All oral paracetamol prescriptions were rationalised to a single option with automatic dose and frequency as above (previously 2 different options unnecessarily).Reminder/rule: A rule of ‘Consultant Approval’ was added to all intravenous paracetamol prescriptions. The intention of this was for a review of the prescription before use to ensure appropriate use and dose/frequency. This could not be forced, so an education package was launched across the unit by the quality improvement group.Prescription details were downloaded from the EP system for 3 month periods pre and post changes. he data was audited by pharmacy undergraduate students for prescribing accuracy.ResultsThe forced function, automation and standardisation options were implemented with 100% compliance. The ‘consultant approval’ rule was followed in 23% of cases. Consultant review led to a 58.6% reduction of IV paracetamol prescriptions on the unit and zero prescriptions for the first 2 months post implementation. The usage of oral paracetamol increased accordingly. This change corresponded to an overall reduction rate of 41.7% for intravenous paracetamol prescriptions.ConclusionsThis project demonstrates how changes that increase automation within prescribing can reduce error and that implementation is more successful than education. A limitation of our data analysis was that we did not measure the effect on pain relief or pain scores in the patients who did not receive IV paracetamol compared to those who did.ReferencesCafazzo JA, et al. From discovery to design: the evolution of human factors in healthcare. Healthcare Quarterly 2012; 15: 24–29.Patel Ms, et al. Nudge units to improve the delivery of healthcare NEJM 2018; 378: 214–216.

RF Helicon-based Inductive Plasma Thruster (IPT) Design for an Atmosphere-Breathing Electric Propulsion system (ABEP)

Challenging space missions include those at very low altitudes, where the atmosphere is source of aerodynamic drag on the spacecraft. To extend such missions lifetime, an efficient propulsion system is required. One solution is Atmosphere-Breathing Electric Propulsion (ABEP). It collects atmospheric particles to be used as propellant for an electric thruster. The system would minimize the requirement of limited propellant availability and can also be applied to any planet with atmosphere, enabling new mission at low altitude ranges for longer times. Challenging is also the presence of reactive chemical species, such as atomic oxygen in Earth orbit. Such species cause erosion of (not only) propulsion system components, i.e. acceleration grids, electrodes, and discharge channels of conventional EP systems. IRS is developing within the DISCOVERER project, an intake and a thruster for an ABEP system. The paper describes the design and implementation of the RF helicon-based inductive plasma thruster (IPT). This paper deals in particular with the design and implementation of a novel antenna called the birdcage antenna, a device well known in magnetic resonance imaging (MRI), and also lately employed for helicon-wave based plasma sources in fusion research. This is aided by the numerical tool XFdtd®. The IPT is based on RF electrodeless operation aided by an externally applied static magnetic field. The IPT is composed by an antenna, a discharge channel, a movable injector, and a solenoid. By changing the operational parameters along with the novel antenna design, the aim is to minimize losses in the RF circuit, and accelerate a quasi-neutral plasma plume. This is also to be aided by the formation of helicon waves within the plasma that are to improve the overall efficiency and achieve higher exhaust velocities. Finally, the designed IPT with a particular focus on the birdcage antenna design procedure is presented.

The Lunar Polar Hydrogen Mapper CubeSat Mission

The Lunar Polar Hydrogen Mapper (LunaH-Map) mission will map the distribution of hydrogen around the lunar South Pole using a miniature neutron spectrometer. The mission builds upon a decade of lunar science, which has revealed both regional and more localized enrichments of water ice near the lunar poles. Localized enrichments are primarily within permanently shadowed regions (PSRs) and craters throughout the South Pole. The spatial extent of these regions is often below the resolution of previous neutron instruments that have flown on lunar missions. The neutron leakage spectrum from planetary surfaces is primarily sensitive to hydrogen abundance in the top meter of regolith, however, for neutron spectrometers with omnidirectional sensitivity, the spatial resolution is limited by the spacecraft orbital altitude above the surface. A low altitude measurement from a distance on the same scale of the PSRs could spatially isolate and constrain the hydrogen enrichments both within and around within those regions. A small spacecraft mission is ideally suited to acquire the low-altitude measurements required to localize hydrogen enrichments using neutron spectroscopy at the lunar South Pole. LunaH-Map will use a solid iodine ion propulsion system, X-Band radio communications through the NASA Deep Space Network, star tracker, Command & Data Handling System, and EPS systems from Blue Canyon Technologies, solar arrays from MMA Designs, LLC, mission design and navigation by KinetX. Spacecraft systems design, integration, qualification, test, and mission operations are performed by Arizona State University, AZ Space Technologies and Qwaltec.

Adoption and Use of E-Procurement: A Case Study in HM Sdn. Bhd.

The adoption and usage rate of electronic-procurement (eP) in Malaysia has been relatively slow since the beginning of eP implementation. This highlights the need to understand the inhibitor factors of eP adoption and usage among suppliers in Malaysia. This study examined the adoption and use of eP by the HM Sdn. Bhd. construction company (HM), and its contribution to the Management Information System (MIS) planning strategy in the organisation. An in-depth case study approach was employed in this study. The respondents consisted of 21 individuals from middle and top management levels of HM using purposive sampling procedure. The data were collected via interview and analysed using narrative analysis method. The finding of this study highlighted that complexity and compatibility are the key inhibitor factors in the adoption and use of eP among middle management and top management in the company. Failure to maximise eP advantages can reduce the competitiveness of HM in the market. Furthermore, the management had spent a huge investment to make the eP system become reality.

Study on the Dispersion of Aramid Pulp in Epoxy Resin System

In order to improve the uniformity of dispersion of aramid pulp (AP) in an epoxy resin (EP) system containing the EP and curing agent, a series of treatments including the surface cleaning, colloid mill grinding, freeze-drying of APs were carried out in this article. In addition, the composites were prepared by mixing the untreated and treated APs and EP system with the AP mass fractions of 0, 0.1, 0.3, 0.5 and 0.7%. The APs and their dispersion behaviors in EP system were characterized by scanning electron microscope (SEM), fiber quality analyzer, specific surface area tester and optical microscope, moreover, the impact strength and section morphology of composites after impact damage were tested and characterized by a universal material testing machine and SEM.

Aminobenzothiazole-substituted cyclotriphosphazene derivative as reactive flame retardant for epoxy resin

Aminobenzothiazole-substituted cyclotriphosphazene derivative (ABCP) was successfully synthesized and used as reactive flame retardant to improve the fire safety of epoxy resin (EP). The chemical structure of ABCP was confirmed by Fourier transform infrared spectroscopy (FTIR), 1H and 31P nuclear magnetic resonance (NMR), high-resolution mass spectroscopy (HR-MS) and elemental analysis (EA). The curing behavior, thermal stability, thermo-mechanical property and flame retardancy of the prepared EP systems were studied. The differential scanning calorimeter (DSC) results indicated that ABCP induced the anionic polymerization of EP and facilitated the addition reaction between EP and 4,4′-diamino-diphenyl sulfone (DDS). The thermogravimetric analysis (TGA) results indicated that ABCP accelerated the thermal degradation of EP matrix and contributed to the formation of more residual chars with better thermo-oxidative stability. The dynamic mechanical analysis (DMA) results indicated that EP/DDS/ABCP thermosets exhibited higher storage modulus at 50 °C and their glass transition temperature (Tg) values were slightly reduced by 6–10 °C, in comparison with EP/DDS thermoset. The combustion test results revealed the fire hazards of EP/DDS/ABCP thermosets were effectively reduced. Compared with EP/DDS thermoset, the limiting oxygen index (LOI) value of EP/DDS/ABCP-1.2 thermoset was increased to 31.2% and the sample passed UL94 V-0 rating; the average of heat release rate (av-HRR), peak of heat release rate (pk-HRR) and total heat release (THR) values of EP/DDS/ABCP-1.2 thermoset were reduced by 36.5%, 53.7% and 34.5%, respectively; particularly, the fire growth rate (FIGRA) of EP/DDS/ABCP-0.6 thermoset was reduced by half. The research on flame retardant mechanism disclosed that ABCP played dominated flame retardant effect in condensed phase.

The impact of electronic prescribing systems on healthcare professionals\u2019 working practices in the hospital setting: a systematic review and narrative synthesis

BackgroundThe aim of this systematic review was to synthesise peer-reviewed literature assessing the impact of electronic prescribing (eP) systems on the working practices of healthcare professionals (HCPs) in the inpatient setting and identify implications for practice and research.MethodsWe searched PubMed, Medline, Embase, Cochrane and the Cumulative Index to Nursing Allied Health Literature databases for studies published from inception to November 2018. We included controlled, uncontrolled, observational and descriptive studies that explored the effect of eP on HCPs’ working practices in an inpatient setting. Data on setting, eP system and impact on working practices were extracted. Methodological quality was assessed using the Mixed Methods Appraisal Tool. Emergent themes were identified and subjected to narrative synthesis. The protocol was registered with PROSPERO (registration CRD42017075804).ResultsSearches identified 1301 titles and abstracts after duplicate removal. 171 papers underwent full-text review. A total of 25 studies met the inclusion criteria, from nine different countries. Nineteen were of commercial eP systems. There were a range of study designs; most (n = 14) adopted quantitative methods such as cross-sectional surveys, ten adopted qualitative approaches and a further one used mixed methods. Fourteen of the 25 studies were deemed to be of high quality. Four key themes were identified: communication, time taken to complete tasks, clinical workflow, and workarounds. Within each theme, study findings differed as to whether the effects of eP on HCPs’ working practices were positive or negative.ConclusionThere is a lack of consensus within the literature on the impact of eP on HCPs’ working practices. Future research should explore the strategies resulting in a positive impact on HCPs’ working practices and learn from those that have not been successful.

Benzimidazolyl-substituted cyclotriphosphazene derivative as latent flame-retardant curing agent for one-component epoxy resin system with excellent comprehensive performance

Epoxy resin (EP) is inherently inflammable and most flame retardants used now unavoidably deteriorate other properties of EP. Moreover, the components of EP system tend to be formulated as one-component system for large-scale industrial production instead of being blended just before use. In order to overcome these issues, benzimidazolyl-substituted cyclotriphosphazene (BICP) was synthesized and utilized as latent flame-retardant curing agent for EP. According to the curing and rheological behavior studies, BICP maintained chemically inert towards EP at room temperature and could rapidly cure EP when heated. The combustion test results indicated the outstanding flame retardancy of EP/BICP thermosets. With 10.7 wt% addition of BICP, the limited oxygen index (LOI) of EP/BICP-12 thermoset was as high as 33.5% and UL94 V-0 rating was achieved; the peak of heat release rate (pk-HRR), average of heat release rate (av-HRR), total heat release (THR) and fire growth rate (FIGRA) of EP/BICP-12 thermoset were decreased by 69.8%, 33.2%, 34.7% and 71.8%, respectively, compared with those of the neat EP thermoset. Most attractively, other properties of the EP/BICP thermosets were not impaired despite of the enhancement of flame retardancy. Compared with the neat EP thermoset, the EP/BICP thermosets showed comparable mechanical properties and improved dielectric properties. Especially, the Tg values of EP/BICP thermosets (except for EP/BICP-8 sample) were around 190 °C, 34 °C higher than that of the neat EP thermoset. All these results demonstrated that EP/BICP system with remarkable comprehensive performance has the potential to achieve wider application in key fields.

Influences of graphene oxide addition on mechanical properties of aramid fiber reinforced composites

In this paper, the graphene oxide (GO) was prepared by the modified Hummers' method in advance, and the obtained GO was used as a kind of filler added into the epoxy resin (EP) system (including the EP and corresponding curing agent) with different contents (relative to the total weight of the GO-EP system hybrid) ranging from 0.1 to 0.4 wt% to improve the mechanical properties of the aramid fiber reinforced composites (AFRC) through the autoclave forming technology. Then, a series of mechanical properties of the AFRC were measured according to the relevant test standards. Results showed that partial mechanical properties of the AFRC, especially the interlayer property, changed with the different contents of GO. Nevertheless, the tensile strength and tensile modulus of the AFRC presented no obvious changes for different contents of GO. Overall, the matrix phase EP system modified by the GO played an important role in the interlayer toughness of AFRC without reducing its tensile property. This was because the addition of the small amount of GO could prevent the generation of stress concentrations caused by the gaps between the reinforcing phase aramid fibers (AFs) and matrix phase EP system owing to their poor bondings.

Fabrication of one-component epoxy resin systems using maleic acid modified imidazole derivatives

A series of maleic acid modified imidazole derivatives (IM-MA, 2MI-MA and 2EI-MA) were synthesized via the Michael addition reaction of maleic acid (MA) with imidazole (IM), 2-methylimidazole (2-MI) and 2-ethylimidazole (2-EI), respectively. 1H nuclear magnetic resonance (NMR), Fourier Transform Infrared (FTIR) spectra and Elemental analysis (EA) were used to verify the structure of maleic acid modified imidazole derivatives. The maleic acid modified imidazole derivatives were used as latent curing agents for epoxy resin (EP). Differential scanning calorimeter (DSC) under dynamic and isothermal condition was used to study the curing behavior of the prepared EP systems. The curing reactivity of maleic acid modified imidazole derivatives were significantly suppressed, compared with the common imidazole compounds. The EP systems containing maleic acid modified imidazole derivatives possessed excellent storage stability of at room temperature, due to the electron-withdrawing effect of carboxyl reduced the nucleophilicity of imidazole ring and the intermolecular hydrogen bond formed between carboxyl and 3-position nitrogen atom further restrained the nucleophilicity of imidazole ring. What’s more, the maleic acid modified imidazole derivatives regained fast curing ability towards EP under heating condition. Taking advantage of these characteristics, the maleic acid modified imidazole derivatives were suitable for preparing one-component EP systems.

Facile strategy and mechanism of greatly toughening epoxy resin using polyethersulfone through controlling phase separation with microwave‐assisted thermal curing technique

ABSTRACTToughening has been the essential issue for developing high‐performance thermosetting resins. Herein, starting from polyethersulfone (PES) and bisphenol A epoxy resin (EP), a facile strategy is developed to prepare tough resins through controlling phase structure with microwave‐assisted thermal curing. PES/EP resins cured with the assistance of microwave curing (m‐PES/EP) have two major differences compared with those using traditional heat curing (t‐PES/EP), one is high degree of phase separation, and the other is phase separation mechanism. Initial phase separation of all t‐PES/EP resins follows spinodal decomposition mechanism, while those of m‐PES/EP systems with 8 wt% and 18 wt% of PES follow nucleation and growth mechanism. These differences are derived from the fact that microwave curing has much faster phase separation rate and curing reaction rate than thermal curing owing to the higher thermal effect. Differences in phase structure bring different macro performances, and m‐PES/EP systems have higher impact strengths, fracture toughnesses, and flexural strengths than t‐PES/EP resins. This investigation provides a facial and effective way of developing higher performance thermoplastic/thermosetting resin system through controlling phase structure. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2020,137, 48394.

Heat and humidity performance of EPS and Rock wool board external thermal insulation system

A coupled heat and humidity transfer model of external thermal insulation wall is established, and the accuracy of the model is verified by the field test data. Taking Shanghai, a typical hot summer and cold winter area, as an example, this paper simulated and analysed the effects of different climatic conditions (winter and summer) and types of insulation board (rock wool and EPS) on the thermal and humidity properties of concrete-mortar-insulation-mortar external insulation wall. The results show that the temperature variation of the bonding mortar on the inside of the insulation board is much smaller than that on the outside of the insulation board due to the thermal insulation effect; the relative humidity of the bonding mortar layer in the external insulation system of rock wool can reach more than 80% within 7 days in summer, which has a high risk of falling off; and the relative humidity of the coating mortar layer can reach about 73% within 7 days in winter, which is likely to become mildewed; The resistance to moisture migration of rock wool is weaker than that of EPS.