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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.

Geopolymerization is a new method for treating water treatment residue (WTR)from water purification plants to reduce the amount of stored land in urban areas. Polymeric bond formation depends on the curing conditions. In this study, the curing conditions suitable for subsequent treatment to save energy consumption and production costs in the future application were investigated.TheWTR had a high aluminosilicate content with low alkaline activity, sofly ash (FA) was added to FAandWTR mixtures inthe ratio of 40 and 60weightpercent(% in wt.), respectively.The moisture content of the mixtures ranged in 12–15%, suitable for semi-dry pressing to form pellets. After this formation, the geopolymer samples were cured under different conditions (room temperature, microwaveoven,in dryerat 110°C,and in autoclave with hydrothermalcondition). The experimental results showed that the hydrothermal samples had better properties, such as pH

Background The present means of confirming the cure of intra-operative polymethyl methacrylate (PMMA) cement are to wait for the remainder cement to harden. To our knowledge, there is no available technique to determine the precise moment of cure for in-vivo cement beneath the tibial tray. This study uses a novel means to determine cement curing time in two environments. One environment represents the operating theater, and the other environment attempts to model cement conditions under the tibial tray during surgery. Materials and methods We determined the temperature-versus-time plot of cement curing using the following two temperature sensors: one in a simulated implanted tibial tray and another in the remainder cement. We performed 55 tests using dental methyl methacrylate cement mixed in the same ratio as the orthopedic cement. To simulate in vivo conditions, a simulated stainless-steel tibial tray was implanted on a cancellous bone substitute (Sawbones, Vashon Island, WA, USA) using standard cement technique and subsequently placed in a 90°F (32.2 °C) circulating water bath. We positioned a temperature sensor in the cement mantel and positioned a second sensor in a portion of the remaining cement. The temperature from both sensors was measured simultaneously, beginning at 5 min after mixing and continuing for 20 min. The first derivative of the temperature provided the precise curing time for each condition. We analyzed the results of 55 repeated experiments with an independent samples t-test. Results With the described technique, we were able to accurately determine the moment of cure of the cement beneath the simulated tray. There was a mean difference between cure time of 5 min and 26 s (p value Conclusions We validated that our technique was successful in determining the precise time to cure in two different environments. Level of evidence This was not a clinical trial and did not involve patients as such the level of evidence was Grade A: Consistent 1 and 2.

Two new precursors for focused electron beam-induced deposition (FEBID) of cobalt silicides have been synthesized and evaluated. The H3SiCo(CO)4 and H2Si(Co(CO)4)2 single-source precursors retain the initial metal ratios and show low sensitivity to changes in the FEBID parameters such as acceleration voltage, beam current, and precursor pressure. The precursors allow the direct writing of material containing ∼55 to 60 at % total metal/metalloid content combined with high growth rates. During the deposition process an average of ∼80% of the carbonyl ligands are cleaved off in these planar deposits. Postgrowth electron curing does not change the deposits' composition, but resistivities decrease after the curing procedure. Temperature-dependent electrical properties indicate the presence of a granular metal for both cured samples and the as-grown Co2Si deposit, while the as-grown CoSi material is on the insulating side of the metal-insulator transition. The observed magnetoresistance behavior is indicative of tunneling magnetoresistance and is substantially reduced upon postgrowth irradiation treatment.

Ceramic matrix composites (CMC) exhibit increased crack resistance and resistance to mechanical and thermal shock impacts retaining at the same time the valuable properties of monolithic ceramics. Therefore, they are widely used as parts of heat-loaded elements of aviation and rocket technology, in nuclear power industry, etc. LPI-method (liquid polymer infiltration) of CMC production is based on the impregnation of a skeleton of ceramic fibers with an organosilicon polymer, formation of a preceramic matrix by polymer technology, and subsequent high-temperature pyrolysis resulting in formation of a reinforced ceramic matrix. Ceramics obtained from polymer precursors have a predominantly amorphous structure which determines its high thermal stability. Moreover, introduction of the nanosized particles of carbides, borides and nitrides of refractory metals (Zr, Ti, Hf) into the matrix of a ceramic composite stabilizes its amorphous structure up to temperatures of 1500 - 1600°C. We present the results of studying the preceramic compositions based on polycarbosilane and polyorganosilazanes modified with Hf and Ta atoms. It is shown that introduction of the modifying additives Hf and Ta into the polyorganosilazane composition shifts the curing interval of the compositions towards lower temperatures. The yield of the gel fraction is 73.3 and 82.7 wt.%, respectively. The weight loss of pyrolysate samples heated to 1400°C in air does not exceed 0.5%. The physical and mechanical properties, as well as the thermal oxidative stability of novel ceramic composite materials obtained on the base of the studied compositions and carbon reinforcing filler are analyzed. It is shown that the density of CMC samples increases by 1.5 times with an increase in the number of impregnation cycles and reaches the maximum value of 1950 kg/m3 with five impregnation cycles of the filler with a composition based on polyorganosilazane modified with Ta. The results obtained can be used in the development of new CMCs.

In this study, the ultraviolet (UV) radiation curing process and furnace curing process for curing aerosol jet printed nickel oxide (NiO) nanoparticle thin films were investigated. NiO has a negative temperature coefficient and can be used to fabricate temperature sensors. Four UV power settings (for 10 min) and four furnace temperatures (for 1 h) were used to cure the aerosol jet printed sensors. The resultant sensor resistance at 100 °C and 180 °C was measured, and the sensor’s sensitivity was characterized by a B value. Confocal microscopy was performed to characterize the sensor surface. The 60% UV power setting yields the lowest resistance and the highest B value among all sensors. The analysis of variations shows that the UV power setting is not a significant factor in the resistance and B value, while the furnace temperature is a significant factor. This indicates that UV curing is a more robust method and does not need to be optimized to achieve good results. The UV curing process not only reduces the required curing time but also improves the performance of the temperature sensor.

Transverse cracking in continuously reinforced concrete pavement (CRCP) develops over time and may exhibit irregular patterns such as cluster cracks, Y-shaped cracks, and divided cracks. These undesirable cracking patterns can increase the probability of premature spalling and punchouts. Ideally, a uniform transverse cracking pattern with small crack widths leads to favorable long-term performance in CRCP. An experimental field project was constructed with internally cured concrete and active cracking to control crack initiation timing, patterns, and properties. Prewetted fine lightweight aggregate was used for internal curing, and edge notches of 2 in. depth and 2 ft length every 4 ft along the test section were sawcut for active crack control. The three experimental CRCP sections in Illinois were monitored for crack spacing, crack width, and formation of undesirable cracks over a 4-year period. Internally cured concrete significantly reduced the undesirable crack patterns relative to the control section. Internally cured concrete coupled with active crack concrete produced superior crack patterns and properties, that is, uniform crack spacing of 3.6 ft without cluster cracks, 0.2 mm surface crack width, and only a small number of undesirable cracks. Active crack control produced a higher number of transverse cracks near the terminal joint (last 150 ft) compared with the control section. Moisture and temperature management with active crack control during construction of the CRCP provided a desirable crack pattern and properties that should increase the overall service life of a pavement.

In this study, the ballistic behavior of protective armor plates (PaP) obtained by curing between high structural strength AA7075-T651 aluminum plates by reinforcing with glass balls of two different rubber mixtures whose damping properties were developed with carbon nanotube and glass bubbles fillers were investigated. A total of six PaPs at 27, 30, and 35 mm heights were prepared using two different matrix damping rubbers. High-strength liner rubber used in air bellows is vulcanized on the front and back surfaces of PaPs. Between the PaPs, Ø15.875 and Ø6.747 mm, borosilicate glass balls were placed in a particular arrangement that coincides with the middle of the matrix rubber and does not have any gaps. Liner rubber cured on the front face has managed to hold the energy by forming a layer like clothing around the bullet cores. Glass balls between PAPs play an essential role in the energy absorption of GB-filled mixtures. In contrast, in MWCNT-filled mixtures, they act as a second damping element. The ballistic performance of PAPs prepared with multiwalled carbon nanotubes was determined to be better than those prepared with Glass Bubbles. Thanks to the superior mechanical properties and high aspect ratio of MWCNTs, the penetration and swelling heights of the matrix damping rubbers prepared to have excellent results compared to glass bubbles. With the increase in the thickness of the PaPs prepared with MWCNTs, the deformation effect of the penetration depth and bulging height created by the bullet on the anterior and posterior surfaces decreased. As the thickness of PaP increased from 27 mm to 35 mm, penetration depth decreased by 38%, and bulging height reduced by 35%. The amount of penetration and swelling increased in PaPs using rubber filled with glass bubbles. As the plate thickness increased, the damping feature decreased and the glass balls were activated, and the bullet was stopped.

Carbon fiber-reinforced polymer composites have been increasingly used by the aerospace, automobile, and other industries due to their high specific stiffness and strength properties. Manufacturing polymer composites using conventional prepreg curing is time-consuming and energy-intensive. Microwave curing of composites is an attractive alternative technology to manufacture composites with exceptional processing speed and energy savings. In this work, a traditional microwave oven was modified and used to manufacture composite panels. The void content, short beam strength properties, flexural properties, and impact response of the microwave cured panels were evaluated. Composite panels (control) were manufactured using carbon/epoxy prepreg cured in walk-in oven. The performance of microwave cured composite specimens was compared against the performance of conventional walk-in oven cured composite specimens. Results showed that the short beam strength and flexural strength of panels cured in the microwave oven remained approximately the same as the control specimen, however, the flexural modulus, the impact peak force, and the rebound energy increased by 12%, 6% and 18% respectively for the panels manufactured through microwave curing.

Objective This in vitro study investigated the influence of resin coating on the bonding performance of self-adhesive resin cements in single-visit computer-aided design (CAD)/computer-aided manufacturing (CAM) resin restorations. Materials and method CAD/CAM resin (1.5-mm thick) was mounted on 20 noncoated and 20 resin-coated human dentin surfaces using dual-cured self-adhesive resin cements (Panavia SA Cement Plus or Panavia SA Cement Universal, Kuraray Noritake Dental) in either self-curing or dual-curing mode. These specimens were sectioned into beam-shaped sticks and subjected to microtensile bond strength tests after 24 h of water storage. The obtained data were statistically analyzed with three-way analysis of variance (ANOVA) and t tests (α = 0.05). Results The three-way ANOVA results revealed the significant influence of resin coating, resin cement, and curing mode. Resin coating and light curing led to higher bond strengths in almost all groups. Resin-coated dentin with Panavia SA Cement Plus exhibited a mean bond strength greater than 35 MPa in both self-curing and dual-curing modes. Conclusions In single-visit CAD/CAM resin restorations, resin coating, resin cement selection, and curing mode influenced the bonding performance of self-adhesive resin cements. In addition, resin coating and light curing increased the bond strength of self-adhesive resin cements. Resin coating and light curing are encouraged for predictable bonding performance of dual-cured self-adhesive resin cements in single-visit CAD/CAM resin restorations.

Manufacturing of Y-branch coupler depends on high technology production equipment and in-factory accuracy assembly tools. The manufacturing of a 1×2 Y-branch symmetric and asymmetric waveguide coupler based on the mould replication process and Epoxy OG142 as an optical core is presented; an alternative to provide a less complex technique. The polymer optical waveguide adopted two basic designs: the 1×2 Y-branch symmetric coupler as the core structure and the 1×2 asymmetric coupler that allows non-symmetric optical splitting. This paper focused on the main structure fabrication of the 1×2 symmetric and asymmetric waveguide coupler that produces a power output. The fabrication was done by engraving acrylic to produce a master mould using CNC machining tools for optical devices. Both 1×2 devices were made via soft lithography, which duplicated the pattern from the master mould onto a second mould to produce an actual device. Optical polymer epoxy OG142 was injected into the second mould, of which the product was then put on top of acrylic. The device was completed after curing the optical polymer glue, epoxy OG142, by exposing the assembly on the second mould under UV light until both parts bonded. The difference between the simulation and design TOFR value was only ±2%. This showed that the simulation and design are in good agreement, which provides similar performance.

The purpose of this study was as a feasibility study of the utilization of oleamide as a new additive for natural rubber (NR) filled with silica using the semi-efficient vulcanization system. Silica fillers used as much as 30 parts per hundred parts rubber (phr). Oleamide was obtained from the synthesis of oleic acid with urea. Oleamide was inserted into the silica filled NR compounds with the varied composition of 0.0 phr; 2.0 phr; 4.0 phr; 6.0 phr, and 8.0 phr. The influence of oleamide on the curing characteristic of the silica filled NR compounds was observed. It was obtained that the oleamide functions as a curative and also a plasticizer. The greater the levels of oleamide added, the shorter the scorch time and optimum curing time were. Oleamide also decreased the minimum torque with addition up to 8.0 phr. The greater the levels of oleamide was, the lower the minimum torque was. Oleamide also increased the maximum torque and torque difference of the silica-filled NR composites at the addition of 2.0 phr. The 2.0 phr was the optimum composition of the oleamide.

Polyfurfuryl alcohol (PFA) resin consists of low and high molecular weight oligomeric chains which are differently involved in cross-linking reactions. The dependence of PFA curing kinetics to its molecular weight was investigated by differential scanning calorimetry. To this end, PFA resin was synthesized by cationic polymerization of furfuryl alcohol in the presence of maleic anhydride and fractionated to four fractions by precipitation fractionation. The fractionation efficiency was then examined by software-based deconvolution of GPC chromatograms. Effect of molecular weight of the fractions on their curing kinetics was studied by determining the curing enthalpy and activation energy using Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa isoconversional models. A reduction in molecular weight, e.g., 291.72 g.mol−1, resulted in a 20 kJ mol−1 drop in the cure activation energy and decreased the curing enthalpies, eq. 9.57, 7.97 and 9.87 J.g−1 at heating rates of 5, 10 and 15 °C.min−1, respectively. Taking such dependency into consideration, a curing mechanism was highlighted among different reported mechanisms for PFA cross-linking reactions.

Consuming enough protein is a very important part of a balanced and healthy diet. Complete proteins are those in which all essential amino acids are present. In meat products, like hams, many different reactions occur during ageing and storage. For example, the production of free amino acids or the production of biogenic amines is formed by decarboxylation. In this study, the presence of these amino acids and biogenic amines, as well as the quality properties of cured hams during curing and ageing, were investigated.The meat samples were immersed into 100 g L−1 NaCl brine. The curing took 20 days, followed by smoking and ageing for 35 days (12 °C, 75% RH). The wet-cured ham samples were analysed for changes in NaCl concentration (at 3 parts: surface, core, bottom layer). Moreover, color, water activity, denaturation temperature and enthalpy (Differential Scanning Calorimetry), free amino acids (FAAs) and biogenic amines (BAs) were also evaluated.

Purpose Concrete is a building material widely used for the infrastructural development. Cement is the binding material used for the development of concrete. It is the primary cause of CO2 emission globally. The purpose of this study is to develop sustainable concrete material to satisfy the present need of construction sector. Geopolymer concrete (GPC) is a sustainable concrete developed without the use of cement. Therefore, investigations are being conducted to replace the cement by 100% with high calcium fly ash (FA) as binding material. Design/methodology/approach High calcium FA is used as cementitious binder, sodium hydroxide (NaOH) and sodium silicates (Na2SiO3) are used as alkaline liquids for developing the GPC. Mix proportions with different NaOH molarities of 4, 6, 8 and 10 M are considered to attain the appropriate mix. The method of curing adopted is ambient and oven curing. Workability, compressive strength and microstructure characteristics of GPC are analysed and presented. Findings An increase of NaOH in the mix decreases the workability. Compressive strength of 29 MPa is obtained for Mix-I with 8 M under ambient curing. A polynomial relationship is obtained to predict the compressive strength of GPC. Scanning electron microscope analysis is used to confirm the geo-polymerisation process in the microstructure of concrete. Originality/value This research work focuses on finding some alternative cementitious material for concrete that can replace ordinary portland cement (OPC) to overcome the CO2 emission owing to the utilisation of cement in the construction industry. An attempt has been made to use the waste material (high calcium FA) from thermal power plant for the production of GPC. GPC concrete is the novel building material and alternative to conventional concrete. It is the ecofriendly product contributing towards the improvement of the circular economy in the construction industry. There are several factors that affect the property of GPC such as type of binder material, molarity of activator solution and curing condition. The novelty of this work lies in the approach of using locally available high calcium FA along with manufactured sand for the development of GPC. As this approach is rarely investigated, to prove the attainment of compressive strength of GPC with high calcium FA, an attempt has been made during the present investigation. Other influencing parameter which affects the strength gain has also been analysed in this paper.

In this study, the nonisothermal differential scanning calorimetry (DSC) was carried out to evaluate the curing reaction of fiber/epoxy laminates. The optimal curing process of the prepreg was obtained by T-β extrapolation method and nth-order reaction curing kinetic equation. The bending strength, impact strength and thermodynamic properties of the composite laminates with different ply orientations were investigated, respectively. The results show that the apparent activation energy and the reaction order of the prepregs are 82.89 kJ/mol and 0.92, respectively. The curing process of carbon fiber/epoxy resin prepreg is 130 ℃ /60min + 160 ℃/30 min. The bending strength of [0]10 laminate is 1948.3 MPa, which is 11.8 times higher than that of [+ 45/-45]5s laminate, and 96.4% higher than that of [0/90]5s laminate. The impact strength of [0]10 laminate is higher than that of [+ 45/-45]5s and [0/90]5s laminates. The glass transition temperature (Tg) of the laminates is 142 ~ 146 ℃, and the loss factor of [0]10 laminate is significantly higher than that of [+ 45/-45]5s and [0/90]5s laminates. This research provides a theoretical basis for the further application of prepregs to fiber composite materials.

Metal oxide nanofillers are a special type of additives in rubber composites that impart special qualities such as thermal resistance, tensile strength, electrical conductivity and heat capacity to rubbers. The heat conductivity of metal oxide through the rubber matrix reduces the vulcanization time of the rubber nanocomposites. Hence, the present work focused on the enhancement of these properties in natural rubber (NR) using zinc ferrite (ZnFe2O4) nanoparticles were prepared by a simple two-roll mill mixing technique. Structure, morphology, crystalline nature, cure characteristics, swelling, thermal and mechanical properties of the NR composites containing ZnFe2O4 were analysed in detail. FTIR and UV analysis proved the interaction of zinc ferrite with the macromolecular chain of NR. The XRD patterns of composite films revealed a decrease in amorphousness of NR with well-dispersed crystalline peaks of nanoparticles in the polymer. SEM images evidenced the morphological changes caused by dispersing zinc ferrite in the NR matrix. TEM analysis showed the uniform attachment of nanoparticles in the polymer. Glass transition temperature obtained from DSC was improved with the addition of zinc ferrite. The results from TGA showed that the presence of ZnFe2O4 in the polymer matrix greatly increases the thermal stability of NR. The metal oxide nanofiller significantly reduced the cure and scorch time of the NR composites. The mechanical properties of rubber nanocomposites showed that the addition of ZnFe2O4 improved their modulus, tensile strength, hardness, abrasion resistance and heat build-up, whereas the elongation at break and resilience decreases. The permeation and diffusion of nanocomposites were observed to be diminished with the size of penetrating solvents and also with the loading of filler. Overall, zinc ferrite nanoparticles could be used as a potential filler for improving the processability, mechanical strength, thermal stability and solvent resistance of natural rubber.

The effect of relative humidity on the curing of alkoxysilane functional alkyds and reactive diluents was evaluated. Alkoxysilane functional alkyds and tung oil-based reactive diluents were synthesized and used as additives in varying amounts in alkyd coatings. Looking at modified alkyd versus modified reactive diluent allows for the comparison of the humidity effect on high and low molecular weight alkoxysilane functional additives. The coatings were cured at 25 and 75% relative humidity and evaluated for drying time, coating and tensile properties, and gel content. It was found that at higher humidity, the alkoxysilane-containing samples improved properties significantly when compared to the control alkyd.

The article presents the results of a study of the effect of vacuuming on the curing processes of liquid‑glass mixtures. The method of conducting experiments using an original laboratory vacuum installation and the mechanisms of curing a liquid‑glass mixture with various hardening methods are described. Studies have shown that vacuuming can signifi antly accelerate the curing and increase the strength of the mixture while reducing the content of the silicate binder. This; in turn; facilitates the knockability of liquid‑glass mixtures and expands the prospects for using these environmental friendly mixtures in foundry as an alternative to sands based on organic binders.

A curing system has been developed for obtaining high-strength compositions matrix, which is used in the production of composites based on reinforced carbon fiber using prepreg technology with a curing temperature of . A technology has been developed for combining an epoxy oligomer with a curing agent and modifier. The pot life of the prepared prepregs is at least 15 days.

In general, building materials exposed to the marine environment are more prone to deteriorates than others. There are three main zones of the marine environment named atmospheric zone, tidal zone and submerged zone. This article investigated the effect of different curing conditions named water curing, air curing, seawater curing and wet/dry curing on the compressive strength and microstructure properties of alkali-activated slag (AAS) pastes with and without microsize metakaolin (mK) particles over a period of up to one year. The wet/dry curing was used to simulate the effect of the tidal zone, of which the specimens were submerged in seawater for 18 h followed by 6 h of air drying per day. The slag was partially replaced with mK at ratios fluctuated from 0 to 12% with a step of 2%, by weight. A fixed concentration of sodium silicate was used as an alkaline activator. After initial curing, the specimens were exposed to the aforementioned treatment conditions for 3, 6 and 12 M. The phase composition and microscopic structure of the neat AAS and AAS/mK samples were tested by X-ray diffraction (XRD), thermogravimetric analysis (TGA/DTG) and scanning electron microscopy (SEM). The results showed that the deterioration in the specimens exposed to the simulated tidal zone is more severe than those submerged in seawater. The neat AAS pastes showed better strength and microstructure than those blended with mK.

A new kind of bisphenol A-type epoxy resin (E51) system cured at room temperature was prepared using ether bond- and fluorine-containing aromatic diamine, including 4,4′-(Hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline (HFBAPP) and 2,2-Bis[4-(4-aminophenoxy)phenyl]propane (BAPP), and acrylic acid (HAA) as hardeners. The curing behavior of epoxy resin was investigated by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) Spectroscopy. The thermal properties, dynamic thermomechanical properties, tensile properties, and dielectric properties of the cured epoxy resin at room temperature were evaluated with thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), universal tensile testing machine, and vector network analyzer, respectively. The surface morphology of the tensile fracture specimen was observed by scanning electron microscope (SEM). The results showed that the curing reaction for this kind of epoxy resin system can be conducted at room temperature without external heating. Compared to BAPP and 4,4′-Diaminodiphenyl methane (DDM), the cured E51/HFBAPP + HAA system demonstrated the best comprehensive properties, such as high thermal stability, high glass transition temperature and storage modulus, high tensile strength and modulus, and low dielectric constant and dielectric loss values at 2–18.3 GHz, which are mainly attributed to the introduction of flexible ether bonds and CF3 groups into crosslinked epoxy network. SEM testing confirmed that E51/HFBAPP + HAA and E51/BAPP + HAA systems displayed good toughness.

Organo-Montmorillonite (o-MMT) nanoclay added polybenzoxazine resin (type I composites) were prepared with varying amounts of clay (0, 1, 2, 4 and 6 wt %). Clay dispersion, changes in curing behaviour and thermal stability were assessed in type I composites. Findings from these studies of type I composites were used to understand thermal stability, mechanical, and mass ablation rate behaviour of nanoclay added carbon fiber reinforced polybenzoxazine composites (type II). Interlaminar shear strength and flexural strength of type II composites increase by 25% and 27%, respectively at 2 wt% addition of clay. An oxy-acetylene torch test with a constant heat flux of 125 w/cm2 was used to investigate mass ablation rate of type II composites. The ablation rate has increased as the weight percentage of clay has increased. This is contradicting to type I composites with up to 6 wt% clay and type II composites with up to 4 wt% clay, which have improved thermal stability. The microstructure of the ablated composites was examined using scanning electron microscopy. Increased ablation rates are due to the reaction of charred matrix with nanoclay, which exposes bare fibers to the ablation front, resulting in higher mechanical erosion losses.

Nanocomposites have received much attention as construction materials, adhesives, and sealants because of the strong interfacial interactions between nano-sized fillers and matrix. However, dispersing the nano-sized fillers in the polymer matrix is challenging because of their tendency to agglomerate. In this study, a glycidyl terminated polysiloxane (g-PDMS) was synthesized and used to disperse fumed silica (nano-sized silica aggregates) in a BPADG/D230 system. The kinetic parameters of the g-PDMS/BPADG/D230 curing were obtained through non-isothermal DSC analysis. The apparent activation energy and reaction order of the epoxy resin/D230 system were calculated to be 51.82 kJ/mol and 0.91, respectively. Next, the effect of fumed silica on the properties of the nanocomposites was investigated. Compared to neat epoxy, the maximum strength, Young's modulus, fracture toughness and fracture energy of the nanocomposite with 5 phr (parts per hundred parts of epoxy resin) fumed silica were increased by 27%, 61%, 76% and 79%, respectively. Lastly, the fracture toughening mechanisms of the nanocomposites were examined using SEM images of the fractured surfaces of single-edge notched specimens after a three-point bending test.

High-performance and ultra-high-performance concrete have been increasingly used as building materials in modern construction, and their superior properties derived from a tailored microstructure. In this study, Rietveld quantitative X-ray diffraction analysis was adopted to investigate phase evolutions of four cementitious pastes with varied addition of fly ash or silica fume at very low water/binder ratios. The results indicate that the phase changes concerning the contents of the major clinker phases mainly happen within the first 7 d. The content of portlandite (CH) in pure cement paste increases monotonically while, due to pozzolanic reaction, it decreases in blended pastes between 7 and 28 d. At early age, the addition of silica fume accelerates the hydration of cement, while the introduction of fly ash shows significant retardation especially at 1 d. The degree of hydration (DOH) of cement is mainly determined by the effective water/cement ratio of the paste, and the incorporation of fly ash, while initially producing little reaction, results in a higher DOH of cement. With steam curing, the content of CH significantly decreases in the blended pastes, which indicates a promoted pozzolanic reaction.

Steam is used to provide heating and moisture in the curing process for the production of precast concrete (PC) construction elements. The generation of steam requires large amounts of fossil fuels. This study considers the incorporation of solar thermal energy into the steam curing of PC construction elements for reducing the need for fossil fuels and associated CO2 emissions. For this purpose, the board made of composite phase change material covers the inner surface of the main sun-facing wall in the heating & curing building. The PCM board is heated by sun rays and accumulates thermal energy during the PCM's phase transition, and this energy then is released to the indoor environment of the building, reducing the amount of steam required to maintain a certain level of temperature during the curing process. The energy consumption simulation software, EnergyPlus, and two physical models (built on the scale of 1:3) were used to study the effects of two different PCMs on the thermal performance of such new type of heating & curing buildings. Composite PCMs considered were GH-33 and GH-37 with 33 and 37 °C melting temperatures developed by the research team. The theoretical and experimental results are in good agreement and demonstrate that, compared to the GH-33, GH-37 PCM increases the temperature of the inner surface of the main sun-facing wall and the upper surface temperature of the PC construction element by 3.4 and 1.4 °C, respectively. The heat accumulation and discharge rates also were greater by 62%. For the investigated design of the building and given location in China, the deployment of studied PCM wall panels results in a reduction in the annual energy consumption and CO2 emissions by 58.6 GJ and 5 tons, respectively. The method developed for applying solar energy and selecting PCMs for augmenting steam curing of PC construction elements can be deployed in different geographical regions.

We present an experimental and theoretical investigation of the thermal and mechanical properties of modified polymer networks based on epoxy resin, 2,4-toluene diisocyanate, polytetramethylene oxide and dimethylbenzylamine. With variations in the curing temperature and the ratio of the diol, diisocyanate components and epoxy resin, epoxy urethane-containing isocyanurate polymers are modified. For reaction systems cured below 100°C, the polymers contain many flexible chain structures and become rubbery at ~60°C. A processing temperature above 120°C leads to a significant composition change, which affects the properties of the resulting systems. The glass transition temperature of the synthesized networks increases to 225°C. The elasticity modulus increases by 107%. The yield strength at compression with increasing curing temperature from 120 to 200°C is accompanied by improved mechanical and thermal properties of the samples. The yield strength is increased by 48%, the elastic modulus by 107%, the Brinell hardness by 40%, and the Shore hardness by 20%. The glass transition temperature increases to 225°C.

The aim of the present study is to apply an embedded resistance wire technique for curing of thermosetting resins as well as for the self-healing of thermoplastic polymers. The work consists of two parts. In the first part, Kanthal resistance wires embedded in a resin plate acted as heating elements when direct electrical current was flowing through them (Joule heating). During heating, the temperature was continuously monitored using a thermal camera, and accurate temperature times for fixed position diagrams as well as temperature positions for fixed time diagrams were calculated. The effects of curing with this method were evaluated by studying the three-point bending mechanical behavior of the cured resin, comparing it with the corresponding behavior of the same resin when cured using a conventional oven curing method at the same temperature. In the second part of the present work, the possibility of using the same technique for healing existing notches and flaws in a PET thermoplastic is explored. We examined whether providing energy through the resistance wires created the right amount of heat to heal the thermoplastic, or, more specifically, whether it closed the notches and eliminated the abrasions that were artificially created on the specimens. The technique using embedded resistance wires worked equally well, with interesting and promising preliminary results regarding the curing of thermoset resins and the healing of thermoplastics.

A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices.

Unexpected ice accumulation tends to cause many problems or even disasters in our daily life. Based on the superior electrothermal and photothermal function of the carbon nanotubes, we introduced a superhydrophobic/electrothermal/photothermal synergistically anti-icing strategy. When a voltage of 15 V was applied to the superhydrophobic sample, the surface could rapidly melt the ice layer (~ 3 mm thickness) within 530 s at the environmental temperature of − 25 °C. When the near-infrared light (808 nm) irradiates on the superhydrophobic sample, the ice could be rapidly removed after 460 s. It was found that the superhydrophobicity helps the melted water to roll off immediately, and then solves the re-freeze problem the traditional surfaces facing. Moreover, the ice can be completely melted with 120 s when the superhydrophobic/electrothermal/photothermal synergistically anti-icing strategy was utilized. To improve the mechanical robustness for practical application, both nanoscale carbon nanotubes and microscale carbon powders were utilized to construct hierarchical structure. Then these dual-scale fillers were sprinkled onto the semi-cured elastomer substrate to prepare partially embedded structure. Both hierarchical structure and partially embedded structure were obtained after completely curing the substrate, which imparts excellent abrasion resistance (12.50 kPa, 16.00 m) to the prepared sample. Moreover, self-healable poly(urea–urethane) elastomer was introduced as the substrate. Thus, the cutted superhydrophobic sample can be mended by simply contacting at room temperature.

Objective This in vitro study was aimed to determine the effect of composite polymerization methods with universal adhesive on push-out bond strength in coronal dentin. Materials and Methods Using 48 healthy premolar teeth, the almost conical access cavities were excised to the canal entry. Cavity preparations were treated with a universal adhesive in the self-etch mode. Teeth were randomly divided into four groups (n = 12). It was used to restore the cavities with a bulk-fill composite; Tetric N-Ceram, a conventional composite; Filtek Z250, a dual-cure composite; Rebilda DC VOCO, and chemical cure composite; Master-Dent. After applying 10,000 thermal cycles, 1-mm incisions were made in coronal dentin, and slices were placed in a UTM machine in a special jig and tested for push-out bond strength at a crosshead speed of 0.5 mm/min. Data were analyzed using one-way analysis of variance and Games–Howell tests (p Results The highest mean bond strength was of the conventional composite (18.36 ± 5.63) and the lowest mean of bond strength was for the dual-cure composite (5.10 ± 2.74). There was a significant difference among the means of bond strength for various composite resins curing (p Conclusion The bulk-fill and conventional light-cured composites had higher bond strength than self- and dual-cured composite resins.

The use of various physical influences is an economical and highly effective direction for regulating and improving the characteristics of the modified reinforced polymer composite materials developed in this work. The methods of energy effects studied in this work were used at the stage of impregnation of technical threads of various chemical nature with an oligomeric binder and a hardener (when preparing prepregs by the traditional method) or with a binder solution and a curing system (when preparing prepregs by the method of layered application of components) Based on the conducted research, a classification of the applied methods of physical modification according to the principle of the influence of energy fields is proposed. The studied methods of energy effects are divided into orienting and energetically energizing effects. The first group includes treatments with constant magnetic (PMP) or electric fields (PEP), and constant mechanical loads. The second group includes energy effects that have a wave nature (energetically energizing), and vibration, ultrasonic effects, and ultraviolet radiation are attributed to them. Modification methods of the first group contribute to a decrease in the mobility of binder molecules during curing, while the formation of branches of polymer chains occurs during the curing process, which leads to a predominant increase in the destructive stress during static bending. Energetically energizing effects contribute to the relative acceleration of the process of linear growth of polymer chains during curing, which is accompanied by the formation of a more sparsely cross-linked mesh structure, which leads to a predominant increase in impact strength. Of the two competing processes in the curing of epoxy oligomers, this one requires a higher activation energy, which is confirmed by the results of studies. Analyzing the results obtained, it can be concluded that the modification methods used in the work allow not only to obtain polymer composite materials with high strength characteristics, but also to directly adjust the properties of composites depending on the requirements for the products. Orienting modification methods lead to hardening of the resulting polymer composite material with a predominant increase in the destructive stress during static bending from 20 to 47%. When using energetically energizing influences in the technology of producing reinforced reactoplasts, the impact strength increases mainly from 19 to 40%.

The possibility of developing conductive rubber based on tire regenerate and conductive carbon black OMCARB CH85 is shown. The vulcanizing characteristics of the regenerates obtained by thermomechanical devulcanization using a curing group and conductive carbon black were studied. It is shown that, after thermomechanical devulcanization, a re-vulcanization due to preservation of sulfide bonds occurs only in the presence of sulfur and vulcanization accelerators. A flocculation effect was found upon the introduction of OMCARB CH85 into the regenerate. It is shown that tensile strength and Shore A hardness are increased with an increase in the content of conductive carbon black in the regenerate. However, owing to insufficient dispersion, the carbon black admixture exceeding the optimum quantity results in a decrease in maximum relative elongation at break and diminished resistance to abrasion is observed. The study of the volume resistivity showed that the rubbers obtained belong to semiconductor materials. The dependence of resistivity on temperature in the range from 10 to 80°C is plotted. It is shown that the effect of a positive thermal coefficient is observed in all samples. The values of the positive temperature coefficient of resistance in the temperature range of 10–80°C are 0.054–0.285 K–1.

In this study, the impact of two types of polymer on the stress–strain behavior, elastic modulus and toughness of cement paste, were investigated and quantified. The cement paste was modified with two types of polymer up to 0.06% (based on the dry weight of cement), and the samples were cured at different curing times (1, 3, 7, and 28 days) before testing. Polymers increased cement flowability by 7%–26% and lowered the water/cement ratio (w/c) by 12%–43%, based on the types of polymer and polymer content. The nonlinear Vipulanandan p-q model was used to predict the stress–strain behavior of modified cement, and the results were compared to the β model. The elastic modulus (E) at different strain levels and total toughness (TT) of the modified cement was determined by differentiating and integrating the Vipulanandan p-q model. When 0.06% polymers were added to cement paste, the compressive strength increased by 107–257%. During the early curing age, the cement modified with polymer was able to withstand large deformations that mean increase the ductility of the materials, but with increasing curing, the cement modified with polymers become brittle and the strain at failure reduced. Adding polymers to the cement paste creates an amorphous gel that fills the spaces between cement particles with working fibers net or meshes covering the cement particles, which cause a reduction in the voids, porosity and increasing the density of the cement, subsequently the mechanical properties significantly increased.

The modern production of products made of composite materials based on thermosetting binders is mainly based on the use of pre – impregnated reinforcing technical threads-prepregs. The binder used for such semi-finished products must meet two important technological requirements: have a low reactivity (high viability) when stored in the temperature range from -5 to +25 ° C and the ability to adjust the curing time at the molding temperatures of the product. To eliminate the disadvantages of the traditional method of obtaining polymer composite materials, to improve their strength characteristics and reduce the cost of the resulting reinforced composites, it is proposed to use the method of layered application of components. The essence of the method consists in layer-by-layer impregnation of the fibrous filler with a binder solution, and then a developed curing system consisting of an amine hardener that prevents the interaction of the hardener with the resin under storage conditions and protective polymer emulsions. The binder-filler system is activated only at an elevated temperature under curing conditions. It is established that the optimal parameters for processing by direct pressing of the pre-pegs components obtained by the method of layer deposition are a pressure of 15 MPa and a temperature of160-170 ?С with a pressure exposure of 15 minutes. If you get products by winding, then for such products, heat treatment for 6 hours at a temperature of 120 ?С is optimal. In the conditions of forming products, that is, at an elevated temperature and at an increased pressure, the mutual diffusion of components occurs due to the movement of oncoming flows. Oligomeric molecules from the resin volume diffuse from the inner layer to the outer one, and the components of the curing system meet them from the outer layer to the inner one. The method of layered application of components makes it possible to create a macroheterogenic system of interpenetrating polymer meshes in the contact area of sequentially applied layers. The result of the research is an increase in the shelf life, the viability of prepregs (up to 10 days) and an improvement in the complex of physical and mechanical properties of composites: the destructive stress during static bending increases to 60 %, during dynamic bending (impact) - up to 50 %. The use of carboxymethylcellulose as a protective polymer provides higher indicators of the studied properties than when using butadiene styrene latex as a protective polymer..

Background: Nowadays, the esthetics demand is continuously increasing; therefore, metal-free materials are widely used, like a zirconia-based ceramic, which is conveniently fabricated via computer-aided design and computer-aided manufacturing (CAD/CAM) system for restorations from single to full mouth rehabilitation. Objective: This study evaluated the effect of pre-curing pressure on the shear bond strength of zirconia to the resin cement. Methods: A total of sixty-three sandblasted cylindrical zirconia mounted in autopolymerizing resin were randomly assigned to three groups; Group 1: no treatment (control), Group 2: negative pressure, and Group 3: positive pressure to resin cement after resin cement application and resin composite columns bonded to zirconia. Thirty-three of the samples were stored in distilled water at 37 °C for 24 hr before the shear bond strength test for thirty samples and three samples were cross-sectionally cut for interfacial observation with FESEM. Another thirty samples were thermocycled for 5,000 cycles in distilled water at 5°C to 55 °C before testing. The shear bond strength and failure mode were evaluated. Examination of the bonding interface was also done. Results: The results were analyzed using two-way ANOVA. The means of shear bond strength of non-thermocycle of the control group were 8.01 ±1.74 MPa, 9.10 ±1.90 MPa, and 9.14 ±2.58 MPa, whereas that of thermocycle group were 5.71 ±0.84 MPa, 5.53 ±0.68 MPa, and 5.68 ±0.77 MPa in zero pressure group, negative pressure group, and positive pressure group, respectively. It showed no statistically significant differences in shear bond strength in all pressure groups (p > 0.05). The pre-curing pressure did not influence the shear bond strength of the zirconia and resin cement. Conclusion: There was no difference in the shear bond strength between the pressure groups and the no treatment control group. The positive and negative pressure did not influence the shear bond strength of the zirconia and resin cement.

Most developing countries have hot climate, ordinary jobsites characterized by reduced of human resources, equipment and infrastructures. The objective of this article is to make an experimental study of the influence of the hot climate such as that of Algeria, on the different properties of concrete in the fresh state, such as excessive water evaporation from the concrete surface, increased demand for water, increased slump loss corresponding to additional water on job-site, higher plastic shrinkage cracking and difficulty in controlling air content. At the hardened state, we could mention a reduction of strength at 28 days, decreased durability resulting from cracking at long-term period. To show the problems linked to concreting under these conditions and to present the appropriate solutions concrete or mortar can withstand the conditions in which it is implemented. Thus, negative effects caused principally by hot weather concreting motivated the choice of the such study. The research experimental work conditions in which the cementitious matrix was kept concerned two different environments, namely hot and dry climate conditions (t = 40°, h = 0%) alike the climate of the region of M'sila., and that of a medium with a hot and humid environment (t = 40°, h = 100%). The output of the investigation demonstrated the crucial role of the cure method in hot regions. The comparison of results for a reference concrete kept in air without any curing measures with two curing types simulating hot weather environment of the region M’sila was undertaken. These obtained outcome results were discussed based on the influence of climatic conditions to conclude procedures for hot weather concreting and suitable cure methods.

The carboxy groups abundantly and densely present on 2,2,6,6-tetramehylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofibers (TEMPO-CNFs) have been chemically modified to prepare resin composites with high thermal dimensional stability. A primary-amine-terminated polyalkylene glycol (PAG) with number-average degree of polymerization of 2222 was reacted with the carboxy groups in the TEMPO-CNFs through amide bonds at PAG amidation degrees of 22%, 44%, and 76% of the carboxy groups in the TEMPO-CNFs by changing the reaction conditions. These surface PAG-amidated TEMPO-CNFs were nanodispersed in methyl ethyl ketone (MEK), mixed with the polyurethane acrylate monomer, and PAG-amidated TEMPO-CNF/polyacrylate resin composites were prepared by ultraviolet-light curing. When PAG-amidated TEMPO-CNFs with amidation degree of 44% were used, the tensile modulus and thermal dimensional stability of the PAG-amidated TEMPO-CNF/polyacrylate resin composite remarkably improved. This was because the TEMPO-CNF elements were homogeneously distributed in the polyacrylate resin matrix, which was confirmed by atomic force microscopy observation and percolation theory. In contrast, when epoxy resin was used as the composite matrix, the above PAG-amidated TEMPO-CNFs did not have high thermal dimensional stability. However, when a dual surface-modified TEMPO-CNF sample containing phenyl amides and PAG-ammonium/carboxylate salt structures at amidation and amine/carboxylate salt formation degrees of 80% and 6% of the carboxy groups in the TEMPO-CNFs, respectively, the thermal dimensional stability of the neat epoxy resin remarkably improved. Thus, the carboxy groups on the TEMPO-CNF surfaces have to be suitably modified, such as by PAG amide or phenyl amide/PAG-ammonium salt dual structures, depending on the matrix resin used.

Stable biobased waterborne Pickering dispersions of acrylated epoxidized soybean oil (AESO) were developed using chitin nanocrystals (ChNCs) as sole emulsifier without any additives. Thin AESO-ChNC nanocomposite films were produced by UV-curing thin-coated layers of the AESO emulsion after water evaporation. The kinetics of photopolymerization were assessed by monitoring the consumption of the AESO acrylate groups by infrared spectroscopy (Fourier transform infrared (FTIR)). The curing was faster in the presence of ChNCs, with a disappearance of the induction period observed for neat AESO. The coating of AESO droplets with a thin layer of ChNCs was confirmed by scanning electron microscopy (SEM) observation. SEM and transmission electron microscopy (TEM) images revealed the honeycomb organization of ChNCs inside the cured AESO-ChNC films. The mechanical, thermal, and optical properties of the nanocomposite films were studied by dynamic mechanical analysis (DMA), tensile testing, differential scanning calorimetry (DSC), and transmittance measurement, as a function of ChNC content. The inclusion of ChNCs is strongly beneficial to increase the stiffness and strength of the cured films, without compromising its optical transparency. The ability of ChNCs to act as an emulsifier for AESO in replacement of synthetic surfactants and their strong reinforcing effect in UV-cured films offer new opportunities to produce waterborne stable dispersions from AESO for application in biobased coatings and adhesives.

The aim of this study is to optimize and functionalize Agave americana fibres with varying process parameters (concentration of 3-MPTMS, pH of solution and curing temperature) using Box–Behnken method. The properties of functionalized fibres were analyzed by using XRD, FTIR-ATR, TGA, CHNS and SEM. The crystallinity of cellulose I increased due to acid hydrolysis and it was studied by XRD. FTIR-ATR showed thiol grafting on cellulose. Quantitative determination of silane loading was observed by TGA. Percentage of sulphur content was observed using elemental composition, which indicated the successful functionalization of thiol on fibre. Further, SEM analysis showed that the surface of functionalized fibre was rough and porous.

The nanocomposite surface coating film samples were prepared by high-speed mechanical mixing of novolac epoxy resin (EEW 180 eq/gm) and a varying amount of nano-CaCO3 (0–5 wt%) for 30 min. Further, these mixtures were used to cast 100 microns films on the metal/glass panels and subjected to cure at 110o C for 1 h and post-cure at 80 oC for 5 h. The nanocomposite surface coating film samples were tested for mechanical properties (viz. impact resistance, scratch hardness, adhesion, and flexibility) and resistance to artificial seawater (ASW). It was observed that 4 wt% nano-CaCO3 containing film sample showed maximum impact strength, scratch hardness, adhesion, and flexibility, and resistance to ASW compared to neat epoxy and other nanocomposite film samples. The curing behavior of nanocomposite film samples was analyzed by DSC. The reactivity effect of nano-CaCO3 blending on epoxy resin by FTIR spectroscopy, morphological studies by SEM, and surface gloss by Triglossometer were also investigated.

ZnO nanowires were grown on a ZnO:Al polycrystalline surface by using a hydrothermal growth technique. Details about the effects of the hydrothermal solution parameters (such as the curing time, curing temperature and solution molarity) and the physical properties of the solution (such as the structural characterization, surface morphology and optical and electrical properties) were determined for the ZnO nanowires. The diameter of the nanowires was increased with the curing time. The maximum transmittance was detected when the ZnO nanowires cured for 3 h. With the increasing hydrothermal growth time, the transmittance value of nanowires was decreased based upon a disorganized structure on the surface with the time due to the incline of the longer nanowires. Hence, the thicker nanowire formation affected the electrical resistivity and transmittance of the nanowires. The flower-like ZnO nanostructures were observed at the some parts of the film for the nanowires grown in 35 and 45 mM solutions. The flower-like structures had a length of ~ 4 μm, a root size of ~ 1000 nm and a tip size of ~ 900 nm.

One of the failure mechanisms associated with asphalt paving layers, especially on steel deck bridges, is large permanent deformation, which adversely affects its long-term performance in service. Thus, epoxy resin was introduced in asphalt paving industry to tackle permanent deformation of asphalt mixtures due to its thermosetting nature. In this review, epoxy resin as a dominant component of the epoxy-asphalt composite system was first considered, followed by a discussion on its curing methods and curing mechanism. Furthermore, the physicochemical property and mechanical performance of epoxy asphalt and epoxy asphalt mixture were thoroughly examined. Crosslink density of epoxy asphalt dictates its viscosity and thus the allowable construction time. Phase separation and dispersion of asphalt particles in the epoxy matrix was observed for epoxy-asphalt composite, and it showed superior elastic behavior and deformation resistance capability when compared with conventional asphalt materials. Furthermore, epoxy asphalt mixture exhibited significantly higher compressive strength, much better rutting resistance, and superior durability and water resistance properties. However, its low-temperature cracking resistance was slightly compromised.

In this research, the mechanical characteristics and durability of mixtures containing calcium aluminate cement (CAC) and polymer materials have been evaluated. The investigated polymers were two types of commercial polymers including Styrene butadiene rubber (SBR) and Styrene acrylic. The levels which the polymers have been used were 5, 15 and 25% by weight of cement and the water-cement ratio was kept constant at 0.38. In order to investigate and compare the influences of polymer materials on the durability characteristics and mechanical properties, the tests to determine the compressive strength, flexural strength, tensile strength, coefficient of rapid chloride migration (RCM), water sorptivity and water absorption were carried out. The specimens were cured under wet conditions at early ages (7 days) and air cured at later ages (After 7 days until the time of testing). According to the results, the plain calcium aluminate cement mix had high early strengths and appropriate durability characteristics. However, increasing the chloride permeability was observed due to the conversion of the early hydrate products to the stable ones. Despite the lower compressive strenths, modification of the mixtures with polymers led to improvements in the mechanical characteristics such as flexural and tensile strengths, It is also worth noting that the reduced compressive strength of the modified polymer mixes compared to the plain mix was decreased with age, approaching the values abserved for the plain mix. Significant influences on reducing the sorptivity rates, rapid chloride migration coefficient and water absorption were also observed for the polymer modified mixes. However, the mixes with Styrene acrylic did not have enhanced performance in the wet curing conditions. It appears that the Styrene butadiene rubber mixes could provide more suitable results compared to the Styrene acrylic ones. Comparing the results at different ages revealed that dry curing period had a significant effect on the strength growth process, mechanical and durability properties of the polymer modified mortars.

Purpose This paper aims to address the problem of uncertain product quality in digital light processing (DLP) three-dimensional (3D) printing, a scheme is proposed to qualitatively estimate whether a layer is printed with the qualified quality or not cured . Design/methodology/approach A thermochromic pigment whose color fades at 45°C is prepared as the indicator and it is mixed with the resin. A visual surveillance framework is proposed to monitor the visual variation in a period of the entire curing process. The exposure region is divided into 30 × 30 sub-regions; gray-level variation curves (curing curves) in all sub-regions are classified as normal or abnormal and a corresponding printing control strategy is designed to improve the percentage of qualified printed objects. Findings The temperature variation caused by the releasing reaction heat on the exposure surface is consistent in different regions under the homogenized light intensity. The temperature in depth begins to rise at different times. The temperature in the regions near the light source rises earlier, and that far from the light source rises later. Thus, the color of resin mixed with the thermochromic pigment fades gradually over a period of the entire solidification process. The color variation in the regions with defects of bubbles, insufficient material filling, etc., is much different from that in the normal curing regions. Originality/value A temperature-sensitive organic chromatic chemical pigment is prepared to present the visual variation over a period of the entire curing process. A novel 3D printing scheme with visual surveillance is proposed to monitor the layer-wise curing quality and to timely stop the possible unqualified printing resulted from bubbles, insufficient material filling, etc.

The review focuses on structural acrylic adhesives (SAAs), which belong to second-generation acrylic adhesives. The complex composition of such adhesives is shown, and the role of various SAA components in achieving the target physicochemical, mechanical, and thermal properties of joints based on multicomponent acrylic adhesives is discussed. Particular attention is paid to the analysis of the possibilities of using SAAs with borane initiating curing systems for bonding substrates with low surface energy and the effect of the chemical structure of the components used in formulation on the durability and properties of the resulting adhesive. Comparison of the properties of SAAs and other types of reactive adhesives showed that structural acrylic adhesives have a set of properties that are in many ways superior to the known structural epoxy and polyurethane adhesives. The areas of application of these adhesives are briefly discussed.

Accelerating the polymerisation of adhesives has been a long-established field of research in context of adhesive bonding technology as long curing times - sometimes up to days - represent a decisive disadvantage in contrast to most mechanical joining techniques like riveting or screwing. In addition to, e.g., curing via UV, microwave or IR radiation, electromagnetic induction represents a promising solution for speeding up the cure of polymers. With this method, adhesively bonded components are subjected to an alternating electromagnetic field (EMF) that induces heat in EMF-sensitive materials, e.g., steel or aluminium. If intrinsic EMF-sensitivity of the materials to be bonded is not given, different types of susceptors like meshes, fibres or particles are added to the adhesive in order to be heated inductively and thus cure the adhesive from the inside. Recent research has focused on a special type of susceptors, so-called Curie particles (CP), which can only be heated inductively up to their specific Curie temperature (Tc) at which CP-induced heating automatically stops. As a result, a curing process is created that eliminates the need for external temperature monitoring while simultaneously preventing overheating of the bond. As underlying curing kinetics - most importantly polymerisation enthalpy and curing time - significantly differ depending on the considered adhesive, induction times needed to achieve full cure must currently be determined through costly preliminary investigations on an experimental level. Thus, to contribute for a more efficient and controllable bonding process, the present study aimed at developing a numerical model based on the Finite Element Method (FEM) and capable of predicting the curing degree a in dependency of curing temperature profiles TCure(t) and the CP content ccp. For this purpose, the curing kinetics of two fundamentally different 2K epoxy adhesives were linked to a transient heat flow simulation based upon experimentally determined heat loads. The validation of the developed FEA technique was successfully carried out using the example application of inductively cured large-scale Glued-in rod (GiR) specimens, whereby experimentally determined temperature profiles showed excellent agreement with the numerical predictions. The present paper focused on presenting preliminary experimental work as well as all analytical methods implemented for the numerical modelling.