One of the most challenging factors affecting impression quality and good marginal fit is the gingival retraction method, which aims to separate the gingiva from the tooth to expose the finishing line of the prepared ...One of the most challenging factors affecting impression quality and good marginal fit is the gingival retraction method, which aims to separate the gingiva from the tooth to expose the finishing line of the prepared tooth. Bleeding and contamination from the crevicular fluid may compete for space with the impression material within the sulcus, leading to indistinct preparations and a lack of detail at the margin. In addition, such procedures might damage the PDL and cause permanent recession. Flowable composite cable, as opposed to traditional retraction cords, offers the proper marginal seal and visibility during the impression record because of its lower viscosity, improved adaptability, and elastic properties. The aim of this report is to present a brand-new, innovative method for controlling gingival hemorrhage in addition to the gingival retraction in restorative and prosthodontic treatment by utilizing a flowable composite during the final impression record procedure. In these case reports, the flowable composite cord technique is used instead of traditional gingival cords to modify and refine the gingival tissue before taking the traditional final impression or digital scan. Two cases were done for patients undergoing fixed prosthodontics and veneer treatment within a 2-year follow-up period. In addition, the flowable composite cord was used as temporary restoration before the final prosthetic cementation or under the provisional crowns. As a result, clean and healthy gingival tissues render cementation of the final prosthesis quicker and easier to perform. The patients in both cases claimed that their prosthodontic treatments, which involved the application of a flowable composite cord to temporarily retraction the gingiva, had produced good outcomes at the yearlong follow-up. In conclusion, the flowable composite cord technique is found to be a useful tool to improve the quality of impressions in fixed prosthodontics by providing excellent access for impression material to record fine details of the finish line of the prepared tooth structure, and to alter the inflamed tissue into a healthy tissue.展开更多
Using non-toxic,low-volatile glyoxal to completely replace formaldehyde for preparing urea-glyoxal(UG)resin adhesive is a hot research topic that could be of great interest for the wood industry.However,urea-glyoxal(U...Using non-toxic,low-volatile glyoxal to completely replace formaldehyde for preparing urea-glyoxal(UG)resin adhesive is a hot research topic that could be of great interest for the wood industry.However,urea-glyoxal(UG)resins prepared by just using glyoxal instead of formaldehyde usually yields a lower degree of polymerization.This results in a poorer bonding performance and water resistance of UG resins.A good solution is to pre-react urea to preform polyurea molecules presenting already a certain degree of polymerization,and then to condense these with glyoxal to obtain a novel UG resin.Therefore,in this present work,the urea was reacted with hexamethylene diamine to form a polyurea named HU,and then this was used to react it with different amounts of glyoxal to synthesize hexamethylenediamine-urea-glyoxal(HUG)polycondensation resins,and to use this for bonding plywood.The results show that the glyoxal can well react with HU polyuria via addition and schiff base reaction,and also the HUG resin exhibits excellent bonding strength and water resistance.The shear strength of the plywood bonded with this HUG at 160°C hot press temperature as high as 1.93 MPa,2.16 MPa and 1.61 MPa,respectively,which meets the requirement of the China national standard GB/T 9846-2015(≥0.7 MPa),and can be a good choice as a wood adhesive for industrial application.展开更多
Silicon-containing aryl acetylene resin(PSA)is a new type of high-temperature resistant resin with excellent oxidation resistance,whereas antioxidant reaction mechanism of PSA resin under ultra-high temperatures still...Silicon-containing aryl acetylene resin(PSA)is a new type of high-temperature resistant resin with excellent oxidation resistance,whereas antioxidant reaction mechanism of PSA resin under ultra-high temperatures still remains unclear.Herein,the oxidation behavior and mechanisms of PSA resin are systematically investigated combining kinetic analysis and Reax FF molecular dynamics(MD)simulations.Thermogravimetric analysis indicates that the oxidation process of PSA resin undergoes two main steps:oxidative mass gain and oxidative degradation.The distributed activation energy model(DAEM)is employed for describing oxidation processes and the best-fit one is obtained using genetic algorithms and differential evolution.DAEM model demonstrates that the oxidative weight gain stage is dominated by two virtual reactants and the oxidative degradation stage consists of three virtual reactants.Correspondingly,the observation of MD reaction pathways indicates that oxygen oxidation of unsaturated structures occurs in the initial stage,which results in the formation of PSA resin oxides.Furthermore,cracked pieces react with O_(2)to generate CO and other chemicals in the second step.The resin matrix's great antioxidation resilience is illustrated by the formation of SiO_(2).The analysis based on MD simulations exhibits an efficient computational proof with the experiments and DAEM methods.Based on the results,a two-stage reaction mechanism is proposed,which provides important theoretical support for the subsequent study of the oxidation behavior of silica-based resins.展开更多
With the application of resins in various fields, numerous waste resins that are difficult to treat have been produced. The industrial wastewater containing Cr(Ⅵ) has severely polluted soil and groundwater environmen...With the application of resins in various fields, numerous waste resins that are difficult to treat have been produced. The industrial wastewater containing Cr(Ⅵ) has severely polluted soil and groundwater environments, thereby endangering human health. Therefore, in this paper, a novel functionalized mesoporous adsorbent PPR-Z was synthesized from waste amidoxime resin for adsorbing Cr(Ⅵ). The waste amidoxime resin was first modified with H3PO4 and ZnCl_(2), and subsequently, it was carbonized through slow thermal decomposition. The static adsorption of PPR-Z conforms to the pseudo-second-order kinetic model and Langmuir isotherm, indicating that the Cr(Ⅵ) adsorption by PPR-Z is mostly chemical adsorption and exhibits single-layer adsorption. The saturated adsorption capacity of the adsorbent for Cr(Ⅵ) could reach 255.86 mg/g. The adsorbent could effectively reduce Cr(Ⅵ) to Cr(Ⅲ) and decrease the toxicity of Cr(Ⅵ) during adsorption. PPR-Z exhibited Cr(Ⅵ) selectivity in electroplating wastewater. The main mechanisms involved in the Cr(Ⅵ) adsorption are the chemical reduction of Cr(Ⅵ) into Cr(Ⅲ) and electrostatic and coordination interactions. Preparation of PPR-Z not only solves the problem of waste resin treatment but also effectively controls Cr(Ⅵ) pollution and realizes the concept of “treating waste with waste”.展开更多
Dental resin composites(DRCs)are popular materials for repairing caries or dental defect,requiring excellent properties to cope with the complex oral environment.Filler/resin interface interaction has a significant im...Dental resin composites(DRCs)are popular materials for repairing caries or dental defect,requiring excellent properties to cope with the complex oral environment.Filler/resin interface interaction has a significant impact on the physicochemical/biological properties and service life of DRCs.展开更多
The aim of this study is to investigate the color change of different restoration thicknesses, backgrounds and resin cement colors on lithium disilicate and zirconium reinforced lithium silicate materials in vitro. In...The aim of this study is to investigate the color change of different restoration thicknesses, backgrounds and resin cement colors on lithium disilicate and zirconium reinforced lithium silicate materials in vitro. In this study, IPS emax CAD (LT C14) and Celtra Duo (LT C14) are used as full ceramic materials, and Variolink Esthetic LC (warm, neutral) used as resin cement and Tokuyama Estelite Sigma Quick (A3, A2) is used as composite materials. A total of 160 samples in the form of 40 pieces of 5 × 5 0.4 mm thick 40 pieces of 5 × 5 0.6 mm thick square discs from each of the all-ceramic materials in block form were obtained using a water jet device (DWJ1525-FA;Dardi International Corporation, Nanjing, China). Glass ceramic samples produced in 2 different thicknesses were cemented on 2 different backgrounds with 2 different resin types of cement. Color measurements of the samples before and after cementation were performed on a grey background with spectrophotometer Vita EasyShade V (Vita Zahnfabrik, Bad Sackingen, Germany) and color parameters (L*, a*, b*, ΔE) were calculated according to the CIE Lab (Commission Internationale de L’Eclairage) system. Average values for each group (ΔE) were not affected by ceramic type, material thickness, background color, resin cement color, and the interaction of these four variables (p > 0.05). When the triple interactions between the groups were examined, there were no statistically significant differences (p > 0.05). In the evaluation of pairwise interactions between two groups (material type-material thickness, material type-background color, and thickness of material-background interactions) statistically significant differences (p Implications: The material type, thickness, background and cement color used did not cause any statistically significant color change in lithium disilicate and zirconium-reinforced lithium silicate glass ceramic materials (p > 0.05).展开更多
A pyrolysis experiment was carried out on a Dongying Depression kerogen sample to separate the resin from the oil. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with a positive-ion detector w...A pyrolysis experiment was carried out on a Dongying Depression kerogen sample to separate the resin from the oil. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with a positive-ion detector was used to detect the relative proportional changes in the compounds of the resin. During the whole pyrolysis experiment, the relative ratio of resin exceed 10% of the soluble component at each temperature point. Five compounds were detected from the resin: N1, N1O1, N1O_(2), O1, and O_(2). To research the changes in the proportions of the compounds during pyrolysis clearly, these five compounds were divided into three classes: N1, N1Ox, and Ox. The N1 class has the largest proportion in resin at the beginning of the pyrolysis, while Ox class has the least proportion. And the relationship between the number and the molecular mass of three classes compound was researched. With increasing maturity, the proportion of N1 and the N1Ox class decreased rapidly, while the Ox class increased slowly. Through researching these resin compounds, it was found that an inversion in the proportions of above three compounds appeared at the end of the oil window. At the same time, we found that the DBE and carbon number of resin compounds have changed obviously during the pyrolysis: the DBE increased, while the carbon number decreased significantly. And the details of the change of each compound have been researched. This research extends our knowledge of judging the maturity of crude oil during the pyrolysis through the characteristics of compounds in resin and provides the new index based on resin for the evaluation of thermal evolution stage and hydrocarbon generation capacity of source rocks.展开更多
A flame retardant containing multiple antiflaming elements usually exhibits high-efficient flame retardancy. Here, a novel P/N/Si-containing ammonium polyphosphate derivative(APTES-APP) is synthesized from ammonium po...A flame retardant containing multiple antiflaming elements usually exhibits high-efficient flame retardancy. Here, a novel P/N/Si-containing ammonium polyphosphate derivative(APTES-APP) is synthesized from ammonium polyphosphate(APP) and silane coupling agent(3-aminopropyl)triethoxysilane(APTES)via cation exchange, which is quite different in the chemical structure from APTES-modified APP for retaining silicon hydroxyls. APTES-APP is highly efficient for the epoxy resin. 8%(mass) APTES-APP imparts excellent flame retardancy to the epoxy resin, with a V-0 rating at the UL-94 test(1.6 mm)and an LOI value of 26%(vol). The peak heat release rate and total smoke production of the flameretardant epoxy resin are decreased by 68.1% and 31.3%, respectively. The synergy of P/N/Si contributes to the well-expanded char residue with a strong and dense surface layer, which is a very good barrier against heat and mass transfer. Besides, there is no significant deterioration in the mechanical properties of flame-retardant epoxy resin thanks to silicon hydroxyls forming hydrogen bonds with epoxy molecules. Meanwhile, other molecules can be grafted onto APTES-APP via these silicon hydroxyls, if needed.Briefly, this work has developed a new strategy for amino silane as flame retardants. In conjunction with a low-cost and simple preparation method, APTES-APP has a promising prospect in the high-performance flame-retardant epoxy.展开更多
The kinetic behavior of esterification between methacrylic acid and methanol catalyzed by NKC-9 resin was studied in a fixed bed reactor.The reaction was conducted in the temperature range of 323.15 to 368.15 K with t...The kinetic behavior of esterification between methacrylic acid and methanol catalyzed by NKC-9 resin was studied in a fixed bed reactor.The reaction was conducted in the temperature range of 323.15 to 368.15 K with the molar ratio of reactants from 0.8 to 1.4 under certain pressure.The measurement data were regression with the pseudo-homogeneous(P-H),Eley-Rideal(E-R),and Langmuir-Hinshelwood(L-H)heterogeneous kinetic models.Independent adsorption experiments were implemented to gain the adsorption equilibrium constants of four components.Among the above three models,the L-H model exhibited the best fitting results.The stability of NKC-9 was evaluated by long-term running with the yield of methyl methacrylate no decrease during 3000 h operation.The structure and physicochemical properties of the new and used catalyst were performed by several characterizations including thermogravimetric analysis(TG),scanning electron microscope(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR)and so on.展开更多
The successful manufacture of thick composites is challenging since the highly exothermic nature of thermoset resins and limited temperature control make avoiding the onset of detrimental thermal gradients within the ...The successful manufacture of thick composites is challenging since the highly exothermic nature of thermoset resins and limited temperature control make avoiding the onset of detrimental thermal gradients within the composite relatively difficult.This phenomenon is mainly caused by exothermic heat reactions.The so-called Michaud's model has been largely used in the literature to reduce the gap between experience and simulation with regard to the effective prediction of the temperature cycle in these processes.In this work,another solution is proposed to simulate the curing process for thick composites,namely preheating the resin to activate the curing reaction before resin injection into the mold.A good agreement between the experiment and the simulation is found.Moreover,in order to minimize the thermal gradient in the final composite,the thermophysical properties of the fiber and the torque(temperature,time)of the Plate have been varied leading to interesting results.展开更多
The study characterized the curing behaviors of phenol formaldehyde(PF)resin under different vacuum degrees and explored the properties of 9-ply plywood panels hot-pressed under both vacuum and atmospheric conditions....The study characterized the curing behaviors of phenol formaldehyde(PF)resin under different vacuum degrees and explored the properties of 9-ply plywood panels hot-pressed under both vacuum and atmospheric conditions.The changes in core temperature and moisture content of the plywood mats during hot pressing were investigated as well.It was found that the gel times and gel temperatures of PF resin decreased with the increase of vacuum degree using a self-made device.FTIR spectra indicated the degree of polycondensation of hydroxymethyl gradu-ally increased with the increase in temperature.It was also observed that a higher degree of vacuum led to a slower polycondensation reaction rate of PF resin.During different hot-pressing processes,the bonding strengths in the innermost and uppermost gluelines of the vacuum hot-pressed plywood panels were up to 30%–50%higher than their counterparts of conventional hot-pressed products.A less difference in the bonding strengths between these two gluelines was also observed for vacuum hot-pressed products.In addition,the core of vacuum hot-pressed plywood was found to have a greater heating rate and higher temperature at thefinal stage of hot pressing,which was beneficial to cure the PF resin.The results from this study indicate a promising potential of introducing a vacuum during hot pressing to improve the quality and productivity of plywood products and provide a basis for adopting vacuum to hot press wood composites.展开更多
This article presents the first applied results of using citric acid in combinations with a melamine-urea-formal-dehyde(MUF)resin for bonding wood veneers.The chemical reactions involved are shown based on a MALDI ToF...This article presents the first applied results of using citric acid in combinations with a melamine-urea-formal-dehyde(MUF)resin for bonding wood veneers.The chemical reactions involved are shown based on a MALDI ToF analysis of the reaction of the MUF resin with citric acid.The preliminary results of the physical and mechanical properties of the LVL prepared are also presented.Veneers from Populus sp were used to manufacture 5-layer laminated veneer lumber(LVL)of small dimensions.Five combinations of the amount of citric acid,MUF spread rate and pressing parameters were tested.LVL bonded with 20%of citric acid+100 g/m^(2)of MUF,hot-pressed using a 3-step process with maximum 1.5 MPa of pressure yielded the board with better dimensional stability and mechanical properties.It could be concluded that citric acid in combination with MUF can be used for bonding wood veneer and the research should be continued to study further the parameters involved and to enhance the results.展开更多
We improved the adhesion between silicon based insulating materials and epoxy resin composites by adding the adhesion promoter cycloborosiloxane(BSi,cyclo-1,3,3,5,7,7-hexaphenyl-1,5-diboro-3,7-disiloxane).The experime...We improved the adhesion between silicon based insulating materials and epoxy resin composites by adding the adhesion promoter cycloborosiloxane(BSi,cyclo-1,3,3,5,7,7-hexaphenyl-1,5-diboro-3,7-disiloxane).The experimental results show that the addition of BSi in the silicone rubber(SR)system significantly increases the tensile shear strength between BSi and epoxy resin(EP),reaching 309%of the original value.On this basis,the mechanism of BSi to enhance the adhesion effect was discussed.The electron deficient B in BSi attracted the electron rich N and O in EP to enhance the chemical interaction,combined with the interfacial migration behavior in the curing process,to improve the adhesion strength.This study provides the design and synthesis ideas of adhesive aids,and a reference for further exploring the interface mechanism of epoxy resin matrix composites.展开更多
In view of the effective perception demand of PD(Partial Discharge)insulation defect of in-service GIS(Gas Insulated Switchgear),the external UHF(Ultra High Frequency,0.3−3 GHz)sensing technology for GIS PD insulation...In view of the effective perception demand of PD(Partial Discharge)insulation defect of in-service GIS(Gas Insulated Switchgear),the external UHF(Ultra High Frequency,0.3−3 GHz)sensing technology for GIS PD insulation defect fromresin hole is studied in this paper.Firstly,rectangular waveguide theory is used to analyze the electromagnetic wave propagation characteristics from rectangular resin hole in GIS disc insulator.It is found that the energy of leaked electromagnetic wave mainly concentrates in the frequency band above 1 GHz.Then based on this frequency band characteristics,a cavity-backed bowtie sensor for GIS PD external detection is designed optimized by HFSS finite element software,in band of 1–3 GHz,its maximum VSWR is 7,the minimum is 1.1,the average is 2.9,and in band of 0.3–1 GHz,the maximum and minimum VSWR is 42.8 and 7,the average is 20.6.Finally,a sensor prototype is made,its sensitivity experiment is carried out on 220 kV GIS,experimental results show that the designed sensor can stably detect the PD electromagnetic wave signal leaked fromthe resin hole,and the signal energy in frequency band range is consistent with the theoretical analysis results.展开更多
We present a simple hot press-based method for processing La(Fe,Si)13-based compounds consisting of La–Fe–Co–Si–C particles and phenolic resin. The magnetic entropy change △S per unit mass for the La Fe_(10.87)Co...We present a simple hot press-based method for processing La(Fe,Si)13-based compounds consisting of La–Fe–Co–Si–C particles and phenolic resin. The magnetic entropy change △S per unit mass for the La Fe_(10.87)Co_(0.63)Si_(1.5)C_(0.2)/phenolic resin compounds have nearly the same magnitude with the base materials. With the content of phenolic resin of 5.0 wt%, the compound conductivity is 3.13 W·m^(-1)·K^(-1). In order to measure the cooling performance of La(Fe,Si)13-based compounds,the La(Fe_(11.6-x)Co_(x))Si_(1.4)C_(0.15)(x =0.60, 0.65, 0.75, 0.80, 0.85)/phenolic resin compounds were pressed into thin plates and tested in a hybrid refrigerator that combines the active magnetic refrigeration effect with the Stirling cycle refrigeration effect. The test results showed that a maximum cooling power of 41 W was achieved over a temperature span of 30 K.展开更多
Blockage in the storage and transportation of waste resin is a difficult problem in the radioactive waste treatment process of nuclear power plants.In this study,in order to solve the problems of unstable resin transp...Blockage in the storage and transportation of waste resin is a difficult problem in the radioactive waste treatment process of nuclear power plants.In this study,in order to solve the problems of unstable resin transport concentration and easy blockage of conveying equipment and pipelines in nuclear power plants in China,a set of non⁃stirring conveying devices is developed,and theoretical calculations,simulation analysis and experimental verification are carried out.By transporting resin using the no stirring conveying device developed in this paper,it is not only to eliminate the risk of blockage and ensure the safety of transportation,but also to adjust the concentration of conveying resin to change the transport efficiency according to the operating conditions.The effective bearing rate of waste resin storage tank can be improved,so that the comprehensive performance of waste resin storage and transportation in nuclear power plants can be greatly improved.展开更多
The poor bonding performance between aqueous adhesives represented by melamine-urea formaldehyde(MUF)resins and reed straw hinders their applications in the field of non-wood-based panels.Multi-hydroxyl polymers are h...The poor bonding performance between aqueous adhesives represented by melamine-urea formaldehyde(MUF)resins and reed straw hinders their applications in the field of non-wood-based panels.Multi-hydroxyl polymers are highly reactive and are often used as crosslinkers.This study fabricated a resin with a strengthened crosslinked structure by combining a multi-hydroxyl polymer and MUF resin prepolymer.The reed particleboard was prepared by using this resin as an adhesive and reed stalk as the matrix.The results show that neighboring molecules combined to form C–O–C bonds that strengthened the cross-linked structure of the resin.In addition,the viscosity of the resin was increased,and a continuous adhesive layer on the surface of reed particles was formed,which slowed the penetration of reed particles.The adhesive layer significantly improved the mechanical properties of the reed particleboard.The maximum modulus of rupture(MOR),modulus of elasticity(MOE),and internal bonding strength(IB)of the reed particleboard were 33.53,4126,and 0.79 MPa,respectively.The IB of the board was 3.3 times higher than that of the reed particleboard prepared with a conventional MUF resin.Reed straw is a non-wood biomass material that has the advantage of sustainable development and may replace woodbased materials to produce particleboard.This resin-prepared reed particleboard is expected to be used in areas such as custom furniture and engineering materials.展开更多
In this study,the durability of a new polymer carbonfiber-reinforced epoxy resin used to produce composite material in the aerospacefield is investigated through analysis of the corrosion phenomena occurring at the micr...In this study,the durability of a new polymer carbonfiber-reinforced epoxy resin used to produce composite material in the aerospacefield is investigated through analysis of the corrosion phenomena occurring at the microscopic scale,and the related infrared spectra and thermal properties.It is found that light and heat can con-tribute to the aging process.In particular,the longitudinal tensile strength displays a non-monotonic trend,i.e.,itfirst increases and then decreases over time.By contrast,the longitudinal compressive and inter-laminar shear strengths do not show significant changes.It is also shown that the inter-laminar shear strength of carbonfiber/epoxy resin composites with inter-laminar hybrid structure is better than that of pure carbonfiber materials.The related resistance to corrosion can be improved by more than 41%.展开更多
The mechanical properties of Portland cement differ from the weakly consolidated shallow formation in deep water.This results in undesired abrupt changes in the compressive strength and elastic modulus at the cement–...The mechanical properties of Portland cement differ from the weakly consolidated shallow formation in deep water.This results in undesired abrupt changes in the compressive strength and elastic modulus at the cement–formation interface.In this study,a water-borne epoxy resin was applied as a strengthening material to reinforce the weakly consolidated shallow formation and protect the cement sheath from potential failure.The mechanical properties of the unconsolidated clay were tested,including their changes with increases in the temperature and curing time.In addition,the effects of the seawater,cement slurry alkaline filtrate,and saltwater drilling fluid were evaluated.As confirmed by the results,the strengthening fluid was excellent at reinforcing the unconsolidated clay,with a compressive strength of 2.49 MPa(after curing for 7 days),even at a dosage of 5%.A cement slurry filtrate with a high pH was suitable to produce the required strengthening of the formation,especially its early age strength.It should also be pointed out that the used fluid exhibited good compatibility with the saltwater drilling fluid and seawater behaved well as a diluent for the strengthening fluid.展开更多
文摘One of the most challenging factors affecting impression quality and good marginal fit is the gingival retraction method, which aims to separate the gingiva from the tooth to expose the finishing line of the prepared tooth. Bleeding and contamination from the crevicular fluid may compete for space with the impression material within the sulcus, leading to indistinct preparations and a lack of detail at the margin. In addition, such procedures might damage the PDL and cause permanent recession. Flowable composite cable, as opposed to traditional retraction cords, offers the proper marginal seal and visibility during the impression record because of its lower viscosity, improved adaptability, and elastic properties. The aim of this report is to present a brand-new, innovative method for controlling gingival hemorrhage in addition to the gingival retraction in restorative and prosthodontic treatment by utilizing a flowable composite during the final impression record procedure. In these case reports, the flowable composite cord technique is used instead of traditional gingival cords to modify and refine the gingival tissue before taking the traditional final impression or digital scan. Two cases were done for patients undergoing fixed prosthodontics and veneer treatment within a 2-year follow-up period. In addition, the flowable composite cord was used as temporary restoration before the final prosthetic cementation or under the provisional crowns. As a result, clean and healthy gingival tissues render cementation of the final prosthesis quicker and easier to perform. The patients in both cases claimed that their prosthodontic treatments, which involved the application of a flowable composite cord to temporarily retraction the gingiva, had produced good outcomes at the yearlong follow-up. In conclusion, the flowable composite cord technique is found to be a useful tool to improve the quality of impressions in fixed prosthodontics by providing excellent access for impression material to record fine details of the finish line of the prepared tooth structure, and to alter the inflamed tissue into a healthy tissue.
基金supported by the Yunnan Provincial Natural Science Foundation (202201AU070222,202201AT070045,202101BD070001-074)Scientific Research Fund Project of Yunnan Provincial Department of Education (2022J0490)financed by the 111 Project (D21027).
文摘Using non-toxic,low-volatile glyoxal to completely replace formaldehyde for preparing urea-glyoxal(UG)resin adhesive is a hot research topic that could be of great interest for the wood industry.However,urea-glyoxal(UG)resins prepared by just using glyoxal instead of formaldehyde usually yields a lower degree of polymerization.This results in a poorer bonding performance and water resistance of UG resins.A good solution is to pre-react urea to preform polyurea molecules presenting already a certain degree of polymerization,and then to condense these with glyoxal to obtain a novel UG resin.Therefore,in this present work,the urea was reacted with hexamethylene diamine to form a polyurea named HU,and then this was used to react it with different amounts of glyoxal to synthesize hexamethylenediamine-urea-glyoxal(HUG)polycondensation resins,and to use this for bonding plywood.The results show that the glyoxal can well react with HU polyuria via addition and schiff base reaction,and also the HUG resin exhibits excellent bonding strength and water resistance.The shear strength of the plywood bonded with this HUG at 160°C hot press temperature as high as 1.93 MPa,2.16 MPa and 1.61 MPa,respectively,which meets the requirement of the China national standard GB/T 9846-2015(≥0.7 MPa),and can be a good choice as a wood adhesive for industrial application.
基金financially supported by National Natural Science Foundation of China(22008073,22078100,21878091)Shanghai Sailing Program(20YF1410600)。
文摘Silicon-containing aryl acetylene resin(PSA)is a new type of high-temperature resistant resin with excellent oxidation resistance,whereas antioxidant reaction mechanism of PSA resin under ultra-high temperatures still remains unclear.Herein,the oxidation behavior and mechanisms of PSA resin are systematically investigated combining kinetic analysis and Reax FF molecular dynamics(MD)simulations.Thermogravimetric analysis indicates that the oxidation process of PSA resin undergoes two main steps:oxidative mass gain and oxidative degradation.The distributed activation energy model(DAEM)is employed for describing oxidation processes and the best-fit one is obtained using genetic algorithms and differential evolution.DAEM model demonstrates that the oxidative weight gain stage is dominated by two virtual reactants and the oxidative degradation stage consists of three virtual reactants.Correspondingly,the observation of MD reaction pathways indicates that oxygen oxidation of unsaturated structures occurs in the initial stage,which results in the formation of PSA resin oxides.Furthermore,cracked pieces react with O_(2)to generate CO and other chemicals in the second step.The resin matrix's great antioxidation resilience is illustrated by the formation of SiO_(2).The analysis based on MD simulations exhibits an efficient computational proof with the experiments and DAEM methods.Based on the results,a two-stage reaction mechanism is proposed,which provides important theoretical support for the subsequent study of the oxidation behavior of silica-based resins.
基金supported by the National Natural Science Foundation of China (No.52364022)the Natural Science Foundation of Guangxi Province,China (Nos.2023JJA160192 and 2021GXNSFAA220096)+1 种基金the Guangxi Science and Technology Major Project,China (No.AA23073018)the Guangxi Chongzuo Science and Technology Plan,China (No.2023ZY00503).
文摘With the application of resins in various fields, numerous waste resins that are difficult to treat have been produced. The industrial wastewater containing Cr(Ⅵ) has severely polluted soil and groundwater environments, thereby endangering human health. Therefore, in this paper, a novel functionalized mesoporous adsorbent PPR-Z was synthesized from waste amidoxime resin for adsorbing Cr(Ⅵ). The waste amidoxime resin was first modified with H3PO4 and ZnCl_(2), and subsequently, it was carbonized through slow thermal decomposition. The static adsorption of PPR-Z conforms to the pseudo-second-order kinetic model and Langmuir isotherm, indicating that the Cr(Ⅵ) adsorption by PPR-Z is mostly chemical adsorption and exhibits single-layer adsorption. The saturated adsorption capacity of the adsorbent for Cr(Ⅵ) could reach 255.86 mg/g. The adsorbent could effectively reduce Cr(Ⅵ) to Cr(Ⅲ) and decrease the toxicity of Cr(Ⅵ) during adsorption. PPR-Z exhibited Cr(Ⅵ) selectivity in electroplating wastewater. The main mechanisms involved in the Cr(Ⅵ) adsorption are the chemical reduction of Cr(Ⅵ) into Cr(Ⅲ) and electrostatic and coordination interactions. Preparation of PPR-Z not only solves the problem of waste resin treatment but also effectively controls Cr(Ⅵ) pollution and realizes the concept of “treating waste with waste”.
基金the support from the National Natural Science Foundation of China(Grant nos.81921002,82201115)China Postdoctoral Science Foundation(no.2021M702166)the Innovative Research Team of High-level Local Universities in Shanghai,Oral and Maxillofacial Regeneration and Functional Restoration。
文摘Dental resin composites(DRCs)are popular materials for repairing caries or dental defect,requiring excellent properties to cope with the complex oral environment.Filler/resin interface interaction has a significant impact on the physicochemical/biological properties and service life of DRCs.
文摘The aim of this study is to investigate the color change of different restoration thicknesses, backgrounds and resin cement colors on lithium disilicate and zirconium reinforced lithium silicate materials in vitro. In this study, IPS emax CAD (LT C14) and Celtra Duo (LT C14) are used as full ceramic materials, and Variolink Esthetic LC (warm, neutral) used as resin cement and Tokuyama Estelite Sigma Quick (A3, A2) is used as composite materials. A total of 160 samples in the form of 40 pieces of 5 × 5 0.4 mm thick 40 pieces of 5 × 5 0.6 mm thick square discs from each of the all-ceramic materials in block form were obtained using a water jet device (DWJ1525-FA;Dardi International Corporation, Nanjing, China). Glass ceramic samples produced in 2 different thicknesses were cemented on 2 different backgrounds with 2 different resin types of cement. Color measurements of the samples before and after cementation were performed on a grey background with spectrophotometer Vita EasyShade V (Vita Zahnfabrik, Bad Sackingen, Germany) and color parameters (L*, a*, b*, ΔE) were calculated according to the CIE Lab (Commission Internationale de L’Eclairage) system. Average values for each group (ΔE) were not affected by ceramic type, material thickness, background color, resin cement color, and the interaction of these four variables (p > 0.05). When the triple interactions between the groups were examined, there were no statistically significant differences (p > 0.05). In the evaluation of pairwise interactions between two groups (material type-material thickness, material type-background color, and thickness of material-background interactions) statistically significant differences (p Implications: The material type, thickness, background and cement color used did not cause any statistically significant color change in lithium disilicate and zirconium-reinforced lithium silicate glass ceramic materials (p > 0.05).
基金financially supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA14010102).
文摘A pyrolysis experiment was carried out on a Dongying Depression kerogen sample to separate the resin from the oil. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with a positive-ion detector was used to detect the relative proportional changes in the compounds of the resin. During the whole pyrolysis experiment, the relative ratio of resin exceed 10% of the soluble component at each temperature point. Five compounds were detected from the resin: N1, N1O1, N1O_(2), O1, and O_(2). To research the changes in the proportions of the compounds during pyrolysis clearly, these five compounds were divided into three classes: N1, N1Ox, and Ox. The N1 class has the largest proportion in resin at the beginning of the pyrolysis, while Ox class has the least proportion. And the relationship between the number and the molecular mass of three classes compound was researched. With increasing maturity, the proportion of N1 and the N1Ox class decreased rapidly, while the Ox class increased slowly. Through researching these resin compounds, it was found that an inversion in the proportions of above three compounds appeared at the end of the oil window. At the same time, we found that the DBE and carbon number of resin compounds have changed obviously during the pyrolysis: the DBE increased, while the carbon number decreased significantly. And the details of the change of each compound have been researched. This research extends our knowledge of judging the maturity of crude oil during the pyrolysis through the characteristics of compounds in resin and provides the new index based on resin for the evaluation of thermal evolution stage and hydrocarbon generation capacity of source rocks.
基金financially supported by the National Natural Science Foundation of China (22178242)。
文摘A flame retardant containing multiple antiflaming elements usually exhibits high-efficient flame retardancy. Here, a novel P/N/Si-containing ammonium polyphosphate derivative(APTES-APP) is synthesized from ammonium polyphosphate(APP) and silane coupling agent(3-aminopropyl)triethoxysilane(APTES)via cation exchange, which is quite different in the chemical structure from APTES-modified APP for retaining silicon hydroxyls. APTES-APP is highly efficient for the epoxy resin. 8%(mass) APTES-APP imparts excellent flame retardancy to the epoxy resin, with a V-0 rating at the UL-94 test(1.6 mm)and an LOI value of 26%(vol). The peak heat release rate and total smoke production of the flameretardant epoxy resin are decreased by 68.1% and 31.3%, respectively. The synergy of P/N/Si contributes to the well-expanded char residue with a strong and dense surface layer, which is a very good barrier against heat and mass transfer. Besides, there is no significant deterioration in the mechanical properties of flame-retardant epoxy resin thanks to silicon hydroxyls forming hydrogen bonds with epoxy molecules. Meanwhile, other molecules can be grafted onto APTES-APP via these silicon hydroxyls, if needed.Briefly, this work has developed a new strategy for amino silane as flame retardants. In conjunction with a low-cost and simple preparation method, APTES-APP has a promising prospect in the high-performance flame-retardant epoxy.
基金the National Natural Science Fund for Distinguished Young Scholars(22025803)supported by the National Natural Science Foundation of China(22178338)+1 种基金the Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy(YLU-DNL Fund 2021018)the financial support of project“Research and development and industrial application of new catalytic materials for green synthesis of MMA to replace highly toxic HCN”(Hebei,20374002D)。
文摘The kinetic behavior of esterification between methacrylic acid and methanol catalyzed by NKC-9 resin was studied in a fixed bed reactor.The reaction was conducted in the temperature range of 323.15 to 368.15 K with the molar ratio of reactants from 0.8 to 1.4 under certain pressure.The measurement data were regression with the pseudo-homogeneous(P-H),Eley-Rideal(E-R),and Langmuir-Hinshelwood(L-H)heterogeneous kinetic models.Independent adsorption experiments were implemented to gain the adsorption equilibrium constants of four components.Among the above three models,the L-H model exhibited the best fitting results.The stability of NKC-9 was evaluated by long-term running with the yield of methyl methacrylate no decrease during 3000 h operation.The structure and physicochemical properties of the new and used catalyst were performed by several characterizations including thermogravimetric analysis(TG),scanning electron microscope(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR)and so on.
文摘The successful manufacture of thick composites is challenging since the highly exothermic nature of thermoset resins and limited temperature control make avoiding the onset of detrimental thermal gradients within the composite relatively difficult.This phenomenon is mainly caused by exothermic heat reactions.The so-called Michaud's model has been largely used in the literature to reduce the gap between experience and simulation with regard to the effective prediction of the temperature cycle in these processes.In this work,another solution is proposed to simulate the curing process for thick composites,namely preheating the resin to activate the curing reaction before resin injection into the mold.A good agreement between the experiment and the simulation is found.Moreover,in order to minimize the thermal gradient in the final composite,the thermophysical properties of the fiber and the torque(temperature,time)of the Plate have been varied leading to interesting results.
文摘The study characterized the curing behaviors of phenol formaldehyde(PF)resin under different vacuum degrees and explored the properties of 9-ply plywood panels hot-pressed under both vacuum and atmospheric conditions.The changes in core temperature and moisture content of the plywood mats during hot pressing were investigated as well.It was found that the gel times and gel temperatures of PF resin decreased with the increase of vacuum degree using a self-made device.FTIR spectra indicated the degree of polycondensation of hydroxymethyl gradu-ally increased with the increase in temperature.It was also observed that a higher degree of vacuum led to a slower polycondensation reaction rate of PF resin.During different hot-pressing processes,the bonding strengths in the innermost and uppermost gluelines of the vacuum hot-pressed plywood panels were up to 30%–50%higher than their counterparts of conventional hot-pressed products.A less difference in the bonding strengths between these two gluelines was also observed for vacuum hot-pressed products.In addition,the core of vacuum hot-pressed plywood was found to have a greater heating rate and higher temperature at thefinal stage of hot pressing,which was beneficial to cure the PF resin.The results from this study indicate a promising potential of introducing a vacuum during hot pressing to improve the quality and productivity of plywood products and provide a basis for adopting vacuum to hot press wood composites.
基金financed under the scheme of Laboratory of Excellence ARBRE by the French Agence Nationale de la Recherche(ANR).
文摘This article presents the first applied results of using citric acid in combinations with a melamine-urea-formal-dehyde(MUF)resin for bonding wood veneers.The chemical reactions involved are shown based on a MALDI ToF analysis of the reaction of the MUF resin with citric acid.The preliminary results of the physical and mechanical properties of the LVL prepared are also presented.Veneers from Populus sp were used to manufacture 5-layer laminated veneer lumber(LVL)of small dimensions.Five combinations of the amount of citric acid,MUF spread rate and pressing parameters were tested.LVL bonded with 20%of citric acid+100 g/m^(2)of MUF,hot-pressed using a 3-step process with maximum 1.5 MPa of pressure yielded the board with better dimensional stability and mechanical properties.It could be concluded that citric acid in combination with MUF can be used for bonding wood veneer and the research should be continued to study further the parameters involved and to enhance the results.
基金the Core Research Facilities of College of Chemistry and Molecular Sciences and Wuhan University Test Center and Open Fund of Hubei Key Laboratory of Aerospace Power Advanced Technologythe Open Fund of Hubei Key Laboratory of Aerospace Power Advanced Technologythe Special Fund for Industrial and informatization Industry Foundation Reconstruction and High Quality Development of Manufacturing Industry(No.TC220H068)。
文摘We improved the adhesion between silicon based insulating materials and epoxy resin composites by adding the adhesion promoter cycloborosiloxane(BSi,cyclo-1,3,3,5,7,7-hexaphenyl-1,5-diboro-3,7-disiloxane).The experimental results show that the addition of BSi in the silicone rubber(SR)system significantly increases the tensile shear strength between BSi and epoxy resin(EP),reaching 309%of the original value.On this basis,the mechanism of BSi to enhance the adhesion effect was discussed.The electron deficient B in BSi attracted the electron rich N and O in EP to enhance the chemical interaction,combined with the interfacial migration behavior in the curing process,to improve the adhesion strength.This study provides the design and synthesis ideas of adhesive aids,and a reference for further exploring the interface mechanism of epoxy resin matrix composites.
基金supported by Science and Technology Project of SGCC(Research on Key Technologies for Fault Diagnosis and Early Warning of Intermittent Discharge in UHV GIS:524625200028).
文摘In view of the effective perception demand of PD(Partial Discharge)insulation defect of in-service GIS(Gas Insulated Switchgear),the external UHF(Ultra High Frequency,0.3−3 GHz)sensing technology for GIS PD insulation defect fromresin hole is studied in this paper.Firstly,rectangular waveguide theory is used to analyze the electromagnetic wave propagation characteristics from rectangular resin hole in GIS disc insulator.It is found that the energy of leaked electromagnetic wave mainly concentrates in the frequency band above 1 GHz.Then based on this frequency band characteristics,a cavity-backed bowtie sensor for GIS PD external detection is designed optimized by HFSS finite element software,in band of 1–3 GHz,its maximum VSWR is 7,the minimum is 1.1,the average is 2.9,and in band of 0.3–1 GHz,the maximum and minimum VSWR is 42.8 and 7,the average is 20.6.Finally,a sensor prototype is made,its sensitivity experiment is carried out on 220 kV GIS,experimental results show that the designed sensor can stably detect the PD electromagnetic wave signal leaked fromthe resin hole,and the signal energy in frequency band range is consistent with the theoretical analysis results.
基金supported by the National Natural Science Foundation of China (Grant Nos. 52171054 and 52171195)the National Natural Science Foundation for Distinguished Young Scholars (Grant No. 51925605)。
文摘We present a simple hot press-based method for processing La(Fe,Si)13-based compounds consisting of La–Fe–Co–Si–C particles and phenolic resin. The magnetic entropy change △S per unit mass for the La Fe_(10.87)Co_(0.63)Si_(1.5)C_(0.2)/phenolic resin compounds have nearly the same magnitude with the base materials. With the content of phenolic resin of 5.0 wt%, the compound conductivity is 3.13 W·m^(-1)·K^(-1). In order to measure the cooling performance of La(Fe,Si)13-based compounds,the La(Fe_(11.6-x)Co_(x))Si_(1.4)C_(0.15)(x =0.60, 0.65, 0.75, 0.80, 0.85)/phenolic resin compounds were pressed into thin plates and tested in a hybrid refrigerator that combines the active magnetic refrigeration effect with the Stirling cycle refrigeration effect. The test results showed that a maximum cooling power of 41 W was achieved over a temperature span of 30 K.
基金Sponsored by the Independent Scientific Research Fund of China Nuclear Power Engineering Co.,Ltd(Grant No.KY1744).
文摘Blockage in the storage and transportation of waste resin is a difficult problem in the radioactive waste treatment process of nuclear power plants.In this study,in order to solve the problems of unstable resin transport concentration and easy blockage of conveying equipment and pipelines in nuclear power plants in China,a set of non⁃stirring conveying devices is developed,and theoretical calculations,simulation analysis and experimental verification are carried out.By transporting resin using the no stirring conveying device developed in this paper,it is not only to eliminate the risk of blockage and ensure the safety of transportation,but also to adjust the concentration of conveying resin to change the transport efficiency according to the operating conditions.The effective bearing rate of waste resin storage tank can be improved,so that the comprehensive performance of waste resin storage and transportation in nuclear power plants can be greatly improved.
基金supported by the Hunan Province Science and Technology Major Project[2021NK1050]Strategic Research and Consulting Project of the Chinese Academy of Engineering:Research on Green and Low-Carbon Technology Innovation Strategy of Wood-Based Panel Industry[2022-XY-62]+1 种基金Changsha Science and Technology Project[kq2004096]Hunan Provincial Technical Innovation Platform and Talent Program in Science and Technology[2016TP1013].
文摘The poor bonding performance between aqueous adhesives represented by melamine-urea formaldehyde(MUF)resins and reed straw hinders their applications in the field of non-wood-based panels.Multi-hydroxyl polymers are highly reactive and are often used as crosslinkers.This study fabricated a resin with a strengthened crosslinked structure by combining a multi-hydroxyl polymer and MUF resin prepolymer.The reed particleboard was prepared by using this resin as an adhesive and reed stalk as the matrix.The results show that neighboring molecules combined to form C–O–C bonds that strengthened the cross-linked structure of the resin.In addition,the viscosity of the resin was increased,and a continuous adhesive layer on the surface of reed particles was formed,which slowed the penetration of reed particles.The adhesive layer significantly improved the mechanical properties of the reed particleboard.The maximum modulus of rupture(MOR),modulus of elasticity(MOE),and internal bonding strength(IB)of the reed particleboard were 33.53,4126,and 0.79 MPa,respectively.The IB of the board was 3.3 times higher than that of the reed particleboard prepared with a conventional MUF resin.Reed straw is a non-wood biomass material that has the advantage of sustainable development and may replace woodbased materials to produce particleboard.This resin-prepared reed particleboard is expected to be used in areas such as custom furniture and engineering materials.
文摘In this study,the durability of a new polymer carbonfiber-reinforced epoxy resin used to produce composite material in the aerospacefield is investigated through analysis of the corrosion phenomena occurring at the microscopic scale,and the related infrared spectra and thermal properties.It is found that light and heat can con-tribute to the aging process.In particular,the longitudinal tensile strength displays a non-monotonic trend,i.e.,itfirst increases and then decreases over time.By contrast,the longitudinal compressive and inter-laminar shear strengths do not show significant changes.It is also shown that the inter-laminar shear strength of carbonfiber/epoxy resin composites with inter-laminar hybrid structure is better than that of pure carbonfiber materials.The related resistance to corrosion can be improved by more than 41%.
基金supported by the Natural Science Foundation of China(51804332,51974355)Major Scientific and Technological Projects of CNPC(ZD2019-184-003)+1 种基金Provincial Geological Exploration Fund of Guizhou Province(208-9912-JBN-UTS0)Shandong Provincial Natural Science Foundation(ZR2017LEE005).
文摘The mechanical properties of Portland cement differ from the weakly consolidated shallow formation in deep water.This results in undesired abrupt changes in the compressive strength and elastic modulus at the cement–formation interface.In this study,a water-borne epoxy resin was applied as a strengthening material to reinforce the weakly consolidated shallow formation and protect the cement sheath from potential failure.The mechanical properties of the unconsolidated clay were tested,including their changes with increases in the temperature and curing time.In addition,the effects of the seawater,cement slurry alkaline filtrate,and saltwater drilling fluid were evaluated.As confirmed by the results,the strengthening fluid was excellent at reinforcing the unconsolidated clay,with a compressive strength of 2.49 MPa(after curing for 7 days),even at a dosage of 5%.A cement slurry filtrate with a high pH was suitable to produce the required strengthening of the formation,especially its early age strength.It should also be pointed out that the used fluid exhibited good compatibility with the saltwater drilling fluid and seawater behaved well as a diluent for the strengthening fluid.
