Application Of Resin Research Articles

[89Zr]ZrCl4 for direct radiolabeling of DOTA-based precursors

IntroductionZirconium-89 (89Zr) is a positron emitter with several advantages over other shorter-lived positron emission tomography (PET) compatible radiometals such as gallium-68 or copper-64. These include practically unlimited availability, extremely low cost, greatly facilitated distribution logistics, positron energy fit for medical PET imaging, and sufficiently long physical half-life to enable PET imaging at later time points for patient-specific dosimetry estimations. Despite these apparent benefits, the reception of 89Zr in the nuclear medicine community has been tepid. The driving factor for the absence of broader adaptation is mostly routed in its final formulation — [89Zr]zirconium oxalate. While serving as a suitable precursor solution for the gold standard chelator deferoxamine (DFO), [89Zr]Zr-oxalate is inaccessible for the most commonly used chelators, such as the macrocyclic DOTA, due to its pre-chelated state.Consequently, pioneering work has been conducted by multiple research groups to create oxalate-free forms of [89Zr]Zr4+, either via chemical conversion of oxalate into other counterion forms or via direct radiochemical isolation of [89Zr]ZrCl4, showing that [89Zr]Zr-DOTA complexes are possible and stable. However, this success was accompanied by challenges, including complex and labor-intensive radiochemical processing and radiolabeling procedures as well as the relatively minuscule conversion rates. Here, we report on the direct production of [89Zr]ZrCl4 avoiding oxalate and metal contaminants to enable efficient radiolabeling of DOTA constructs. MethodsWe based our direct production of [89Zr]ZrCl4 on previously reported methods and further optimized its quality by including an additional iron-removing step using the TK400 Resin. Here, we avoided using oxalic acid and effectively minimized the content of trace metal contaminants. Our two-step purification procedure was automated, and we confirmed excellent radionuclide purity, minimal trace metals content, great reactivity over time, and high specific molar activity. In addition, DOTA-based PSMA-617 and DOTAGA-based PSMA-I&T were radiolabeled to demonstrate the feasibility of direct radiolabeling and to estimate the maximum apparent specific activities. Lastly, the biodistribution of [89Zr]Zr-PSMA-617 was assessed in mice bearing PC3-PIP xenografts, and the results were compared to the previously published data. ResultsA total of 18 batches, ranging from 6.9 to 20 GBq (186 to 541 mCi), were produced. The specific molar activity for [89Zr]ZrCl4 exceeded 0.96 GBq (26 mCi) per nanomole of zirconium. The radionuclidic purity was >99 %, and the trace metals content was in the <1 ppm range. The [89Zr]ZrCl4 remained in its reactive chemical form for at least five days when stored in cyclic olefin polymer (COP) vials. Batches of 11.1 GBq (300 mCi) of [89Zr]Zr-PSMA-617 and 14.4 GBq (390 mCi) of [89Zr]Zr-PSMA-I&T, corresponding to specific activities of 11.1 MBq/μg (0.3 mCi/μg), and 14.4 MBq/μg (0.39 mCi/μg), respectively, were produced. [89Zr]Zr-PSMA-617 animal PET imaging results were in agreement with the previously published data. ConclusionIn this work, we report on a suitable application of TK400 Resin to remove iron during [89Zr]ZrCl4 radiochemical isolation. The breakthrough allows for direct radiolabeling of DOTA-based constructs with [89Zr]ZrCl4, leading to high apparent molar activities and excellent conversion rates.

Syringaldehyde‐DOPO derivative for enhancing flame retardancy and mechanical properties of epoxy resin

AbstractWith the wide application of epoxy resins in adhesives, electronic packaging materials, and aerospace fields, it is necessary to prepare high‐performance flame‐retardant epoxy resins to reduce the fire risk caused by their flammability. In this study, the rigid structure intermediate Schiff base (DMDA‐SH) was synthesized by condensation reaction of syringaldehyde (SH) with O‐Tolidine (DMDA). Then, DMDA‐SH‐DOPO, a novel P/N‐structured biobased flame‐retardant curing agent, was synthesized by addition reaction with 9,10‐dihydro‐9‐oxaza‐10‐phosphame‐10‐oxide (DOPO) and was applied to the preparation of intrinsic flame‐retardant epoxy resin. As expected, DMDA‐SH‐DOPO has good flame‐retardant properties due to the synergistic action of N/P elements. Epoxy resin with only 2.5% DMDA‐SH‐DOPO (P = 0.16%) can pass the UL‐94 V‐0 test. Compared with DGEBA/DDM, DMDA‐SH‐DOPO‐7.5's (P = 0.49%) peak heat release rate was reduced by 48.4% and the limiting oxygen index (LOI) reached 27%, making it a flame‐retardant material. From the point of view of carbonaceous residue performance, the expansion height of carbon residue after DMDA‐SH‐DOPO‐7.5 combustion is significantly increased, and the amount of carbon residue at 800°C is increased by 36.4%. In addition, appropriate DMDA‐SH‐DOPO can effectively improve the bending property of epoxy resin. This study provides a new idea for preparing renewable high‐performance intrinsic flame‐retardant epoxy resin.

Multi-technique characterization and thermal degradation study of epoxy modified resins designed for multifunctional applications

Tetraglycidyl methylene dianiline (TGMDA) was mixed with 1,4-Butanediol diglycidyl ether (BDE) (in a 4:1 mass ratio) and with a stoichiometric amount of the curing agent diaminodiphenyl sulfone which was solubilized at 120 °C for 20 min in the liquid mixture TGMDA + BDE. The so obtained unfilled epoxy resin matrix, denoted as ER, was blended with glycidyl polyhedral oligomeric silsesquioxane and carbon nanotubes in suitable proportions to obtain binary and ternary mixtures. Characterization of the formulated materials was performed using different experimental techniques, such as Dynamic mechanical analysis, Thermogravimetry (TG), Field emission scanning electron microscopy. Furthermore, the investigation of the flame behavior was carried out by the limiting oxygen index and mass loss calorimeter measurements. Direct current measurements and investigation by Tunneling atomic force microscopy of the conductive nanodomain map allowed the evaluation of the electrical properties of the developed nanofilled systems. The TG data related to thermal decomposition of ER and its binary and ternary mixtures were processed according to isoconversional kinetic analysis by assuming a non-Arrhenian behavior of the temperature function, and lifetime prediction was estimated at suitable relatively low temperatures and possible relation between the thermal stability and the presence of each component was discussed. This method of kinetic analysis paves the way for the possibility of evaluating in a more realistic way, on the basis of thermal stability, the potential application of structural resins with primary load functions in contact with hot areas of aeronautical aircraft engines.

A comparative machinability analysis of aged and freshly manufactured epoxy resins through orthogonal machining experiments

Applications of thermoset epoxy resins in load-bearing fibre-reinforced polymer (FRP) composites are decisive, mainly due to their excellent material properties, low viscosity before hardening and good adhesion with the reinforcing fibres. Although numerous experiences on the machinability of FRPs have been published, these experiences can be only indirectly adapted to pure epoxy resins. Reflecting on the lack of knowledge on the machinability of epoxy resins, the main aim of the present study is to compare the machinability of aged and freshly manufactured epoxy resins. Half of the epoxy specimens were naturally aged in a continental climate environment for a year, while the other half was manufactured prior to the orthogonal machining experiments. The experiments were conducted in a dry condition in a Kondia B640 machining centre. The cutting speed and the uncut chip thickness were varied systematically. The cutting force was measured by a KISTLER 9257B dynamometer, and the machined surfaces were characterised by a Mitutoyo SJ400 surface tester and a Keyence VR-5000 3D profilometer. The experimental results prove that the aged epoxy degraded significantly; thus, the specific cutting force is significantly smaller than that of freshly manufactured epoxy. However, the surface quality was not significantly influenced by the polymer degradation.

Removal of carcinogenic chromium(VI) from effluent of electroplating industry using adsorptive separation

AbstractThe wastewater from an electroplating industry contains chromium VI which is highly carcinogenic at a typical level of 21.5 to 47 mg L−1 which should be reduced to acceptable value of 0.05 mg L−1 for the water to be suitable for drinking purpose. In this study, Tulsion A23 resin was applied as an adsorbent for successful removal of Cr(VI), also dealing with understanding the effect of various parameters on extent of removal of the contaminant. It was elucidated that contact time of 120 min is required for the equilibrium and the optimum pH value was 5 and the optimum resin loading was 4 g L−1 at which 97% Cr(VI) removal was observed. Different adsorption isotherm models were applied and it was elucidated that Langmuir model was the best fit with R2 as 0.99. In the case of kinetic study, pseudo‐second order model was best fitted with higher R2 value. The regeneration of the resin was performed using 3 M NaOH and it was shown that after the three cycles of regeneration, the resin showed 82% Cr(VI) removal. Overall, successful application of Tulsion A23 resin was demonstrated for the removal of Cr(VI) from real effluent for the first time.

Durability of Prestressed Piles in a Leachate Environment.

Prestressed pipe piles are common concrete components characterized by dense concrete structures and favorable mechanical properties, and thus, extensively used as coastal soft soil foundations. However, their durability in harsh environments has not been fully clarified. In this study, leachate from an actual landfill site was collected from the east coast of China as the corrosive medium, and the corrosion process was accelerated by electrifying prestressed pipe piles. The results demonstrated that the concentration of chloride ions in the concrete of the prestressed pile increased with the increase in corrosion time. Moreover, the experimental corrosion of these prestressed piles in the drying-wetting cycle proved to be the most severe. However, a protective layer of epoxy resin coating can effectively inhibit the diffusion of chloride ions into the interior of the piles. The final theoretical corrosion amounts of the piles were 1.55 kg, 1.20 kg, and 1.64 kg under immersion, epoxy resin protection, and a drying-wetting cycle environment. The application of epoxy resin reduced chloride penetration by 22.6%, and the drying-wetting cycle increased chloride penetration by 5.8%, respectively, with corresponding corrosion potentials following similar patterns. The actual corrosion depth of the welding seam was 3.20 mm, and there was a large corrosion allowance compared with the requirement (6.53 mm) for the ultimate bending moment. In summary, these prestressed piles exhibited good durability in a leachate environment.

Removal of beryllium (Be2+) from aqueous solution by 5-sulfosalicylic acid-loaded anion-exchange resin

This study presents the preparation and application of a 5-sulfosalicylic acid-loaded anion-exchange resin to remove Be2+ from aqueous solutions. Optimization efforts focused on critical parameters, including resin dosage, initial solution pH, and the influence of interfering ions. Results indicate an optimal resin dose of 0.3 g and a working pH of ≥ 4.0 for maximal Be2+ removal efficiency. Kinetic analysis reveals rapid removal kinetics, with 99% removal achieved within 45 min. Notably, the resin exhibits remarkable selectivity, maintaining consistent removal rates for Be2+ even in the presence of common interfering ions such as Na+, K+, Ca2+, Mg2+, and Fe2+. Sorption isotherms fitting the Langmuir model further support the resin's effectiveness in Be2+ removal. Thermodynamic evaluation suggests the removal process is spontaneous (∆G° < 0) and endothermic (∆H° > 0), indicating favorable energetics. Crucially, the Be-loaded resin is easily regenerated using 0.1 M HCl, enhancing its practical applicability. These results highlight the effectiveness and potency of the prepared resin in Be2+ removal, suggesting promising solutions for addressing environmental contamination.

Effect of Condensed Water at an Alumina/Epoxy Resin Interface on Curing Reaction.

The adhesion of epoxy adhesives to aluminum materials is an important issue in assembling parts for lightweight mobility. Aluminum surfaces typically possess an oxide layer, which readily adsorbs water. In this study, the aggregation states of water and its effect on the curing reaction were examined by placing a water layer between an amorphous alumina surface and a mixture of epoxy and amine components. This study used molecular dynamics simulations and density functional theory calculations. Before the reaction, water molecules strongly adsorbed onto the alumina surface, aggregating excess water. Some water diffused into the epoxy/amine mixture, accelerating the diffusion of unreacted substances. This led to faster reaction kinetics, particularly in proximity to the alumina surface. The adsorption of water molecules onto the alumina surface and the aggregation of excess water were similarly observed even after the curing process. Subsequently, the interaction between the alumina surface and various functional groups of the epoxy/amine mixture was evaluated before and after the reaction. Epoxy monomers had little interaction with the alumina surface before the reaction, whereas hydroxy groups formed by the ring-opening reaction of epoxy groups exhibited notable interaction. Conversely, sulfonyl and amino groups in amine compounds formed hydrogen bonds with OH groups on the alumina surface before the reaction. However, after the reaction, amino groups weakened their interaction with the alumina OH groups as they transformed from primary to tertiary during the curing reaction. Both epoxy and amine monomers/fragments similarly interacted with water molecules, both before and after the reaction. The insights gained from this study are expected to contribute to a better understanding of the impact of moisture absorption on the application of epoxy resins.

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

Lost circulation, a recurring peril during drilling operations, entails substantial loss of drilling fluid and dire consequences upon its infiltration into the formation. As drilling depth escalates, the formation temperature and pressure intensify, imposing exacting demands on plug materials. In this study, a kind of controllable curing resin with dense cross-network structure was prepared by the method of solution stepwise ring-opening polymerization. The resin plugging material investigated in this study is a continuous phase material that offers effortless injection, robust filling capabilities, exceptional retention, and underground curing or crosslinking with high strength. Its versatility is not constrained by fracture-cavity lose channels, making it suitable for fulfilling the essential needs of various fracture-cavity combinations when plugging fracture-cavity carbonate rocks. Notably, the curing duration can be fine-tuned within the span of 3–7 h, catering to the plugging of drilling fluid losing of diverse fracture dimensions. Experimental scrutiny encompassed the rheological properties and curing behavior of the resin plugging system, unraveling the intricacies of the curing process and establishing a cogent kinetic model. The experimental results show that the urea-formaldehyde resin plugging material has a tight chain or network structure. When the concentration of the urea-formaldehyde resin plugging system solution remains below 30%, the viscosity clocks in at a meager 10 mPa·s. Optimum curing transpires at 60 °C, showcasing impressive resilience to saline conditions. Remarkably, when immersed in a composite saltwater environment containing 50000 mg/L NaCl and 100000 mg/L CaCl2, the urea-formaldehyde resin consolidates into an even more compact network structure, culminating in an outstanding compressive strength of 41.5 MPa. Through resolving the correlation between conversion and the apparent activation energy of the non-isothermal DSC curing reaction parameters, the study attests to the fulfillment of the kinetic equation for the urea-formaldehyde resin plugging system. This discerning analysis illuminates the nuanced shifts in the microscopic reaction mechanism of the urea-formaldehyde resin plugging system. Furthermore, the pressure bearing plugging capacity of the resin plugging system for fractures of different sizes is also studied. It is found that the resin plugging system can effectively resident in parallel and wedge-shaped fractures of different sizes, and form high-strength consolidation under certain temperature conditions. The maximum plugging pressure of resin plugging system for parallel fractures with outlet size 3 mm can reach 9.92 MPa, and the maximum plugging pressure for wedge-shaped fractures with outlet size 5 mm can reach 9.90 MPa. Consequently, the exploration and application of urea-formaldehyde resin plugging material precipitate a paradigm shift, proffering novel concepts and methodologies in resolving the practical quandaries afflicting drilling fluid plugging.

An Overview of Recycling Phenolic Resin.

Over a century ago, phenolic formaldehyde (PF) resin was developed and continues to increase in yield due to its diverse applications. However, PF resin is a thermosetting plastic lacking fluidity and moldability, which are nondegradable in natural environments, leading to severe threats to fossil resources as well as global environmental crises. As a result, recycling PF resin is extremely important. In this review, we provide the recent advances in the recycling of PF resin, which includes mechanical recycling, chemical recycling, and utilization of carbon-based materials. The advantages and disadvantages of each strategy are evaluated from a green chemistry perspective. This article aims to attract interest in PF resin design, synthesizing, application and recycling, offering useful suggestions.

Synthesis of aminopyrazine‐based fire resistant additive and its application in epoxy resin

AbstractA new fire retardency APD was synthesized successfully by the condensation between 2‐aminopyrazine and DOPO, and target product APD was characterized by NMR. Absorption peak at 12.6 ppm in 31P NMR verified complete consumption of the reactant DOPO and further confirmed the structure of APD. The safety of epoxy resin (EP) in fire disaster was dramatically improved by introduction of APD. Epoxy resin modified with 8% APD succeeded in vertical burning (UL‐94) test with V‐0 rating and limited oxygen index (LOI) of EP/8% APD was also improved to 33.9%. Cone calorimeter (CC) test further exhibited fire resistant effect of APD on EP in detail. 11.0 g APD reduced total heat release of 100 g EP to 35.1% and reduced total smoke product of 100 g EP to 19.9%. Char residue from CC test of EP/8% APD was analyzed by Raman, XPS, SEM, and FTIR tests. The results of these tests indicated that compact morphology of char residue from EP/8% APD possessed a positive effect in blocking fire spread.Highlights APD was synthesized and fire resistant EP was made. EP/APD acquired outstanding fire resistance and moderate mechanical properties. APD played fire resistant role in gas phase and condensed phase.

Ultrasonic-Assisted Decoloration of Polysaccharides from Seedless Chestnut Rose (Rosa sterilis) Fruit: Insight into the Impact of Different Macroporous Resins on Its Structural Characterization and In Vitro Hypoglycemic Activity.

Pigments within polysaccharides pose significant challenges when analyzing their structural characteristics and evaluating their biological activities, making decolorization a crucial step in purifying these biomolecules. In this research, a novel approach using ultrasound-assisted static adsorption with macroporous resins was employed to decolorize polysaccharides extracted from seedless chestnut rose (Rosa sterilis S. D. Shi) fruit (RSP). Among the fourteen tested resins, AB-8, D101, D4020, HPD100, and S8 were identified as the most effective, demonstrating superior decoloration efficiency and polysaccharide recovery. Further examinations of RSPs treated with these five resins revealed distinct effects on their uronic acid levels, monosaccharide makeup, molecular weight, surface structure, and hypoglycemic properties. The RSP treated with HPD100 resin stood out for having the highest uronic acid content, smallest particle size, and lowest molecular weight, leading to the most notable inhibition of α-glucosidase activity through a mixed inhibition model. The application of HPD100 resin in the decolorization process not only potentially preserved the macromolecular structure of RSP but also enhanced its hypoglycemic efficacy. These findings provide a solid theoretical basis for further exploring RSP as a component of functional foods, underscoring the effectiveness of the ultrasound-assisted resin adsorption method in polysaccharide purification.

Preparation of itaconic acid-modified epoxy resins and comparative study on the properties of it and epoxy acrylates

Abstract To investigate the potential applications of bio-based epoxy resins across diverse fields, this study synthesized a bio-based epoxy resin using itaconic acid (EIA) as the precursor material and compared its thermal, mechanical, and electrical properties with those of epoxy acrylate (EA). The findings indicate that the glass transition temperature and the 5% thermal decomposition temperature of the EIA-cured system are higher than those of EA. The breakdown field strength of the EIA-cured system is slightly higher than that of EA (35.58 kV·mm−1), suggesting that EIA exhibits stronger electrical properties compared to EA. Mechanical property tests demonstrate that the tensile strength, elongation at the fracture point, and Shore hardness of the EIA-cured system are superior to those of EA. In conclusion, EIA, serving as a matrix resin, is influenced by cross-linking density and intramolecular ester bonding and exhibits close electrical strength but superior mechanical, thermal, and degradation properties than EA.

Organic-inorganic hybrid epoxy resin coating with high thermal stability and hydrophobicity for corrosion protection prepared by (3-aminopropyl) triethoxysilane as a bridging agent

The corrosion protection application of epoxy resin (EP) in high-temperature environments is greatly restricted due to thermal stability limit and inherent hydrophilicity. In this study, a hybrid epoxy resin was synthesized by grafting hexadecyltrimethoxysilane (HDTMS), 1 H,1 H,2 H,2 H-perfluorodecyltrimethoxysilane (PFDTMS), and tetraethyl orthosilicate (TEOS) onto the molecule of epoxy resin, using (3-aminopropyl) triethoxysilane (APTES) as a bridging agent. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses revealed the presence of C-N bonds and Si-O-Si bonds in the hybrid epoxy resin, confirming the success of the hybridization. Compared to pure epoxy resin, the hybrid epoxy resin coating effectively enhances the thermal stability while maintaining both corrosion resistance and hydrophobicity. Thermal gravimetric analysis (TGA) indicated that the initial decomposition temperature (T5%) of the hybrid epoxy resin coating increased from 327°C to 372°C. This enhancement is attributed to the introduction of Si-O-Si bonds and an increase in cross-linking density in the hybrid epoxy resin. Water contact angle measurements showed that with the introduction of C-F bonds and long carbon chains, the contact angle increased from 71° to 106°. The hydrophobic hybrid epoxy resin coating maintained a contact angle of 100° at 300°C for 300 hours. The transition from hydrophilicity to hydrophobicity improves the corrosion resistance of the coating.

Mechanical characterization of PEEK-CF/PEEK sandwich structures prepared via a combination of fused filament fabrication and epoxy post-bonding

Poly-ether-ether-ketone (PEEK) and carbon-fiber-reinforced PEEK (PEEK-CF) are examples of engineering thermoplastics with exceptional mechanical properties. In the context of Fused Filament Fabrication (FFF), the interlayer bonding between PEEK and PEEK-CF has a significant impact on the mechanical properties of printed components. Epoxy resin is used to enhance the interfacial bonding between PEEK and PEEK-CF due to its remarkable adhesive properties, while preserving the dimensional and weight attributes of the bonded sandwich structure. The application of epoxy resin as a post-processing technique enables the creation of intricate geometric designs within the bonded sandwich structures. This study presents a straightforward technique for producing sandwich structures using PEEK and PEEK-CF, followed by improving their mechanical properties through isothermal annealing. We conduct systematic single-factor experiments to explore the mechanical advantages of FFF-printed PEEK and PEEK-CF via three-point bending tests on individually printed monolithic specimens. Furthermore, mono-material specimens are bonded using epoxy resin to form dual-material bending specimens. Our findings reveal an optimal sequence: after isothermal annealing, mono-material specimens bonded with epoxy resin exhibit superior flexural strength and modulus. In addition, an in-depth examination of the meso-structure and fracture morphology of FFF-printed sandwich structures after bonding and heat treatment reveals insights into toughening and reinforcement mechanisms. This analysis is complemented by corresponding finite element simulations to validate the results. Notably, our research highlights the successful optimization of interlayer structures, facilitating the creation of sandwich structures with superior mechanical performance.

Evaluation of tensile strength and flexural strength of GFRP composites in different types of matrix polymers

Resin selection has a crucial role in determining the properties and performance of GFRP composites; this study aims to investigate the effects of different resin types, specifically epoxy, bisphenol, ripoxy, and polyester, on the mechanical strength of GFRP composites.The composites were fabricated using the conventional method of hand lay-up technique with a fiber to matrix ratio of 60:40 wt%. The glass fibre laminate arrangement consists of 4 layers, two layers of Woven Roving Mat (WRM) fibres (0/90) and 2 layers on the outer side of the Chopped Strand Mat (CSM). The composite specimens were molded using the ASTM D-838 tensile test standard and ASTM D-790 for the bending test.The research results found that the maximum tensile strength was obtained by GFRP composite with ripoxy matrix type of 181.6 MPa, strain of 0.028%, and flexural strength of 1387 MPa. Composites using polyester matrices can generally be classified as splitting in multiple areas where failure occurs in various areas, but the composite has very high strength.Material experiments conducted on a scientific laboratory scale may not fully reflect the behaviour of composites in actual conditions. Furthermore, aspects such as environmental influences, sustained stresses, or fatigue effects may need to be considered in further research. This evaluation also does not consider the effects of long-term exposures or ageing on the mechanical properties of GFRP composites. Investigating the behaviour of materials over long periods can provide important insights into their durability and reliability in practical applications.In GFRP composites, the application of resin to the fibres is critical. The performance and mechanical characteristics of GFRP composites are largely determined by the polymer matrix. Composites with epoxy, polyester, or bisphenol matrices can be compared to composites with the most equivalent tensile strength values, but composites with ripoxy matrices can be suggested. However, the GFRP composite with bisphenol matrix has an excellent bending strength value. As a result, numerous applications exist for implementing matrix selection in producing GFRP composites.The reliability of the tensile properties of GFRP composites was obtained using the ripoxy matrix type. Furthermore, the reliability of the flexural properties of the composites was obtained using the bisphenol matrix type.

Synthesis of a Novel P/N-Triazine-Containing Ring Flame Retardant and Its Application in Epoxy Resin.

To meet the environmental protection and flame retardancy requirements for epoxy resins (EPs) in certain fields, in this study, a novel triazine-ring-containing DOPO-derived compound (VDPD), derived from vanillin, 2,4-Diamino-6-phenyl-1,3,5-triazine, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), was synthesized using a one-pot method. Flame-retardant epoxy resin (FREP) was prepared by adding various ratios of VDPD to EP and curing with 4,4-diaminodiphenylmethane (DDM). The curing behavior, thermal stability, mechanical properties, and flame-retardant properties of the FREP were examined in various tests. According to the results, when the amount of VDPD added to the EP increased, the glass transition temperature of the FREP decreased linearly, and the flame-retardant properties gradually improved. With a 0.4 wt.% P content, the vertical burning rating of EP/DDM/VDPD-0.4 (according to the theoretical content of VDPD) reached the V-0 level, and the LOI value reached 33.1%. In addition, the results of a CCT showed that the peak heat release rate (PHRR) of EP/DDM/VDPD-0.4 decreased by 32% in comparison with that of the EP. Furthermore, compared with those of the EP, the tensile strength of EP/DDM/VDPD-0.4 decreased from 80.2 MPa to 74.3 MPa, only decreasing by 6 MPa, and the tensile modulus increased. Overall, VDPD can maintain the mechanical properties of EP and effectively improve its flame-retardant properties.

Shear bond strength between conventional composite resin and alkasite-based restoration used in sandwich technique: An in vitro study.

The success of layered restorations necessitates the utilization of an improved restorative material compatible with composite restorations. Therefore, in this line of research, the strength of adhesion of conventional resin-based dental composite to different filling materials was tested. Conventional composite resin was bonded to four restorative materials (Group I: conventional glass ionomer cement (GIC), Group II: resin-modified glass ionomer cement, Group III: flowable composite, and Group IV: Cention-N) received no surface treatment (Subgroup A: control), sandblasting using 50-µm aluminum oxide particles (Subgroup B), sandblasting and resin adhesive (Subgroup C), acid etch and resin adhesive (Subgroup D), or self-etch resin adhesive (Subgroup E). After 24 h, the strength of adhesion between the conventional composite resin and the other tested filling materials was estimated by using a universal testing machine and compared using one-factor analysis of variance and Tukey's method. The conventional GIC had the minimum values of adhesion strength while the flowable composite and Cention-N had the maximum values of adhesion strength (P < 0.05). The treatment of the used restorative materials with sandblasting and resin adhesive boosted the adhesion strength (P < 0.05). The surface treatment of GIC-based materials with either acid etch and resin bonding agent or self-etch resin bonding agent boosted the adhesion strength (P < 0.05). Cention-N sandblasted and coated with resin adhesive before the application of conventional composite resin in layered restorations is a potential alternative to GIC-based restorations and flowable composite.

A novel phosphorus/nitrogen-containing vinyl imidazolium ionic liquid for improving flame retardancy and mechanical properties of vinyl ester resin, and its carbon fiber composites

In daily life, the application of vinyl ester resin (VER) and its carbon fiber composites is limited by their flame retardancy and mechanical properties. In this work, we synthesized an ionic liquid, VIDHP, from diethyl hydroxymethyl phosphate (DHP) and 1-vinylimidazole (VIM). VIDHP can not only cross-links with VER but also enhances the interaction between the resin and the carbon fiber. The flame retardancy and mechanical properties of VER and its carbon fiber composites were effectively improved by the addition of VIDHP. In particular, the addition of 15 wt% VIDHP increased the flexural strength and flexural modulus of the carbon fiber composites by 29.3 % and 42.4 %, while reducing the total heat release and total smoke release by 15.4 % and 18.4 %. The flame retardant mechanism of VIDHP was also investigated. This approach provides a new idea to improve the flame retardant and mechanical properties of VER and its carbon fiber composites.

Does the universal adhesive's film thickness affect dentin-bonding effectiveness?

To investigate the influence of adhesive resin application modalities on the film thickness of the adhesive resin and the effectiveness of a two-step universal adhesive (UA) bonded in self-etch (SE) bonding mode to high C-factor class-I cavity-bottom dentin. After application of the primer of G2-Bond Universal (G2B, GC), the adhesive resin was applied into standard class-I cavities (human molars) following four application modalities: (1) one layer, strongly air-blown; (2) one layer, gently air-blown; (3) two layers, each gently air-blown; (4) one layer, not air-blown. After being restored with composite, each tooth was sectioned to obtain one micro-specimen (n = 10), of which the adhesive resin film thickness was measured using optical microscopy. The micro-tensile bond strength (μTBS) was tested immediately or upon 100,000 thermocycles. Statistical analyses involved Kruskal-Wallis and Mann-Whitney U testing (p < 0.05). G2B's μTBS was significantly affected by the adhesive resin application modality and aging. Gently air-blowing the adhesive resin resulted in significantly higher immediate μTBS than strong air-blowing or no air-blowing. No significant difference in μTBS was found between single or double gently air-blown adhesive resin applications. The adhesive resin film thickness significantly varied with the application modalities. A too thin or too thick adhesive resin film thickness adversely affected bond strength of the two-step UA applied in SE mode and high C-factor condition. The adhesive resin layer thickness can affect the bonding performance of two-step UAs in high C-factor cavities. Dental clinicians remain advised to avoid improper air-blowing of UAs and strictly follow the application instructions.