Preparation Of Resin Research Articles

How does the occlusal contact region influence the mechanical fatigue performance and fracture region of monolithic lithium disilicate ceramic crowns?

ObjectiveTo characterize the effect of the occlusal contact region on the mechanical fatigue performance and on the fracture region of monolithic lithium disilicate ceramic crowns. Materials and methodsMonolithic lithium disilicate ceramic crowns were machined in a CAD/CAM system and adhesively luted onto glass-fiber reinforced epoxy resin preparations with resin cement. The crowns were divided into three groups (n = 16) according to load application region (cusp tip: restricted to cusp tips; cusp plane: restricted to cuspal inclined plane; or mixed: associating tip cusp and cuspal inclined plane). The specimens were submitted to a cyclic fatigue test (initial load: 200 N; step-size: 100 N; cycles/step: 20,000; loading frequency: 20 Hz; load applicator: 6 mm or 40 mm diameter stainless steel) until observing cracks (1st outcome) and fracture (2nd outcome). The data were analyzed by the Kaplan-Meier + Mantel-Cox post-hoc tests for both outcomes (cracks and fracture). Finite element analysis (FEA), occlusal contact region, contact radii measurements, and fractographic analyzes were performed. ResultsThe mixed group presented worse fatigue mechanical behavior (550 N / 85.000 cycles) compared to the cuspal inclined plane group (656 N / 111,250 cycles) (p < 0.05) for the first crack outcome, while the cusp tip group was similar to both groups (588 N / 97,500 cycles) (p > 0.05). The mixed group had the worst fatigue behavior (1413 N / 253,029 cycles) in relation to the other groups (Cusp tip: 1644 N / 293,312 cycles; Cuspal inclined plane: 1631 N / 295,174 cycles) considering the crown fracture outcome (p < 0.05). FEA showed higher tensile stress concentration areas just below the load application region. In addition, loading on the cuspal inclined plane induced a higher tensile stress concentration in the groove region. The most prevalent type of crown fracture was the wall fracture. Groove fracture was observed in 50% of the loading specimens exclusively on the cuspal inclined plane. ConclusionLoad application on distinct occlusal contact regions affects the stress distribution pattern and consequently the mechanical fatigue performance and fracture region of the monolithic lithium disilicate ceramic crowns. A combination of loading at distinct regions is recommended to promote better evaluation of the fatigue behavior of a restored set.

Preparation and physicochemical characterization of emulsion alkyd resins from cottonseed, Hura crepitans L. seed and palm kernel oils

The growing environmental concerns have led to the formulation of new coating strategies by employing inherently waterborne binders as a key component in order to eliminate the toxic volatile organic solvents from protective coatings. Hura crepitans L. seed oil (HCSO) was extracted from the seed pulp via solvent extraction and characterized using standard methods. Cottonseed oil (COSO), palm kernel oil (PKO), and HCSO were used in the formulation of emulsion alkyd resins (EMAR) via a two-stage alcoholysis-polyesterification process followed by the introduction of maleic anhydride in the polymer backbone and neutralization of the free acid functionality with triethylamine (TEA). Three grades EMAR (50%) were prepared using these oils, phthalic anhydride, glycerol, and maleic anhydride. The percentage yield of HCSO was 87.93%. While the iodine and acid values of HCSO were 145.90 g I2/100 g and 1.26 mg KOH/g respectively. COSO emulsion alkyd (CWAR), HCSO emulsion alkyd (HWAR), and PKO emulsion alkyd (PWAR) were highly soluble in water, while the iodine value of 81.38 gI2/100g, 85.02 gI2/100g, and 10.45 gI2/100g was recorded for CWAR, HWAR, and PWAR respectively. The solid content of the binders varied between 84.88 – 85.48%. While the viscosity varied between 1756.00 – 1768.00 mpa.s. HCSO and COSO can serve as good starting raw materials for the synthesis of environmentally friendly waterborne alkyd resin.

Preparation and properties of a novel waterborne epoxy resin modified emulsified asphalt

Waterborne epoxy resin is one alternative to enhance bond strength and storage stability for waterproof adhesive layer. Grafting copolymerization is selected in this paper as one experimental case to investigate its properties and also a feasible innovative preparation. The impact of the preparation process on the grafting rate of acrylic monomer was also considered. Moreover, the effect of the amount of acrylic monomer on the centrifugation stability and particle size of the emulsions was studied, where the infrared spectra were used to verify that hydrophilic groups incorporated into the main body of the aqueous epoxy resin. Main tests for modified emulsified asphalt are designed as it pulls out strength and storage stability under various temperature. The results showed that the highest grafting rate of acrylic monomer was achieved at the grafting temperature of 110℃ and grafting time of 2 h. The centrifugal stability of the emulsion was optimum when the amount of acrylic monomer reached 30%, at this time, the median particle size of the emulsion was 160 nm; the infrared spectrum showed that the epoxy resin main chain successfully introduced hydrophilic group (–COOH) at 1720 cm−1. When the amount of water-borne epoxy resin exceeded 40%, the pull-out strength of waterborne epoxy resin modified emulsified asphalt increased significantly at 25℃ and 40℃, and its storage stability was optimized when the content of waterborne epoxy resin reached 50%. The waterproof adhesive layer material prepared in this study has potential application value for improving the quality of bridge deck pavement and construction projects.

High-Strength, Degradable and Recyclable Epoxy Resin Based on Imine Bonds for Its Carbon-Fiber-Reinforced Composites

Carbon fiber (CF) is widely used in the preparation of carbon-fiber-reinforced polymer composites (CFRP) in which it is combined with epoxy resin due to its good mechanical properties. Thermosetting bisphenol A epoxy resin, as one of the most common polymer materials, is a non-renewable resource, leading to a heavy environmental burden and resource waste. To solve the above problems and achieve high mechanical and thermal properties comparable to those of bisphenol A, herein, a high-performance, degradable and recyclable bio-based epoxy resin was developed by reacting the lignin derivative vanillin with 4-amino cyclohexanol via Schiff base. This bio-based epoxy resin showed a Young's modulus of 2.68 GPa and tensile strength of 44 MPa, 36.8% and 15.8% higher than those of bisphenol A epoxy, respectively. Based on the reversible exchange reaction of the imine bond, the resin exhibited good degradation in an acidic environment and was recoverable by heat treatment. Moreover, the prepared epoxy resin could be used to prepare carbon fiber (CF)-reinforced composites. By washing off the epoxy resin, the carbon fiber could be completely recycled. The recovered carbon fiber was well preserved and could be used again for the preparation of composite materials to realize the complete recovery and utilization of carbon fiber. This study opens a way for the preparation of high-performance epoxy resin and the effective recycling of carbon fiber.

Facile preparation of magnolol-based epoxy resin with intrinsic flame retardancy, high rigidity and hydrophobicity

Facile preparation of magnolol-based epoxy resin with intrinsic flame retardancy, high rigidity and hydrophobicity

Surfactant effect on DLP fabrication of silica fibre preforms

Three-dimensional (3D) printing based on digital light processing (DLP), for its great advantage in dealing with material and structural complexities, is being engaged for the fabrication of custom-designed silica optical fibre preforms. Resin preparation and printing are key processes critical to DLP fabrication of optical fibre preforms with high silica loading. In this work, the surfactant effect on preparation of resin and DLP printing of optical fibre preforms for higher silica loading is investigated. Based on our experimental studies of the rheological and photocuring properties of resins and the quality of printed silica fibre preforms, we find that, in the case where 2-phenoxyethanol (POE) is usually added as the surfactant, the resin has higher viscosity and results in poorer preform quality. By removing POE from resin ingredients and designing a multi-step resin processing with appropriate settling and degassing processes, fibre preforms with high silica loading up to 0.8 (w/w) have been successfully fabricated.

Fabrication of bioactive glass scaffolds by stereolithography: Influence of particle size and surfactant concentration

For decades, bioactive glass (BAG) has been utilized as a competent bone substitute owing to its intrinsic properties, such as outstanding biocompatibility and bioresorbability. Stereolithography (SL) is an additive manufacturing technology used to produce highly accurate three-dimensional BAG-based bone substitutes. However, the preparation of BAG-based SL resin is always a challenge, especially because of the inevitable sedimentation of BAG particles. In this study, BAG particles with different sizes were prepared by dry grinding (BAGdry, greater particle size) and wet grinding (BAGwet, finer particle size). Then, BAGdry or BAGwet SL resins with various amounts of surfactant were analyzed. The sedimentation rate for BAG powder increased with increasing particle size but decreased with increasing amounts of surfactant added to the resin. BAGwet SL resins had a longer shelf life, so printing could still be finished after 14 days, whereas BAGdry SL resins were no longer useable after 5 days. However, the BAG particle size did not affect the printing accuracy or scaffold strength. According to our results, BAG-based SL resin fabricated with BAGwet (particle size <1.6 μm) and 5 wt% surfactant exhibited better resistance to sedimentation.

High-performance adhesives modified by demethylated lignin for use in extreme environments

Lignin-modified epoxy resin (LER) is a promising alternative to bisphenol A in the preparation of epoxy resins.

Preparation and characterization of water-reducible polyester resin based on waste PET for insulation varnish.

Water-reducible polyester resin (WRPE) for insulation varnish was prepared from waste polyethylene terephthalate (PET), glycerol (GL), and phthalic anhydride (PA) via depolymerization and condensation. PET was depolymerized via glycolysis at different molar ratios of PET/GL (PET repeating unit/GL molar ratios: 1.6, 1.3, and 1.0) with zinc acetate as a catalyst at 220-230 °C. The resulting glycolytic products (GPs) were reacted with PA at contents of 5, 7.5, 10, 12.5, and 15 wt%, based on the total weight. The prepared WRPEs were dissolved in phenol, neutralized with aqueous ammonia to pH = 7-7.5, and diluted in water. The WRPEs were cured with hexamethoxymethyl melamine resin (HMMM, WRPE : HMMM = 70 : 30, based on the dry mass) at 140 °C for 2 h. The formation of GPs, WRPE, and WRPE-HMMM was investigated using Fourier transformer infrared spectroscopy and proton nuclear magnetic resonance spectroscopy; the thermal properties were characterized using thermogravimetric analysis and differential scanning calorimetry. The electrical insulation strength and volume resistivity of the cured films with PA content were investigated. This strength and volume resistivity first increased with increasing PA content and then decreased above 10 wt%. The results show that WRPE with a PA content of 10 wt% exhibits optimal insulation properties.

Eco-friendly synthesis of cardanol-based AB monomer for formaldehyde-free phenolic thermosets

Oxidative cleavage of cardanol to a single-component AB monomer allows the preparation of bio-based formaldehyde-free phenolic resins.

Preparation and Performance Analysis of Epoxy Acrylic Resin for Repairing Asphalt Pavement Diseases

Preparation and Performance Analysis of Epoxy Acrylic Resin for Repairing Asphalt Pavement Diseases

Silica infiltration on translucent zirconia restorations: Effects on the antagonist wear and survivability.

To assess potential antagonist wear and survival probability of silica-infiltrated zirconia compared to glass-graded, glazed, and polished zirconia. Table top restorations made of 3Y-TZP (3Y), 5Y-PSZ (5Y), and lithium disilicate (LD) were bonded onto epoxy resin preparations. Each zirconia was divided into five groups according to the surface treatment: polishing; glaze; polishing-glaze; glass infiltration; and silica infiltration. The LD restorations received a glaze layer. Specimens were subjected to sliding fatigue wear using a steatite antagonist (1.25×106 cycles, 200N). The presence of cracks, fractures, and/or debonding was checked every one/third of the total number of cycles was completed. Roughness, microstructural, Scanning electron microscopy, wear and residual stress analyses were conducted. Kaplan-Meier, Mantel-Cox (log-rank) and ANOVA tests were performed for statistical analyses. The survival probability was different among the groups. Silica infiltration and polishing-glaze led to lower volume loss than glaze and glass-infiltration. Difference was observed for roughness among the zirconia and surface treatment, while lithium disilicate presented similar roughness compared to both glazed zirconia. Scanning electron microscopy revealed the removal of the surface treatment after sliding fatigue wear in all groups. Compressive stress was detected on 3Y surfaces, while tensile stress was observed on 5Y. 3Y and 5Y zirconia behaved similarly regarding antagonist wear, presenting higher antagonist wear than the glass ceramic. Silica-infiltrated and polished-glazed zirconia produced lower antagonist volume loss than glazed and glass-infiltrated zirconia. Silica-infiltrated 3Y and lithium disilicate restorations were the only groups to show survival probabilities lower than 85%.

Preparation and characterization of diamine-functional bisphthalonitrile resins with self-promoted cure behavior

Preparation and characterization of diamine-functional bisphthalonitrile resins with self-promoted cure behavior

Preparation of All Amorphous PMMA Resins Based on the Graft Architecture with a Flexible Main Chain for Simultaneous Enhancement of Thermal and Mechanical Toughness

AbstractThis study shows the design of poly(methyl methacrylate) (PMMA)‐based glassy polymers with simultaneous improvement of thermal resistance and mechanical toughness, based on the graft architecture with a low glass transition (Tg) flexible main chain. The microphase‐separated structure of the flexible main chain and the glassy graft chains in this design may be key to these improved properties. Notably, the graft copolymer depicts the ductile fracture, and the microscopy observation for the fractured sample exhibits the presence of abundant void formation with relatively homogenous size and interval throughout the sample. The void formation could originate from the preferential fracture of aggregated flexible components distributed throughout the sample, indicating the effective role of the flexible main chain on the suppression of the internal stress. The novelty of the present study is on the use of simple graft architecture for enhancing the toughness of glassy resins. This idea is indeed distinct from the conventional approach to improve toughness by adding plasticizer or rubber particles, therefore opening a new method for the creation of high‐functional glassy polymers.

Preparation and Properties of Epoxy Resin and Polyurethane Blend Resin-Based Low-Infrared-Emissivity Coatings

A low-infrared-emissivity composite coating with outstanding mechanical properties and low glossiness was prepared by using an epoxy resin and polyurethane blend modified resin, flake brass powder, the silane coupling agent KH560, and a dispersant as an adhesive, a functional pigment, and interface modifiers, respectively. The effects of the mass ratios of epoxy resin and polyurethane, the addition amount of flake brass powder, the addition amount of KH560, and the addition amount of dispersant on the coating performance were systematically discussed. The results show that the coating has lower emissivity (0.424) and glossiness (28.8) when the mass ratio of epoxy resin to polyurethane is 6:4 and the addition amount of brass powder is 50 wt%. Using KH560 to modify the interface structure of the coating, KH560 can form chemical bond with the resin matrix and flake brass powder so as to obviously improve the impact strength and flexibility of the coating. The addition of the dispersant can obviously enhance the dispersion state of the flake brass powder in the coating and thus enhance the reflection intensity of infrared light for the coating, such that the emissivity of the coating is obviously reduced. When the addition amount of KH560 is 7 wt% and the addition amount of the dispersant is 9 wt%, the coating has the optimal emissivity (0.332), glossiness (9.0), adhesion strength (grade 1), impact strength (50 kg·cm), and flexibility (1 mm) at the same time. The above mentioned low-infrared-emissivity coating has an important application prospect in the field of infrared stealth for various aircraft.

Improved Synthetic Route of Incorporation of Nanosilicon Species into Phenol-Formaldehyde Resin and Preparation of Novel ZnAl-Layered Double-Hydroxide Hybrid Phenol-Formaldehyde Resin.

Hybrid phenol-formaldehyde (PF) resins represent one of the most important niche groups of binding systems for composites. New industrial needs, environmental requirements, and price fluctuations have led to further research on materials with enhanced mechanical and thermal properties. The preparation of novel hybrid materials can be achieved by inclusion of various elements or functional groups in the organic polymer phenolic framework. Herein, we report the synthesis and characterization of a PF-based hybrid material with different nanoscale silicone species and ZnAl-layered double hydroxide (LDH). The main goals of this study were to improve the synthetic pathways of hybrid resin, as well as to prepare granulated composite materials and test samples and determine their characterization. Added inorganic species increased the glass-transition temperature by a minimum of 8 °C, which was determined using differential scanning calorimetry (DSC). Rheological properties (melting viscosity and flow distance) of the hybrid resin were measured. The homogeneity of distribution of added species across the organic matrix was evaluated with scanning electron microscopy (SEM). With synthesized new hybrid-binding systems, we prepared different granulated composite materials and evaluated them with the measurements of rheological properties (flow curing characteristics). Tensile strength of samples, prepared from granulated composite material, improved by more than 5%.

Green preparation of robust hydrophobic bio-based epoxy resin with low dielectric constant

Epoxidized soybean oil (ESO) thermosets show poor performance owing to the low cross-linking density and flexibility of their backbone structure. Herein, fully bio-derived benzoxazine (GD) cured ESO thermosets (PGEs) with high-performance were prepared through a green process. As a curing agent, GD improved the cross-linking density and rigidity of ESO resins. Moreover, different types of hydrogen bonds formed in the PGEs, further strengthening the intermolecular interactions. Therefore, the glass transition temperature (Tg) and tensile strength of PGEs attained 93 °C and 34 MPa, respectively, which are higher than those reported for conventional ESO resins. Additionally, PGEs exhibited substantial hydrophobicity and a low dielectric constant, which can be associated with complex intermolecular and intramolecular hydrogen bonds within the thermoset network. Furthermore, as the GD content in PGE increased, the dielectric constant and water absorption of the polymer reduced to 2.72 % and 0.52 %, respectively. Herein, the preparation of novel all-biological ESO thermosets using GD as the curing agent is reported, providing a green and convenient strategy for the design of high-performance ecological materials.

High-performance and fire-resistant epoxy thermosets derived from plant-derived ferulic acid

Development of epoxy thermosets derived from biomasses with intrinsic flame retardancy and high mechanical performances is of increasing demand. Here we synthesize a novel epoxy monomer (DGEFA) from ferulic acid that can be directly obtained from many plants and offers intrinsic flame retardancy due to its conjugation structure. By using 4,4’-diaminodiphenylmethane (DDM) as a curing agent, the cured epoxy resin (DGEFA-DDM) possesses a high glass transition temperature (178.5 °C). The DGEFA-DDM also exhibits high mechanical performances, i.e., tensile strength of 84.7 MPa and flexural strength of 145.1 MPa. Besides, the DGEFA-DDM presents a char yield of 40.6 % under N2, a V-1 rating of UL-94 and a limiting oxygen index of 32.8 %. The cone calorimeter test shows that the DGEFA-DDM has low heat and smoke release performances with a total heat release of 49.2 MJ/m2 and a total smoke production of 16.0 m2, indicating a high intrinsic flame retardancy. This work provides a simple way for the preparation of epoxy resins from bio-based feedstocks possessing physical properties and fire safeties.

Co-curing preparation of flame retardant and smoke-suppressive epoxy resin with a novel phosphorus-containing ionic liquid

Phosphorus-containing ionic liquid derivatives have been proven to be effective flame retardants for epoxy resin (EP). Flame retardants can accelerate the curing process and improve flame retardancy and smoke suppression of EP composites, which is challenging. In this paper, a novel phosphorus-containing ionic liquid (TPP-PF6) was synthesized and used both as a co-curing agent with 4,4′-diaminodiphenylmethane (DDM) and as a highly effective flame retardant for EP. It has been found that TPP-PF6 was conducive to improve the char formation of EP to inhibit the smoke release at high temperatures. For EP/TPP-PF6 composites, the flame-retardant performance was enhanced rapidly with the increase of TPP-PF6. With only 2 wt% of TPP-PF6, EP/2.0TPP-PF6 reached a UL-94 V-0 rating and a limiting oxygen index of 30.3%. The peak heat release rate, total heat release, and total smoke production values of EP/2.0TPP-PF6 were reduced by 36.32%, 45.81%, and 15.1% compared with those of pure EP, respectively. The thermal degradation products and flame retardant mechanism in gas and condensed phases were studied. It was found that TPP-PF6 had flame retardant effect in the barrier effect of the condensed phase and the quenching effect of the gas phase. This work explores the high-efficiency flame retardant and smoke-suppressive structures with co-curing properties for EP, thus promoting the wide application of EP materials.

Preparation and characterization of acrylic resins with bioactive glasses

This study aimed to prepare a bioactive acrylic material by adding different types of glasses. Commercially available polymerized acrylic resin was mixed with 10% of four different types of glasses in the powder form and cured. Flexural strength, sorption, and solubility of the samples were tested according to ISO 20795-1:2013. The total number of samples used in the tests were 60. The materials were placed in artificial saliva of pH 4 and 7, and elution was performed for 0, 1, 28, and 42 days. The collected samples were analyzed using inductively coupled plasma atomic emission spectrometry to detect Ca, P, and Si ions and using ion chromatography to detect F ions. The materials obtained after modification with glasses showed lower compressive strength compared with pure polymethyl methacrylate but met the standard requirements. Two glass types showed higher solubility values compared with the value defined by the ISO standard. Biomin C and S53P4 released Ca, P, and Si ions, respectively, after 42 days in artificial saliva. Acrylic resins modified with 10% Biomin C and S53P4 glasses can be a valuable source of Ca and P ions under acid conditions for 28 and 42 days.