Degradation Of Resin Research Articles

Characterization of Electrical Tree Degradation of Epoxy Resin under Thermal and Temperature Stresses by Photoelastic Effect

Characterization of Electrical Tree Degradation of Epoxy Resin under Thermal and Temperature Stresses by Photoelastic Effect

Stability Qualification of Resins/Metallic Oxide Composites for Surface Oxidative Protection.

The accelerated degradation of alkyd resins via γ-irradiation is investigated using non-isothermal chemiluminescence. The stability qualification is possible through the comparison of emission intensities on a temperature range starting from 100 °C up to 250 °C under accelerated degradation caused by radiolysis scission. The measurements achieved in the samples of cured state resin modified by various inorganic oxides reveal the influence of metallic traces on the aging amplitude, when the thermal resistance increases as the irradiation dose is augmented. Even though the unirradiated samples present a prominent chemiluminescence intensity peak at 80 °C, the γ-processed specimens show less intense spectra under the pristine materials and the oxidation starts smoothly after 75 °C. The values of activation energies required for oxidative degradation of the sample subjected to 100 kGy are significantly higher in the composite states than in the neat resin. The degradation mechanism of polymerized resins is discussed taking into account the effects of fillers on the stability of studied epoxy resin at various temperatures when the degradation and crosslinking are in competition for the decay of free radical.

Efficient degradation of amine cured epoxy resin via the cleavage of C-N bond by amphiphilic dodecylbenzenesulfonic acid

Amine-cured epoxy resin (EP) is often compounded with carbon fiber (CF) used for wind power blades due to its excellent performance. However, the insolubility and infusibility of service-life-expired carbon fiber reinforced epoxy resin (CFREP) hinder its sustainable recycling. We reported a new strategy for efficient degradation of EP and CFREP with 0.5 mol% amphiphilic dodecylbenzenesulfonic acid (DBSA) in aqueous system. It was found that the strong lipophilicity of DBSA accelerated its enrichment on EP surface, and further promoted the diffusion of DBSA and H2O to the resin bulk phase. As a result, the degradation ratio of the EP powder reached 100 % at 190 °C only in 10 h. The characterization of FT-IR and NMR proved that the degradation mechanism of EP was the selective cleavage of C-N bond catalyzed by H+. The resin degradation products (RDP) containing active hydrogen were used to prepare polyurethane (PU) with good mechanical properties. This method achieves complete recycling of waste CFREP in aqueous systems.

Hydrolytic degradation and biomineralization of amine-cured epoxy resin based on glycidate

Hydrolytic degradation and biomineralization of amine-cured epoxy resin based on glycidate

INSIGHT INTO THE OXIDATIVE DEGRADATION OF PHENOLIC RESIN DESTINED FOR THE CORROSION PROTECTION OF METALLIC SURFACES

The effects on the stability under accelerated degradation of phenolic resin used for the corrosion inhibition of metallic surfaces in aeronautical and nuclear spare parts are evaluated by nonisothermal chemiluminescence (CL) at four different heating rates: 5, 10, 15, and 20 ⁰C min-1. The simulation of the interface interaction between the metallic bodies and protection layers is achieved by the addition of metallic oxides as corrosion promoters: Gd2O3, CeO2, Pr2O3, MgO, MnO2, Cr2O3, and In2O3. These metallic atoms may be the main alloying elements that are present in the compositions of special application products. The presence of a specific peak in the CL spectra between 160 and 177°C proves the oxidation activity of filler in the connection of electronic interference. The differences between the emission intensities of the studied formulations certify the unlike contributions of alloying components. The heating rate plays also the role of oxidation factor that influences the refreshing surrounding atmosphere. The present results define the thermal technological limits of peculiar operation conditions for any metallic item subjected to a high level of warranty. The initiation of degradation in phenolic resin is done by -irradiation when free fragments are provided for the interaction with metallic structures. The development of oxidation is analyzed by the modification of CL emission intensities from room temperature to 250°C. The diminution of this process parameter over 200°C is found an essential factor for the preservation of surface integrity.

Surface Degradation of DGEBA Epoxy Resins Cured with Structurally Different Amine Hardeners: Effects of UV Radiation.

In this study, the effects of three diamine curing agents (aromatic, cycloaliphatic, aliphatic) on the photochemical behavior of bisphenol A diglycidyl ether networks were comparatively examined. In order to monitor structural changes and study the curing agents' action mode, the cured epoxy resins were characterized before and after photoirradiation by means of Fourier-transform infrared spectroscopy, contact angle, differential scanning calorimetry, scanning electron microscopy, and energy-dispersive X-ray analysis, mass loss, and color modification measurements. Water absorption tests were also conducted. The cured epoxy resins are to be used in different multicomponent polymer materials for outdoor protection. The presence of the cycloaliphatic hardener led to reduced water absorption, and after UV irradiation, an increase in the glass transition temperature and lowest mass loss of the corresponding cured epoxy resin compared to the ones cured with aromatic and aliphatic hardener.

Changes in physicochemical characteristics of cation exchange resins by high dose gamma irradiation

Chemical and thermal characteristics of cation exchange resins were examined after irradiation of gamma rays. The degradation of cation exchange resins was mainly observed at doses of up to 500 kGy, whereas the balance between degradation and cross-linking reactions was sustained at 700 kGy. While the carbon content decreased significantly up to a maximum dose of 500 kGy, it showed an increase at higher doses. Conversely, the oxygen content exhibited a decrease in contrast to the carbon content. The continuous reduction in sulfur content was attributed to the decomposition of sulfonic groups. Gamma-ray irradiation caused a decrease in the initiation temperature of sulfonic groups and PS-DVB, but unlike the chemical properties of cation exchange resins due to gamma-ray irradiation, the thermal properties of resins remained unaffected.

Nickel-Catalyzed C(sp3)-O Hydrogenolysis via a Remote-Concerted Oxidative Addition and Its Application to Degradation of a Bisphenol A-Based Epoxy Resin.

In this work, we developed a nickel-catalyzed transfer hydrogenolysis of 1-aryloxy-3-amino-2-propanols, which is a model compound of an amine-cured bisphenol A (BPA)-based epoxy resin. Mechanistic investigation revealed that the hydroxy group acts as the hydrogen donor to generate α-aryloxy ketone, which undergoes an unprecedented remote-concerted oxidative addition of the C(sp3)-O bond as suggested by DFT calculation. Successful application of this method was demonstrated by the degradation of a diamine-cured BPA-based epoxy resin, in which BPA was directly recovered from the resin.

Role of Fe Complexes as Initiators in the Oxidative Degradation of Amine Resins for CO2 Capture: Molecular Modeling and Experimental Results Compared

Role of Fe Complexes as Initiators in the Oxidative Degradation of Amine Resins for CO₂ Capture: Molecular Modeling and Experimental Results Compared

A Comprehensive Review on the Thermal Stability Assessment of Polymers and Composites for Aeronautics and Space Applications.

This review article provides an exhaustive survey on experimental investigations regarding the thermal stability assessment of polymers and polymer-based composites intended for applications in the aeronautical and space fields. This review aims to: (1) come up with a systematic and critical overview of the state-of-the-art knowledge and research on the thermal stability of various polymers and composites, such as polyimides, epoxy composites, and carbon-filled composites; (2) identify the key factors, mechanisms, methods, and challenges that affect the thermal stability of polymers and composites, such as the temperature, radiation, oxygen, and degradation; (3) highlight the current and potential applications, benefits, limitations, and opportunities of polymers and composites with high thermal stability, such as thermal control, structural reinforcement, protection, and energy conversion; (4) give a glimpse of future research directions by providing indications for improving the thermal stability of polymers and composites, such as novel materials, hybrid composites, smart materials, and advanced processing methods. In this context, thermal analysis plays a crucial role in the development of polyimide-based materials for the radiation shielding of space solar cells or spacecraft components. The main strategies that have been explored to improve the processability, optical transparency, and radiation resistance of polyimide-based materials without compromising their thermal stability are highlighted. The combination of different types of polyimides, such as linear and hyperbranched, as well as the incorporation of bulky pendant groups, are reported as routes for improving the mechanical behavior and optical transparency while retaining the thermal stability and radiation shielding properties. Furthermore, the thermal stability of polymer/carbon nanocomposites is discussed with particular reference to the role of the filler in radiation monitoring systems and electromagnetic interference shielding in the space environment. Finally, the thermal stability of epoxy-based composites and how it is influenced by the type and content of epoxy resin, curing agent, degree of cross-linking, and the addition of fillers or modifiers are critically reviewed. Some studies have reported that incorporating mesoporous silica micro-filler or microencapsulated phase change materials (MPCM) into epoxy resin can enhance its thermal stability and mechanical properties. The mesoporous silica composite exhibited the highest glass transition temperature and activation energy for thermal degradation among all the epoxy-silica nano/micro-composites. Indeed, an average activation energy value of 148.86 kJ/mol was recorded for the thermal degradation of unfilled epoxy resin. The maximum activation energy range was instead recorded for composites loaded with mesoporous microsilica. The EMC-5p50 sample showed the highest mean value of 217.6 kJ/mol. This remarkable enhancement was ascribed to the polymer invading the silica pores and forging formidable interfacial bonds.

Molecular dynamics simulation of epoxy resin properties at different C=N contents

In response to the green development strategies of countries all over the world, research on degradable epoxy resins has attracted widespread attention. The introduction of reversible covalent bonds in the conventional cross-linked structure of epoxy resins is one of the methods to achieve degradation of epoxy resins, and most researchers use molecular dynamics simulations in their preliminary studies to investigate the feasibility of the introduction of reversible covalent bonding schemes. The purpose of this paper is to investigate the feasibility of introducing C=N into the cross-linked structure of epoxy resins. Four formulation schemes of vanillin-based monoepoxides with the curing agent 4,4′-methylenebis(cyclohexylamine) were designed, and the molecular dynamics simulation method was used to cross-link them. The changes in the cross-linking degree, structural parameters before and after cross-linking, free volume fraction, and C=N content before and after cross-linking were investigated. The effects of different C=N contents on the thermal properties such as glass transition temperature and thermal expansion coefficient, as well as the mechanical properties such as the elastic modulus and shear modulus of this epoxy resin, were investigated. The bond-breaking characteristics of C=N, C–N, and C–O were compared by density of states and differential charge density simulations. Then the degradation mechanism of epoxy resin after the introduction of C=N was illustrated. The results show that as the specific gravity of the curing agent molecule increases, the cross-linking degree tends to increase. The cross-linked model has reduced volume, increased density, decreased energy, and a more stable structure. After crosslinking, the gaps between the segments in the system become smaller, and the fraction of free volume decreases as the proportion of crosslinking agent molecules increases. The C=N content in epoxy resin shows an increasing trend first and then decreases with the increase in the proportion of the curing agent. The glass transition temperature of the material increases with the increase in C=N content, while the coefficient of thermal expansion decreases with the increase in C=N content. The elastic modulus and shear modulus of the material show an increasing trend with the increase in C=N content, with a relatively gradual change in magnitude. Compared with C–N and C–O bonds, the C=N bond is weaker in strength, has a greater polarity, and is more prone to cleavage and degradation.

Thermal degradation and curing kinetic study of urea formaldehyde/l-tyrosine composites

In this study, the prepolymers (TYF) were prepared by formaldehyde and l-tyrosine, different amounts of TYF were added to prepare TYF modified urea-formaldehyde adhesives (LUF), and the gel time of resin, formaldehyde emission and wet shear strength of the plywood were tested. This result indicated that the optimal addition amount was 3 wt%, and the formaldehyde emission of plywood decreased by 23% to 0.57 mg/L, and the wet shear strength increased by 47% to 1.47 MPa. The thermal degradation and curing characteristics of urea-formaldehyde (UF) and LUF resins were characterized by thermogravimetric (TG) and differential scanning calorimetry (DSC), and the kinetic parameters were analyzed. The results showed that TYF could reduce the formaldehyde emission and improve the wet shear strength significantly. Moreover, the thermal degradation activation energy (Eα) of UF resin was increased, and the thermal stability was enhanced. Although the initial and peak curing temperatures of LUF were higher, but the LUF cured more easily than the UF once the curing temperature was reached.

Thermochemical recycling of epoxy resin composites reinforced with carbon fiber

The aim of this study was to recovery carbon fiber present in composite materials with epoxy resin matrix using a thermochemical recycling way. A full factorial design was proposed with two factors: the degradation temperature (DT) and the number of thermal baths (NB), which were evaluated in a range of 600°C–650°C and 0–2 baths, respectively, for 30 min. The responses were burn-off degree (BO) and tensile strength. The BO indicated that the temperature as well as the number of thermal baths have positive effects and, therefore, contribute to the degradation of the epoxy resin. Regarding the tensile strength, higher DT promotes a more pronounced effect in that response, but its interaction with NB causes greater damage to the surface of the carbon fiber. A new recycling condition was evaluated and compared with commercial carbon fiber. The results of tensile strength indicated it is possible to test similar applications for both recovered fiber and commercial fiber. The morphological characterizations showed that recycled materials preserved their physical structure, and all surface groups were removed throughout the thermochemical degradation process. In addition, the SEM analyzes indicated the preservation of the wefts after recycling, although residual matrix and the beginning of sizing destruction were observed. Thermochemical recycling proved to be an effective and better way to reuse carbon fiber instead of landfill and incineration.

Recycling of both resin and fibre from wind turbine blade waste via small molecule-assisted dissolution

Wind energy has significant growth potential and applicability on a global scale, but approximately 2.4% of wind turbine blades must be decommissioned annually. The majority of blade components can be recycled; however, wind blades are rarely recycled. In the present study, an alternative method was presented involving a small molecule-assisted technique based on a dynamic reaction that dissolves waste composite materials containing ester groups to recycle end-of-life wind turbine blades. This effective process requires temperatures below 200 °C, and the major component, i.e., resin, can be easily dissolved. This method can be applied to recycle composite materials, such as wind turbine blades and carbon fibre composites comprising fibres and resins. Depending on the waste, up to 100% of the resin degradation yield can be achieved. The solution used for the recycling process may be reused multiple times and can be reused to obtain resin-based components and create a closed loop for this type of material.

Influence of heating rate and atmospheric conditions on the thermal response of CFRP and its constituents

The thermal stability of carbon fibre-reinforced polymer (CFRP) and its constituents (neat epoxy resin and carbon fibre) are studied in terms of mass loss using a thermogravimetry technique at different heating rates and two atmospheric conditions (air and pure nitrogen). By interpreting the mass loss over a temperature range of 25–900 °C, it was possible to identify the specific mechanisms of polymer degradation. In an oxygen-free pure nitrogen atmosphere, the thermal degradation of epoxy resin used as the composite's matrix is strongly inhibited up to the temperature of 400 °C, after which it undergoes thermal decomposition, in contrast to the carbon fibre reinforcement that does not degrade in nitrogen. In an air atmosphere, however, the CFRP and its constituents degrade via a complex reaction pathway encompassing three endothermic reactions (pyrolysis of the epoxy resin, oxidation of the residue from the first pyrolysis reaction and carbon fibre oxidation) that overlap and one endothermic reaction in nitrogen (pyrolysis of the epoxy resin). A deconvolution technique based on fitting log-normal distributions to the first derivative of the mass loss data has also been undertaken to separate the thermal decomposition reactions for each CFRP to understand the effect of each reaction's contribution. It can be used to evaluate complex thermal degradation processes that can be characterised by finding the respective kinetic parameters of each reaction, e.g. by using combined kinetics analysis.

Effects of microstructure on radiolytic degradation of nuclear grade cationic resins: Gel versus macro-porous

A study was undertaken to evaluate the effect of gamma radiation on the physico-chemical and functional properties of strong cationic ion exchange resins with varying microstructures i.e., gel and macro-porous type, used in purification systems of water-cooled nuclear reactors. The effect of metal ion loading on degradation behavior was probed to simulate the in-situ irradiation scenario in used resin. The resins are expected to undergo physico-chemical and functional degradation due to different oxidizing and reducing species from water radiolysis. Nevertheless, evaluating the extent of degradation based on the morphological and structural differences was of interest. The extent of resin degradation was estimated by analyzing the change in pH, conductivity, total organic carbon (TOC), chemical oxygen demand (COD) and the extent of reactive site loss from the leached ions. Leaching of SO42− ions and the formation of lower organic acids resulted in decreased pH and increased conductivity, TOC and COD values. The change in exchange capacity and physical and structural changes in the irradiated resin's surface was probed with X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) and Field emission scanning electron microscopy (FE-SEM). Gel resin showed more significant functional group loss, while hydrogen generation was more from macroporous resin due to its more rigid and dense structure.

Oxidative liquefaction as an alternative method of recycling and the pyrolysis kinetics of wind turbine blades

Oxidative liquefaction of wind turbine blades (WTBs) is carried out in a controlled environment having temperature ranges of 250–300 °C, pressure 20–40 bar, oxidant concentration of 15–45%, a reaction time of 30–90 min, and a waste-to-liquid ratio of 5–25 %wt. Fourier transform infrared spectroscopy (FTIR) in the wavenumber range from 650 to 3200 cm−1, analytical pyrolysis at 500 °C was performed. Thermogravimetric analysis (TGA) was employed at a temperature range of 30–800 °C at heating rates of 2, 4, 8, and 16 K/min. The kinetics of WTBs pyrolysis were analyzed using the Fraser-Suzuki (FS) deconvolution method and a model-based kinetic modeling procedure. Oxidative liquefaction resulted in higher resin degradation of WTBs and the production of liquid chemical compounds. Gas chromatography with flame ionization detection (GC-FID) was used to investigate the insight into these chemical compounds which were mostly fatty acids. The resin degradation yield was found to be in the range of 55–100% while volatile fatty acid (VFA) concentrations were from 28.90 to 210.59 g/kg-WTBs. In addition, analysis of variance (ANOVA) have been performed to provide the optimal reaction conditions to maximize the process outputs and minimize the energy consumption to make the process economically feasible.

An experimental investigation and process optimization of the oxidative liquefaction process as the recycling method of the end-of-life wind turbine blades

The article contextualizes and expands upon research related to oxidative liquefaction of wind turbine blades for resin degradation and glass fiber recovery, presented at the 17th SDEWES conference series on Sustainable Development of Energy, Water and Environmental Systems 2022. The effect of five different parameters, including reaction temperature, residence time, pressure, waste-to-liquid ratio, and oxidant concentration, on resin degradation, has been studied in detail. Experiments were performed in the temperature range of 250 °C–350 °C with a residence time of 30–90 min, at a pressure of 20–40 bar, a waste-to-liquid ratio of 5–25%, and oxidant concentrations of 15–45% by weight. The maximum resin degradation yield achieved was in the range of 95–100% against the different combinations of tested parameters, and its minimum value was 43%, but detailed analysis revealed that the waste-to-liquid ratio is the key parameter affecting resin degradation yield. In addition, energy consumption is one of the important parameters determining the economic feasibility of the process, so a detailed optimization of the experimental plan based on maximum resin degradation and energy consumption has also been performed to identify the most suitable conditions that support the implication of the process at a larger scale.

The potential of salivary albumin to degrade composite resin.

The purpose of this study was to evaluate whether artificial saliva formulations with different concentrations of albumin affected the surface roughness, flexural strength and microhardness of a composite resin. Specimens (25x2x2mm) of a nanofilled composite (Filtek Z350XT, 3M/ESPE) were prepared and analyzed for average surface roughness (Ra/pm). The specimens were then allocated to 6 groups (n=30), to be treated with different salivary albumin concentrations: 0, 10, 50, 100, 200, 400 pg/mL. The specimens were stored in their respective artificial saliva groups, half of them for 24 h and the remainder for 180 days (artificial saliva renewed weekly), after which they were submitted to a new Ra reading, and tested for three-point flexural strength (FS, MPa). The specimens stored for 180 days were analyzed for Knoop microhardness (KH, Kg/mm2). Data were submitted to two-way ANOVA (Ra and FS) and one-way ANOVA (KH). Although Ra increased (p < 0.001) and FS decreased (p < 0.001) from 24 hours to 180 days of storage, the albumin concentration did not significantly affectRa (p = 0.168), FS (p = 0.477) or KH (p = 0.378). The esterolytic action of albumin did not increase the artificial-saliva-induced hydrolytic degradation of the composite resin.

Degradation and Failure Phenomena at the Dentin Bonding Interface.

Damage in the bonding interface is a significant factor that leads to premature failure of dental bonded restorations. The imperfectly bonded dentin-adhesive interface is susceptible to hydrolytic degradation and bacterial and enzyme attack, severely jeopardizing restorations' longevity. Developing caries around previously made restorations, also called "recurrent or secondary caries," is a significant health problem. The replacement of restorations is the most prevailing treatment in dental clinics, leading to the so-called "tooth death spiral". In other words, every time a restoration is replaced, more tooth tissue is removed, increasing the size of the restorations until the tooth is eventually lost. This process leads to high financial costs and detriment to patients' quality of life. Since the complexity of the oral cavity makes prevention a challenging task, novel strategies in Dental Materials and Operative fields are required. This article briefly overviews the physiological dentin substrate, features of dentin bonding, challenges and clinical relevance. We discussed the anatomy of the dental bonding interface, aspects of the degradation at the resin-dentin interface, extrinsic and intrinsic factors affecting dental bonding longevity, perspectives on resin and collagen degradation and how these subjects are connected. In this narrative review, we also outlined the recent progress in overcoming dental bonding challenges through bioinspiration, nanotechnology and advanced techniques to reduce degradation and improve dental bonding longevity.