Degradation Of Resin Research Articles

Exploring features in chromatographic profiles as a tool for monitoring column performance

In the biopharmaceutical industry, chromatography resins have a finite number of uses before they start to age and degrade, typically due to losses of ligand integrity and/or density. The “health” of a column is predicted and validated by running multiple cycles on representative scale-down models and can be followed by real-time on-going validation during commercial production.Principal Component Analysis (PCA), Partial Least Square (PLS), Similarity Scores and Single One Point-MultiParameter Technique (SOP-MPT) along with machine learning principles were applied to explore the hypothesis that there is predictive capability of latent variables in chromatography absorbance profiles for process performance (step yield) and product quality (aggregates, fragments, host cell proteins (HCP) and DNA, and Protein A ligand).The first stage of this study is described in this paper: a MabSelect SuRe™ chromatography column was cycled with a method to establish the “normal” baseline for process performance and product quality, followed by runs using a harsher NaOH Cleaning in Place (CIP) procedure (with a higher NaOH concentration than that recommended by the vendor) to accelerate resin degradation. The different mathematical analytical tools correlated with resin degradation of the column (reflected in decreasing step yield and binding capacity with increasing running cycle), specifically when using the Wash, Elution and Strip phases of the chromatography method. Monomer, HCP and DNA content were not significantly impacted and therefore a correlation with product quality was inconsequential. Importantly, this work shows proof-of-concept that while more traditional methods of measuring resin integrity such as the height equivalent to a theoretical place (HETP) and Asymmetry (As) measurements could not detect changes in the integrity of the resin, PCA, PLS, Similarity Scores and SOP-MPT (to a lesser extent) applied to the absorbance data were capable of anticipating issues in the chromatography bed by identifying atypical outcomes.

Initial stage degradation of GFRP bars based on functional group ratio change using FTIR in high temperature and alkaline solution

Although extensive research has been conducted on the use of glass fibre-reinforced polymer (GFRP) bars in concrete, one factor that hinders their widespread use in civil engineering is the lack of prediction of degradation properties in concrete for long-term applications. This paper presents the tensile strength (TS) retention and microstructure evolution of GFRP bars in high-temperature and alkaline solutions by Fourier transform infrared (FTIR) spectroscopy. The test results indicated that with TS retention above 70%, the main reason for the mechanical property loss was resin degradation. Significant chemical degradation of the rod surface, namely, the breaking of ester bonds and the formation of carboxylates, was observed by FTIR and scanning electron microscopy (SEM). However, when the TS retention was less than 70%, damage to the bars was induced by debonding of the resin/fibre and localized damage to the resin and fibres. Finally, the relationship between the functional group ratio change and TS retention of GFRP was established using FTIR, revealing a linear relationship and introducing a coefficient k for modification. This can provide a scientific basis for the subsequent method to predict the degree of mechanical property degradation of GFRP bars by FTIR monitoring of the functional group ratio change.

Closed-loop recycling and degradation of guaiacol-based epoxy resin and its carbon fiber reinforced composites with S-S exchangeable bonds

The waste and desertion of petroleum-based epoxy resins have attracted increasing concerns on the damage and pollution to the environment because they are difficult to reprocess and reuse after curing. Once broken or injured, the recovery or degradation of composites is a tough challenge owing to their permanently cross-linked networks. In this paper, a novel guaiacol-based epoxy resin (BGF-EP) was prepared from renewable resources instead of conventional petroleum-based bisphenol A, curing with 4-aminophenyl disulfide (AFD). The epoxy vitrimer BGF-EP-AFD had appreciable thermal stability (Tg:143 °C, Td5%:295 °C), sufficient mechanical properties (tensile strength:55.54 MPa, elongation at break:12.23%) and stress relax from 300 min at 130 °C to 27.5 s at 200 °C. And the vitrimer could be reprocessed into a complete film. More excitingly, an efficient strategy was proposed to dissolve the cured resin and recycle its carbon fiber reinforced composites in a closed loop in an appropriate mixing solution (50%DMF/50%β-ME) at room temperature. The recovered carbon fibers are not altered and remain intact for the next utilization as confirmed by SEM. This work contributes the development of guaiacol-based renewable functional materials and provides a feasible and economical way to recycle and reprocess the carbon fiber reinforced epoxy composites.

Durability of graphene-modified epoxy vinyl resin served as matrix phase of composite bar in simulated concrete environment

The polymer resin is usually used as an adhesive for repairing and strengthening concrete structures or served as the matrix phase of composite bar. Because the alkaline environment of concrete makes polymer resin degradation with time, the toughening modification of polymer resin has great significance. Herein, the effects of nanofiller content and exposure time on the durability of graphene-modified epoxy vinyl resin in the simulated ordinary concrete environment were evaluated by the accelerated aging method at 60 °C. The results indicated that the addition of 0.3 wt% graphene made the tensile, compressive, flexural strengths and fracture toughness of epoxy vinyl resin samples improve by 18.5%, 2.6%, 29.7% and 22.1% compared to the plain resin samples, respectively. Meanwhile, a novel multi-stage compressive constitutive model was proposed to describe the stress-strain response of polymer-based composite. Additionally, a series of tests illustrated that the durability of graphene-modified epoxy vinyl resin samples was enhanced after exposure to the simulated concrete environment. The degradation degrees of tensile, compressive, flexural strength and fracture toughness of the samples with a 0.3 wt% incorporating content of graphene declined by 7.9%, 10.4%, 5.5% and 10.4% after twenty-eight days of exposure compared to those of the exposed plain resin samples, respectively.

Influence of Surface Discharge on Resin Degradation in Decay-like Fracture of Composite Insulators

Composite insulators have gradually become the preferred approach for electrical insulation in power systems, especially in polluted areas. Composite insulators consist of three main components: the shed, rod, and end fitting. Insulators withstand mechanical stresses via rods that are composed of glass-fiber-reinforced epoxy (GFRE). However, regardless of the high tensile strength of GFRE rods, in real-life operation, abnormal fractures have frequently been reported all over the world, which substantially increase the risk of major accidents in power systems. Fractural accidents mainly consist of brittle and decay-like fractures, which exhibit rather different morphologies at the cross sections. Brittle fracture has been effectively eliminated, while the mechanism of decay-like fracture has still not been clearly revealed. In this study, surface discharge tests were applied to investigate the discharge influence on the degradation of GFRE. The test successfully simulated the composition variation of the rods in real-life composite insulators with decay-like fractures. Moreover, it confirmed that the distinction between the characteristics of brittle fracture and decay-like fracture stems from epoxy degradation due to hydrolysis and carbonization. In addition, the respective influences of the resin type, glass fiber type, and acid liquid immersion on the degradation process were probed, and the degradation mechanism proposed in this research was verified. Based on the results, measures for preventing the development of decay-like fractures in real-life operations were determined.

A Reactive Molecular Dynamics Study on Crosslinked Epoxy Resin Decomposition under High Electric Field and Thermal Aging Conditions.

To reveal the microscopic mechanism of synergetic thermal-electrical degradation during a partial discharge process in epoxy insulation materials, the decomposition of crosslinked epoxy resin is investigated using reactive molecular dynamics simulations under high electric field and thermal degradation conditions. Bond-boost acceleration method is employed in reactive molecular dynamics simulations to successfully establish epoxy polymer models with a crosslink degree of 93%. Active molecular species derived from electrical partial discharges are considered in the current work. Small molecule products and decomposition temperature in the degradation process under an electric field are calculated to elucidate the effect of nitric acid and ozone molecules, being the active products generated by electrical partial discharges, on the synergetic thermal-electrical degradation of epoxy resin. Both nitric acid and ozone exacerbate thermal impact decomposition of crosslinked epoxy polymer by decreasing initial decomposition temperature from 1050 K to 940 K and 820 K, respectively. It is found that these active products can oxidize hydroxyl groups and carbon-nitrogen bridge bonds in epoxy molecular chains, leading to the aggravation of epoxy resin decomposition, as manifested by the significant increase in the decomposed molecular products. In contrast, thermal degradation of the epoxy resin without the active species is not expedited by increasing electric field. These strongly oxidative molecules are easily reduced to negative ions and able to obtain kinetic energies from electric field, which result in chemical corrosion and local temperature increase to accelerate decomposition of epoxy insulation materials.

Investigation of pyrolysis for the recovery of metallic values from ball grid arrays.

The massive generation of electronic waste has led to a significant interest in sustainable metal recovery and recycling. Ball grid arrays, mounted on printed circuit boards, are identified as a potentially valuable source of metals (Cu, Ni, Au, Ag, Pb, and Sn). In this study, pyrolysis is found as a promising treatment for the degradation of the epoxy resin of ball grid arrays. As a consequence, the liberation of metallic values and glass fibers is attained. The thermal analysis revealed that the major degradation occurs in the temperature range of 300-650°C, with overall activation energy estimated as ~ 243kJ/mol. The concentration of CO gas reaches a maximum value at a comparatively lower residence time with an increase in pyrolysis temperature. The metal enrichment was significantly influenced by the variation in pyrolysis temperatures with an optimal condition chosen as 600°C. The metallic fractions (Cu, Ni, Ag, and Au) were separated from the glass fibers by water-based density separation and enriched in the sink product by three-fold. The recovery of Cu, Ni, Ag, and Au is achieved at 97%, 88%, 95%, and 96%, respectively. The metal fraction can be either used as a feedstock for the Cu smelting process or can be subjected to selective hydrometallurgical treatment. The glass fiber fraction comprises of Si, Al, and Ca oxides with potential application in laminate fabrication. High-quality gaseous products can be reutilized as fuel for other metallurgical processes. It can be concluded that 100g of BGA yielded Cu ~ 23.7g, Ni ~ 0.57g, Ag ~ 23.4mg, and Au ~ 73mg after pyrolysis and density separation, which is equivalent to 1.35kg, of primary Cu ore, 0.042kg Ni ore, 4.68kg Ag ore, and 14.6kg Au ore.

Recycling of ammonia-cured epoxy resin by oxidative degradation of nitric acid assisted by swelling agent

Because of its high crosslinking density, compact structure and stable performance, epoxy resin is difficult to be degraded, which leads to serious environmental pollution problems. In this work, using dipropylene glycol dimethyl ether as swelling agent and nitric acid as oxidant, the degradation of amine cured epoxy resin was studied. Results are as follows: The degradation rate obtained by swelling agent assisted oxidation degradation method is much higher than that obtained by oxidation degradation method only. And the degradation rate of the epoxy resin even reached 100 % at 100 °C only in an hour under the condition of swelling agent assisted nitric acid. FT-IR and GC–MS showed that the degradation was mainly caused by that the CN bond in the molecular chain was gradually weakened and fractured finally. The molecular weight of the degradation product was relatively dispersive, which was composed of low molecular polymer and small fragments, and the molecular weight of low molecular polymer was about 2167. And the degradation products primarily contain 4-isopropylphenol and (allyloxy)benzene rings. This work provides a new way to solve the problem about the degradation, recycling and pollution of epoxy resin.

The Impact of Saliva and Oral Microbiome on Restorative Dental Materials

Saliva and the oral microbiome play critical roles in the performance and longevity of dental restorative materials. Saliva's buffering capacity, pH regulation, and remineralization impact the durability and stability of materials. Variations in saliva composition among individuals can influence wear resistance and surface degradation of these materials. This review explores the intricate relationship between saliva, the oral microbiome, and restorative dental materials, emphasizing their mutual influences and the implications for dental practice. The oral microbiome, consisting of diverse microorganisms, further complicates this interaction. Bacterial adhesion, biofilm formation, and microbial metabolism significantly affect the integrity of restorative materials. For example, the degradation of composite resins by oral bacteria and their acidic byproducts can compromise the mechanical properties of these materials. Clinical manifestations of these interactions include deterioration of composite resin restorations, biofilm formation, and corrosion of amalgam restorations. Recognizing these manifestations is crucial for dentists to implement timely interventions and personalized management strategies. Regular monitoring and timely intervention, coupled with advancements in biomaterials, are key to enhancing the durability and effectiveness of restorative dental treatments.

Affinity of K+to organic matter promotes reactions: degradation of super stable phenolic epoxy vinyl ester resin to value-added chemicals

An efficient catalytic system was developed to cleave the ester bond of highly stable waste thermoset phenolic epoxy vinyl ester resin and recover value-added chemicals.

High-Efficiency Carbon Fiber Recovery Method and Characterization of Carbon FIBER-Reinforced Epoxy/4,4'-Diaminodiphenyl Sulfone Composites.

Globally, the demand for carbon fiber-reinforced thermosetting plastics for various applications is increasing. As a result, the amount of waste from CFRPs is increasing every year, and the EU Council recommends recycling and reuse of CFRPs. Epoxy resin (EP) is used as a matrix for CFRPs, and amine hardeners are mainly used. However, no research has been conducted on recycling EP/4,4'-diaminodiphenyl sulfone (DDS)-based CFRP. In this study, the effect of steam and air pyrolysis conditions on the mechanical properties of re-cycled carbon fiber (r-CF) recovered from carbon fiber-reinforced thermosetting (epoxy/4,4'-diaminodiphenyl sulfone) plastics (CFRPs) was investigated. Steam pyrolysis enhanced resin degradation relative to N2. The tensile strength of the recovered r-CF was reduced by up to 35.12% due to oxidation by steam or air. However, the interfacial shear strength (IFSS) tended to increase by 9.18%, which is considered to be due to the increase in functional groups containing oxygen atoms and the roughness of the surface due to oxidation. The recycling of CFRP in both a steam and an air atmosphere caused a decrease in the tensile strength of r-CF. However, they were effective methods to recover r-CF that had a clean surface and increased IFSS.

Effect of elevated temperature on physical and mechanical properties of engineered bamboo composites

The aim of this study is to investigate the effect of elevated temperature on the physical and mechanical properties of two engineered bamboo composites (EBCs). The experiments were conducted on bamboo scrimber (BS) and glued-laminated bamboo (GLB) heated at the elevated temperatures from 40 ℃ to 250 ℃ for half an hour. The result showed that the heat had a significant effect on the physical and compressive behaviors of the EBCs. The ratio of mass loss increased with the temperature, while the density showed the opposite. The color changes were not conspicuous when the temperatures were from ambient condition to 160 ℃, but the surface darkening was found at temperature above 190 ℃. BS samples increased in thickness and width, while GLB samples showed as shrinkage at the elevated temperatures. The compressive strength in parallel-to-grain reached a maximum at 160 ℃, which is considered to be a turning point for compressive strength. The increase of the compressive strength can be associated to water release and solidification of adhesive inside the material, while the decrease of strengths is attribute to the degradation of phenol formaldehyde resin and bamboo polymers at high temperatures, particular for the temperature from 190 ℃ to 250 ℃. With the increase of temperature, the failure mode of the samples changed from ductile failure to brittle failure in parallel-to-grain. In perpendicular-to-grain direction, it presented crushing failure in BS, and the delamination of glue layers to crushing in GLB.

Degradation of vinyl ester resin and its composites via cleavage of ester bonds to recycle valuable chemicals and produce polyurethane

Vinyl ester resins (VER) and its composites are widely used in chemical industry and municipal engineering. However, its dense three-dimensional network structure makes its degradation and recycling a great challenge. Herein, a novel, efficient and green degradation system gamma-valerolactone (GVL)–H2O/p-toluene sulfonic (PTSA) was developed to degrade VER and its composites. VER was completely degraded in the GVL-H2O/PTSA at 210 °C and 0.6 MPa. By combing SEM-EDS, IR, NMR, GPC and MALDI-TOF-MS analysis, it was clarified that VER swelled well in GVL, allowing the transfer of PTSA and H2O through the resin matrix. The ester bonds in VER were cleaved via hydrolysis with H2O catalyzed by the sulfonic acid of PTSA, and high value-added polymer products, i.e., copolymer of styrene and methacrylic acid (SMAA) and bisphenol-A diglycidyl ether (DGEBA), were recycled, which accounted for ca. 87.0 wt% of raw VER. DGEBA can be recycled to prepare a new PU material. The GVL-H2O/PTSA system was also effective for degrading UPR and VER-containing composites. This work provides a practical strategy for chemical degradation and recovery of thermoset VER resins.

Recovery of carbon fiber-reinforced polymer waste using dimethylacetamide base on the resin swelling principle.

The mechanical recycling method of the carbon fiber-reinforced polymer (CFRP) has the advantages of simple process, less pollution and low cost, but only low utilization value of carbon fibers in powder or short fibers form can be obtained. To reduce the length and strength loss of the recycled carbon fibers, a novel and cost-effective dimethylacetamide (DMAC) swelling technique was developed to achieve rapid delamination of the CFRP laminates under mild conditions (120°C-160°C, 1h). The corresponding swelling ratios and mass-loss rates of cured epoxy resin (CEP) were about 121.39%-157.39% and 0-0.69%, respectively. Excessive swelling of CEP in DMAC resulted in the cracking of the resin matrix between the adjacent carbon fiber layers. Thus the CFRP laminates were delaminated into soft single carbon fiber layers, which showed excellent cutting performance and reinforcing properties. The delamination products were cut into thin strips of different sizes and vacuum bag molded into new CFRP laminates. The flexural strength and tensile strength of the newly produced CFRP laminates were about 76.38%-90.98% and 94.61%-98.54% of the original CFRP laminates, respectively. More importantly, the chemical compositions of DMAC and CEP were unchanged during the physical swelling process. No organic pollutants (caused by resin degradation) were generated. And the used DMAC can be easily recycled by filtration. Therefore, this study provides a strategy for low-cost and high-valued recycling of CFRP waste.

Gamma Radiation Induced Degradation and Leaching Behavior of Ion Exchange Resin

Objectives : The objectives of this study were to investigate gamma radiation induced degradation and leaching behavior of nuclide and/or organic complexing agent adsorbed ion exchange resin.Methods : Cation exchange resin (IRN 77) and anion exchange resin (IRN 78) widely used in nuclear power plants were purchased. Cobalt ion and EDTA were used to represent nuclide and organic complexing agent adsorbed to ion exchange resins. Cation and anion exchange resin adsorbed cobalt ion and/or EDTA were radiated by 60Co nuclide. The radiation dose rate was 10 kGy/hr and total doses were 0, 300, 500, and 700 kGy.Results and Discussion : The sulfone and quaternary ammonium functional groups of gamma radiated ion exchange resin were degraded, indicating nuclide/organic complexing agent would be leached from ion exchange resin. It was shown that degradation of anion exchange resin was worse than that of cation exchange resin. While the high concentrations of cobalt ion and organic matter were observed in leachate from anion exchange resin, those in leachate from cation exchange resin were very low. For mixed cation and anion exchange resin, the leaching behavior of mixed resin was improved. This shows that disposal in the form of a mixed ion exchange resin was evaluated as a safer method than that of a cation or anion exchange resin alone.Conclusion : The adsorbed nuclide and organic complexing agent were leached from ion exchange resin by gamma irradiation. The leaching behavior of cation and anion exchange resin was improved by using mixed ion exchange resin.

A maddock mixer design that mitigates gels in polyethylene resin film applications

Maddock mixers are ubiquitous in plastics processing for single-screw extruders and injection molding plasticators due to their low cost to build and their ability to provide a uniform level of dispersive mixing. If the mixer is designed properly, all entering solid polymer fragments and certain types of gels can be trapped and dispersed into the matrix resin. Many mixers that are used commercially, however, provide lower levels of dispersive stress mixing than required by the process and they can degrade polyethylene (PE) resins. This paper will describe the mechanisms that are occurring in a Maddock mixer and develop guidelines for obtaining optimal mixing stresses while mitigating resin degradation.

Recovery of Lead (II) Ions from Aqueous Solutions Using G-26 and MTS9570 Resins with Sulfonic/Phosphonic Functional Groups

This study presents Pb(II) recovery/removal from water solutions using two different commercial ion-exchange resins, i.e., Dowex G-26 with sulfonic functional group and Puromet™ MTS9570 with sulfonic and phosphonic functional groups. Overall, 100% Pb(II) recovery/removal by both resins was obtained at solution pH 3.5, resin dosage 25 g/L, adsorption time 30 min, room temperature, and initial Pb(II) concentration 1000 mg/L. Langmuir, Freundlich, and Temkin isotherms were used to model the experimental data. The mechanism of the adsorption process was investigated using kinetic and thermodynamic models. The experimental data fitted very well with the pseudo-second-order kinetic model, and thermodynamic analysis showed that the adsorption of Pb(II) from acidic solution onto both resins was a spontaneous and endothermic process in nature. Regeneration of the resins loaded with lead ions was tested for three cycles to evaluate the resin recyclability. Good stability of G-26 and performance degradation of MTS9570 resin was observed.

Reliability Behavior of A Resin-Free Nanosilver Paste at Ultra-Low Temperature of 180°C

• Large-area (20 × 20 mm 2 ) bonding successfully achieved by a trimodal particle system • The resin-free trimodal paste could sintered under ultra-low temperature of 180°C • Excellent thermo-mechanical reliability was achieved by proposed resin-free paste In this paper, excellent thermo-mechanical reliability of resin-free silver sintering for large-area (20 × 20 mm 2 ) bonding was successfully achieved by using a trimodal particle system composed of nano-, submicron-, and micron-sized Ag particles. After 1000 cycles of the thermal shock (TS) test, the transient thermal impedance ( Z th ) increase of the proposed resin-free silver paste sintered at 180°C under 2 MPa and 5 MPa is only 5.8% and 6.1%, respectively. Due to the avoidance of resin degradation, the obtained resin-free silver paste as-sintered under 5 MPa exhibt outstanding shear strength (>12.5 MPa) even after 1000 cycles TS test. The obtained cross-sectional microstructure can confirms the excellent thermo-mechanical reliability of the sintered resin-free silver paste, which exhibits a denser and more homogeneous bonding layer with a porosity as low as 12.5%. Furthermore, distinct indications of plastic flow can be observed on the fracture surfaces of corresponding joints before and after aging, which further confirm the superiority of proposed resin-free sintering method. The development of novel resin-free silver paste successfully promotes the thermo-mechanical reliability of silicon carbide (SiC) power devices at a low processing temperature of 180°C, and greatly benefits the practical application of SiC power devices.

Catalytic Activity of Nickel and Iron Sulfides in the Degradation of Resins and Asphaltenes of High-Viscosity Oil in the Presence of Carbonate Rock Under Hydrothermal Conditions

Catalytic Activity of Nickel and Iron Sulfides in the Degradation of Resins and Asphaltenes of High-Viscosity Oil in the Presence of Carbonate Rock Under Hydrothermal Conditions

Accelerated weathering of Compreg with phenol-formaldehyde resin treated top veneers of European white oak (Quercus ssp., L.) and teak (Tectonia grandis, L.F.)

The weather resistance of Compreg surfaces depends on various factors, such as top veneer type, impregnating resin, and protective topcoats. Artificial weathering tests were performed for the first time on material types with oak and teak top veneer surfaces. Both showed strong surface brightening due to resin degradation and subsequent photobleaching of the exposed veneer surface. Directly pressed, phenolic resin-impregnated cellulose paper overlays caused significant surface stabilization.