Removal Of Resin Research Articles

Shaping ability of ProTaper Gold and WaveOne Gold nickel-titanium rotary instruments in simulated S-shaped root canals

Background/purposeGold metal technology improves flexibility and the resistance to cyclic fatigue of the endodontic mechanical files. This study compared the performance of ProTaper Gold (PTG) multiple file system and WaveOne Gold (WOG) single file system in simulated S-shaped root canals, which represents one of the most challenging root canal morphology. Materials and methodsForty S-shaped canals (n = 20 canals/per group) in resin blocks were instrumented to an apical size of 0.25 mm using PTG and WOG Primary, respectively. The total amount of resin removal, canal transportation, centering ratio, and the degree of canal straightening were measured in Photoshop CS6 software. Statistical analysis was performed by using Mann–Whitney U-test (α = .05). ResultsNone of the files fractured during the instrumentation. The WOG group removed significantly less amount of resin at 0, 3, 6, 7 and 9 mm from the apex (P < .05). The WOG group remained more centered in canals at 0 mm from the apex (P < .05). The PTG group showed a better centering ability and less canal transportation at 4, 5 and 6 mm from the apex (P < .05). In the coronal curvature portion, the use of WOG Primary significantly decreased curvature angle and increased radius compared with PTG instruments (P < .05). There was no significant difference between the two groups in terms of the apical curvature angle and radius change (P > .05). ConclusionThe WOG Primary file has a less aggressive dentin cutting and more centered apical preparation. The PTG system is more advantageous in shaping the coronal curvature of S-shaped canal.

Shaping ability of three nickel-titanium rotary instruments in simulated L-shaped canals: OneShape, Hero Shaper, and Revo-S

BackgroundShaping ability of a file plays an important role during instrumentation in an endodontic treatment. This study aimed to compare the shaping ability of OneShape (OS), Hero Shaper (HS), and Revo-S (RS) instruments in simulated L-shaped canals.MethodsForty-eight simulated L-shaped canals were prepared to an apical size of 25 using OS, HS, and RS (all from Micro-Mega SA, Besançon, France), (n = 16 canals/group) systems. The amount of resin removed after each canal's preparation was measured and compared after producing a composite image made from the superimposition of pre and post-instrumented canals. Canal aberrations and the preparation time were also recorded. The data were statistically analysed by using ANOVA, Tukey, and Chi-square tests.ResultsOne file fractured during instrumentation in the RS group. A significant difference was found at the apical end of the prepared simulated canal between the groups, with RS showing the least amount of resin removal from the inner side of the canals and HS showing the highest amount of resin removal from the outer side (P < 0.05). Regarding the total width of the canals after preparation, a significant difference was found between the groups at the apical end and the straight portion of the canals, and RS removed the least amount of resin at the straight portion of the canals (P < 0.05). No statistically significant differences were found between the different instruments regarding canal aberrations' incidence (P > 0.05).ConclusionsAll of the files showed a tendency to straighten the canals, whereas OS files maintained the original canal curvatures well.

Effect of different resin removal methods on enamel after metal and ceramic bracket debonding : An in vitro micro-computed tomography study.

The aim of this study was to conduct an in vitro evaluation of the effects of different adhesive debonding and polishing techniques performed after metal and ceramic bracket removal on enamel using micro-computed tomography (micro-CT). This study was performed on 42 extracted maxillary first premolars divided into 2main groups and 6subgroups as follows: metal (group1) or ceramic (group2) brackets were bonded to the teeth, then, after debonding, one of three different methods was used to remove the residual adhesive: tungsten carbide burs with pumice(A), fiber-reinforced composite burs and polishing paste(B), or Sof-Lex discs(C; 3M Dental, St Paul, MN, USA). The samples were evaluated by micro-CT before bracket bonding (T0) and after resin removal (T1). Demineralization area, demineralization depth, demineralization volume, mineral density, and mineral volume were measured. At T1, demineralization area was significantly larger in groups1A and2A compared to groups1B, 1C, 2B, and2C (P = 0.001). Group2A (ceramic bracket/tungsten carbide-pumice) had the highest demineralization volume (P = 0.001). When the groups were compared in terms of change from T0 to T1, groups1A and2A showed significantly larger changes in demineralization area compared to the other 4groups (P = 0.001). The increase in demineralization volume was larger in group2A compared to all other groups (P = 0.001). All resin removal methods damaged the enamel surface to varying degrees. Regardless of bracket type, the use of tungsten carbide and pumice should be avoided when cleaning the tooth surface after debonding. Use of composite burs and Sof-Lex discs in particular after the debonding of ceramic brackets will help minimize damage.

In situ impregnation of continuous thermoplastic composite prepreg for additive manufacturing and automated fiber placement

Components made from thermoplastic composites (TPC) by additive manufacturing (AM) and automated fiber placement (AFP) are gaining popularity because of the material system’s inherent advantages over thermosets, but high material costs and limited production flexibility are hindering more widespread use. This paper discusses prototyping, fluid flow modeling, and testing of a novel in situ preimpregnator (prepregger) for lower-cost TPC feedstock used in AM and AFP. Prior attempts by researchers to address this technical need have generally resulted in low-quality prepreg with low fiber volume fraction (Vf) and high void content, which can be explained by Darcy’s law applied to the highly viscous polymer melts. Uniformly spreading the fiber tow thin before impregnation is the key to rapid and complete impregnation. Based on initial experiments with a flexible experimental setup to quickly test concepts, a prototype prepregger consisting of dry fiber payout reel with slight torsional resistance, fixed pin fiber spreader, double slot die coater fed with polymer melt from a microextruder, consolidator with pultrusion exit die, and prepreg downstream drive mechanism was designed and built. Predictions from a steady-state flow model of the coating die/microextruder system assuming creeping flow and Newtonian fluid behavior agreed well with experimental flow measurements for a variety of polymer melts and operating conditions. Once ideal input parameters were determined, prepreg tape specimens exhibited complete impregnation but low Vf and excessive encapsulation due to insufficient consolidation and removal of excess resin. Experiments where pultrusion dies were used for filament manufacturing showed significantly improved Vf and prepreg quality. Future work is suggested to facilitate commercialization of this promising process technology.

Pyrolysis of heavy hydrocarbons in weathered petroleum-contaminated soil enhanced with inexpensive additives at low temperatures

Pyrolysis is a promising technology for the remediation of soil contaminated with petroleum hydrocarbons. However, for weathered petroleum-contaminated soil (WPCS) with massive recalcitrant heavy hydrocarbons, pyrolysis still has the drawback of high energy consumption. To reduce energy consumption, commonly used inexpensive additives, including Fe2O3, Al2O3, K2CO3, CaO, HZSM-5, and red mud, were selected to strengthen the pyrolysis of heavy hydrocarbons in WPCS. The removal of the total petroleum hydrocarbon (TPH) content from WPCS increased as the dosage of additives increased from 1% to 5% at 400 °C for 30 min, and increased slightly or even decreased when the additive dosage was further increased to 10%. The reduction rates of the TPH content in soil treated with 5% additives of K2CO3, CaO, Fe2O3, red mud, HZSM-5, and Al2O3 increased by 26.16%, 25.65%, 25.53%, 23.93%, 23.15%, and 20.75%, respectively. Among these additives, CaO exhibited the best performance for the removal of aromatics (73.00%) and asphaltenes (72.44%), while Fe2O3 exhibited the best performance for the removal of resins (52.25%). The removal mechanisms of heavy hydrocarbons using additives during WPCS pyrolysis were proposed based on a combination of thermogravimetric analysis and the iso-conversional Flynn–Wall–Ozawa method. The reduction in the activation energy when additives were included during WPCS pyrolysis was closely related to whether the additives participated in the reaction and to the type of pyrolysis product. The soil characterization results demonstrated that the investigated additives would not severely impact further soil cultivation. The additive-assisted pyrolysis of WPCS is expected to reduce the required energy input by 34.71% compared to the traditional pyrolysis method, thus providing an energy-efficient and cost-effective method for treating petroleum-contaminated soil in future engineering applications.

Electrochemical determination of boron using the signal suppression of mannitol on a gold nanoparticle coated p-Aminothiophenol polymer electrode

In this study, a glassy carbon electrode (GCE) modified with gold nanoparticles (AuNPs) and coated with electropolymerized p-aminothiophenol (p-ATP) was used as a modified electrode (GC/AuNPs/PATP electrode) for the indirect electrochemical determination of boron (B) using boric acid-mannitol complexation. The developed electrode showed good electroactivity for B determination. Firstly the current intensity of mannitol was measured, then B (as H3BO3) was added to the medium and the unreacted mannitol was measured. The decrement in current intensity was recorded against B concentration to build linear calibration curves within the range of 5–50 mg L−1 of B using square wave voltammetry (SWV), and the oxidation peak potential of mannitol was observed at 0.97 V. The limit of detection (LOD) and limit of quantification (LOQ) were 1.43 mg L−1 and 4.77 mg L−1, respectively. Boron (5 mg L−1) was determined with quantitative recovery in the presence of 100-fold concentration (except 5-fold for Fe3+) levels of the potentially interferent ions (Cl−, SO42−, HCO3−, CO32−, NO32−, PO43−, NH4+, Cu2+, Mg2+, Ca2+, Na+, K+, Fe3+) in water using the proposed SWV method. Fe3+ and Cu2+ interferences could be overcome with cation exchange resin removal. Additionally, boron was determined in synthetic and real seawater samples. The proposed SWV method was statistically validated against the spectrophotometric carmine method using seawater, antibacterial hand sanitizer gel and boron/potassium nitrate (BPN) pyrotechnic formulation.

Influence of manufacturing parameters on the mechanical properties of nano-reinforced CFRP by carbon nanofibers

One of the most relevant problems of nano-reinforced resins is the uniform dispersion of nanoparticles. This problem is even more relevant when they are involved in the production of laminated composites. In this case, in addition to the agglomeration of nanoparticles, air bubbles are also very frequent during the manufacturing process of laminated composites with nano-reinforced resins. These air bubbles are even more frequent in the manual lay-up process. In this context, this study intends to study some manufacture parameters in order to maximize the mechanical properties. For this purpose, the mixer rotation speed, the dispersion time of the nanoparticles and the vacuum time applied to the system were analyzed in detail. It was found that the mixing time is very dependent on the rotation speed used and there is an ideal vacuum time. A short vacuum time allows air bubbles to exist in the resin, while a long time promotes a decrease in mechanical properties due to the removal of resin in the laminates and, consequently, the fibers are not fully wet.

Endodontic guide for the conservative removal of a fiber-reinforced composite resin post

Prosthetic dentistry involves functional and esthetic restoration. Some situations require the use of fiber-reinforced composite resin posts that help preserve restorations. However, if the initial treatment fails, a new endodontic intervention may be required for fiber-reinforced composite resin post removal. This procedure can be complex and challenging but can be facilitated with guided endodontics. This clinical report describes the use of a prototyped guide created with virtual planning for fiber-reinforced composite resin post removal. The guide improved patient safety, shortened the treatment time, and eliminated the need for a new restoration.

Особенности солюбилизирующего действия амфифильных соединений при обессмоливании целлюлозы

The necessity to improve the existing technology of pulp deresination, in particular, to reduce the surfactants consumption and decrease the environmental load, led to a combination of existing methods of resin removal with the use of enzymatic treatment. The basis of the pulp deresination mechanism by amphiphilic compounds is the solubilization of resinous substances. Thus, the establishment of the patterns of this process and its control predetermines the success of implementation of the selected technology. The features of solubilization of triolein and rosin in the lipase-based systems of individual nonionic surfactants, the enzyme, as well as their synergistic mixtures with the determination of solubilization capacities of micelles and the possible mechanism of solubilizate incorporation into them were studied using spectrophotometry, pH measurement and dynamic light scattering. It was found that synthamide-5 has a low deresination capability in spite of the high solubilization capacity of its micelles and the production of aggregates with a hydrodynamic radius up to 98 nm after diffusion of rosin into them. It is likely that compact micellar structures with a developed surface, which are implemented in mixed systems of amphiphilic compounds, including the presence of synthamide-5 in them, are more preferable for successful deresination of pulp semi-finished products. The addition of lipase leads to an increased solubilization capacity of mixed aggregates and an increase in the intensity of solubilizate molecules incorporation. Thus, depending on the nature of the amphiphilic compound, there is a different mechanism for solubilizate incorporation into micelles. Determination of the size of associates in mixed systems showed the absence of enzyme denaturation, which predicts the successful application of such cooperative systems for deresination of fiber semi-finished products. It is found that the solubilizing capability of the studied systems on resin modeling objects correlates with their deresination capability with respect to different fiber semi-finished products.

Cyclic fatigue resistance and shaping ability of heat-treated nickel-titanium instruments after repeated use.

To evaluate the effect of multiple-use and sterilization on cyclic fatigue and shaping ability of heat-treated nickel-titanium (NiTi) rotary instruments. A total of 120 acrylic blocks with S-shaped canals were photographed and prepared by HyFlex CM, ProTaper Next, and Twisted File. Ten new sets of each rotary instruments were used for four times. The autoclaving process was repeated after each use. Pre- and post instrumentation images were superimposed. The amount of resin removal and canal transportation by each system was measured in eleven different points. Instruments were subsequently subjected to a cyclic fatigue test in a double-curved artificial canal. The means and standard deviations of the number of cycles to failure (NCF) were calculated and statistically analyzed (P < 0.05). No fractures occurred during the shaping of the simulated canals. The ProTaper Next removed the greatest amount of resin, whereas the Twisted File had the lowest values at all levels. Repeated clinical use and sterilization resulted in a decrease in the resin removal at most levels in Twisted File and ProTaper Next. In terms of canal transportation, an increase in a limited number of levels was detected after repeated use of all rotary files. Twisted File had the greatest cyclic fatigue resistance, followed by HyFlex CM and ProTaper Next (P < 0.05). The effects of repeated use and autoclaving on the cyclic fatigue resistance of HyFlex CM, ProTaper Next, and Twisted File were not significant. Canal transportation increased mostly in the apical region. The amount of resin removal decreased as the number of use increased for ProTaper Next and Twisted File instruments.

The Removal of Cured Urea-Formaldehyde Adhesive towards Sustainable Medium Density Fiberboard Production: A Review

Medium density fiberboard (MDF) is an engineered wood product that has density and specific gravity similar to solid wood, ranging from 600 to 800 kg/m3 of density and 0.6 to 0.8 of specific gravity. This makes MDF suitable to partially replace solid wood, particularly for interior application. Approximately over than 100 million m3 of MDF are produced in 2020, resulting in a large amount of waste MDF will be generated in the next 20 years. MDF is produced using urea-formaldehyde (UF) resins adhesive. UF resins adhesive is a poly-condensation product of urea and formaldehyde via an alkaline acid two-step reaction. Sustainable MDF production is required as the world is facing climate change and deforestation. Recycling is a way to support sustainable production in the engineered wood products manufacturing. Many attempts have been done to find ways to recycle waste MDF. The main problem is UF resins, which bond the MDF panel fibers. In order to re-manufacture the waste MDF into new recycled MDF, UF resins should be eliminated from the waste MDF before being used. The presence of UF resins in MDF can interfere with the utilization of the recycled fibers, whether it will be used as a raw material for new MDF or other composite products. This paper reviews the process of removal of cured UF resins from waste MDF panel by considering the hydrolytic stability of cured UF resins for MDF recycling, providing a comprehensive review of how cured UF resins can be removed from waste MDF and characterization of recycled fibers obtained from recycling prior to re-manufacturing of recycled MDF panel.Keywords: hydrolysis, medium density fiberboard, resin, recycling, resin removal, urea-formaldehyde

Method to fabricate porous multifunction β-cyclodextrin modified resin for ultrafast and efficient removal of Cu(II) and bisphenol A

Herein, a simple and green method to fabricate β-cyclodextrin (β-CD) porous cross-linked polymer modified poly(chloromethylstyrene) (PS-Cl) resin, namely, PS@CM-CDP, for ultrafast and efficient removal of heavy metal ions and organic pollutants from aqueous solution was reported. The selected (PS-Cl) was used as a matrix; meanwhile, the β-CD was formed on the surface of PS-Cl under a rigid cross-linking agent of tetrafluoroterephthalonitrile nitrile. The structure and surface elements distribution of PS@CM-CDP were characterized using FT-IR, TG, SEM, XPS, and BET. The resultant PS@CM-CDP with a relatively high maximum adsorption capacity for Cu(II) and BPA can reach 121.88 and 8.25 mg g−1, respectively, and the spherical nature of the resin makes conventional β-CD polymers easy to recycle 6 times without significantly decreased. The possible adsorption mechanism was also proposed. Industrial wastewater adsorption methods have been used into practice, and the practice presents considerable prospects in the aspects of column for water treatment.

Cobalt-loaded resin can effectively remove arsenic in wastewater

Most current arsenic(As(V)) removal technologies are designed for low-As(V) wastewater. Consequently, the efficacy of treating high-As(V) wastewater with these technologies is generally unsatisfactory. Here, the Cobalt(Co)-loaded resin removal of As(V) in wastewater and its mechanism are discussed. Rapid adsorption and a slow equilibrium were achieved during the reaction, and the As(V) removal efficiency exceeded 99% within 0–30 min with an initial As(V) concentration of 100 mg/L. The adsorption capacity of the Co-loaded resin was as high as 116 mg/g. The Co-loaded resin has the best As(V) removal efficiency when the pH = 8. The adsorption kinetics of the Co-loaded resin material revealed the adsorption behavior. FTIR and XPS studies showed that As(V) was removed on the Co-loaded resin material, and As(V) was primarily removal through ion exchange adsorption and chemical co-precipitation. Thus, this Co-loaded resin material provides a simple and effective means to remove As(V) from high-As(V) wastewater.

Influence of debinding and sintering conditions on the composition and thermal conductivity of copper parts printed from highly loaded photocurable formulations

Metal 3D printing based on the photopolymerization reaction (Digital Light Processing—DLP) of an organic matrix in which metal particles are embedded is a developing technology. This technology requires a step of resin removal and densification by sintering to obtain a metal part. This process has been applied to copper. Photocurable formulations with a high loading rate of copper powder of 60 vol.% were developed and suitable for DLP printing with thicknesses > 25 µm. Debinding and sintering cycles were investigated on specimens fast cured by gamma irradiation to save materials and time. A debinding in air at 400 °C and sintering in hydrogen lead to a C content of 0.018 wt.%, similar to the raw copper powder and slightly higher oxygen content. The low thermal conductivity of 250 W·m−1·K−1 highlighted the harmful effect of phosphorus from the powder and photoinitiators such as BAPO. The C and O contents and the thermal conductivity measured on copper parts printed by DLP confirm the results obtained on specimens cured by gamma irradiation.

Comparison of the enamel surface roughness before bonding and after debonding by diamond, tungsten carbide and fiber reinforced composite burs under AFM an in-vitro study

Introduction: The bonding of orthodontic attachments directly to etched enamel surface is an example of clinical application of a simplified procedure. With modifications of the acid etch technique and resin systems, the removal of the directly bonded attachments and finishing of the underlying enamel have become an acute clinical problem. Aims and Objectives: To evaluate the enamel surface roughness observed under atomic force microscope (AFM) in following methods: 1. Before bonding; 2. Removal of residual resin after debonding with 3 different burs. Fine diamond bur Tungsten carbide bur Fiber reinforced composite bur Materials and Methods: Sixty premolar teeth were divided into 3 equal groups and the buccal surface were subjected to AFM to obtain Ra, Rq, Rmax initial roughness values. The brackets were bonded with a light-cured adhesive and debonded with posterior debonding plier. Residual resin was removed with different burs in 3 groups respectively and subjected to final AFM measurements. Results of roughness were analysed with the use of repeated measurement analysis of variance and independent t-test respectively. Results: It was found out that parametric values were statistically insignificant with P value >0.001 in prebond condition & statistically significant after resin removal with P value Conclusion: Fiber reinforced composite bur created smoother surface after debonding when compared to diamond and tungsten carbide bur. Keyword: Fine diamond bur, Tungsten carbide bur, Fiber reinforced composite bur, Residual resin, AFM.

Impact of household vinegar on calculus removal and mechanical properties of orthodontic resin.

This study evaluated calculus removal efficacy of household vinegar and its effect on autopolymerizing orthodontic resin following repeated immersion. A total of 72sectioned specimens of orthodontic retainers with calculus deposits following cleaning with the help of immersion in vinegar of different dilutions between 12.5% and 100%, tap water, effervescent tablets, and mechanical debridement were digitally analyzed. Changes in Ca and Fe ions in vinegar were assessed by atomic emission spectroscopy (AES). For mechanical testing, autopolymerizing polymethyl methacrylate (PMMA) samples were similarly grouped and immersed for 78cycles and their flexural strength and hardness measured. Fourier-transform infrared spectroscopy (FTIR) was performed to evaluate changes in their chemical composition. One-way analysis of variance (ANOVA) and Tukey's test were used to analyze the differences in the mean flexural strength and hardness between the groups (p ≤ 0.05). Aminimum immersion of 2 h in 25% vinegar solution combined with brushing attained efficiency of 74.13 ± 22% calculus removal. Whereas, tap water and effervescent tablets had 15% and 49% efficiency, respectively. AES results showed diffusion of Ca ions from calculus into the vinegar solution as aplausible mechanism for its structural weakening and removal. Results of mechanical testing showed that undiluted vinegar solution affected the flexural strength of PMMA and this effect was significantly different from that of the effervescent tablets and the remaining vinegar concentrations. There was no significant difference in hardness between the groups. The FTIR showed no changes in the chemical composition of PMMA samples following repeated immersions. Vinegar can be useful in the removal of calculus from dental appliances but should be used in diluted forms to minimize side effects.

Tooth color alteration after debonding in orthodontic patients with adhesive removal using composite bur or tungsten carbide bur: a single center, randomized controlled clinical trial

Introduction: The objective of this study was to determine whether recently developed fiber reinforced composite burs provided better results by comparing tooth discoloration after debonding of orthodontic brackets.Methods: A split-mouth, randomized controlled trial was carried out in one orthodontic office; including 23 patients with intact, vital and caries-free four upper incisors aged 12 to 30 years who completed their fixed orthodontic treatment. For each patient, upper central and lateral incisors on each side of the mouth were randomly selected to remove the adhesive with either a tungsten carbide bur (TC) (n = 46) or a fiber-reinforced composite bur (FC) (n=46). Color evaluation of each tooth was conducted at two time points: immediately after finishing and polishing procedure and two months afterwards. The primary outcome would be the amount of color change in each group during the post treatment phase. The participants, the person assessing the color change and the statistician were blinded to TC group assignment. Color changes in each group were analyzed with the Paired T-test. The color change corresponding to the resin removal method was also statistically analyzed with the Independent T-test at ?=0.05 as the level of significance.Results: 86 teeth, 43 in each group, were analyzed. The ?E value was 3.713±1.161, for teeth finished TC and 2.114±0.514 for teeth finished with FC (p&lt;0.01).Conclusion: adhesive removal with FC bur results in a more color-resistant tooth surface in comparison with tungsten carbide bur.

Effectiveness of the static-guided endodontic technique for accessing the root canal through MTA and its effect on fracture strength.

(1) To evaluate the effectiveness of the static-guided (SG) endodontics technique for accessing the root canal through the mineral trioxide aggregate (MTA) and (2) to evaluate the effect of this technique on the fracture strength of teeth. Thirty mandibular premolars were used in the present study. After standard coronal access cavity preparation, root canals were prepared up to size #80 to simulate an immature root apex. White MTA was placed approximately 3 mm below the cementoenamel junction (CEJ), as placed in regenerative endodontic procedures. After the MTA had set, the cavity was restored with a resin composite material. The teeth were randomly divided into two groups (n = 15). In the control group, the composite resin and MTA were removed without any guide. In the SG-access group, a cone beam computed tomography (CBCT) scan was performed, 3D-printed guides were designed and fabricated, and then the composite resin and MTA were removed with a guide. One inexperienced operator performed the removal of the composite resin and MTA in all groups. Pre- and post-operative periapical radiographs were taken. The mishaps and time to penetration to root canal were recorded. After that, the root canals were filled, and the access cavities were restored. The samples were subjected to a fracture strength test. Data were analyzed using Mann-Whitney U, independent samples of T test, and chi-square tests at 95% confidence level (P = 0.05). There were significant differences between the control and SG-access groups in terms of mishaps and time to penetration to the root canal through the MTA barrier (P < 0.05). The SG-access group required the shorter time as compared with the control group. Mishaps did not occur in the SG-access group. The SG-access group exhibited the significantly preserved fracture resistance of the teeth as compared with the control group (P < 0.05). Non-restorable failure occurred more frequently in the control group than in the SG-access group. Within the limitations of the present study, the SG endodontic technique yielded favorable results with respect to time, mishaps, and fracture strength. The static-guided endodontics technique may provide advantages to the clinician for MTA removal.

Epoxy Resin Removal Technique in Cross-section Cuts for SEM

Epoxy Resin Removal Technique in Cross-section Cuts for SEM

Application of pyrolysis to remove hydrogen from an organic nuclear waste

The work deals with the removal by slow pyrolysis of epoxy resin from samples of spent nuclear fuel embedded in this polymer. Beyond the nuclear field, epoxy resin removal by pyrolysis is a typical issue for the recovery of metals in electronic waste. The main objective is to find the optimal conditions to remove hydrogen in the residual solid waste, in order to avoid hydrogen production by radiolysis during storage and so to prevent any risk of overpressure and explosion. The condensable pyrolysis products (tar-water mixture) and the char were characterised and quantified by elemental analyses, while the permanent gases were quantified by gas chromatography. A data reconciliation method was applied to adjust the values of raw measurements in order to complete the mass balances for both C, H, O and N elements and pyrolysis products. After studying the impact of temperature on the pyrolysis balance, experiments on a pilot furnace were conducted at 450 °C, in the frame of a parametric study of the heating rate, argon gas flow rate, resin mass and plateau time. At fixed temperature, we show that the plateau time is the only significant parameter for minimizing the residual hydrogen content in the char.