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At least 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

High Temperature Anode Recycle Blower for Solid Oxide Fuel Cell, Phase II (Final Report)

Broad commercialization of solid oxide fuel cells (SOFCs) requires anode offgas recycle blowers (ARCB) that are specifically designed for handling the challenging operating conditions presented by the SOFC process gases. Otherwise, they can be susceptible to frequent maintenance, low reliability, and short life. This report presents details of a DOE-funded Phase II effort conducted by Mohawk Innovative Technology, Inc. (MiTi®) for the development and testing of an oil-free, low cost, high-temperature centrifugal ARCB based on compliant foil bearing (CFB) technology for support of a 100 kW solid oxide fuel cell power plant. This Phase II builds on the results of a successful Phase I development project that resulted in the demonstration of a low TRL-6 prototype, shown in Figure 1. This Phase II final report presents design improvements over the Phase I prototype, presents the assembled test ARCBs, and discusses the advantages of this novel technology, particularly its long life and maintenance-free operation, which are derived from the use of CFBs. Also included are preliminary techno-economic analysis considerations for cost-effective deployment of the technology. The specific objectives of this project, as stated in the statement of program objectives (SOPO) were 1) to follow the methodology of design for manufacturing (or manufacturability) and assembly for implementing improvements identified as part of the Phase I effort with the purpose of reducing cost, enabling mass production, and facilitating the commercialization of a revised ARCB design, and 2) to fabricate four complete ARCB units based on the revised design and demonstrating their performance in both a laboratory setting and in an actual SOFC power plant. Execution of this SOPO would be supported by a number of technical tasks resulting in the fabrication and testing of the prototypes. To this end, MiTi continued the teaming relationship started during Phase I of the program with subcontracting partner FuelCell Energy, Inc. (FCE), which integrated (under a parallel effort funded by DOE Award DE-FE0026199) a modular 200 kWe SOFC power plant. MiTi and FCE coordinated to ultimately incorporate one of MiTi’s ARCB prototypes into one of the 100 kWe SOFC Modular Power Blocks (MPB) that constitute the core of FCE’s SOFC power plant for in-situ long-duration testing. Additionally, MiTi would explore the scalability and extendibility of the technology to other applications, as well as conduct a basic techno-economic analysis.

03 NATURAL GAS↗
DOE OSTI2013

Improving the Estimates of Waste from the Recycling of Used Nuclear Fuel - 13410

Estimates are presented of wastes arising from the reprocessing of 50 GWD/tonne, 5 year and 50 year cooled used nuclear fuel (UNF) from Light Water Reactors (LWRs), using the 'NUEX' solvent extraction process. NUEX is a fourth generation aqueous based reprocessing system, comprising shearing and dissolution in nitric acid of the UNF, separation of uranium and mixed uranium-plutonium using solvent extraction in a development of the PUREX process using tri-n-butyl phosphate in a kerosene diluent, purification of the plutonium and uranium-plutonium products, and conversion of them to uranium trioxide and mixed uranium-plutonium dioxides respectively. These products are suitable for use as new LWR uranium oxide and mixed oxide fuel, respectively. Each unit process is described and the wastes that it produces are identified and quantified. Quantification of the process wastes was achieved by use of a detailed process model developed using the Aspen Custom Modeler suite of software and based on both first principles equilibrium and rate data, plus practical experience and data from the industrial scale Thermal Oxide Reprocessing Plant (THORP) at the Sellafield nuclear site in the United Kingdom. By feeding this model with the known concentrations of all species in the incoming UNF, the species and their concentrations in all product and waste streams were produced as the output. By using these data, along with a defined set of assumptions, including regulatory requirements, it was possible to calculate the waste forms, their radioactivities, volumes and quantities. Quantification of secondary wastes, such as plant maintenance, housekeeping and clean-up wastes, was achieved by reviewing actual operating experience from THORP during its hot operation from 1994 to the present time. This work was carried out under a contract from the United States Department of Energy (DOE) and, so as to enable DOE to make valid comparisons with other similar work, a number of assumptions were agreed. These include an assumed reprocessing capacity of 800 tonnes per year, the requirement to remove as waste forms the volatile fission products carbon-14, iodine-129, krypton-85, tritium and ruthenium-106, the restriction of discharge of any water from the facility unless it meets US Environmental Protection Agency drinking water standards, no intentional blending of wastes to lower their classification, and the requirement for the recovered uranium to be sufficiently free from fission products and neutron-absorbing species to allow it to be re-enriched and recycled as nuclear fuel. The results from this work showed that over 99.9% of the radioactivity in the UNF can be concentrated via reprocessing into a fission-product-containing vitrified product, bottles of compressed krypton storage and a cement grout containing the tritium, that together have a volume of only about one eighth the volume of the original UNF. The other waste forms have larger volumes than the original UNF but contain only the remaining 0.1% of the radioactivity. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2013

Analysis of fuel options for the breakeven core configuration of the Advanced Recycling Reactor

A trade-off study is performed to determine the impacts of various fuel forms on the core design and core physics characteristics of the sodium-cooled Toshiba- Westinghouse Advanced Recycling Reactor (ARR). The fuel forms include oxide, nitride, and metallic forms of U and Th. The ARR core configuration is redesigned with driver and blanket regions in order to achieve breakeven fissile breeding performance with the various fuel types. State-of-the-art core physics tools are used for the analyses. In addition, a quasi-static reactivity balance approach is used for a preliminary comparison of the inherent safety performances of the various fuel options. Thorium-fueled cores exhibit lower breeding ratios and require larger blankets compared to the U-fueled cores, which is detrimental to core compactness and increases reprocessing and manufacturing requirements. The Th cores also exhibit higher reactivity swings through each cycle, which penalizes reactivity control and increases the number of control rods required. On the other hand, using Th leads to drastic reductions in void and coolant expansion coefficients of reactivity, with the potential for enhancing inherent core safety. Among the U-fueled ARR cores, metallic and nitride fuels result in higher breeding ratios due to their higher heavy metal densities. On the other hand, oxide fuels provide a softer spectrum, which increases the Doppler effect and reduces the positive sodium void worth. A lower fuel temperature is obtained with the metallic and nitride fuels due to their higher thermal conductivities and compatibility with sodium bonds. This is especially beneficial from an inherent safety point of view since it facilitates the reactor cool-down during loss of power removal transients. The advantages in terms of inherent safety of nitride and metallic fuels are maintained when using Th fuel. However, there is a lower relative increase in heavy metal density and in breeding ratio going from oxide to metallic or nitride Th fuels relative to the U counterpart fuels. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2012

Treatment of Radioactive Metallic Waste from Operation of Nuclear Power Plants by Melting - The German Way for a Consistent Recycling to Minimize the Quantity of Radioactive Waste from Operation and Dismantling for Disposal - 12016

During maintenance of nuclear power plants, and during their decommissioning period, a large quantity of radioactive metallic waste will accrue. On the other hand the capacity for final disposal of radioactive waste in Germany is limited as well as that in the US. That is why all procedures related to this topic should be handled with a maximum of efficiency. The German model of consistent recycling of the radioactive metal scrap within the nuclear industry therefore also offers high capabilities for facilities in the US. The paper gives a compact overview of the impressive results of melting treatment, the current potential and further developments. Thousands of cubic metres of final disposal capacity have been saved. The highest level of efficiency and safety by combining general surface decontamination by blasting and nuclide specific decontamination by melting associated with the typical effects of homogenization. An established process - nationally and internationally recognized. Excellent connection between economy and ecology. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Rad Waste Cost/Volume Reduction Using New Monitoring/Decon Techniques, Launderable Items and Recycling - 19297

The use of improved radiation monitoring and decontamination techniques significantly reduces the cost and volume of Canadian radioactive waste via recycling/reuse. Over 2,700 metric tons of scaffolding and tooling have been released for unrestricted use back to the owners or recycled as non-radioactive scrap metal over the last 10 years. Additionally, using reusable launderable items reduces the cost over single use Radiological Personal Protective Equipment (RPPE) and plastic wraps and has eliminated thousands of cubic meters of Canadian station waste each year for over 10 years. The combined effect is the significant volume reduction of radioactive waste in a low risk, cost effective, manner. This paper and presentation will highlight the processes and showcase the types of materials decontaminated. The intent is to make waste generators aware of new processes that could be applied to the waste materials stored in their vaults or generated during a refurbishment/decommissioning project as well as day-to-day power generation operations. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Innovative Projects on RW Recycling from the French 'Investments for the Future' Program - 20023

The extent and duration of French dismantling operations require to anticipate at the earliest possible stage the management of the large volumes of radioactive waste that will be generated, and to engage collectively in sustainable innovation processes. To anticipate all constraints and requirements related to radioactive waste management and secure the long-term compatibility with waste disposals, the French State has decided to give to Andra, within the 'Investissements d'Avenir' program, an endowment to support innovation at all steps of radioactive waste life cycle with a special emphasis on the dismantling process. Currently, some 30 R and D projects dealing with the optimization of dismantling radioactive waste management are underway. They aim at providing strong innovations in terms of characterization, processing, conditioning and disposal of post dismantling radioactive waste. A specific focus will be made on those dealing with radioactive waste and radionuclides recycling. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

The Primary and Recycling Sources of OH During the NACHTT-2011 Campaign: HONO as an Important OH Primary Source in the Wintertime

We present OH observation results during the NACHTT-11 field campaign at the Boulder Atmospheric Observatory in Weld County, Colorado. The observed OH levels during the daytime (at noon) were ~ 2.7 × 106 molecules cm-3 at the ground level (2 m above ground level, AGL). HONO and ozone photolysis were the two dominant photochemical OH production pathways during the field campaign. However, alkene ozonolysis, found an important source for OH by two previous winter season OH observations, was a minor contribution to OH primary production (~5 %). To evaluate recycling sources of OH from HO2 and RO2, an observation constrained University of Washington Chemical Mechanism (UWCM) box model is employed to simulated ambient OH levels with different model scenarios. For the base run without constraining observed HONO, the model simulated OH significantly underestimates the observed OH level (20.8 times in the morning and 7.2 times in the daytime). This indicates that the known HONO sources incorporated in the UWCM model cannot explain the observed HONO level. Once HONO is constrained by the observation, the discrepancy between observation and model simulation improves (5.1 times in the morning and 2.1 times in the daytime) but still out of the measurement uncertainty range (35 %). We explore two possible reasons for the observed unexplainably high wintertime OH levels. First, potential roles of Cl atoms produce organic peroxy radicals from the reactions between Cl atmos and alkane compounds. However, the Cl levels during the observation period are estimated very low (~ 103 atoms cm-3) to explain the enhanced OH levels. Second, Impacts of higher HONO levels on the ground was evaluated. Strong HONO gradient towards ground was observed especially during the early morning (6 am to 8 am) was observed and the lowest level available for the HONO observation during the campaign is 5 m AGL. Once we assume the twice of the observed HONO levels averaged between 5 m to 15 m at 2 m AGL, model predicted OH levels agree well within the observation uncertainty range. Wintertime photochemistry has not been investigated as much as the summer season. The results of this study along with a limited number of winter OH observations clearly urge further investigation on tropospheric oxidation capacity in the winter season considering implications of tropospheric oxidation capacity to the short-lived climate forcers especially methane.

Kim, S.↗
DOE OSTI2014

Reactions Between Water Soluble Organic Acids and Nitrates in Atmospheric Aerosols: Recycling of Nitric Acid and Formation of Organic Salts

Atmospheric particles often include a complex mixture of nitrate and secondary organic materials accumulated within the same individual particles. Nitrate as an important inorganic component can be chemically formed in the atmosphere. For instance, formation of sodium nitrate (NaNO3) and calcium nitrate Ca(NO3)2 when nitrogen oxide and nitric acid (HNO3) species react with sea salt and calcite, respectively. Organic acids contribute a significant fraction of photochemically formed secondary organics that can condense on the preexisting nitrate-containing particles. Here, we present a systematic microanalysis study on chemical composition of laboratory generated particles composed of water soluble organic acids and nitrates (i.e. NaNO3 and Ca(NO3)2) investigated using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and Fourier transform infrared micro-spectroscopy (micro-FTIR). The results show that water-soluble organic acids can react with nitrates releasing gaseous HNO3 during dehydration process. These reactions are attributed to acid displacement of nitrate with weak organic acids driven by the evaporation of HNO3 into gas phase due to its relatively high volatility. The reactions result in significant nitrate depletion and formation of organic salts in mixed organic acids/nitrate particles that in turn may affect their physical and chemical properties relevant to atmospheric environment and climate. Airborne nitrate concentrations are estimated by thermodynamic calculations corresponding to various nitrate depletions in selected organic acids of atmospheric relevance. The results indicate a potential mechanism of HNO3 recycling, which may further affect concentrations of gas- and aerosol-phase species in the atmosphere and the heterogeneous reaction chemistry between them.

Aerosols↗
DOE OSTI2024

Redesigned Nylon 6 Variants with Enhanced Recyclability, Ductility, and Transparency

Abstract Geminal ( gem −) disubstitution in heterocyclic monomers is an effective strategy to enhance polymer chemical recyclability by lowering their ceiling temperatures. However, the effects of specific substitution patterns on the monomer's reactivity and the resulting polymer's properties are largely unexplored. Here we show that, by systematically installing gem ‐dimethyl groups onto ϵ‐caprolactam (monomer of nylon 6) from the α to ϵ positions, both the redesigned lactam monomer's reactivity and the resulting gem ‐nylon 6’s properties are highly sensitive to the substitution position, with the monomers ranging from non‐polymerizable to polymerizable and the gem ‐nylon properties ranging from inferior to far superior to the parent nylon 6. Remarkably, the nylon 6 with the gem ‐dimethyls substituted at the γ position is amorphous and optically transparent, with a higher T g (by 30 °C), yield stress (by 1.5 MPa), ductility (by 3×), and lower depolymerization temperature (by 60 °C) than conventional nylon 6.

Tian, Jun‐Jie↗
DOE OSTI2015

Structural evolution of recycled tire rubber in asphalt

ABSTRACT The performance of recycled‐tire‐rubber‐modified asphalt mainly depends on the structure of rubber in the asphalt. The effects of the curing temperature, mixing time, and shearing on the evolution of the chemical structure and morphological structure of crumb rubber in asphalt were investigated. The crosslink density, compositions, and morphological evolution of the residual crumb rubber were characterized. The results show that the structure evolution of tire rubber in asphalt was greatly affected by the curing temperature. At a low curing temperature (180°C), the crosslinking network of the tire rubber was broken down, and this led to the partial dissolution of natural rubber (NR). However, at high curing temperature (240°C), the dissolution of NR, synthetic rubber, carbon black, and inorganic filler was observed. The released carbon black covered with a thin layer of bound rubber dispersed at a microstructured or nanostructured size in the asphalt. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133 , 42954.

Yao, Hongru↗
DOE OSTI2020

Sustainable Direct Recycling of Lithium-Ion Batteries via Solvent Recovery of Electrode Materials

Separation of electrode materials from their current collectors is an enabling step toward recovering critical materials from spent lithium-ion batteries. In this study, a highly efficient, cost-effective, and environmentally sustainable separation process was developed for that purpose. Ethylene glycol, a vital commodity chemical as an antifreeze and polymer precursor, is used to delaminate electrode materials at low temperatures in seconds without altering the crystalline structure and morphology of active electrode materials. The recovered current collectors were intact without any corrosion. The authors also found that the solvent could be continuously reused, leading to the development of a closed-loop ecosystem and lithium-ion battery circular economy. The ultrafast delamination was driven by the competitive inhibition of binding through the weakening of hydrogen bonding. The ethylene glycol-based separation is a sustainable electrode recovery process that paves the way for battery recycling.

25 ENERGY STORAGE↗
DOE OSTI2021

Reducing Antisolvent Use in the STRAP Process by Enabling a Temperature–Controlled Polymer Dissolution and Precipitation for the Recycling of Multilayer Plastic Films

The recently reported processing strategy called solvent-targeted recovery and precipitation (STRAP) enables deconstruction of multilayer plastic packaging films into their constituent resins by selective dissolution. It uses a series of solvent washes that are guided by thermodynamic calculations of polymer solubility. In this work, the use of antisolvents in the STRAP process was reduced and solvent mixtures were considered to enable the temperature-controlled dissolution and precipitation of the target polymers in multilayer films. This was considered as a means to further improve the STRAP process and its estimated costs. Two STRAP approaches were compared based on different polymer precipitation techniques: precipitation by the addition of an antisolvent (STRAP-A) and precipitation by decreasing the solvent temperature (STRAP-B). Both approaches were able to separate the constituent polymers in a post-industrial film composed primarily of polyethylene (PE), ethylene vinyl alcohol (EVOH), and polyethylene terephthalate (PET) with near 100 % material efficiency. Technoeconomic analysis indicates that the minimum selling price (MSP) of the recycled resins with STRAP-B is 21.0 % lower than that achieved with STRAP-A. This provides evidence that thermally driven polymer precipitation is an option to reduce the use of antisolvents, making the STRAP process more economically and environmentally attractive. A third process, STRAP-C, was demonstrated with another post-industrial multilayer film of a different composition. Here, the results demonstrate that this process can also recover polymers at similar costs to those of virgin resins, indicating that the STRAP technology is flexible and can remain economically competitive as the plastic feed complexity is increased.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Kinetic Monte Carlo Tool for Kinetic Modeling of Linear Step-Growth Polymerization: Insight into Recycling of Polyurethanes

A kinetic Monte Carlo model of polyurethane polymerization which explicitly tracks the polymer sequences is developed and shared. Here this model is benchmarked against theoretical and experimental polyurethane data and used to investigate the effect on oligomer distributions of unequal reactivity of the first and second isocyanate to react. The reverse reactions using thermodynamic consistency are then added to the framework, and analogous to the addition polymerization concept of ceiling temperature, equilibrium chain length distributions at various temperatures are calculated. For a mixture of three monomers AA, BB, and CC, where BB and CC do not react with one another, are present in stoichiometric proportions, and have different enthalpies of reaction with AA, an odd-even effect emerges. Odd length chains are more likely than even length chains for temperatures at which BB and CC have significantly different equilibrium conversions. The concept of ceiling temperature that is typically cited for addition polymers is extended here to provide a measure of conditions under which depolymerization for recycling is favored.

condensation polymerization↗
DOE OSTI2024

Phosphorus recycling by mineral-catalyzed ribonucleotide cleavage on iron and manganese oxides

Abstract Phosphorus is an essential element influencing both food security via plant fertilization, and water pollution through excessive phosphorus use, yet the phosphorus cycle in ecosystems is poorly known. In particular, beyond adsorption, the role of iron and manganese oxides in catalyzing the abiotic dephosphorylation of biomolecules is debated. Here, we studied the reactions of ribonucleotides, containing different phosphate bonding, with goethite, hematite, and birnessite. We employed both high-resolution mass spectrometry of solution species and molecular modeling simulations of ribonucleotide-mineral complexes. Results disclose an up to fivefold preferential hydrolytic cleavage of a phosphoanhydride bond over a phosphoester bond, indicating that mineral-catalyzed reactions reflect the hierarchy reported for the activity of phosphatase enzymes. The fourfold higher catalytic reactivity of goethite and birnessite versus hematite is explained by mineral-specific binding rather than surface area differences. Corresponding simulated adsorbate conformations at the water–mineral interfaces are proposed. Overall, our findings provide new insights on the catalytic recycling of organic phosphorus species by mineral oxides.

58 GEOSCIENCES↗
DOE OSTI2018

Modification of Thermo-Mechanical Properties of Recycled PET by Vinyl Acetate (VAc) Monomer Grafting Using Gamma Irradiation

Vinyl acetate (VAc) monomer of different percentage was grafted onto the recycled polyethylene terephthalate (r-PET) films using gamma irradiation. The properties of these modified films were characterized by Fourier transform infrared spectroscopy (FTIR), mechanical properties testing (Tensile strength, Elongation at break), dynamic mechanical analysis (DMA) and thermo-gravimetric analysis (TGA). The Tensile Strength (TS) of the modified PET film increased by 132.25 % to the highest value of 50.12 MPa at 15% VAc monomer concentration at 3 kGy gamma dose, while the elongation at break (EB) decreased by 31.83 %. FTIR was used to investigate the molecular interaction of the modified films. TGA revealed that curve of the modified PET film shifted toward higher temperature region by 95 °C, which is very close to that of PET film made from virgin flakes. The results indicate that modified PET films of better mechanical and thermal properties were successfully prepared using VAc monomer grafting by gamma irradiation technique.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Recycled Poly(Ethylene Terephthalate)/Clay Nanocomposites: Rheology, Thermal and Mechanical Properties

Polymer nanocomposites containing recycled poly(ethylene terephthalate) (r-PET) as a polymer matrix and Cloisite{sup ®} 10A as a reinforcement were prepared through melt compounding. First, a masterbatch containing 20 wt% of Cloisite{sup ®} 10A clay was prepared and later diluted with neat r-PET to obtain nanocomposites containing 1, 2, 4 and 6 wt% of clay. The rheological, thermal, mechanical and morphological properties of the PET–clay nanocomposites were characterized. The complex viscosity of the nanocomposites gradually increases with increase in clay content. The storage modulus and loss modulus of nanocomposite containing 1 wt% of clay was similar to neat r-PET but increases with increase in clay content. Incorporation of clay into a r-PET slightly increases the crystallisation temperature and degree of crystallinity due to the heterogenous nucleating effect of clay. Thermal stability and glass transition temperature of nanocomposite containing Cloisite{sup ®} 10A clay at lower loadings was similar to r-PET and gradually decreases with increase in clay content. The tensile properties of PET–clay nanocomposites increased gradually with clay content. The impact strength of nanocomposites was not altered until 4 wt% and decreased at 6 wt%. Morphological investigations indicated homogeneous dispersion of clay in r-PET.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Preparation of Low-Density Microcellular Foams from Recycled PET Modified by Solid State Polymerization and Chain Extension

Recycled polyethylene-terephthalate (RPET) bottle regrinds were physically foamed after two types of industrially feasible molecular weight increasing processes. Intrinsic viscosity (IV) of initial waste (0.71 dL/g) increased both after reactive extrusion carried out using a multifunctional epoxy-based chain extender (0.74 dL/g) and after solid state polycondensation (SSP) (0.78 dL/g), while capillary rheometry revealed higher degree of branching in the chain extended PET material. Despite the relatively low IV values (below 0.80 dL/g), physical foaming, a mild and cost-efficient way, was successful in both cases, uniform microcellular foam structures with void fractions ranging between 75 and 83% were achieved. During the experiments morphology change in the materials was tracked by differential scanning calorimetry (DSC) besides recording IV values. The IV drop during foaming was between 0.03 and 0.10 depending on the pre-processing technology. Structure of foams produced from the two different modified RPET materials was compared with each other based on scanning electron microscopic imaging of cryogenic fracture surfaces. The average cell diameters were measured to be 213 and 360 µm in the case of chain extended and SSP-modified materials, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Natural and Accelerated Aging on the Mechanical Performance of a Composite Based on Recycled Multilayer Carton

A composite elaborated from waste material was studied for its proposed use as a wood plastic composite. Multilayer food cartons and recycled high density polyethylene were used for the elaboration of laminates, in a proportion of 55% and 45% volume fraction, respectively. The samples were subjected to an aging in an accelerated weathering (AW) chamber for 0, 500, 1000 and 2000 h with UVB radiation, temperature and humidity cycles. Samples exposed to natural weathering (NW) for 0, 1300, 2600 and 5200 h, in a warm sub-humid environment were also studied, the aim being to elucidate a correlation of the useful lifespan of the material. In both cases, after the exposure, three-point bend tests were performed to evaluate the effect on the mechanical properties. The analysis of the degradation process was carried out by infrared spectroscopy, indicating that the AW and NW samples showed deterioration of the material in different proportions. By mean of thermal analysis, it was possible to associate the degradation with the appearance and/or growth of the endothermic peaks, showing a variation in the melting temperature as the time of exposure to AW and NW increased, resulting in a change in the crystallinity percentage. The modulus of rupture (MOR) and the flexural modulus of elasticity decreased by 20% in samples subjected to AW for 2000 h; while in the samples exposed to NW, required of 5200 h to obtain a reduction of 16% in the MOR.

36 MATERIALS SCIENCE↗