Hydrothermal Aging Resistance Research Articles

Biomimetic mineralization of silicon dioxide onto carbon fiber for elevated interfacial properties and hydrothermal aging resistance of carbon fiber/epoxy composites

AbstractA carbon fiber‐tannic acid‐silicon dioxide (CF‐TA‐SiO2) reinforcement with a “diatom frustule‐like” structure was built via biomimetic mineralization to boost the performance of carbon fiber/epoxy resin (CF/EP) composites. As a bio‐based polyphenolic compound, TA was used to modulate the mineralization of SiO2, and the easy agglomeration of SiO2 was effectively avoided. The interfacial adhesion of the CF/EP composites was considerably heightened by improving the roughness and wettability of CF as well as by increasing the interfacial interactions between CF and the EP. Compared with the pristine composites, the flexural strength, interlaminar shear strength and interfacial shear strength of the CF‐TA‐SiO2/EP composites increased by 41.2%, 56.6%, and 50.4%, respectively. Moreover, the introduction of Si‐O‐Si and C‐O‐Si bonds at the interface led to a remarkable improvement in the hydrothermal aging resistance. This research provides a novel interfacial design for advanced composites with excellent interfacial properties, which broadens the application of these composites in hygrothermal environments.Highlights A “diatom frustules‐like” structure was successfully constructed on the CF surface. This biomimetic mineralization was simple and environmentally friendly. This method solved the problem of easy agglomeration of SiO2. The interfacial properties of composites were obviously improved. The hydrothermal aging resistance of composites was enhanced.

Effect of grain boundary segregation and oxygen vacancy annihilation on aging resistance of cobalt oxide-doped 3Y-TZP ceramics for biomedical applications

Abstract This study aims to investigate the diffusion stabilization process of nano-Co2O3 during the non-precursor transformation of 3Y-TZP. 3Y-TZP was set as the control group, and the experimental groups were 0.1–0.3 mol% nano-Co2O3-doped 3Y-TZP. The samples were prepared by the ball milling process, isostatic cool pressing, and sintering. All samples were hydrothermally treated at 134°C and 2 bar for different time periods. The resistance to low-temperature degradation of nano-Co2O3-doped 3Y-TZP was analyzed by X-ray diffraction. The microstructure of zirconia ceramic samples was determined by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and electron paramagnetic resonance studies. The addition of nano-Co2O3 into 3Y-TZP resulted in higher hydrothermal aging resistance than 3Y-TZP. The addition of 0.2 mol% nano-Co2O3 dopants resulted in the highest hydrothermal aging resistance among nano-Co2O3-doped 3Y-TZP ceramics. The grain sizes of 3Y-0.2Co are smaller than those in the control group. With the increase of cobaltous oxide doping contents, the segregation of Co3+ ions at the crystal boundary increased. The content of oxygen vacancies on the surface of the sample increased with the increase of the Co2O3 doping content. The oxygen vacancy concentrations of 3Y-0.2Co increased obviously after aging. 3Y-0.1Co, 3Y-0.3Co, and the control showed decreased oxygen vacancy concentrations after aging. Trivalent element doping of 3Y-TZP effectively improved the aging resistance of 3Y-TZP. The addition of 0.2 mol% nano-Co2O3 resulted in the highest hydrothermal aging resistance. Improved aging resistance is attributed to the nano-Co2O3 doping resulting in the 3Y-TZP grain size inhibition, grain boundary segregation of cobalt ions, and oxygen vacancy maintenance. This work is expected to provide an effective reference for the development and application of budget dental materials by regulating grain boundary engineering.

Preparation and properties of ternary rare earth co-stabilized zirconia ceramics for dental restorations

High fracture toughness and excellent hydrothermal aging resistance are the characteristics required for dental ceramic materials, but the widely used dental ceramic currently (3Y-TZP) does not exhibit. Aiming to solve this problem, a ternary rare earth co-stable zirconia ceramic (1.5Y5.5Ce0.3La-ZrO2) was prepared by a coating method based on a co-doping strategy. The sintering process, densification evolution, mechanical properties, resistance to hydrothermal aging and biocompatibility of 1.5Y5.5Ce0.3La-ZrO2 ceramic were studied. The results show that 1200 °C is the best pre-sintering temperature, and the machinability and controllability of shrinkage can meet the needs. When the final sintering temperature is 1600 °C, it has the best performance. Compared with 3Y-TZP, the bending strength is about 8.7% higher (912.48 MPa), and the fracture toughness is about 76.6% higher (10.49 MPa m1/2). Furthermore, its resistance to hydrothermal aging is significantly enhanced, greatly extending the service life of the material. The biosafety of 1.5Y5.5Ce0.3La-ZrO2 ceramics was evaluated, and the results showed that the material had no cytotoxicity. To sum up, 1.5Y5.5Ce0.3La-ZrO2 ceramics is a promising dental biomaterial, which has a broad application prospect in oral restoration.

Fabrication of hydrothermal ageing resistant of 3 mol % yttria‐stabilised tetragonal zirconia polycrystalline via microwave sintering

AbstractThe influence of microwave sintering on the densification, mechanical performances, microstructure evolution and hydrothermal ageing behaviour of pure 3 mol % yttria‐stabilised tetragonal zirconia polycrystalline (3Y‐TZP) ceramics was compared with conventional sintered samples. Green bodies were sintered via conventional pressure‐less and microwave sintering method between 1200 °C to 1400 °C with dwelling time and firing rate at 120 min, 10 °C/min and 1 min, 20 °C/min. Result showed that reduced processing temperature and holding time is possible with microwave sintering technique for fabricating good resistant zirconia sample with bulk density, Young's modulus, and Vicker's hardness that are comparable to samples sintered with conventional method. However, the microwave sintered samples suffered from hydrothermal ageing where their average grain size is above critical size. The enhancement of hydrothermal ageing resistance of the sintered samples is associated with the decreasing grain size of the sintered samples instead of sintering method.

Evolution hydrothermal aging resistance mechanism study of zirconium and manganese doped CeO2 catalysts in soot catalytic combustion based on low Miller indices crystal surface effect

The thermogravimetric analysis (TGA) experiments were carried out to reveal the mechanism of Zr and Mn doping on catalytic activity of CeO2 catalyst both fresh and after hydrothermal aging, and the lattice morphology and valence changes were characterized by means of Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and H2-temperature programmed reduction (H2-TPR). Density functional theory (DFT) and molecular thermodynamics calculations were applied to investigate the change in catalytic activity, crystal surface energy and crystal morphology caused by hydrothermal aging. The maximum reaction rate temperature of fresh Mn/CeO2 (389 °C) is similar to that of CeO2 (371 °C) and lower than that of Zr/CeO2 (447 °C), but the catalytic performance of CeO2 decreases more severely after hydrothermal aging. The catalyst crystals show different degrees of crystal surface migration after hydrothermal aging, which leads to the reduction of Ce3+/Ce4+ ratio and the active sites shift. DFT calculations indicate that the doping of Zr and Mn reduces the surface energy of the low Miller indices surface and increases the oxygen vacancy formation energy, leading to better thermal stability and lower catalytic activity. The Zr and Mn doping also changes the adsorption energy and Gibbs free energy of H2O, which dominates the migration of (1 1 1) to (1 1 0) and (1 0 0) in the vapor environment. The crystal surface migration mechanism of CeO2 catalysts doped with Zr and Mn induced by H2O molecules at high temperature obtained in this study can provide a valuable addition to the regeneration of CeO2 catalysts in the after-treatment systems of diesel engines.

Enhanced bioactivity and hydrothermal aging resistance of Y-TZP ceramics for dental implant.

Although yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) ceramics have been widely used as restorative materials due to their high mechanical strength, unique esthetic effect, and good biocompatibility, their general application to implant materials is still limited by their biological inertness and hydrothermal aging phenomenon. Existing studies have attempted to investigate how to enhance the bioactivity or hydrothermal aging resistance of Y-TZP. Still, more studies need to be done on the modification that combines these two aspects. In this study, Y-TZP was prepared by 77S bioactive glass (BG) sol and akermanite (AKT) sol infiltration and microwave sintering, which provided Y-TZP with high bioactivity while maintaining resistance to hydrothermal aging. Results of phase composition evaluation, microstructural characteristics, and mechanical property tests showed that modified Y-TZP specimens exhibited little or no tetragonal-to-monoclinic (t → m) transformation and maintained relatively high mechanical properties after accelerated hydrothermal aging treatment. The in vitro biological behaviors showed that the introduction of 77S BG and AKT significantly promoted cell adhesion, spreading, viability, and proliferation on the surface of modified Y-TZP ceramics. Therefore, this modification could effectively enhance the bioactivity and hydrothermal aging resistance of Y-TZP ceramics for its application in dental implant materials.

Evolution hydrothermal aging mechanism for Ag/CeO2 catalysts in regeneration of catalytic diesel particulate filter with DFT calculation.

In order to avoid the high cost of existing precious metal catalyst like Pt, Ag/CeO2 was the most promising catalysts for mobile source soot emission control technologies, but there was a clear trade-off between hydrothermal aging resistance and catalytic oxidation performance hindered the application of this catalyst. In order to reveal the hydrothermal aging mechanism of Ag/CeO2 catalysts, the TGA (thermogravimetric analysis) experiments were investigated to reveal the mechanism of Ag modification on catalytic activity of CeO2 catalyst between fresh and hydrothermal aging and were also characterized with the related characterization experiments to in-depth research the lattice morphology and valence changes. The degradation mechanism of Ag/CeO2 catalysts in vapor with high-temperature was also explained and demonstrated based on density functional and molecular thermodynamics theories. The experimental and simulation data showed that the catalytic activity of soot combustion within Ag/CeO2 decreased more significantly after hydrothermal aging than CeO2 due to the less agglomerated, which caused by the decreased in OII/OI and Ce3+/Ce4+ compared with CeO2. As shown in density function theory (DFT) calculation, the decreased surface energy and the increased oxygen vacancy formation energy of the low Mille index surface after Ag modification led to the instability structure and the high catalytic activity. Ag modification also increased the adsorption energy and Gibbs free energy of H2O on the low Miller index surface compared to CeO2, indicating that the desorption temperature of H2O molecules in (1 1 0) and (1 0 0) was higher than (1 1 1) in CeO2 and Ag/CeO2, which led to the migration of (1 1 1) crystal surfaces to (1 1 0) and (1 0 0) in the vapor environment. These conclusions can provide a valuable addition to the regenerative application of Ce-based catalysts in diesel exhaust aftertreatment system the aerial pollution.

Degenerating effect of transformation and loss of active sites on NH3-SCR activity during the hydrothermal aging process for Cu-SSZ-13 molecular sieve catalyst

A series of Cu-SSZ-13 small-pore molecular sieve catalysts are prepared by the ion-exchange method, analyzed, and tested by changing the synthesis ratio, and performing hydrothermal aging treatment under various aging conditions to explain the degree of influence. The investigations are carried out to reveal that when the Si/Al ratio is 10, the catalyst has the best comprehensive performance and ZCuOH sites are more prone to transformation and loss than Z2Cu sites during the hydrothermal aging process. In-situ DRIFTS experiments and DFT molecular simulation calculations are used to explain the reasons for the degradation of catalytic performance caused by the hydrothermal aging, which completes the study of the hydrothermal aging mechanism for Cu-SSZ-13 molecular sieve catalysts. The result shows that Z2Cu active sites exhibit better hydrothermal aging resistance than ZCuOH, the catalyst is more sensitive to aging temperatures than durations, and its limit of the aging temperature is about 850 ℃.

Enhanced Bioactivity and Hydrothermal Aging Resistance of Y-TZP Ceramics for Dental Implant

Enhanced Bioactivity and Hydrothermal Aging Resistance of Y-TZP Ceramics for Dental Implant

Physicochemical, mechanical and electrical properties of epoxy-based syntactic foam under thermal and hydrothermal aging conditions

In this study, epoxy resin containing hollow polymeric microspheres as an insulating material was synthesized and subjected to thermal and hydrothermal aging. Scanning electron microscopy (SEM) and three-dimensional computed tomography (3D CT) were used to examine the internal structures of the specimens as they aged. Thermogravimetric analysis (TGA) and Fourier transform infrared spectra (FT-IR) helped to elucidate the physical and chemical changes associated with aging. Tensile, flexural, dynamic mechanical analysis (DMA), and other mechanical tests were used to examine the mechanical properties of the syntactic foams (SFs) as they aged. Electrical tests such as the leakage current and breakdown strength were used to measure how effectively the SF materials maintained their insulating characteristics with aging. By comparing the aged and unaged specimens, the aging mechanism of the SF was elucidated. The findings demonstrated that the epoxy resin matrix composite foam packed with hollow polymeric microspheres had little effect on thermal aging and exhibited good hydrothermal aging resistance. The microstructures of the specimens subjected to thermal aging barely changed; however, hydrothermal aging resulted in dramatic changes. Notably, the comprehensive properties of the SF increased during thermal aging and hydrothermal aging, possibly due to an increase in secondary crosslinking density after a certain period of aging. The thermal and hydrothermal aging specimens had maximum tensile strengths of 14 and 13 MPa, respectively. The tensile strength dropped as aging time increased to 11.6 and 7 MPa, respectively. Furthermore, while the breakdown strengths of the hydrothermal samples continued to fall, the breakdown strengths of the thermal specimens initially increased and subsequently decreased, with a maximum value of 40.76 kV/mm. This was possibly related to the fact that the crosslinking reaction dominated the thermal aging process, whereas hydrothermal aging had numerous implications on the characteristics of the SF materials. This study showed that the SF filled with hollow polymeric microspheres had the potential for long-term durability in hot and humid environments, supporting its application as an insulation material in composite insulation cores. • The aging-time related micromorphology, physicochemical, mechanical and electrical performance of the syntactic foam are investigated by accelerated thermal aging and hydrothermal aging tests. • Both thermal and hydrothermal aging diminish the characteristics of specimens, while hydrothermal aging exhibits a more serious threat to the overall performance. • The trend of water absorption of epoxy resin-based syntactic foam shows non-Fick law. • The results of three-dimensional computed tomography reveal that thermal and hydrothermal aging increase the number and length of pores.

Research Progress on Sulfur Deactivation and Regeneration over Cu-CHA Zeolite Catalyst

Benefiting from the exceptional selective catalytic reduction of NOx with ammonia (NH3-SCR) activity, excellent N2 selectivity, and superior hydrothermal durability, the Cu2+-exchanged zeolite catalyst with a chabazite structure (Cu-CHA) has been considered the predominant SCR catalyst in nitrogen oxide (NOx) abatement. However, sulfur poisoning remains one of the most significant deterrents to the catalyst in real applications. This review summarizes the NH3-SCR reaction mechanism on Cu-CHA, including the active sites and the nature of hydrothermal aging resistance. On the basis of the NH3-SCR reaction mechanism, the review gives a comprehensive summary of sulfate species, sulfate loading, emitted gaseous composition, and the impact of exposure temperature/time on Cu-CHA. The nature of the regeneration of sulfated catalysts is also covered in this review. The review gives a valuable summary of new insights into the matching between the design of NH3-SCR activity and sulfur resistance, highlighting the opportunities and challenges presented by Cu-CHA. Guidance for future sulfur poisoning diagnosis, effective regeneration strategies, and a design for an efficient catalyst for the aftertreatment system (ATS) are proposed to minimize the deterioration of NOx abatement in the future. Finally, we call for more attention to be paid to the effects of PO43- and metal co-cations with sulfur in the ATS.

Mechanically robust, hydrothermal aging resistant, imine-containing epoxy thermoset for recyclable carbon fiber reinforced composites

Imine compounds have been proved to possess great potential in the design and preparation of sustainable epoxy thermosets. However, it is still a great challenge to develop imine-containing hardener with definite structure due to the randomness of condensation reaction between aldehydes and primary amines. Herein, a novel amine hardener containing imine bond is synthesized successfully by selecting 4-imidazole formaldehyde and 3-aminobenzylamine as raw materials. The asymmetric structure of raw material can avoid uncontrollable reaction and ensure that this hardener possesses definite chemical structure. Due to high activity of hardener, the resultant epoxy thermosets with high cross-linked density exhibit excellent thermostability and fine hydrothermal aging resistance. Furthermore, such thermosets show good mechanical properties (tensile strength of ∼76 MPa), which are comparable to that of commercial Diglycidyl Ether of Bisphenol A epoxy resin cured by 4,4-Diaminodiphenyl methane. More interestingly, increasing the equivalent ratio of active hydrogen to epoxy can introduce more dynamic covalent C=N linkage into the cross-linked network, thus the epoxy thermoset further achieves the decomposition within 3 h and the corresponding composite laminates also are recycled efficiently under mild condition. This work demonstrates the feasibility and potential of preparing high-performance degradable epoxy thermoset and corresponding recyclable composites based on well-designed imine-containing hardener.

Preparationof self‐emulsifying waterborne polyamide‐imide sizing for carbon fiber and improvement on mechanical performances of carbon fiber reinforced thermoplastic polymer

AbstractRecently, Carbon fiber reinforced thermoplastic polymer (CFRTP) has been widely used in automotive, aviation, and aerospace. However, the traditional epoxy Carbon fiber (CF) sizing for thermosetting composites was unsuitable for high‐performance CFRTP due to the high‐molding temperatures and incompatibility between them. Herein, a novel semi‐aromatic polyamide‐imide (PAI) backbone structure with multi‐ethoxy pendant groups was designed and synthesized via click‐reaction and solvent‐free polymerization. Waterborne PAI sizing was prepared via self‐emulsifying without surfactants. CF/PEEK (polyether‐ether‐ketone) and CF/PEI (polyether‐imide) composites were manufactured. Results showed that novel PAI had excellent thermal stability and solubility, PAI sizing was stable after 6‐month‐storage. Mechanical performances and hydrothermal aging resistance of composites were improved. Compared with commercial‐sized CF (eCF)/PEI, the flexural strength of sCF/PEI increased by 35.2% to 753.47 MPa, and retention rates of them with aging also increased. Noted, mechanisms of interface enhancement were revealed by quantum chemical calculations, ππ stacking and hydrogen bonding between PAI and PEI, PEEK was found.

Interactive effects of NOx synergistic and hydrothermal aging on soot catalytic combustion in Ce-based catalysts

The Thermal gravimetric analysis (TGA) with In-situ Fourier transform infrared Spectrometer (In-FTIR) of fresh/hydrothermal aging Ce-based catalysts was carried out for the soot oxidation at different transition metal Mn, alkali metals K, precious metals Ag and rare earth metal Zr doping which used to extend the hydrothermal aging resistance of CeO2 catalysts. The comprehensive combustion index S, combustion stability index Rw and peak temperature Tp from TG-DTG curves were extracted to evaluate the soot catalytic combustion performance, and the NO2/NO ratio during the combustion process was also measured to analyze the NOx synergistic oxidation performance. The effect of metal oxide doping type, doping ratio and hydrothermal aging time on S, Rw, Tp and NO2/NO ratio was evaluated to reveal the change in soot catalytic combustion performance. The result shows that, compared with PU, the NOx synergistic oxidation performance of various metal oxides modified Ce-based catalysts ranked as K > Ag > Mn > Zr. With the metal oxide doping ratio increased, the soot catalytic combustion performance of K and Zr metal oxides modified Ce-based catalysts decreased, Mn and Ag metal oxides modified catalyst increased. After hydrothermal aging treatment, the NOx synergistic oxidation performance of various metal oxides modified Ce-based catalysts ranked as K > Ag > Mn > Zr. This work is helpful to reveal the basic mechanism of hydrothermal aging metal oxide modified Ce-based catalyst and NOx during soot catalytic combustion process.

Ionic aqueous quaternized Poly(amide-imide) sizing on CF for improving interface and mechanical performance of CFRTP

With the rapid development of automotive, aviation, and aerospace, Carbon fiber reinforced thermoplastic polymer (CFRTP) has been widely used. However, massive commercial surfactants were used in present aqueous sizings for CF in high-performance CFRTP since thermoplastic polymers in sizing were all hydrophobic, which resulted in thermal instability and mechanical performance decrease. To solve this problem, herein, quaternary ammonium salt groups were introduced to poly (amide-imide)(PAI) via click-reaction, a novel quaternized PAI with excellent solubility and thermal stability was synthesized. An aqueous thermoplastic CF sizing was prepared via self-emulsifying of quaternized PAI without surfactants for the first time, which was stable after 12-month-storage. Furthermore, PAI-sized CF with appropriate processability was obtained for the manufacture of CF/PEI (polyether-imide) and CF/PEEK (polyether-ether-ketone) composites. Mechanical performances and hydrothermal aging resistance of composites were all significantly improved. Especially, quantum chemical calculations were employed to reveal the mechanisms of interface strengthening in composites, there were hydrogen bonding and π-π stacking between PAI sizing and PEI, PEEK matrix.

Preparation of CF-GO-SiO2 multi-scale reinforcements based on electrostatic interaction: A non-destructive and simple method to construct hybrid interface layers of carbon fiber reinforced thermoplastic resin composites

A GO-SiO2 hybrid interface layer was prepared by electrostatic adsorption to synergistically improve the weak interface bonding between carbon fiber (CF) and poly(phthalazinone ether ketone) (PPEK). FTIR, Raman and XPS confirmed that GO-SiO2 interface layer is constructed on CF surface. SEM and AFM indicated that the synergistic effect of GO-SiO2 could obviously improve the CF surface roughness. CF-GO-SiO2/PPEK composite exhibits excellent interlaminar shear strength (84.2 MPa), flexural strength (1620 MPa), storage modulus (132.9 GPa) and Tg (285 °C). The GO-SiO2 interface layer improves the mechanical interlocking and wettability between CF and PPEK, and the failure mechanism of the composite changes from interfacial debonding for Untreated CF/PPEK composite to matrix cohesive destruction and fiber breakage for CF-GO-SiO2/PPEK composite. Moreover, the layer is beneficial to the hydrothermal ageing resistance of the composite. This study provides a promising strategy for improving the interfacial properties of advanced thermoplastic composites.

Soluble semi-aliphatic polyimide sizing in CF/PEI composites for improving mechanical performance and hydrothermal aging resistance

Carbon fiber reinforced thermoplastics (CFRTP) inherited special advantages from the thermoplastics, which caused the demand for soaring. However, due to its high molding temperature and the absence of reactive groups, traditional carbon fiber sizing needs to be redesigned. Herein, a suspension formulated from a soluble semi-aliphatic polyimide (S-SA-PI) was used for CF sizing. The effective replacement of the sizing layer on the surface of T300 was clarified by microscopic morphology and surface element content of CFs. The mechanical performance of CF/PEI composites was measured, and the effects of annealing and hydrothermal aging on the mechanical performance were observed. The results show that S-SA-PI sizing can simply improve mechanical performance and hydrothermal aging resistance of CF/PEI. Combining the characteristics of S-SA-PI sizing layer, the mechanism by which S-SA-PI sizing improves the CF/PEI interface was analyzed.

Hydrothermal Aging of ATZ Composites Based on Zirconia Made of Powders with Different Yttria Content.

The presented work concerns the development and investigation of three different grades of ZrO2 materials containing Al2O3 particles (ATZ-Alumina Toughened Zirconia ceramics with 2.3–20 vol.% of alumina). The zirconia powders containing 3 mol.% of yttria were synthesized by a precipitation/calcination method and fabricated from two different zirconia powders with different yttria content. Then, the selected ATZ composites (ATZ-B, ATZ-10 and ATZ-20) were prepared by means of conventional mixing, compacting and sintering at 1450 °C for 1.5 h. The phase composition, microstructure, relative density and basic mechanical properties were determined. Uniform microstructures with relative densities over 99% of theoretical density, hardness values between 12.0–13.8 GPa, flexural strength up to 1 GPa and outstanding fracture toughness of 12.7 MPa⋅m1/2 were obtained. The aging susceptibility of alumina toughened zirconia materials, as a consequence of hydrothermal treatment, was investigated. The aim of this study was to determine the influence of LTD (low temperature degradation) on the tetragonal to monoclinic phase transitions and on the flexural strength of hydrothermally aged specimens. The results were compared to those obtained for commercially available tetragonal zirconia-based materials containing 3 mol.% of yttria. This research shows that ATZ composites that have excellent mechanical properties and sufficient hydrothermal aging resistance can be attained and later used in technical and biomedical applications.

3D coating layers of polyhydroquinone di-imidazopyridine (PIPD) fibers to improve their mechanical, interfacial and antimicrobial properties

The effect of growing CuO nanowires decorated with Ag nanoparticle in the presence of poly(dopamine) (PDA) as intermediate agent on PIPD fiber surface was evaluated. This treatment exhibited significant enhancement of the interfacial and mechanical performance, along with increment of the antimicrobial activity against E. coli as a model for Gram-negative bacteria. The scanning electron microscopy (SEM) validates the growth of CuO NWs and Ag NPs on the surface of PIPD fiber. The X-ray diffraction (XRD), The X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and the ratio of weight loss analyses supported the above results. The interface shear strength (IFSS) between the PIPD fiber and epoxy resin was improved by 72%; and the coated Ag nanoparticles raised the fiber tensile strength (TS) by 13%. The influence of UV radiation and hydrothermal degradation on PIPD fiber was studied, and the UV and hydrothermal aging resistance were both increased by 15% and 22% respectively. The antimicrobial activity analysis results strong efficiency of the coated PIPD fibers by Ag NPs against gram negative bacteria E. coli.

Effect of Hydrothermal Aging on Mechanical Properties and Long-Term Durability of Recycled Polysulfone

The present experimental investigation aims to discover the effect of hydrothermal aging on the mechanical properties of virgin and recycled PSU, as well as the effect of hydrothermal aging on the long-term durability including stress relaxation and creep properties of virgin and recycled PSU. Virgin and recycled PSU specimens were exposed to pure hot water at temperatures of 98 °C for 1, 1.5, 3, 4.5, 6, 9, and 12 months, respectively. Mechanical test of tensile, three-point bending, impact, and fracture toughness was carried out on those aged specimens. To obtain the long-term stress relaxation and creep property, a series of short-time stress relaxation and creep tests were performed by using dynamic mechanical analysis (DMA), and the master curve of long-term stress relaxation modulus and creep compliance was drawn by shifting those short relaxation and creep curve based on the time–temperature superposition principle (TTSP). It was finally concluded that the virgin PSU exhibits excellent hydrothermal aging resistance in tensile, flexural, impact and fracture toughness, stress relaxation, and creep properties, even if it was aged in 98 °C hot water for 1 year. Although the tensile and flexural properties of the unaged recycle PSU are similar to those of virgin PSU, the hydrothermal aging resistance in tensile, flexural, stress relaxation, and creep properties of recycled PSU is worse than that of virgin PSU. In addition, the activation energy required for stress relaxation of PSU is same with that for creep.