Effect Of Water Aging Research Articles

Effects of water aging on the mechanical and anti-biofilm properties of glass-ionomer cement containing dimethylaminododecyl methacrylate

ObjectivesThe aims of this study were to investigate the effects of water aging for up to 6months on the mechanical and anti-biofilm properties of a novel antibacterial glass ionomer cement (GIC) containing dimethylaminododecyl methacrylate (DMADDM). MethodsGIC specimens (n=180) which contained DMADDM (0wt.%, 1.1wt.% or 2.2wt.%) were prepared. The mechanical properties surface roughness, microhardness and the surface charge density of ammonium groups were measured before and after water aging for 3 and 6months at 37°C. Further six months aged specimens (n=216) were worn by 6 volunteers in their oral cavities for 24h and 72h. Biofilm formation was analyzed and rated by fluorescence microscopy (FM) and by scanning electron microscopy (SEM). Biofilm viability was analyzed by FM. ResultsWater aging did not show any adverse effects on the surface roughness and hardness of the material. The surface charge density of the GIC samples containing DMADDM decreased due to the aging procedure, however, was still higher than that of the GIC without DMADDM. In situ biofilm formation was significantly reduced after 24h on DMADDM containing GIC (p<0.05). FM results showed a higher ratio of red/green fluorescence on GIC-DMADDM samples. SignificanceIncorporating DMADDM into GIC affected the material properties in a tolerable manner even after 6months of storage in water. The new GIC is a promising material to affect the biofilm formation on the surface of restorations.

Experimental investigation on impact performance of glass–polypropylene hybrid composites: Effect of water aging

The effect of water aging on the impact performance of glass (G)–polypropylene (P)-reinforced epoxy composites was investigated. Specimens were fabricated using the hand layup process with constant overall fiber volume fraction. Specimens were immersed in distilled water and seawater at room temperature, until reaching their water content saturation point. The dry and water-immersed specimens were subjected to edge-wise and flat-wise impact tests. Fractured surfaces were examined using scanning electron microscopy, SEM. The results showed that the impact performance of G-reinforced epoxy composite has been enhanced through hybridizing it with P-fiber but water uptake has been increased. Water uptake reduces the impact strength of all tested specimens. Composites exposed to seawater absorb less water than those exposed to distilled water. The water absorption percentage and impact performance can be effectively controlled by changing the hybrid configuration, plies stacking sequence and P/G fiber ratio.

Flexural fatigue performance of hybrid composite laminates based on E-glass and polypropylene fibers

An experimental investigation has been conducted to understand the effect of water aging on flexural fatigue performance of unidirectional polypropylene (PP)-glass (G) fiber–reinforced epoxy composites. Test specimens were fabricated using hand lay-up process with a constant total fiber volume fraction. The effects of the reinforcement hybridization, hybrid configuration, and stacking sequences on S–N curves were investigated. Deflection-controlled flexural fatigue tests with a frequency of 25 Hz at zero mean stress have been conducted. A 20% reduction of the initial applied moment was taken as a failure criterion. In the first stage, the flexural fatigue properties of un-aged composite specimens were studied in ambient temperature. In the second stage, flexural fatigue properties were investigated after a preliminary aging step in distilled water for 350 days. The specimen surface temperature rise was measured to ensure that there is no early damage happened in the tested specimens. Results indicated that the hybridization of PP fiber–reinforced composite with G fiber improves its flexural fatigue resistance but increase water uptake. Inter-intraply hybrid laminate with G-fiber layers at the specimen outer faces and PP-fiber layers in the specimen core exhibits the most favorable flexural fatigue behavior, that is, the highest cost ratio and the specific fatigue endurance strength. The water-sorption step induced a significant decrease in fatigue properties of the fabricated specimens. The highest measured temperature rise was observed to be about 9°C for G fiber–reinforced composite.

Effect of Water Aging of Adherend Composite on Repair Bond Strength of Nanofilled Composites.

To evaluate the effect of water aging of adherend composite on repair bond strength to nanofilled composites with specific fillers using different bonding agents. Three nanofilled composites - Beautifil II with S-PRG filler (BE) / Filtek Supreme ultra with nanocluster filler (SP) / Estelite Σ Quick (ES) - and one microhybrid composite, Clearfil APX (AP), were used in this study. The composite disks were immersed in water for different durations (immediate, 1 week, 2 weeks or 1 month), and then the polished surfaces were treated with one of three bonding agents - no treatment (control), application of Clearfil SE One (SE), application of Clearfil SE One plus Clearfil Porcelain Bond Activator (PB) - then filled with a repair composite. The bonded composite disks were subjected to the microshear bond strength (µSBS) test. Additionally, water sorption (Wsp) and solubility (Wsl) of the resin composite were measured. The µSBS data were was statistically analyzed using a three-way ANOVA and t-test with Bonferroni correction for multiple comparisons. Water aging of adherend composite affected the repair bond strength (p < 0.05). For BE, SP, and ES, application of an adhesive agent improved repair bond strengths to water-aged composites (p < 0.05), but adding a silane coupling agent could not (p > 0.05). For AP, the µSBS significantly increased, with control group < SE group < PB group (p < 0.05). Microhybrid composite was a more suitable material for composite repair than nanofilled composite, due to adhesion to exposed, larger silica fillers. S-PRG filler and nanocluster filler in the nanofilled composites played a slight role in improving their repair bonding performances with the bonding agents tested.

Effect of water ageing on the load-unload cyclic behaviour of flax fibre-reinforced thermoplastic and thermosetting composites

In the present work, twill flax fabrics-reinforced thermoplastic and thermosetting composites were subjected to water ageing in order to study its effect on their mechanical properties. Water ageing was conducted by immersing composite specimens into tap water at room temperature until saturation. To assess their mechanical behaviour, the aged composites were subjected to monotonic and load-unload tensile tests completed by Acoustic Emission (AE) recording. The AE records were analysed by the k-means unsupervised pattern recognition algorithm associated with the Principal Components Analysis (PCA) and the Silhouette index. In particular, the load-unload tensile tests highlighted a decrease of about 10% of the aged composites stiffness with respect to unaged ones at high loads. Besides, three classes of damage events were identified and assigned to the damage mechanisms. Finally, the mechanical behaviour of the aged composites is found to exhibit a significant Felicity effect synonymous of a substantial damage induced by water ageing.

Mechanical properties of contemporary resin composites determined by nanoindentation

Objective The objective of this study was to evaluate the Young's modulus (E) and nanohardness (H) of recently developed high viscosity bulk-fill and self-adhering resin composites by using nanoindentation technique. The effect of water aging on these properties was also studied. Materials and methods Four resin composites that fall into the categories of conventional (Filtek Z250 XT; FZ), high viscosity bulk-fill (Filtek Bulk-Fill Restorative Posterior), flowable (Filtek Supreme Ultra Flowable), and self-adhering flowable (Vertise Flow) were evaluated in this study. Ten disc specimens (5 mm × 2 mm) were prepared from each material. After polishing, half the specimens of each material (n = 5) were dry stored and the other half stored in distilled water for 30 days at 37°C. The E and H were determined by nanoindentation test using Bruker CETR-Apex nanoindenter. Ten indentations were made on top surface of each specimen. Statistical analysis was performed using one-way analysis of variance and paired t-test. Results All materials were significantly different from each other regarding both E and H in both testing circumstances. A 30-day water storage caused a significant decrease in E and H of all tested composites except for Filtek Bulk-Fill Restorative Posterior, where its E increased and its H not affected. There was a positive correlation between E and H. Conclusion Generally, both E and H were significantly increased when the filler content increased and they were significantly affected by 30-day water aging. E and H were affected not only by the filler content but also by the quality of resin matrix particularly after water storage.

Antimicrobial and physical characteristics of orthodontic primers containing antimicrobial agents.

To compare the antimicrobial and physical properties of experimental primers containing chlorhexidine (CHX) or ursolic acid (UA) with a commercial primer. Two antibacterial agents, 3 mg each of CHX and UA were incorporated respectively into 1 ml of Transbond XT primer (TX) to form antibacterial primers, TX-CHX and TX-UA. The antimicrobial activity of the three primers (TX, TX-CHX, and TX-UA) against Streptococcus mutans in both planktonic and biofilm phases was analyzed by determining minimum inhibitory and bactericidal concentrations and by performing growth and biofilm assays. Growth and biofilm assays were performed in both the absence and presence of thermocycling in a water tank to analyze the effects of water aging on the antimicrobial activities of primers. After bonding brackets onto bovine incisors using the primers, shear bond strength and mode of fracture were analyzed to compare physical properties. TX-CHX had stronger antimicrobial activity against S. mutans in the planktonic and biofilm phases than did TX or TX-UA. When applied, TX-CHX completely inhibited the growth and biofilm formation of S. mutans . In addition, the antimicrobial activity of TX-CHX was maintained after thermocycling. However, TX-UA did not show significant antimicrobial activity compared with TX. There was no significant difference in either shear bond strength or bond failure interface among the primers. Incorporation of CHX into an orthodontic primer may help prevent enamel demineralization around surfaces without compromising its physical properties.

Repair Bond Strength of Aged Resin Composite after Different Surface and Bonding Treatments.

The aim of this study was to compare the effect of different mechanical surface treatments and chemical bonding protocols on the tensile bond strength (TBS) of aged composite. Bar specimens were produced using a nanohybrid resin composite and aged in distilled water for 30 days. Different surface treatments (diamond bur, phosphoric acid, silane, and sandblasting with Al2O3 or CoJet Sand), as well as bonding protocols (Primer/Adhesive) were used prior to application of the repair composite. TBS of the specimens was measured and the results were analyzed using analysis of variance (ANOVA) and the Student–Newman–Keuls test (α = 0.05). Mechanically treated surfaces were characterized under SEM and by profilometry. The effect of water aging on the degree of conversion was measured by means of FTIR-ATR spectroscopy. An important increase in the degree of conversion was observed after aging. No significant differences in TBS were observed among the mechanical surface treatments, despite variations in surface roughness profiles. Phosphoric acid etching significantly improved repair bond strength values. The cohesive TBS of the material was only reached using resin bonding agents. Application of an intermediate bonding system plays a key role in achieving reliable repair bond strengths, whereas the kind of mechanical surface treatment appears to play a secondary role.

Effect of water ageing on the mechanical and damping properties of flax-fibre reinforced composite materials

The aim of this work is to study the effect of water ageing of quasi-Unidirectional Flax fibre Reinforced Epoxy (UFRE) composites on their mechanical and damping properties. The studied composites were manufactured by press platen process and subjected to water immersion at room temperature. Mechanical and damping properties of unaged and aged materials were investigated using free vibrations. Next, they were dried and tested to study the reversibility of the variation of those properties caused by water ageing. The results showed that water uptake induces a decrease in the bending moduli and an increase in loss factors compared in term of ageing time. It was also proven that those variations are practically reversible in the case of loss factors but irreversible in the case of bending moduli.

Effect of water ageing on nanoindentation response of single hemp yarn/epoxy composites

This paper aims to evaluate the influence of water ageing on nanoindentation response of the in situ components of hemp/epoxy composites. Specific samples have been tested, made of single hemp yarn composites with two different epoxy resins. Analysis of indentation points depending on their location in the yarn microstructure has been performed. Measurements showed the influence of neighbouring fibres on the reduced modulus in the confined resin. Water induces a decrease in nanoindentation properties, and maximum decrease in reduced modulus takes place in the interfacial zone, which shows the significant degradation of the fibre/matrix interface caused by water ageing. Evolutions in the indentation properties induced by water are similar for both partially bio-based and fully synthetic epoxy resin composites. All these results bring insights into the influence of water ageing of each constituent of hemp fibre reinforced composites and give interesting data for developing eco-composite materials.

Burst strength and impact behaviour of hydrothermally aged glass fibre/epoxy composite pipes

This study investigated the effects of water ageing and low-velocity impact loadings on E-glass fibre/epoxy composite pipes subjected to monotonic internal pressure. The pipes, which consisted of six antisymmetric layers with (±55°)3 winding angles, were manufactured by the filament winding process. The specimens were cut from the pipes to the required test length. The specimens were then subjected to the ageing process by being immersed in 80°C tap water for time intervals of 500, 1000, and 1500h. Impact loadings of three different energy levels (5J, 7.5J, and 10J) were applied, which were followed by monotonic burst tests. Scanning electron microscopy images were captured and the correlation between the ageing time and the level of impact energy on the pipes' burst strength was identified. The results indicated that the peak force and displacement increased as the impact energy increased. The monotonic burst test results revealed that the specimens that had been aged and were impacted by higher energy yielded lower burst strength. Weepage and eruption failures were observed depending on the applied impact energies.

Environmental effects on the mechanical behaviour of pultruded jute/glass fibre-reinforced polyester hybrid composites

The environmental degradation of the mechanical properties of pultruded jute and jute/glass hybrid reinforced polyester composites with high fibre volume fraction (0.70) has been investigated with special focus on the effects of water ageing and moderate temperature (up to 80 °C). Water absorption tests were conducted by immersing specimens in distilled water at room temperature until saturation (4076 h). Water absorption curves and characteristic parameters such as coefficient of diffusion and equilibrium moisture content were determined. The composites exhibited a deviation from the Fickian behaviour with a positive role played by the addition of glass fibres in terms of moisture resistance. The influence of water uptake on tensile and flexural properties of composites was evaluated and a significant reduction in both strength and modulus was observed, with a superior strength retention offered by hybrid composites. Acoustic emission (AE) and scanning electron microscopy enabled to identify the weakening of fibre/matrix interface induced by water ageing. The effects of temperature were mitigated by glass fibres if compared with the higher degradation experienced by jute fibres.

Surface potential at the hematite (001) crystal plane in aqueous environments and the effects of prolonged aging in water

The surface potentials of a (001) terminated hematite crystal that was annealed at high-temperature were measured as a function of pH by means of the corresponding single crystal electrode. The surface potential at a given pH did not depend on the electrolyte concentration, and was found to exhibit an inflection point. The shape of the function is in phenomenological agreement with the presence of two distinct surface terminations (O and Fe) that have been previously reported for this surface. Aging of the annealed hematite surface, in aqueous electrolyte medium over 2weeks, leads to a drastic change in the surface potential pH curve. The surface potential becomes that of the ideal O termination. While the O termination data can be modeled using the MUSIC approach, the initial sample that is expected to correspond to the two-domain surface with O and Fe terminations cannot be described within the MUSIC approach based on previously published surface diffraction data. However, the experimental data fall between the O and Fe termination limiting cases when the point of zero potential is placed at the inflection point. The fact that a surface with the two terminations cannot be modeled may be attributed to various issues, three of which are discussed: (i) the general difficulty to average the potential arising from both terminations, which furthermore are short-circuited via the crystal, (ii) the difficulty of treating patchwise heterogeneous surfaces in surface complexation models, and (iii) the incapability of surface complexation models in their present form to describe potential gradients within the solid. Conclusively, we interpret our results as a transformation from a bi-domain surface, to a single domain surface over time under conditions where bulk hematite solubility is low. Accordingly, the oxygen terminated domain should be the more stable one at this single crystal surface at our experimental conditions.

Variations of mechanical properties of jute/polyester composite aged in various media

Woven roving jute fiber-reinforced unsaturated polyester composites were subjected to water absorption tests in order to study the effects of water ageing on the mechanical properties. Composite specimens were immersed in distilled water and salt water up to 2736 h. The water absorption of specimens reached to an equilibrium level after an immersion time of 300 h. It was observed that tensile, flexural, and interlaminar shear strengths (ILSSs) of jute/polyester composites decreased depending on the immersion time. The ILSS values of the composites were reduced by more than 53% for both the distilled water and the salt water after an immersion time of 2736 h.

Characterization of Luffa cylindrica fibers and the effect of water aging on the mechanical properties of its composite with polyester

AbstractLuffa cylindrica of Turkey's Aegean Region was evaluated in terms of fiber characterization and the mechanical properties of its composite with polyester. Characterization of Luffa cylindrica was carried out by Fourier transform infrared spectrophotometer, X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy, and thermogravimetric analysis. Cellulose, hemicellulose, and lignin contents of Luffa cylindirica were also determined. Deconvolutions of XPS data enable determining the distributions of functional groups on the surface of Luffa cylindrica. Luffa cylindrica‐reinforced polyester composite was subjected to water aging under a steam of seawater containing 5% sodium chloride for 170 h at 50°C. After water aging, tensile strength, flexural strength, interlaminar shear strength, and tensile elongation at break values of the composite decreased ∼ 28%, 24%, 45%, and 31%, respectively. However, tensile modulus and flexural modulus did not change significantly. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Effect of water aging on the apatite formation of a low-modulus Ti–7.5Mo alloy treated with aqueous NaOH

The objective of this experiment was to develop biomimetic calcium phosphate coatings on low-modulus Ti–7.5Mo substrates treated with NaOH aqueous solutions and subsequent water aging before soaking them in simulated body fluid (SBF). Specimens of commercially pure titanium (c.p. Ti) and Ti–7.5Mo were initially treated with 5 M NaOH at 60 °C for 24 h, resulting in the formation of a porous network structure composed of sodium titanate (Na2Ti5O11). Afterward, the specimens were aged in distilled water at 80 °C for 12, 24, or 48 h, and subsequently immersed in 1.5SBF at 37 °C for either 1 or 13 days. The calcium phosphate-forming abilities of the c.p. Ti and Ti–7.5Mo achieved by a single NaOH treatment were low, but were significantly increased by the water aging. The amount of calcium phosphate deposited on the Ti–7.5Mo after NaOH treatment and subsequent water aging for 12 or 24 h was much greater than other conditions. The calcium phosphate-coated Ti–7.5Mo has strong potential as an artificial bone substitute or in other hard tissue-replacement materials with heavy load-bearing requirements due to a favorable combination of bioactivity, low elastic modulus, and low processing costs.

Effect of water aging on microtensile bond strength of dual-cured resin cements to pre-treated sintered zirconium-oxide ceramics

Objectives To evaluate the hydrolytic stability of different dual-cure resin cements when luted to zirconia ceramic. Methods Eighteen cylinder-shaped zirconia blocks (Cercon Zirconia, Dentsply) were conditioned with: Group 1, no treatment; Group 2, sandblasting (125 μm alumina–Al 2O 3-particles); Group 3, tribochemical silica coating (50 μm silica-modified Al 2O 3 particles). Ceramic blocks were duplicated in composite resin (Tetric Evo Ceram, Ivoclar-Vivadent). Composite disks were luted to pre-treated ceramic surfaces using: (1) Clearfil Esthetic Cement (CEC; Kuraray); (2) Rely X Unicem (RXU; 3M ESPE); (3) Calibra (CAL; Dentsply Caulk). After 24 h, bonded samples were cut into microtensile sticks (1 mm 2). Half of the sticks were loaded in tension until failure (cross-head speed of 0.5 mm/min). The remaining half was tested after 6 months of water storage at 37 °C. Data was analyzed with three-way ANOVA and Tukey’s test ( P <0.05). Fractographic analysis was performed by SEM. Results After 24 h, bond strength of CEC to zirconia was significantly higher than that of RXU and CAL, independently from the ceramic pre-treatment ( P <0.001). Using CAL, all samples failed prematurely except when luting to sandblasted surfaces. After 6 months of water aging, bond strength of CEC significantly decreased. RXU did not significantly alter bond strengths. Adhesion of sandblasted specimens luted with CAL fell over time. Micromorphological alterations were evident after water storage. Significance Resin–ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. CEC and RXU were both suitable for luting zirconia. Water aging played an important role in the durability of zirconia-to-composite chemical bonds.

Curaua/Glass Hybrid Composite: The Effect of Water Aging on the Mechanical Properties

A hybrid composite associating natural fibers (curaua) and synthetic fibers (E-glass) was developed and investigated. The hybrid is destined for engineering applications as an alternative material to glass fiber composites, mainly in high moisture environments. Thus, an investigation was conducted to evaluate the degradation of the mechanical properties due to water absorption. The hybrid composite is formed of an orthophthalic polyester resin reinforced by layers of glass mats and continuous curaua fibers. Absorption tests were carried out and obtained the composite saturation curve for both distilled water and sea water conditions. A non-hybrid composite (just with curaua fiber), was also evaluated for comparison. The mechanical properties were evaluated through tensile and three-point-bend tests. After the mechanical tests, a fracture characteristics analysis of the tested specimens was carried out.

Effect of aging on the shear bond strength of orthodontic brackets

Bracket loss during the later stages of orthodontic treatment is a relatively frequent occurrence. The purpose of this study was to evaluate and isolate the effect of composite aging, one of many factors that can contribute to decreased bond strength during a normal 24-month orthodontic treatment period. Two orthodontic bonding adhesives--Transbond APC II (3M Unitek, Monrovia, Calif) and Quick Cure adhesive (Reliance Orthodontic Products, Itasca, Ill)--were used to bond brackets to 280 bovine incisors that were stored in distilled water at 37 degrees C for 30 minutes, 24 hours, and 1, 6, 12, 18, and 24 months before shear-peel testing. Bond strength increased over the first 24 hours and then tended to decrease over the next 24 months. The bond strengths (in MPa) for Transbond and Quick Cure, respectively, were as follows: 30 minutes, 14.99 +/- 0.75 and 21.02 +/- 1.79; 24 hours, 20.99 +/- 2.11 and 25.61 +/- 1.96; 1 month, 20.54 +/- 1.58 and 18.96 +/- 1.02; 6 months, 17.77 +/- 1.66 and 19.52 +/- 1.61; 12 months, 14.79 +/- 1.30 and 18.28 +/- 1.43; 18 months, 16.08 +/- 1.37 and 16.19 +/- 1.01; and 24 months, 12.44 +/- 1.06 and 8.62 +/- 1.03. Shear bond strength of orthodontic brackets increases from 30 minutes to 24 hours and then tends to decrease over the next 24 months. The decrease in bond strength due to the effects of composite aging in water appears to be a major factor in the decreased bond strength seen clinically.

Aging studies of light cured dimethacrylate-based dental resins and a resin composite in water or ethanol/water

Objective To study the aging of neat resins, prepared from bis-GMA, UDMA, D 3MA or a mixture of bis-GMA/UDMA/D 3MA (65/20/15 w/w/w), in water or 75% (v/v) ethanol/water 37 °C. Also the study of aging of Heliomolar RO, which is a radiopaque, microfilled, light cured composite, the resin matrix of which is the copolymer of bis-GMA/UDMA/D 3MA (65/20/15 w/w/w). Methods Samples of neat resins and Heliomolar RO prepared by light curing were immersed in water or 75% (v/v) ethanol/water 37 °C, for 1, 7 or 30 days. Then the flexural and tensile strength were determined. The fractured surface of samples after the flexural tests was observed by scanning electron microscopy. Results Bis-GMA and copolymer resin did not showed any significant change in mechanical properties after immersion in water or 75% (v/v) ethanol/water 37 °C, for 30 days. On the contrary UDMA, D 3MA and the composite Heliomolar RO showed a significant decrease. Significance The results obtained showed that the effect of aging in water or ethanol/water solution on mechanical properties of a light cured dimethacrylate resin depends on the chemical structure of resin. In the case of resin composite this effect depends on the filler–matrix bond strength.