This study investigated the thermal properties of three room temperature curing adhesives containing nano particles which were thixotropic and shear thinning which allowed injection into overhead holes when exposed to different environmental conditions. Viscosity and shear stress of the adhesives were measured as a function of shear rate. The thermal behaviour of the adhesives were measured using dynamic mechanical thermal anylisis following exposures to different temperatures and humidities which included temperatures of 20 degrees Celcius, 30 degrees Celcius and 50 degrees Celcius, relative humidities of 65% RH, 75% RH 95% RH soaked in water at 20 degrees Celcius and placed in the oven at 50 degrees Celcius. The dynamic thermal properties reported include storage and loss modulus, the loss tangent and the glass transition temperature ( Tg ). For nano- and micro-particles filled adhesives, the Tg increased with the temperature increase, even though the adhesives was subjected to high humidity and this was due to further cross-linking. The results showed that room temperature cured epoxies were only partially cured at room temperature.
Corrosion is a natural deterioration process that destructs metal surface. Metal of highly
protected by passivation layer such as Stainless Steel 316L also undergoes pitting corrosion
when continuously exposed to aggressive environment. To overcome this phenomenon, application
of epoxy based coating with addition of zinc oxide- poly (3,4-ethylenedioxythiophene)
doped with poly (styrene sulphonate) hybrid nanocomposite additive was introduced as
paint/metal surface coating. The compatibility between these two materials as additive
was studied by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD),
Field Emission Scanning Electron Microscopy/Energy-Dispersive X-ray spectroscopy (FESEM/EDX)
and Transmission Electron Microscopy (TEM) analysis. The effect of nanocomposite
wt.% in epoxy based coating with immersion duration in real environment on corrosion
protection performance was analyzed through potentiodynamic polarization analysis. The
main finding showed that addition of hybrid nanocomposite had increased corrosion protection
yet enhanced corrosion process when excess additives was loaded into epoxy coating.
Addition of 2 wt.% ZnO-PEDOT:PSS was found significantly provided optimum corrosion
protection to stainless steel 316L as the corrosion rate for 0 day, 15 days and 30 days of
immersion duration is 0.0022 mm/yr, 0.0004 mm/yr and 0.0015 mm/yr; respectively.
Root canal treatment (RCT) requires high level of technical skills of the dentist. Its outcome is an important part of evidence-based practice and become the basis of treatment planning and prognostic considerations. Adequate removal of micro-organisms and prevention of recolonization of residual micro-organisms through the placement of root filling with satisfactory coronal seal ensures success. This retrospective record review study aimed to investigate the practices of RCT in Hospital Universiti Sains Malaysia (HUSM) Dental Clinic, Kota Bharu, Kelantan. It involved 333 randomly selected patient records at the HUSM Record Unit. Data was obtained by careful analyses of daily treatment progress sheets and analyzed using SPSS version 12.0. A total of 2996 RCT cases were seen and 59.8% of patients were females. The age range of patients varied from 14 to 64 years. The maxillary anterior teeth were most commonly treated (52.6%). Most operators (99.1%) used step-back technique and 97.6% used files to prepare root canals. The most commonly used material for obturation and sealing was gutta-percha and epoxy resin-based sealer (AH26). About 82.9% used calcium hydroxide as intra-canal medication. About 25.5% of cases had no periapical pathology, 65.8% with pre-existing periapical radiolucencies healed in 1-3 months whereas 2.1% of cases with periapical pathology eventually healed after a year. About 6.9% cases failed after retreatment. The number of radiographs taken was two to four pieces. RCT is a useful intervention to maintain longevity of teeth. Decision making and current updates of methods and materials are essential among practitioners as well as administrators to ensure success.
The aim of this study was to evaluate the antimicrobial activity of a new experimental nano-hydroxyapatite epoxy resin-based sealer (Nanoseal) with several other commercially available sealers; AH26, Tubliseal, Sealapex and Roekoseal against Enterococcus faecalis, Pseudomonas aeruginosa, Streptococcus mutans, Streptococcus sobrinus and Escherichia coli for up to 7 days. Agar diffusion was used in this study. Fifty Muller-Hinton agar plates were prepared and divided into five experimental groups (n = 10), for each micro-organism. Another 10 agar plates were used as positive and negative controls. Endodontic sealers were tested against each micro-organism. Inhibition zones produced were recorded. The results of this study showed that all test materials exhibited inhibition zones towards the tested micro-organisms for 7 days except for Roekoseal, which showed no inhibition zones. Nanoseal and AH26 exhibited similar zones of inhibition. Significant difference was found between Nanoseal and the other tested sealers (P < 0.001).
The aim of this study was to evaluate in vitro the apical sealing ability of cold lateral and system B root filling techniques using dye penetration. Eighty-six extracted single-rooted human teeth were prepared and randomly divided into two experimental groups to be obturated by cold lateral condensation (n = 33) and system B (n = 33). The remaining 20 teeth served as positive and negative controls. The roots were embedded for 72 h in methylene blue dye solution and sectioned transversely for dye penetration evaluation using stereomicroscope. The results of this study showed that cold lateral condensation leaked significantly more (P < 0.001) than system B technique.
Chitosan-ethylene glycol diglycidyl ether/TiO2 nanoparticles (CS-EGDE/TNP) composite was synthesized to be biosorbent for the removal of reactive orange 16 (RO16) dye from aqueous solution. The CS-EGDE/TNP composite was characterized via BET, XRD, FTIR, and SEM-EDX techniques. Response surface methodology (RSM) with Box-Behnken design (BBD) was applied to optimize the adsorption key parameters such as adsorbent dose (A: 0.02-0.08 g/L), RO16 dye concentration (B: 20-80 mg/L), solution pH (C: 4-10), temperature (D: 30-50 °C), and contact time (E: 30-90 min). The adsorption isotherm followed Freundlich model and pseudo-second order (PSO) kinetic model. The adsorption capacity of CS-EGDE/TNP for RO16 dye was 1407.4 mg/g at 40 °C. The adsorption mechanism of RO16 dye on the surface of CS-EGDE/TNP can be attributed to various interactions such as electrostatic attraction, n-π interaction, Yoshida H-bonding, and H-bonding. Results supported the potential use of CS-EGDE/TNP as effective adsorbent for the treatment of acid reactive dye.
The finite element method is gaining acceptance in predicting mechanical response of various loading configurations and material orientations for failure analysis of composite laminates. Both fabrication of laminate samples and experimental procedures are often expensive and time consuming, and hence impractical, especially during the initial design stage. Finite element analyses require minimal amounts of input data, and the resulting stress and strain distributions can be determined throughout each individual ply. Using ANSYSTM, a commercially available finite element package, failure loads were predicted by simulating a uniaxial tensile loading on HTS40/977-2 Carbon/Epoxy composite with [+/-4512s lamination scheme. Two built-in failure theories in ANSYSTM features, viz., Maximum Stress and Tsai-Wu were applied in the simulation. The stress-strain and load-extension curves for both actual testing and FEA were then compared and the results are in good agreement. This paper is intended for researchers who have used or are considering using ANSYSTM for the prediction of failure in composite materials.
The restoration of mechanical properties is desired for creating the self-healing coatings with no corrosion capabilities. The encapsulation of epoxy resins is limited by various factors in urea and melamine formaldehyde microcapsules. An improved method was developed, where epoxy resin was encapsulated by individual wrapping of poly(melamine-formaldehyde) and poly(urea-formaldehyde) shell around emulsified epoxy droplets via oil-in-water emulsion polymerization method. The synthesized materials were characterized analytically. The curing of the epoxy was achieved by adding the [Ni/Co(2-MI)6].2NO3 as a latent hardener and iron acetylacetonate [Fe(acac)3] as a latent accelerator. Isothermal and non-isothermal differential scanning calorimetric analysis revealed lower curing temperature (Tonset = 116 °C) and lower activation energies (Ea ≈ 69-75 kJ/mol). The addition of microcapsules and complexes did not adversely alter the flexural strength and flexural modulus of the epoxy coatings. The adhesion strength of neat coating decreased from 6310.8 ± 31 to 4720.9 ± 60 kPa and percent healing increased from 50.83 to 67.45% in the presence of acetylacetonate complex at 10 wt% of microcapsules.
This study was conducted to determine the influence of the oil palm boiler ash (OPBA) reinforcement on the microstructural, physical, mechanical and thermal properties of epoxy polymer composites. The chemical composition analysis of OPBA revealed that it contains about 55 wt.% of SiO2 along with other metallic oxides and elements. The surface morphology of OPBA showed angular and irregular shapes with porous structures. The influence of OPBA as a reinforcement in epoxy composite was studied with varying filler loadings (10-50 wt.%) and different particle sizes (50-150 μm). The result showed that the incorporation of OPBA in composites has improved the physical, mechanical and thermal properties of the epoxy matrix. The highest physical and mechanical properties of fabricated composites were attained with 30 wt.% loading and size of 50 μm. Also, thermal stability and the percentage of char residue of the composite increased with increasing filler loading. Furthermore, the contact angle of OPBA reinforced epoxy composites increased with the increase of filler loading. The lowest value of the contact angle was obtained at 30 wt.% of filler loading with the OPBA particle size of 50 μm. The finding of this study reveals that the OPBA has the potential to be used as reinforcement or filler as well as an alternative of silica-based inorganic fillers used in the enhancement of mechanical, physical and thermal properties of the epoxy polymer composite.
This work focuses on the fabrication of hybrid bio-composites using green epoxy as the matrix material, hemp (H) and sisal (S) fibre mats as the reinforcements. The hybrid composite with sisal/hemp fibres were fabricated by cost effective hand lay-up technique, followed by hot press with different stacking sequences. Static properties of the composites such as tensile, compressive, inter-laminar shear strengths (ILSS) and hardness were examined. The physical properties such as density, void content, water absorption and thickness swelling were also analyzed. The experimental results indicate that hybrid composites exhibited minor variation in tensile strength when the stacking sequence was altered. The hybrid composite with the intercalated arrangement (HSHS) exhibited the highest tensile modulus when compared with the other hybrid counterparts. Hybrid composites (SHHS and HSSH) offered 40% higher values of compressive strength than the other layering arrangements. HHHH sample exhibited the highest ILSS value of 4.08 MPa. Typical failure characteristics of the short beam test such as inter-laminar shear cracks in the transverse direction, micro-buckling and fibre rupture were also observed.
Present study, deals about isolation and characterization of cellulose nanofibers (CNFs) from the Northern Bleached Softwood Kraft (NBSK) pulp, fabrication by hand lay-up technique and characterization of fabricated epoxy nanocomposites at different filler loadings (0.5%, 0.75%, 1% by wt.). The effect of CNFs loading on mechanical (tensile, impact and flexural), morphological (scanning electron microscope and transmission electron microscope) and structural (XRD and FTIR) properties of epoxy composites were investigated. FTIR analysis confirms the introduction of CNFs into the epoxy matrix while no considerable change in the crystallinity and diffraction peaks of epoxy composites were observed by the XRD patterns. Additions of CNFs considerably enhance the mechanical properties of epoxy composites but a remarkable improvement is observed for 0.75% CNFs as compared to the rest epoxy nanocomposites. In addition, the electron micrographs revealed the perfect distribution and dispersion of CNFs in the epoxy matrix for the 0.75% CNFs/epoxy nanocomposites, while the existence of voids and agglomerations were observed beyond 0.75% CNFs filler loadings. Overall results analysis clearly revealed that the 0.75% CNFs filler loading is best and effective with respect to rest to enhance the mechanical and structural properties of the epoxy composites.
This review paper briefly explains the meaning and characteristics of endocrine disrupting compounds (EDCs). EDCs comprise various types of natural and synthetic chemical compounds that can impede the reproductive action of the endocrine system in animals and humans. Further discussion is on bisphenol A (BPA), one of the examples of EDCs that is extensively used in industries nowadays. It acts as a monomer, which is desired in the production of polycarbonate plastics and epoxy resins. BPA later ends up in environmental compartments (air, water, sediment). In spite of this, BPA is not categorized as a persistent compound and it will be degraded either by photolysis or bacteria. It can only exist between three and five days in the environment. The concentration of BPA varies in different locations depending on the temperature, pH, source and time of sampling. BPA has been frequently debated due to its toxicity and carcinogenicity towards animals and humans. This paper also explains several extraction procedures and analytical methods concerning how to identify BPA in either aqueous or solid samples. However, an additional review is needed in respect of how to handle, reduce the level of BPA in the environment and understand the details concerning the existence of BPA.
The purpose of this in vitro study was to determine if packable resin composite with/without flowable resin composite has the ability to prevent coronal leakage in restored endodontic access openings following aging.
Methyl esters from the triglyceride fraction of the neutral lipids of natural rubber latex were found by gas liquid chromatography to contain about 90% of a furanoid acid. Spectroscopic analysis identified the acid as 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid.
The study of Representative Volume Element (RVE) on Composite Material has been performed in the aim to obtain the relation and effect of fiber volume fraction on its tensile properties which is one of the important mechanical properties for composite designers in automotive and aerospace community.The properties such as fibre content, orientation, dimension of constituent fibres (diameter), level of intermixing of fibres, interface bonding between fibre and matrix, and arrangement of fibres between different types of fibres, influences the mechanical properties of hybrid composite.Representative Volume Element (RVE) for each constituent Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) assumed isotropic behavior for carbon fibre, glass fibre and epoxy resin matrix and assumed to be perfectly bonded interface between fibre and matrix region i.e. strain compatibility at the interface. The scope of study on the micro mechanical modelling via representative volume element (RVE) is limited only to unidirectional composites.The result of parametric study performed deduces that incremental volume fraction of carbon and glass respectively will increase the E11 (Modulus of Elasticity in Tensile Direction) and enhance the tensile properties of both CFRP and GFRP.
Bisphenol A (BPA) is a controversial plastics ingredient used mainly in the production of polycarbonate plastics (PC) and epoxy resins that widely used nowadays in food and drink packaging. Even though BPA is not involved in polyethylene terephthalate (PET) manufacturing, recent study had reported the present of BPA in PET water bottle. This study was conducted to investigate effects storage conditions on release of BPA from PC and PET bottled water as well as to assess health risks associated with consumption. Methods: Solid phase extraction (SPE) was used to extract the samples, followed by analysis using ultra high performance liquid chromatography with fluorescence detector (UHPLC-FLD). The possibility of developing chronic non-carcinogenic health risk among consumers of bottled water was evaluated using hazard quotient (HQ). Results: Results showed that BPA migrated from PC and PET water bottles at concentrations ranging from 9.13 to 257.67 ng/L and 11.53 ng/L to 269.87 ng/L respectively. Concentrations of BPA were higher in PET bottled water compared to PC bottled water across all storage conditions. Higher storage temperature and longer storage duration increased BPA concentrations in PC and PET bottled water. Concentrations of BPA in bottled water which were kept in a car and were exposed to sunlight were higher than control samples which were stored indoor at room temperature. Conclusion: No significant chronic non-carcinogenic health risks were calculated for daily ingestion of BPA-contaminated bottled water; calculated HQ was less than one.
Carbon fiber reinforced epoxy (CFRE) is commonly been used in automotive and aviation industries. However, CFRE composite exhibits the problem of adherence between fiber and matrix. The interface between carbon fiber (CF) and epoxy becomes a weak zone and leads to the debonding defect of fiber and low mechanical properties of composites. The main focus of this study is to fabricate CFRE using carbon nanotubes (CNTs), as the hybrid reinforcement with CF. Ultrasonic method is used to disperse CNTs in distilled water for 20 minutes, followed by deposition of CNTs on CF using electrophoretic deposition (EPD) technique. Hand lay-up assisted vacuum bagging is employed to fabricate CNTs/CF/Epoxy composite. From morphologies, surface topography and peel off testing, it can be confirmed that 30 minutes deposition allowed more CNTs to deposit on CF. The flexural properties shows that 30 minutes deposition inherited high flexural strength, 67.4 MPa and modulus, 8490 MPa.
Fiber composites are known to have poor through-thickness mechanical properties due to the absence of a Z-direction binder. This issue is more critical with the use of natural fibers due to their low strength compared to synthetic fibers. Stitching is a through-thickness toughening method that is used to introduce fibers in the Z-direction, which will result in better through-thickness mechanical properties. This research was carried out to determine the mechanical properties of unstitched and silk fiber-stitched woven kenaf-reinforced epoxy composites. The woven kenaf mat was stitched with silk fiber using a commercial sewing machine. The specimens were fabricated using a hand lay-up method. Three specimens were fabricated, one unstitched and two silk-stitched with deferent stitching orientations. The results show that the stitched specimens have comparable in-plane mechanical properties to the unstitched specimens. For the tensile mechanical test, stitched specimens show similar and 17.1% higher tensile strength compared to the unstitched specimens. The flexural mechanical test results show around a 9% decrease in the flexural strength for the stitched specimens. On the other hand, the Izod impact mechanical test results show a significant improvement of 33% for the stitched specimens, which means that stitching has successfully improved the out-of-plane mechanical properties. The outcome of this research indicates that the stitched specimens have better mechanical performance compared to the unstitched specimens and that the decrease in the flexural strength is insignificant in contrast with the remarkable enhancement in the impact strength.
The aim of this paper is to evaluate the Mode II interfacial fracture toughness and interfacial shear strength of Typha spp. fiber/PLLA and Typha spp. fiber/epoxy composite by using a double shear stress method with 3 fibers model composite. The surface condition of the fiber and crack propagation at the interface between the fiber and the matrix are observed by scanning electron microscope (SEM). Alkali treatment on Typha spp. fiber can make the fiber surface coarser, thus increasing the value of interfacial fracture toughness and interfacial shear strength. Typha spp. fiber/epoxy has a higher interfacial fracture value than that of Typha spp. fiber/PLLA. Interfacial fracture toughness on Typha spp. fiber/PLLA and Typha spp. fiber/epoxy composite model specimens were influenced by the matrix length, fiber spacing, fiber diameter and bonding area. Furthermore, the interfacial fracture toughness and the interfacial fracture shear stress of the composite model increased with the increasing duration of the surface treatment.
Nanosilica particles were utilized as secondary reinforcement to enhance the strength of the epoxy resin matrix. Thin glass fibre reinforced polymer (GFRP) composite laminates of 3 ± 0.25 mm were developed with E-Glass mats of 610 GSM and LY556 epoxy resin. Nanosilica fillers were mixed with epoxy resin in the order of 0.25, 0.5, 0.75 and 1 wt% through mechanical stirring followed by an ultrasonication method. Thereafter, the damage was induced on toughened laminates through low-velocity drop weight impact tests and the induced damage was assessed through an image analysis tool. The residual compression strength of the impacted laminates was assessed through compression after impact (CAI) experiments. Laminates with nanosilica as secondary reinforcement exhibited enhanced compression strength, stiffness, and damage suppression. Results of Fourier-transform infrared spectroscopy revealed that physical toughening mechanisms enhanced the strength of the nanoparticle-reinforced composite. Failure analysis of the damaged area through scanning electron microscopy (SEM) evidenced the presence of key toughening mechanisms like damage containment through micro-cracks, enhanced fiber-matrix bonding, and load transfer.