Improved Wear-Resistant Performance of Epoxy Resin Composites Using Ceramic Particles

This work investigated the effects of using a new fabrication technique to prepare polymer composite on the wear-resistant performance of epoxy resin composites under dry friction conditions. Polymer composite samples with different weight contents of silicon carbide (SiC) particles were manufactured. This paper addresses the wear behavior of the obtained samples. With the suggested technique, the samples were prepared from epoxy/silicon carbide particles using a layer of thin kraft paper to prevent the sedimentation of the ceramic particles and to control the weight content of ceramic in the polymer. Kraft paper was used as a layer in the polymer composite. The hardness, wear resistance, and water absorption capacity of the produced epoxy composite samples prepared using the kraft paper technique were evaluated. The morphology of epoxy composite samples showed a significant improvement in the ceramic distribution and enhancement of interface bonding between ceramic and the polymer. The hardness values of the developed polymer composites were enhanced by up to 42.8%, which was obtained at 18 wt.% SiC particles. Increasing the ceramic content in the epoxy also led to the enhancement of wear resistance compared with pure epoxy. The results of the microstructure study also showed that the kraft paper layers helped in maintaining the distribution of the ceramic particles according to the previously specified content in each layer in the sample. Wear tests showed that the wear rate of the polymer composite decreased with the increase in the ceramic content. This study provides a new recycling method for using old kraft paper in polymer composite manufacturing to improve the distribution of ceramic particles in the polymer matrix.

Four Years of Sediment and Phosphorus Monitoring in the Kraichbach River Using Large-Volume Samplers

Various sampling strategies come into operation to monitor water quality in rivers. Most frequently, grab samples are taken, but they are not suitable for recording the highly dynamic transport of solids and solid-bound pollutants. Composite samples reduce the influence of input and transport dynamics and are better suited to determine the annual river loads. Large-volume samplers (LVSs) produce both a composite sample over a long period of time and an amount of solids which allows for further analyses. In the small sub-catchment area of the Kraichbach river in Baden-Wuerttemberg (Germany) two LVSs have been installed to sample the river flow. The concentration of solids and phosphorus in the supernatant water and the settled sediment in the sampler have been determined and mean concentrations have been derived. Annual river loads were calculated in combination with discharge data from the nearby gauging station. Two sampling strategies of the LVS were tested and compared. For the first strategy, the LVS was used to collect quasi-continuous composite samples throughout the year, whereas, with the second strategy, samples were taken specifically for different flow conditions (low, mean and high flow). This study compares the advantages and constraints of both strategies. Results indicate that the first strategy is better suited to determine annual river loads. Quasi-continuous large-volume composite sampling is recommended for further monitoring campaigns.

Nano-hybridization effects of nano-silica and nano-graphene platelet on mechanical properties of E-glass/epoxy nanocomposites

This study reveals the nano-hybridization effects of nano-graphene platelets (NGPs) and nano-silica (SiO2 nanoparticle), having different structural geometries on the mechanical properties, nano and micro-scale failure behaviors, and nanoscale fracture mechanisms of E-glass/epoxy composites. Tensile, three-point bending, and Charpy impact experiments were applied to determine the mechanical behaviors of 0.5 wt.% NGPs, 4 wt.% nano-silica and 0.5 wt.% NGPs + 4 wt.% nano-silica nanohybrid filled E-glass/epoxy and neat E-glass/epoxy composite samples. Failure of composite samples was examined by microscopy and SEM analysis. FTIR analyses were conducted to interpret the chemical and physical interactions between the nanoparticles and epoxy resin. Nano-hybridization exhibited the highest tensile strength and three-point flexural force for the composite samples. However, the NGPs filled nanocomposites also exhibited the best static tensile toughness and impact energy absorption. The experimental data showed that it was statistically significant as a result of the one-way ANOVA analysis. Remarkably, nano-hybridization of nano-silica and NGPs showed different fracture mechanisms at the nano and micro-scales.

High Density Polyethylene (HDPE) composite mixed with Azadirachta excelsa (Sentang) tree waste flour: Mechanical and physical properties

This article presents the application of plantation waste materials (leaves, branches and trunks) of Azadirachta excelsa (Sentang) tree in order to evaluate and compare their suitability as reinforcement and filler for high density polyethylene (HDPE) thermoplastics. The aim of the study was to investigate the effect of different types of Azadirachta excelsa (Sentang) trunks flour, branches flour and leaves flour fillers on the mechanical and physical properties of HDPE composite. The composite samples were produced using 25%, 35% and 45% by weight of flour filler loading and 2% coupling agent (maleic anhydride) using a twin-screw extruder, followed by injection molding process. The flexural modulus and tensile strength of the composite filled with trunk flour were not significantly different with the composite-filled branch flour. However, there is a significant difference between composite-filled leaf flour when compared to both composite-filled trunk flour and composite-filled branch flours. Overall, composite samples with trunk flour show better mechanical properties, while composite samples with lower filler loadings of 25% exhibit better dimensional stability compared to the other such as 35% and 45% filler loadings. The study also indicated that composite filled with leaf, branch and trunk flours had better mechanical strength than virgin HDPE.

Nutritional and Other Trace Elements and Their Associations in Raw King Bolete Mushrooms, Boletus edulis

The occurrence and associations of Ag, As, Ba, Bi, Cd, Co, Cu, Cs, Hg, Ni, Pb, Rb, Sb, Sr, Tl, U, V, W, and Zn, including data that have not been previously reported on Be, Hf, In, Li, Mo, Nb, Sn, Ta, Th, Ti and Zr, and the sum of (14) rare earth elements (ƩREE), were studied in a spatially diverse collection of the B. edulis caps, stipes, and whole fruiting bodies using a validated procedure with measurement by quadrupole ICP-MS. Toxic Cd and Pb were in B. edulis at concentrations below limits set by the European Union in regulations for raw cultivated mushrooms, while Ag, As, Hg, Sb, Tl, and U, which are not regulated, were at relatively low or typical levels as is usually found in mushrooms from an unpolluted area. The elements Be, Bi, Ga, Ge, Hf, In, Nb, Ta, Th, and W, and also ƩREEs, were found at relatively low concentrations in B. edulis, i.e., with levels from below 0.1 to below 0.01 mg kg−1 dw, and for Ʃ14 REEs, the median was 0.31 mg kg−1 dw. The composite samples of caps showed Ag, Cd, Cu, Cs, Ga, Ge, Hg, Mo, Ni, Rb, Sb, Ti, and Zn at higher concentrations than stipes, while Ba, Co, Hf, Sr, Tl, and Zr were found at higher concentrations in stipes than caps (p < 0.05). Mushrooms were characterized by a low coefficient of variation (CV) of below 20%, between sites for concentrations of As, Cu, Ge, Hg, Ni, V, and Zn, while substantial differences (CV > 100%) were found for Ba, Bi, Co, Hf, Zr, and ƩREEs, and an intermediate variation was found for Sr, W, and U. Principal component analysis performed on mushrooms allowed differentiation with respect to 13 collection sites and separation of a consignment that was specifically contaminated, possibly due to a legacy pollution, with significantly higher levels of Ba, Co, Ga, Li, Nb, Ni, Sr, Th, Ti, Y, Zr, and ƩREEs, and another due to possible recent pollution (Pb-gasoline and also Ni); two due to geological contamination because of the Bi, In, Sc, Sb, Sn, Ta, V and W; and one more, the Sudety Mts. site, which was considered as “geogenic/anthropogenic” due to Ag, As, Be, Cd, Cs, Ni, Pb, Rb, Tl, and U.

Experimental Investigation on Aquatic Waste Water Hyacinth (Eichhorniacrassipes) Plant into Natural Fibre Polymer Composite – Biological Waste into Commercial Product

Present work dealt with evaluating the aquatic wastewater hyacinth plant long fibre reinforced withepoxy polymer composite mechanical strength, absorption, characterization, thermal degradation and stability, surface morphology studies. This research work water hyacinth long fibre is used as a reinforcement material and epoxy polymer matrix material is used as a matrix phase material. By utilizing the compression moulding hot press machine the different weight percentages (20, 25, 30, and 35%) of the hyacinth composite samples areproduced.Converting the biological waste into zero waste and useful product concept is achieved in this research. In this work hyacinth, long fibre is extracted with a new novel mechanical way (fabricated machine) of the extraction process. Hyacinth long fibre composite tensile strength (mechanical strength) is varied from 36.42 to 44.62MPa, flexural strength varied from 47.86 to 59.684MPa, and impact strength varied from 0.5 to 3.5J. After the 8th hour of monitoring the composite samples are attained constant values on both water and chemical absorption studies. By utilizing thermogravimetric analysis, x-ray diffraction method, Fourier transform infrared spectroscopy method the essential functional groups present in the hyacinth composites are identified. Based on the final experiment results the hyacinth fibre composite is highly recommended to the usage of profit oriented products.

Effect of Volume and Renewal of the Storage Media on the Release of Monomer from Dental Composites

This study evaluated the effect of the volume and renewing of storage media on monomer leachability from dental composite. Samples of two dental composites (BEAUTIFIL II Gingiva (BG) and Filtek Bulk-Fill Flowable (FBF)) were stored after polymerization in 1 and 3 milt storage media (ethanol/water 75%) for seven days. Refreshing of storage media was done in half of the samples of each group. The amounts of releasing monomers (UDMA, BisGMA, TEGDMA) in storage media were measured by high-performance liquid chromatography (HPLC). Data was analyzed using two-way ANOVA and t-test (α = 0.05). Elution of TEGDMA and UDMA from both composites was significantly higher in 3 mL storage media. In groups with refreshing of storage media, BisGMA had higher amounts of release. Saturation makes the storage media volume important factor in monomer elution. Refreshing of storage media had significant effect on monomer release before the elution of 50% of total released monomer.

Effect of Thermal Aging on Mechanical Properties and Color Difference of Glass Fiber/Polyetherimide (GF/PEI) Composites

This research study is aimed at evaluating the mechanical characteristics in terms of tensile strength and flexural strength of glass fiber reinforced Polyetherimide (GF/PEI) under different thermal aging. Tensile testing and bending testing were performed on the thermally aged polyetherimide composites. The mechanical properties of the thermally aged samples were also correlated with their color difference. The experimental results showed that both the tensile strength and flexural strength of the GF/PEI composite samples decreased with increasing aging temperature. However, the elastic modulus of the composite samples is nearly independent on the thermal aging. The thermally aged samples exhibited brittle fracture, resulting in low strength and low ductility. The loss in strength after thermal aging could be also linked to the change of their color difference, which can indirectly reflect the change of the strength for the composites after thermal aging.

OPTIMIZATION OF TECHNOLOGY FOR PRODUCING A COMPOSITE BASED ON BARIUM FERRITE AND BARIUM TITANATE

В работе показано, что в результате спекания образцов композита титанат бария (80 объемных %) - феррит бария (20 объемных %) в фарфоровом тигле при температуре 1300 °С возникает эвтектика. В результате сравнения свойств образцов, полученных при различных температурах спекания, установлено, что оптимальные свойства имеют образцы, спеченные при 1250 °С. Проведено сравнение структуры и диэлектрических свойств образцов керамики титаната бария и композита титанат бария (80 объемных %) - феррит бария (20 объемных %), спеченных при температуре 1250°С. Показано, что добавление в состав титаната бария 20% феррита бария повышает значение диэлектрической проницаемости, пироэлектрического коэффициента и пьезоэлектрического модуля d композита в 1,5 - 2 раза по сравнению с керамикой титаната бария, тогда как значение пьезоэлектрического модуля d остается без изменения. Введение в состав керамики титаната бария 20 % феррита бария достаточно для того, чтобы полученный композит имел магнитные характеристики, соответствующий чистому ферриту бария. It is shown in the work that as a result of sintering of composite samples of barium titanate (80 vol. %) - barium ferrite (20 vol. %) in a porcelain crucible at a temperature of 1300 °C, a eutectic appears. As a result of comparing the properties of the samples obtained at different sintering temperatures, it was found that the samples sintered at 1250 °C have optimal properties. The structure and dielectric properties of barium titanate ceramic samples and barium titanate (80 vol. %) - barium ferrite (20 vol. %) composite sintered at a temperature of 1250 °C are compared. It has been shown that the addition of 20% barium ferrite to the composition of barium titanate increases the dielectric constant, pyroelectric coefficient, and piezoelectric modulus d of the composite of 1,5 - 2 times compared to barium titanate ceramics, while the value of the piezoelectric modulus d remains unchanged. The introduction of 20 % barium ferrite into the barium titanate ceramics is sufficient for the resulting composite to have magnetic characteristics corresponding to pure barium ferrite.

Cytotoxic Effects of Bulk-Fill Composites on L929 Fibroblast Cells

Objective: Unlike traditional composite resins, bulk-fill composite resins could be polymerized as thicker layers. This study aims to contribute to the field by investigating the cytotoxic effects of various bulk-fill composite resins on L929 mouse fibroblast cells in vitro. Material and Methods: In our study, six bulk fill and one conventional composite resin were used. Composite resin samples (8×4 mm) were prepared in a sterile cabinet by using a glass mod and polymerizing with a led light device (DTE LUX E, Germany). Composite samples (n:3) of which surface area was calculated according to ISO 10993-12: 2012 standards (3 cm2/ml), were kept in media for 24 h and 72 h in 37 oC incubator, their extracts were filtered in 1:1 and 1:2 proportion and were added on L929 mouse fibroblast cells. Cell viability was examined by the MTT assay and cell death by the LDH test. Cell viability results were evaluated using one-way analysis of variance (ANOVA) test (p<0.05). Results: When the 1:1 extracts from 4 mm thick bulk-fill composite samples were applied on L929 mouse fibroblast cells, cell viability rates showed significant differences compared to the control group at the end of 24 h and 72 h (except for Estelite Bulk Fill Flow). Although the extracts of the tested composite samples at 1:1 and 1:2 ratio at the end of 72 hours caused a decrease in L929 mouse fibroblast cell viability, the cell viability rate of only PRG-containing bulk fill composite and conventional composite remained below the cell viability ratio (70%) specified in ISO standards. Bulk fill composites did not produce toxic effects (except Beautifil Bulk Restorative) according to the LDH test. Conclusions: Despite decreasing in general the cell viability, bulk-fill composite resins used in 4 mm thick layers provided cell viability rates over the acceptability level, except PRG-containing bulk fill composite (Beautifil Bulk Restorative), which was cytotoxic to L929 mouse fibroblasts. Keywords Bulk fill composite; Cytotoxicity; L929 cells; LDH assay.