Search results for "composite"
showing 10 items of 4584 documents
Hydroxypropyl Cellulose Films Filled with Halloysite Nanotubes/Wax Hybrid Microspheres
2021
The design of novel nanocomposite films based on hydroxypropyl cellulose (HPC) and wax/halloysite hybrid microspheres has been reported. In particular, we first prepared wax/clay Pickering emulsions which were characterized by thermogravimetric analysis and microscopy. SEM images allowed more detailed insights on the nanotubes disposition at the wax/water interface, acting as an outer stabilizing shell. Therefore, the cellulosic biopolymer was added, and it was found that HPC enhances the colloidal stability of the particles, preventing their coalescence and sedimentation. The preparation of the composite films was carried out by the solvent casting method, which enabled the development of …
Halloysite nanotubes-based nanocomposites for the hydrophobization of hydraulic mortar
2021
Abstract The treatment of stone surfaces for their protection from ageing caused by natural and anthropogenic effects is an open issue in materials development for Cultural Heritage. We thought interesting to verify the suitability of a modified cellulose biofilm filled with halloysite nanotubes as wax compatibilizers to design a protecting layer. A hydraulic mortar was selected as a stone prototype. To improve the physico-chemical properties of the covering layer, wax microparticles have been incorporated to control transport, consolidation and wettability features. In particular, different application protocols have been studied, namely brushing and spraying, to assess whether the propos…
Chemical and physical modification of hemp fibres by steam explosion technology
2013
In current research attempt has been made to analyse hemp fibres treated with steam explosion (SE) technology. Disintegration of hemp fibres separated from non-retted, dew-retted and dried stems of hemp ('Purini')[1] by alkali treatment and steam explosion (SE) were investigated. An average intensive SE in combination with the hydro-thermal and alkali after-treatment allows decreasing the diameter of hemp fibres and reduce the concentration of non-celluloses components, among them hemicelluloses, lignin, pectin, waxes and water [1;2].
Effect of different dispersing additives on the morphology and the properties of polyethylene-based nanocomposite films
2011
In this work, the use of a polar wax, e.g. amphiphilic Tegomer ® E 525 (TEG) is investigated with the aim of mod- ifying, and possibly improving, the dispersion of an organically modified nanoclay (OMMT), loaded at 5 wt%, in a poly- ethylene matrix (PE) at relatively low loading levels. We have indeed found that the incorporation of low loadings, e.g. 0.5 wt%, of TEG, an amphiphilic block co-polymer, into a PE/OMMT sample results in a substantial improvement of the clay dispersion in the nanocomposite and, consequently, of the mechanical and thermomechanical properties of the films. The achieved results are comparable to those obtained for systems containing traditional dispersing agents su…
Crystalline wax coverage of the imaginal cuticle inCalopteryx splendens(Odonata: Calopterygidae)
2009
Abstract In this study we use high resolution SEM to describe the diversity of wax crystals and their distribution on different morphological structures in male individuals of Calopteryx splendens. The entire cuticle surface of this damselfly, with the exception of ommatidia and ocelli, is covered with crystalline wax in dimensions from submicron to micron range. It is shown that shape - rod-like, plate like, filamentous, etc. -, size, and density of crystals vary on different surfaces and in individuals of different ages. Additionally, we demonstrate different types of damage to the crystalline wax layer: scratches, compressions, wear, and contamination. The primary function of the wax cry…
Laser Cladding of TiC for Better Titanium Components
2011
Pure commercial titanium is widely used because of its high corrosion resistance and lower cost compared with other titanium alloys, in particular when there is no high wear requirements. Nevertheless, the wear resistance is poor and surface damage usually occurs in areas under contact loadings. Laser cladding is a suitable technique for manufacturing precise and defect free coatings of a dissimilar material with higher wear and corrosion resistance. In this work a good understanding of laser metal deposition mechanisms allowed to obtain defect free coatings of Ti6Al4V and TiC metal matrix composite (MMC) using a flash lamp pumped Nd:YAG laser of 1 kW. A complete investigation of the proces…
Fracture Resistance of Partial Indirect Restorations Made With CAD/CAM Technology. A Systematic Review and Meta-analysis
2019
Background: The aim of this systematic review and meta-analysis was to determine the fracture resistance and survival rate of partial indirect restorations inlays, onlays, and overlays fabricated using computer-aided design and computer-aided manufacturing (CAD-CAM) technology from ceramics, composite resin, resin nanoceramic, or hybrid ceramic and to analyze the influence of proximal box elevation on fracture resistance. Materials and methods: This systematic review was based on guidelines proposed by the preferred reporting items for systematic reviews and meta-analyses (PRISMA). An electronic search was conducted in databases US National Library of Medicine National Institutes of Health …
Saccharomyces cerevisiae and Oenococcus oeni immobilized in different layers of a cellulose/starch gel composite for simultaneous alcoholic and malol…
2013
Abstract The production of a two-layer composite biocatalyst for immobilization of two different microorganisms for simultaneous alcoholic and malolactic fermentation (MLF) of wine in the same bioreactor is reported. The biocatalyst consisted of a tubular delignified cellulosic material (DCM) with entrapped Oenococcus oeni cells, covered with starch gel containing the alcohol resistant and cryotolerant strain Saccharomyces cerevisiae AXAZ-1. The biocatalyst was found effective for simultaneous low temperature alcoholic fermentation resulting to conversion of malic acid to lactic acid in 5 days at 10 °C. Improvement of wine quality compared with wine fermented with S. cerevisiae AXAZ-1 immob…
Color stability of Bulk-Fill composite restorations
2020
Made available in DSpace on 2022-04-28T19:29:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-11-01 Background: The color stability of the composite resin is an important property that influences its clinical longevity, which remains an inherent challenge to the material. Thus, the purpose of this study was to evaluate the color stability of bulk-fill resins when exposed to dye. Material and Methods: Cavities were prepared in 80 bovine incisors, which were randomly assigned into 4 groups (n = 20) according with the resin composite used: P60 (Control Group - Filtek P60, 3M/ESPE), FP (Filtek Bulk-Fill Posterior, 3M/ESPE), SDR (SDR, Dentsply) and FF (Filtek Bulk Fill Flow, 3M/ESPE). A…
Partial discharge tests using CIGRE method II
2000
In this paper, the results of an experimental project on insulating material aging, performed in both Denmark and Italy, are reported. This study was concerned with partial discharge (PD) behavior at temperatures between 30 and 80/spl deg/C using CIGRE method II. The material tested was a commercial polymethylmethacrylate (PMMA) which was chosen not for its good dielectric properties but rather because much of its discharge resistance data at ambient temperature is already well documented. A description is given of the theoretical and experimental methodology followed in this work. Mixed Weibull analysis techniques in terms of the PD amplitude and phase distribution characteristics were emp…