In this paper, were study the pervaporation of mono-nitrophenols in a laboratory installation of the Membrane, Materials, and Membrane Processes Group of the Polytechnic University of Bucharest, from aqueous synthetic solutions, to composite membranes with polysulfone matrix (PSf) and nanometric inclusions: Polyaniline (PANI), carbon nanotubes (CNT), magnetic nanoparticles (MNP) and sulfonated polyetheretherketone (PEEK-S). Tests carried out over 144 h at a pressure of 100 mm Hg or 5 L / min air flow at 25oC and pH 7 of the feed solution show that vacuum pervaporation is better than vacuum. The more advanced composite membranes are those with sulfonated polyether-ether cellulose (PSf-PEEK-S) and polyaniline (PSf-PANI) ionizers. The results of airborne pervaporation show that composite membranes (PSf-PEEK-S and PSf-PANI) present a marked difference in flux for the mono-mono-nitrophenol isomers, which could also be found in a technically exploitable selectivity. Thus, in the case of the PSf-PEEK-S composite membrane, the mono-nitro-phenol streams decrease in the order: m-C6H5NO3] o-C6H5NO3] p-C6H5NO3, while for the PSf-PANI composite membrane the order is o-C6H5NO3] m-C6H5NO3] p-C6H5NO3. At the same time, it is noted that the PSf-PEEK-S composite membrane performance is superior during operation, but shows the opposite of the more pronounced drop.
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Collagen is an important natural biopolymer, found in mammal’s body. It is the main structural protein in the extracellular space in the various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals. Its importance increased in last decades. Collagen has many applications in medicine and cosmetics. The work presented in this paper shows one method to obtain collagen films from collagen solutions. These collagen solutions were characterized by rheological measurements. The preparation of the collagen films was performed in the presence of calcium and silicium salts, using glycerin as plasticizer. The collagen was first solubilized and reconstituted, in order to maintain its initial properties.
Due their various applications the fabric reinforced polymer composites are subject of a large number of researches especially for aero- and automotive industry. Regarding the last domain there are huge interests in designing and forming composites with controllable strengthens for car bodies able to protect both the driver and passengers inside and pedestrians in case of unfortunate events. In this regard, based on previous studies developed at the Research and Development Centre for Thermoset Matrix Composites, our proposal is to design the bending behaviour of a fabric reinforced materials by means of changing the bending strength of the polymer matrix using a solvent. 1-Methyl, 2- pyrrolidinone is a well-known polymer solvent that had been used in previous studies as vector to transfer various organic agents into epoxy resins. During those studies it had been noticed that the presence of above mentioned solvent is changing the bending behaviour of polymer samples and induces some properties that are belonging to memory-shape materials. The present study is related to mechanical analysis of a multi-layered material (fabric layers) immersed into an epoxy resin having a graded bending strength.
n the current paper, we aimed to analyze the way in which packing (different polyethylene types) influence the quality of pasteurized melange during storage, packing being realized in units of 1 kg (Tetra Pak) (batch Lexp-1) and units of 5 kg (Bag in box) (batch Lexp-2). Products were stored during a period of 28 days at a temperature of +4°C, qualitative determinations being realized in first day (day 0), at 7 days, at 14 days, 21 days and in day 28 of storage. Were effectuated a sensorial examination and chemical analysis were was established the content in dry matter (%), water (%), proteins (%), content in essential amino acids (isoleucine, methionine, tryptophan, phenylalanine) and non-essential amino acids (alanine, histidine, glycine, serine) (mg/100g) as well as the content in lipids (%) establishing their profile by identification of some saturated fatty acids (16:0 mg/100g and 18:0 mg/100g) and unsaturated fatty acids (16:1 mg/100g and 18:1 mg/100g). After sensorial examinations, the first modifications were observed at the checking effectuated in day 21 for batch Lexp-2, the obtained score being of 18 points, and at checking effectuated in day 28 was given a score of 18 points for melange belonging to batch Lexp-1 and only 14 points for melange from batch Lexp-2. Differences were recorded also in case of chemical composition of products, so for protein content at batch Lexp-1 in first checking day was obtained a mean of 12.730±0.24% and at batch Lexp-2 12.614±0.22%. Differences between those two batches were insignificant (p < 0.05). In case of fat content, at the end of storage period was obtained a mean of 11.256±0.06% for batch Lexp-1 and 11.244±0.11% for batch Lexp-2, differences being insignificant (p < 0.05). Regarding the profile of amino acids and fatty acids, the mean values obtained during whole storage period oscillated from one stage to another, but the differences between those two batches were insignificant (p < 0.05). Pasteurized egg melange suffers certain sensorial modifications during storage, especially on consistency and colouring, modifications which are accentuated mainly by storage conditions. Type of polyethylene utilized for this product hadn’t influenced the nutritive qualities of product.
The aim of this in vitro study was to to evaluate the impact of finishing procedures on the enamel adjacent to composite restorations and to assess if the resistance of the enamel-resin junction to leakage is affected by the use of these instruments. The surfaces of enamel at the joint with composite were observed by scanning electron microscopy, then the microleakages at the enamel margin was assessed using an optical microscope. Finishing with extra-/ ultra-fine carbide burs and extra-fine diamond burs produced a superficial abrasion to the adjacent enamel and did not seem to have a significant influence on the sealing ability of composite resin.
The aim of the study was to investigate the dynamics of the main chemical compounds in the powdered eggs stored under constant environmental conditions (temperature=10±0.5oC; relative humidity=65±1%) and packaged in bags made of different plastic fabric (Lc group = high density polyethylene – HDPE; Lexp group = low density polyethylene – LDPE). The assessments were run to measure the inner water and dry matter contents, as well as the ash, proteins, lipids and nitrogen free extract levels. The analysis of data gathered throughout 90 days of storage suggested that the product packaged in low density polyethylene bags – LDPE (Lexp group) absorbed +0.82% humidity from the environment, compared to Lc group (highly significant differences), lost 0.41% from its initial proteins level and 0.59% of the nitrogen free extract, while lipids and ash values were not affected by the experimental factor (different package). Consequently, it might be concluded that the type and quality of the utilised package could significantly influence the proximate chemical composition, due to the transfers from the outer storage environment toward the inner volume of the package, whose intensity is given by the direct influence of the barrier features of the fabric the packages are made of.
Growing demands from industry for the use of eco-friendly lubricants led research towards finding environmentally friendly products with superior lubricating characteristics. Vegetable oils and synthetic ester oils are competitive base oils used to obtain lubricants with good physico-chemical, rheological and tribotechnical properties, biodegradable lubricants without negative environmental impacts. In this study we aimed the synthesis and characterization of bioesters with lubricant properties, using as acid component the soybean oil fatty acids in conjunction with the following hydroxyl compounds n-buthanol (P1) and 1,2-propilenglycole (P2), respectively. These complex esters were synthesized in a microwave reactor in a single stage in the presence of the catalyst at the reflux temperature. Characterization was carried out in the respective of structural point of view and as a lubricant.
This paper aims to synthesize the main categories of biomaterials (bone substitutes, collagen membranes) used in the reconstruction of oral bone defects and alveolar augmentation by guided bone regeneration technique. The review of literature data shows that guided bone regeneration technique offers reliable and predictable results in the implant-prosthetic treatments.
Resin-based pit and fissure sealant materials are heterogeneous materials with two principal components: the resin matrix and the filler particles. The shear bond strength test holds great importance for providing insight into the adhesion of these materials and, also, it is a screening mechanism for predicting clinical performance. The purposes of the present study are to investigate the structure of surface and the shear bond strength for two commercial pit and fissure sealants, Fissurit (VOCO) and Pit &Fissure (DMP) sealer. Seal Fissurit had the highest shear strength, and the difference was statistically significant between two tested materials.
In lumbar disc herniation a possible functional problem in the ambulation is the Foot-drop syndrome caused by radicular nerve pinching. This causes a dramatic loss in gait cycle efficiency. In the rehabilitation process patients may benefit from wearing a foot orthosis that prevents them from falling and secondary injuries. Evidence in the literature suggests the important correlation between the optimal match of the forces produced during human gait and the rigidity of the constructive materials. The inherent rigidity of the materials plays an important role in determining its biomechanical functions. The paper proposes an experimental and numerical characterization of 3D printed ABS and PLA specimens using a universal traction-compression testing machine and a finite element method numerical simulation.