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Published By Revista De Chimie SRL

0025-5289, 2668-8220

2022 ◽  
Vol 58 (4) ◽  
pp. 47-54
Author(s):  
Gheorghe Batrinescu ◽  
Ioana-Alexandra Ionescu ◽  
Roxana-Elena Scutariu ◽  
Bogdan Chiricuta ◽  
Ionut Cristian Surupaceanu

Results obtained from the characterization of three water samples (one representing the effluent of a municipal treatment plant and the two others representing surface water from the Jiu River/Romania, upstream and downstream of the effluent discharge point) are presented in this study in terms of microplastic content. The water samples were processed by successively passing them through a series of filters with the following dimensions: 5 mm, 0.5 mm (500 im), 0.1 mm (100 im) and then through some microfiltration membranes (MF) type EZ-Pak Membrane Filters (Merk-Millipore) made of a mixture of cellulose esters, with an average pore diameter of 0.45�m. In order to highlight the microplastics in the water samples, their analysis was performed as well as the solid material retained on the microfiltration membranes, by scanning electron microscopy (SEM) using a SEM Quanta FEG 250/Thermo Fischer Scientific. The results obtained highlighted the existence of microplastics in all the analyzed samples, in the known forms presented in the specialized literature: irregular planes, fibers and spheres. Their dimensions are variable, ranging between 3.2 �m and 119.5 �m for irregular plane microplastics and between 3 �m and 15 �m for spherical microplastics. The dimensions of microplastics in the form of fibers are also in the range of tens of �m and cannot be established exactly because in most cases they appear in the form of conglomerates. The treatment plant�s microplastic effluents content led to the modification of the physical-chemical indicators of the water in their natural receptor. Thus, the content of organic matter and total suspended matter in the downstream water compared to the effluent discharge point is higher than in the upstream water. The analysis of microplastics by SEM allows only their highlighting and their geometry, being a first step in the study of the pollution induced by such materials.


2022 ◽  
Vol 58 (4) ◽  
pp. 147-157
Author(s):  
Elena-Felicia Beznea ◽  
Nicusor Baroiu ◽  
Ionel Chirica

A study on the static analysis of a naval panel made of composite sandwich materials is presented. By using FEM, the modeling of a naval floor with a length of 5 m and a width of 2.5 m is performed. Two distinct cases, have been performed: the first model consists of the plate and stiffeners made of steel and the second model concerns a panel made of composite material sandwich type steel / SANFoam103 / steel, and the stiffeners made of steel. A parametric study has been performed. The thickness of the steel faces have 6 mm, and for the core of SANFoam have been selected the thicknesses 5 mm, 10 mm, 20 mm, 40 mm.


2022 ◽  
Vol 58 (4) ◽  
pp. 19-27
Author(s):  
Peng Jian Xiang ◽  
Zhu Xiao Rao ◽  
Sun Shi Dong ◽  
Zhu He Ping

The effect of bamboo fiber content on mechanical properties, moisture permeability and light transmittance of composite membrane was studied. The results show that the tensile strength of the composite film is increased by 30%, and the mechanical properties of PVA film are improved obviously with the addition of bamboo cellulose, which can be used as a good reinforcing material of PVA matrix. Bamboo cellulose composite film is a kind of transparent material because of its high light transmittance.


2022 ◽  
Vol 58 (4) ◽  
pp. 171-178
Author(s):  
Elangovan Kasi ◽  
Mohan Ramakrishnan

The usage of seals in several applications like aircraft engines is mostly made of Fluorocarbon (FKM) elastomer. They are coloured products that enable easier identification based on the applications. In such seals, fillers like carbon black cannot be added to reinforce and improvise the mechanical properties since carbon black does not make it possible to add colours. The properties after ageing are also very critical in sealing application, and they must also be improved. Also, Nanocomposites are the modern and growing trends in the field of polymers that show enormous changes in the properties of the polymers without affecting their basic properties. So, the need for improvisation of FKM seals and the concept of Nanocomposites can be merged to form FKM Nanocomposites with Nano clay and Nano silica as the fillers. The objective of this project is to improve the mechanical properties, better retention of properties after ageing and after fluid interaction of the FKM seals with the aid of Nanofillers. Different proportions of FKM nanocomposites were prepared using modified Nano Kaolin Clay & modified Montmorillonite clay (Cloisite grades). Various mechanical properties like tensile strength, tensile modulus, elongation at break, compression set and tear strength etc., were studied. The test results have shown good improvements while increasing the filler loading. This is helpful to manufacture seals of desired colours thereby avoiding the difficulties faced in the carbon black-filled FKM compounds.


2022 ◽  
Vol 58 (4) ◽  
pp. 84-93
Author(s):  
Mirela Alina Constantin ◽  
Lucian Alexandru Constantin ◽  
Sebastian Aradoaei ◽  
Mihaela Aradoaei ◽  
Mihai Bratu ◽  
...  

Sustainable materials made from recycled materials are an alternative to traditional materials (synthetic ones) and present a lower environmental impact. Due to the fact that natural fibers were successfully used to produce environmentally friendly sound adsorbing materials, biocomposites made from recycled polypropylene (PPR), feathers flour (FF) with / without compatibilizers (C) were obtained and characterized from the point of view of their acoustical behavior. Obtained materials were characterized also from the morphological and compositional point of view by scanning electron microscopy and thermal gravimetric analysis. All tested samples presented sound adsorption properties but the best results were obtained for the biocomposites with FF content of 10%-20%.


2022 ◽  
Vol 58 (4) ◽  
pp. 138-146
Author(s):  
Alina Crina Muresan ◽  
Lidia Benea

In this study different type of composite coatings was obtained by electrodeposition using zinc as matrix and polymeric particles as disperse phase in zinc sulphate electrolyte. The effects of some electrodeposition parameters on the thickness and morphology of obtained composite coatings were analysed by optical microscopy, Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Ray Spectroscopy (EDX) methods. Polymeric particles inclusion into zinc matrix was correlated with imposed electrodeposition parameters. It was observed that the thickness of the coatings is influenced by electrodeposition parameters. From the morphology of the coatings, it could be concluded that pure zinc has a regular surface with hexagonal crystals, while the composite coatings have fine surface structure. Also, the electrodeposition parameters influence the inclusion of the dispersed phase into metallic matrix that will influence further the different properties of the composite materials.


2022 ◽  
Vol 58 (4) ◽  
pp. 28-36
Author(s):  
Velmurugan Natarajan ◽  
Ravi Samraj ◽  
Jayabalakrishnan Duraivelu ◽  
Prabhu Paulraj

This study aims to reveal the consequence of thickness reinforcement on Fiber Laminates (Polyester Resin, Glass Fiber, Aluminum, and Bentonite) and to see if it can enhance the mechanical properties and resistance of laminates. Glass fiber reinforced polymer composites have recently been used in automotive, aerospace, and structural applications where they will be safe for the application s unique shape. Hand layup was used to fabricate three different combinations, including Aluminium /Glass fiber reinforced polyester composites (A/GFRP), Bentonite/Glass fiber reinforced polyester composites (B/GFRP), and Aluminium&Bentonie/Glass fiber reinforced polyester composites (AB/GFRP). Results revealed that AB/GFRP had better tensile strength, flexural strength, and hardness than GFRP and A/GFRP. Under normal atmospheric conditions and after exposure to boiling water, hybrid Aluminium&Bentonite and glass fiber-reinforced nanocomposites have improved mechanical properties than other hybrid composites. After exposure to temperature, the flexural strength, tensile strength and stiffness of AB/GFRP Composites are 40 % higher than A/GFRP and 17.44% higher than B/GFRP Composites.


2022 ◽  
Vol 58 (4) ◽  
pp. 55-64
Author(s):  
Silvia Salavastru ◽  
Irina Andreea Niagu ◽  
Luana Andrei Macovei ◽  
Lucretia Anghel ◽  
Nicolae Sarbu ◽  
...  

Ophthalmic treatments using contact lenses are now used by more and more specialists around the world. Improving contact lens (CL) materials is a condition that is constantly evolving. Contact lens materials are usually composed of polymer hydrogel or silicone hydrogel. The materials used for night contact lenses are gas permeable and they gradual flatten the center of the cornea which decreases the progression of myopia or myopic astigmatism. The aim of this study is to identify, in correlation with the chemical interactions between structural components of contact lenses and their biocompatibility with the surface layer and microtopography of the cornea or sclera, different incidents that occur in patients who have used rigid gas permeable contact lenses. The study was performed on a group of 10 patients who had a follow-up period between 4 and 6 years, who presented regularly for eye examinations. The following clinical parameters were analyzed: ocular refraction before and after wearing night contact lenses, types of contact lens materials, appearance of corneal topography, biomicroscopic examination of the anterior segment of the eye, keratometry, ocular comfort, as well as other incidents regarding this type of lenses. Difficulties caused by wearing contact lenses at night arose due to poor hygiene and maintenance in two cases or due to interruption of lens wear in one case.


2022 ◽  
Vol 58 (4) ◽  
pp. 65-72
Author(s):  
Andra Mihaela Onas ◽  
Iuliana Elena Biru ◽  
Aida Petca ◽  
Razvan Cosmin Petca

Ureteral catheters, commonly known as double j stents according to their specific shape, are largely used worldwide with good results to assure proper renal drainage and to overpass ureteral obstacles successfully. This study deals with the aging behavior of polyurethane-based urinary catheters, explanted at different time intervals: 22 days, 29 days, three months, and eight months respectively. TGA (Thermogravimetric analyses) tests showed significant differences in the thermal behavior of polyurethane-based material, especially at eight months, where a higher thermostability was noticed. Also, the DSC (Differential Scanning Calorimetry) curves presented different shapes for the samples of polyurethane-based urinary catheters after three months and eight months. FTIR (Fourier-Transform Infrared Spectrometry) spectra gave a detailed picture of the chemical trans-formation which has occurred within the material at eight months. All the analyses gave an overview of the aging process of polyurethane-based urinary catheters and showed insights into the chemical/ physical transformations that the polymeric material suffers from prolonged usage.


2022 ◽  
Vol 58 (4) ◽  
pp. 216-221
Author(s):  
Hendra Suherman ◽  
Kamdini Aksa ◽  
Yovial Mahyoedin ◽  
Edi Septe ◽  
Irmayani Irmayani

Kenaf is a nonwoody fibrous plant, and its fibre can be potentially used as a reinforcement in the matrix to produce biocomposite materials. The properties of biocomposite materials are highly dependent on the reinforcing material and the matrix used as a binder. This study used kenaf fibre as a reinforcing material with different compositions (10, 20, and 30 wt.%) and different fibre lengths (1 cm and 3 cm) in the matrix using the casting process. Low viscosity epoxy resin (635 thin epoxy resin) with a viscosity of 6 poise was used as the matrix. The results showed that the highest flexural strength, impact strength and shore hardness were obtained at a 30 wt.% kenaf fibre composition with a 1-cm kenaf fibre length, namely, 85 MPa, 338 KJ/m2 and 98 SHD, respectively. The length of the fibre in the matrix affects the mechanical properties of the resulting biocomposite. This condition is caused by kenaf fibres with a length of 1 cm being more dispersed in the matrix than fibres with a length of 3 cm.


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