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The goal of this research is to show that epoxy resin (ER) / coir fiber mats (CFM) hybrid composite laminates with nano-silica particle (NP) reinforcement improve mechanical characteristics and water absorption. Lately, it has been employed in automotive, aerospace, and structural industries where coir fiber-reinforced polymers are safe for ecologically friendly composite applications. The Compression - Hand layup technique is used to make the epoxy composites reinforced with natural coir fibres and nano-silica particles in various weight fractions (5, 10, 15, 20 and 25% by weight). Mechanical parameters such as tensile, flexural, compressive, impact strength, thermal conductivity and also water absorption of composites are evaluated in this study. Scanning electron microscopy is also used to analyze the surface morphology of cracked surfaces (SEM). Hybrid nanosilica-coir fiber mat reinforced epoxy resin has decreased water absorption (percent) suggesting better mechanical qualities. Furthermore, the hybrid epoxy-containing 20% nano-silica coir mat improves all the said mechanical properties.

The study aims to investigate the influence of TiO2 nanoparticles on the permeation and retention properties of polymeric membranes used in wastewater nanofiltration systems from the medical sector. The research is focused on the influence of the TiO2 nanoparticles concentration on the membrane properties. Additives in general determine enhanced membrane properties like permeation and retention capacity. Hydrophobicityhowever, is decreasing due to the nanoparticles affinity for water and this have an important effect on the permeation properties, at the same time with the decrease in surface roughness, with an important influence on the fouling effect. Membranes with four different concentrations of TiO2 nanoparticles were studied, from 0 to 2% nanoparticles. Results showed that small percent of nanoparticles have an important impact on the permeation properties of the membranes, finding that at 2% nanoparticles the permeation decreases due to the nanoparticles aggregations which are blocking the pores.

Despite important progress in the field of the thin flexible transistor (TFT)-based electronics, a major challenge still exist for organic TFTs to decrease the operating voltage, which is related to the properties of the dielectric and semiconductor layers from the OTFTs structure. In this paper, we present the electrical behavior of two biocompatible polymers, polyvinylpyrrolidone (PVP 360) and polyvinyl alcohol (PVA), regarding the application as insulating layer in thin-film transistors. The PVA and PVP 360 thin films were deposited onto epoxy resin copper double-sided layer and polyethylene tere-phthalate/Indium tin oxide (PET/ITO) substrates by sol-gel method, spin-coating technique. Two sol concentrations (1 and 5 wt. %) were prepared and the contact angle onto the used substrates was measured using a digital microscope camera. The obtained films have been characterized by scanning electron microscopy (SEM) and dielectrical behaviour. For electrical measurements, the metal-insulating-metal (MIM) structure was realized by cooper electrodes deposition at room temperature, onto the top of thin films, by magnetron sputtering method. The current (I) - applied voltage (from -5 to +5 V) curves were measured in air at room temperature (RT), using the Picoammeter homemade device. PVA and PVP 360 thin films showed low leakage currents with values within ± 2 nA for ±5 V range.

The aim of this work is to study the possibility of using the products of aminolytic destruction of polyethylene terephthalate (PET) and their derivatives in polymer composite materials with vibration-absorbing properties, which provide effective damping of vibrations of technogenic and natural origin in a wide temperature and frequency range. The paper considers a modern method of recycling PET waste with a mixture of amino alcohols - monoethanolamine and triethanolamine, taken in two different ratios. As a result of the destruction reaction, terephthalic acid diamide (N, N`-bis (2-hydroxyethyl) terephthalamide) is formed. To accelerate the destruction process, microwave radiation of various powers of 200, 540 and 700 watts was used. The optimal conditions for aminolytic decomposition of PET were determined: the time and power of microwave radiation with PET conversion up to 95% and the yield of the target product (terephthalic acid diamide) 80-85%. The destruction process was carried out according to a closed cycle of using reagents, without the use of catalysts and at atmospheric pressure, which to a certain extent reduces the energy consumption and increases the environmental friendliness of this method of PET decomposition. The aminolytic degradation product of PET (terephthalic acid diamide) was used as a monomer in the polycondensation reaction to obtain a new oligomer (terephthalic acid oligoesteramide). The degree of polymerisation (n) is in this case 7 to 11 (number of chain links). The obtained oligomer and the PET degradation product were investigated as new components in elastomeric compositions based on chloroprene rubber and in compositions based on thermoplastic elastomers. It has been demonstrated that the introduction of an oligomer based on a PET degradation product reduces the viscosity of elastomeric compositions by 25-35%. The study was supported by a grant from the Russian Science Foundation No. 21-79-00301, https://rscf.ru/project/21-79-00301/.

The substantial increase in the use of the FDM (Fused Deposition Modeling) process for the production of plastic parts in ever wider fields has led to the search for methods to improve the quality of the printed parts. In the case of ABS parts (Acrylonitrile Butadiene Styrene), one of the most common and used methods to improve surface quality is the process of acetone steam treatment, but the application of this method also brings more or less negative effects on the part. The main side effects when applying this method is the low breaking strength and loss of part details on the sharp edges. This paper presents a set of contributions on the relationship between surface quality and the level of detail of parts subjected to acetone steam treatment. In order to analyze the influence of the treatment on the details of the parts, a reverse engineering method was used in which a polyarticular arm FARO Edge 7.5 was used to scan the parts and reconstruct them. The study was performed on parts with 20% infill, grid tipe.

With the fourth industrial revolution, Additive Manufacturing started to offer new possibilities of manufacturing, Fused Deposition Modeling being one of the most used processes for fabrication. In this paper, the studied specimens are manufactured based on the Fused Deposition Modeling (FDM) method, with a filament of short carbon fiber and polyethylene terephthalate (PET) matrix, with a variation of the layer thickness. For the resulted specimens the tensile properties are determined according to ASTM D638. The most advantageous results are obtained for the layer thickness of 0.15 mm, with the tensile strength of 58 MPa. Based on the stress-strain curves which are presented in this paper, it also can be assumed that the material is brittle. The results of the mechanical properties are very similar for each group of specimens and it can be assumed that the mechanical properties are homogenous due to the material quality and the machine performances. For all the specimens the rupture location is almost in the same area. Due to the difficulty of carbon fiber filament printing, the manufacturing defectives which appear during the manufacturing process are detected, the most common manufacturing defectives being the material gaps from each specimen, which are identified with microstructural analysis. As failure modes, the most common failure criteria are the delamination and the matrix cracks.

An innovative recycling process for thermoset composite laminates is proposed by thermo-mechanical disassembly and further compression molding of hybrid thermoformable composite plates. Due to the thermo-mechanical process, single cured plies are extracted from the waste laminate. Subsequently re-lamination is performed by interposing thermoplastic films between the reclaimed composite plies. Final consolidation is carried out by compression molding. In order to show the feasibility of the novel recycling technology, carbon fiber reinforced composite plates by autoclave molding were thermo-mechanically disassembled in a manual roll bending machine after heating in oven. Reclaimed cured plies were laminated by alternating thermoplastic interlayers made of low density polyethylene. The hybrid laminate was consolidated at the temperature of 220°C and the holding pressure of 38.5 bar. Results from bending tests on virgin and recycled plates showed the very good agglomeration of the hybrid samples and the optimal preservation of performances of initial cured plies of the virgin material into the recycled plate.

Results on mechanical properties of Tensylon® composites at room temperature are presented. Single-ply and two-ply samples, obtained from the ply-precursor sheet (of two orthogonal layers) have been subjected to: load till failure in traction, at different strain rates (below 10-1 s-1) and cycles of successive loading and unloading and 5 min stress relaxation period. The characteristic times of relaxation are evaluated and the difference in values of Young modulus before and after the relaxation stage is established. A complex cyclic/relaxation test requires a visco-elasto-plastic model of Tensylon®, and allows to quantify it. This model predicts the material behavior in other types of tests: for instance, it predicts strain rate independence of loading to failure in the considered strain rate range. Cyclic tests fulfilled at a fixed strain rate suggest that Tensylon® is an elastoplastic material without noticeable viscosity. The proposed model, additively including nonlinear viscoelasticity and plastic flow with strengthening, shows a satisfactory agreement with experimental data. It also agrees that the material is strain-rate-insensitive in the range 10-3 s-1–10-1 s-1.

Several phenylazophenoxyacetic acid derivatives were obtained starting from azophenols and ethyl chloroacetate by an environmentally friendly approach. The synthesis reaction was carried out in heterogeneous medium using P(AAm-co-DADMAC) copolymer. Good results have been obtained thanks to phase transfer catalysis. Retrosynthetic and structural analysis were performed.

In the recent past, the demand for multifunctional and lightweight materials have increased steadily creating an increase in demand for Hybrid polymer matrix composite which consists multiple fibers in conventional resins. In this study, a hybrid composite comprising of two reinforcements - natural silk fiber and E-Glass fiber - in an Epoxy resin matrix which is a partially eco-friendly composite has been fabricated and the effect of drilling, by using an 8 facet solid carbide drill, on the surface roughness has been studied. Taguchi’s L27 Orthogonal array was used for experimentation by modifying three parameters - feed rate, spindle speed and drill diameter - on three levels (low, medium and high) and thereby studying the effects. From the results of experimentation it has been observed that increase in spindle speed and drill diameter reduces surface roughness however it increases with increase in feed rate. Further, regression analysis and Fuzzy modeling are used in order to determine optimum parameter values to get the desired surface finish. Good agreement between the experimental, regression and fuzzy model is observed with the correlation coefficient of 0.9814 and 0.9677 respectively.