Papers by Keyword: Polymer

Abstract: The article aims to investigate polymer inorganic composites for electromagnetic radiation absorption using potassium titanates. The selected polyamide 6 (durethane brand) and sodium polytitanate materials contain TiО₂, K₂СО_3, and KCl received by charge sintering. Results showed that modification of polyamide 6 with sintering products in the form of a fine powder of potassium polytitanate with particle size 1-5 microns that contain the primary phase K₂O × 2TiO₂ with an admixture of a phase K₂O × 4TiO₂, which increased their strength properties. The optimal content of potassium polytitanate was over 10 % by mass. To fully ensure the reinforcing effect due to the filling of potassium polytitanate polyamide 6, it is necessary to use whiskers K₂O × 6TiO_2, which can be collected by the additional crystallization of the amorphous charge sintering product.

Abstract: Today, biodegradable polymers are used to obtain various functional materials, including for the needs of agriculture. The article describes the current state of the production of polymeric materials, the problems of their operation, as well as the prospects for the creation of new polymeric biodegradable materials for agriculture. It is found that, depending on the method of obtaining a biopolymer-based material, its ability to diffuse water and water absorption is different – non-woven materials have higher performance than film materials. After seed germination, the thermophysical characteristics of the polylactide-based material change, the degree of crystallinity decreases by 7-10%, which indicates the destruction of the crystalline phase.

Abstract: In South China Sea, the natural gas hydrates are usually reserved in argillaceous siltstones. These argillaceous siltstones are weakly cemented and incorporated with the solid hydrates. During the drilling process, the natural gas hydrates may decompose unexpectedly, resulting in the wellbore collapse. To improve the stability of the wellbore, this study develops a wellbore strengthener for water-based drilling fluids used in argillaceous siltstones. Tannic acid/polyvinyl (TA/PVA) alcohol has been adopted for preparing the wellbore stabilizer. A series of experiments have been conducted to investigate the effects of newly developed wellbore strengthener on the mechanical properties of the argillaceous siltstones as well as its mechanisms on the wellbore stability. The experimental results show that the wellbore strengthener developed in this study can significantly improve the compressive strengths of the argillaceous siltstone cores. The AFM characterizations indicate that the adhesion force between the silica (the major compound in argillaceous siltstones) microspheres and the wellbore strengthener can reach up to 2138 nN. Moreover, the SEM images visually show good cementation of the argillaceous siltstones after being treated by the wellbore strengthener. In addition, the wellbore strengthener can also assist in reducing the fluid losses of water-based drilling fluids. It is hopeful that the wellbore strengthener provided in this study help the development of underwater natural gas hydrates.

Abstract: The process of mechanically activating chemical bonds usually involves applying external force. Since mechanical chemistry can be performed without solvents or with minimal amounts of solvent (catalytic quantities), it has become an imperative synthetic tool in multiple fields (e.g., physics, chemistry, and materials science) and is an attractive greener method for preparing diverse molecules. Catalysis, organic synthesis, solid-state medicinal preparation, metal complex synthesis, and many other chemistry fields have benefited from sustainable methods. The purpose of this paper is to shed light on the benefits of using mechanochemical methods to produce a pharmaceutical crystal that is composed of dendrimer nanocrystals. Consequently, we describe and examine the importance of mechanical procedures in forming dendrimers and pharmaceutical crystals in this review.

Abstract: Polylactic acid is a biodegradable polymer with wide range of applications in food packaging and medical industries. Polylactic acid is commonly derived from lactic acid which is made from sugar and starch via bacterial fermentation. Whereas the production of polylactic acid via ring opening polymerization uses lactide as its precursor. This method undergoes reaction with the presence of catalyst. In this research, polylactic acid is produced via ring opening polymerization using different catalyst. However, very few studies conducted on how the catalyst effects the molecular structure of the PLA produced. The main objective is to study the effect of using stannous octoate (SnOct₂) and anhydrous lithium chloride (LiCl) as catalyst in producing PLA. Lactide is reacted with SnOct₂ and LiCl at 130°C at different ratio of lactide to catalyst (Lac/Cat) of 25/1, 50/1 and 100/1 by weight. The resulting PLA is characterized using Fourier Transform Infrared Spectroscopy (FTIR) to analyse the molecular structure and UV-Visible Spectrometer (UV-VIS) to measure the concentration of the PLA obtained. The ratio of Lac/Cat shows significant difference on the PLA with SnOc_t2 as the catalyst but shows no significant difference on the PLA with LiCl as the catalyst. Nevertheless, LiCl can still be used as the catalyst in producing PLA which has been proved by the presence of certain peaks on the FTIR spectrum. However, further investigation needs to be carried out to understand the ROP mechanism when using LiCl as the catalyst.

Abstract: Natural fibers are increasingly used in the polymer industry as bio-composites for a wide range of applications, such as the interior part of the automobile, interior material boards, decking panels, and many others. The presence of cellulose, which is hydrophilic in nature, lessens the mechanical properties of the bio-composites by increasing water uptake into the composites or also may affect the interfacial bonding between the polymer matrix and the fibers because the matrix is hydrophobic. The former may occur due to the surface of the bio-composites being highly exposed to water sources, e.g., high humidity in the air, rainwater, and many more. Thus, an additional layer on the surface of the bio-composites needs to be applied to protect the surface from water sources. The coating may be used for decorative, protective, or both purposes. This study aims to investigate the performance of polymer coating on a bio-composite substrate. The coating solution, chitosan-pectin-calcium chloride (CPC) solution was prepared, and the compatibility and wettability of the coating solution with the polymer-based bio-composites substrate were evaluated. The substrate was dipped into the coating solution for two minutes and hung to allow the excess coating solution to drop while drying the substrate. The performance of coating on the bio-composite substrate is evaluated by measuring the contact angle θ and average maximum bond strength σ_b of the sample with the different numbers of coating layers. It is found that the wettability of the contact angle indicates a lower contact angle for two-layer compared to one layer of the CPC coating due to the hydrophilicity of the coating materials.

Abstract: Polymer dispersed liquid crystals are composite functional materials having a variety of application ranging from display to smart window. These materials consist of liquid crystal in which micron size droplets of polymer is dispersed. In the present study the effect of different concentration of polymer 2-ethyl hexyl acrylate on optical and electrical properties of nematic liquid crystal 4-cynophenyl 4-n-hexyl benzoate were investigated by various techniques. The investigation of textures at different temperatures was performed by polarizing optical microscopy for the determination of phase transition temperature. The fabry perot scattering studies using low powered laser beam was used for the confirmation of phase transition temperature. Various textures were found according to the orientation of liquid crystal and polymer. The optical and electrical properties of pure liquid crystal were found to enhance after dispersing polymer. Our investigation suggest that after dispersing polymer into nematic liquid crystal, the material shows more stability, less flicking and sticking of image for display applications.

Abstract: The production and consumption of non-biodegradable, petroleum-based plastics had an enormous increase in the past few years. Majority of these are used for food packaging. Biodegradable plastics receive much more attraction because they undergo complete degradation without forming any toxic compounds. Nowadays spoilage of food is the main concern faced by food industry. As microbial activity on food surface is the main reason for food spoilage, the integration of antimicrobial agents in biodegradable polymers or the use of biopolymers with inherent antimicrobial property could improve its shelf life. Current review summarizes major findings in the field of antimicrobial polymers, polymer/antimicrobial inorganic composites and polymer/essential oil blends for food packaging applications. India is home to large number of plants having antimicrobial properties. This review also highlights different methods for synthesis of efficient antimicrobial polymer films from these plants in a cost-effective way.

Abstract: When a pure liquid crystal is dispersed into a suitable polymer to form micron-sized droplet, then it is called Polymer-dispersed liquid crystal (PDLC). In the present study, PDLC of different concentrations were prepared by dispersing a conducting polymer poly (3, 4–ethylenedioxy thiophene): poly (styrene sulfonate) into a cholestryl palmitate. The differential scanning calorimetry and fabry perot scattering studies were employed to study thermal and optical properties. It was found that the phase transition for PDLC occurs at a temperature different than those exhibited by pure liquid crystal. The behaviour of PDLC for parallel and perpendicular electric field has been investigated and the dielectric constant is determined. The value of dielectric constant and conductivity were found to increase with increasing concentration of polymer. The bistability and reflective properties of pure cholesteric liquid crystal can be minimized by dispersing polymer which makes material suitable for high contrast at large viewing angles.

Abstract: This paper presents the peridynamic (PD) numerical model for simulating a tensile test until total fracture for a brittle polymeric material namely polymethyl methacrylate (PMMA). U-notched and V-notched specimens were used to investigate the effect of the notches on the elongation and fracture of PMMA. The tensile elongation of PMMA exhibits nonlinearity with respect to the applied load, while the fracture occurs when the material stress has reached the ultimate tensile stress of the material. Similar elongation and fracture properties were applied on PD simulations. Two types of elongation equation are used namely brittle and ductile equations to form PD-brittle and PD-ductile models. The published experimental data of tensile fracture test on notched PMMA specimens are used as reference to validate the simulations of the PD models. The PD numerical force-extension curves have good quantitative similarity for V-notched specimen but adequate quantitative similarity for U-notched specimen. As for the quality of the fractured specimen shape, the PD simulations have good similarity for the V-notched specimen but adequate similarity for the U-notched specimen. The plot of the internal force distribution from the simulations of PD shows good qualitative similarity to the plot of the stress distribution from the published data of FEM in terms of stress concentration. From the PD results, it is observed that the PD-ductile model has better capability in producing accurate simulation of the notched specimens than the PD-brittle model.