Materials Science Forum Vol. 1126

Abstract: The current research focus in our group is on utilizing the polymer material polyimide (PI) as the resistance switching layer for resistive memory. In recent years, PI resistive photomemory (RePM) [1] has been developed, capitalizing on the photosensitive properties of PI films in the ultraviolet light band. PI initially possesses two chemical structures, Aromatic and Quinoid, the PI film undergoes transformation when exposed to ultraviolet light. By employing various processing methods to control the ratio of Quinoid and Aromatic molecular chains in the PI film, and through FTIR measurements of chemical structure changes before and after illumination, we gain insights into the variations in the molecular chain ratio due to different experimental parameters. FTIR analysis reveals that changes in spin coating speed influence the molecular ratio within the film, attributed to differences in molecular chain shapes and lengths. Experimental results demonstrate that optimizing the spin coating process enhances the operational efficiency of RePM, significantly extending data retention time.

Abstract: Nowadays, the enhancement of electrical conductivity in natural rubber has been widely studied by incorporating conductive particles with various techniques into rubber latex. Acetylene black is one of the carbon nanoparticles known for its electrical conductivity property. However, its hydrophobicity leads to poor dispersion in rubber latex. Therefore, admicellar polymerization (AP) technique was chosen to modify particle surface without changing the molecular structure. This technique alters surface hydrophobicity by means of coating ultrathin film of polymer onto the particles. Polypyrrole, a conductive polymer, was chosen to enhance the dispersion of acetylene black. The modified acetylene black was used as the electrically conductive additives in natural rubber. There were four variables in this study: i. the carbon particle-to-surfactant ratio, ii. the agitation speed during the AP step, iii. polymerization temperature, and iv. the surfactant agent-to-monomer ratio. The morphologies of modified particles were observed by SEM and TEM. The results showed that the best conditions yielding the lowest resistivity of conductive rubber at 1:3 for the carbon particle-to-surfactant mass ratio, at 1000 rpm for the agitator speed, in AP step was 4°C for the polymerization, and 1:5 for the mass ratio of the surfactant agent-to-monomer.

Abstract: The heterostructure of composite films filled with conductive fillers can improve the interfacial polarization, which is one of the keywords to enhance the dielectric and ferroelectric properties. In this study, a composite films were created by combining Polyvinylidenefluoride-trifluoroethylenechlorotrifluoroethylene. (PVDF-TrFE-CTFE), Graphene-nanoplatelets (GPN) and Polyvinylidenefluoride-hexafluoropropylene (PVDF-HFP), using the tape casting solution method. The heterostructure of the composite film improved the interfacial polarization, resulting in increased dielectric constant with terpolymer loading and GPN addition. The filled GPN1% film showed a dielectric constant of 21.5 and 13.6 at 100/0 and 70/30, respectively, compared to 17.9 and 11.8 for the 2-phase composite films. Additionally, the terpolymer and GPN loading induced the maximum polarization (Pmax) and changed the PE-loop (hysteresis loop) behavior. The high performance of the PVDF-TrFE-CTFE and GPN composite films in terms of their dielectric constant, dielectric loss, AC conductivity, and polarization performances make them promising materials for electric-capacitor and energy storage applications.

Abstract: The mechanical strength and structural stability of gelatin film were enhanced by crosslinking with dialdehyde cellulose (DC), having an aldehyde content of 65%. However, the elasticity of the film was improved by plasticizers. The recent work aims to examine the effect of plasticizer type on the characteristics of the gelatin film crosslinked with DC (GDC). The results demonstrated that the weight loss of the films increased after 24 hours of immersion in distilled water, resulting in diminished structural stability compared to the GDC film without adding a plasticizer. Insignificant differences in mechanical properties were observed among the GDC-plasticizer films. The GDC film with glycerol had the most vivid yellow hue, followed by the ones with PEG and sorbitol, respectively. Following a better appearance, the GDC film supplemented with sorbitol could be a potential candidate for packaging application.

Abstract: The properties and the performance of Thermally Stable Diamond Composite (TSDC) directly affect the applications of TSDC in engineering. The failure risk of the TSDC cutting tips during a cutting process is affected by many factors, including the Depth of Cut (DOC) of the pick with the TSDC tip. The DOC is an important indicator in mining and construction industries because it directly affects productivity and pick failures. In existing studies, DOC is usually treated as a deterministic variable. However, due to the drum vibration during a cutting process, the DOC during production often varies randomly around its nominal value. This study investigates the influence of the randomly varied DOC on the performance and failure characteristics of TSDC tipped rock cutting picks, in combination with random resultant angle. Monte Carlo simulation method is applied. It is found that the variation in DOC can have considerable influence on the failure characteristics of the TSDC cutting tips, although this influence is affected by the resultant angle and attack angle. This characteristic is important for optimising the design and application of the TSDC tipped picks.

Abstract: Stress relaxation is one of the methods used to characterize polymer foam materials. Stress relaxation data are valuable and provide important information, as they can prevent failure or unsafe usage of these materials under different loads. The aim of this study is to introduce the artificial neural network (ANN) technique for predicting the stress relaxation of polymer foam over time. The neural network model was constructed with relaxation time, stress, and strain as input parameters, and normalized stress relaxation as the output. The results demonstrate that the ANN model achieved highly accurate predictions for stress.

Abstract: Ternary polymer blends of ferroelectric Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP, heterostructure Polyurethane (PU) with hard and soft segments, and amorphous Polymethyl methacrylate (PMMA) has been investigated on energy storage performances and electrocaloric effect. The microstructure phase of polymer blends has been analyzed using the X-ray diffraction (XRD) technique. The frequency-dependence of dielectric properties for polymers blend has been conducted. The ferroelectric, energy storage and electrocaloric properties of polymers blend depending on temperature were studied. The result showed that the dielectric constant of PVDF-HFP@PU composite is higher than PVDF-HFP@PMMA composites due to the strong interfacial polarization effect and contribution of the polymer blend. Moreover, it was noted that the crystalline–amorphous interface properties depend on the polymer blend with PU and PMMA, resulting in ferroelectric, energy storage and electrocaloric properties when temperature increases. Therefore, the comparison based on heterostructure and amorphous structure for series polymer blends can be used to predict practical devices.

Abstract: Studying of the strength characteristics of polymer composite materials, which are used in the structures for various applications, is an important subject for research. Here one of the major issues is the development of fastening techniques to maximize the strength characteristics of composite fibers. Based on the modification of the available test methods, a set of specimens and devices has been developed to determine the shearing (cut) strength from the fastener hole to the edge of the composite part. For this purpose, we used the modified specimen sequentially shearing along the contour after each test cycle in order to find the required parameter depending on the distance from the fastener to the part edge. According to the result of experimental studies, possible types of shearing test and shear test failures were identified. It is demonstrated that shearing strength and shear strength in the specimen plane are different characteristics with no correlation between them. It is found that a shearing in the classic sense is observed only for high-anisotropy structures when they are loaded in the more rigid direction, whereas the complex modes of failure occur for the heavily reinforced composites used. For example, during testing a pure shearing was observed in 0° planes in the specimens with the package structure of [0^°_0.7; ±45^°_0.2; 90^°_0.1], while it was observed both for the holes drilled in 0° and 22.5° directions in the specimen with the structure of [0^°_0.8; ±45^°_0.2]. We obtained the quadratic engineering dependence to predict shearing strength of the heavily reinforced basic composite. Based on processing of the experimental results, a recommendation has been made on the need for constant experimental support of the design process, which can be implemented by the proposed specimen and testing device.

Abstract: This research work is about characterization of the mechanical properties of two newly developed nanocomposite materials. The produced nanocomposites are made by mixing either Nano date palm particles (NDPP) or Nano Titanium Dioxide particles (NTiO₂P), as a reinforcement filler, with recycled polypropylene (rPP). Particularly, downsizing the date palm microfibers generated from waste to Nano-sized lignocellulose fillers has been accomplished by using a ball milling machine. The powdering process is conducted at a high speed of 12 cycles (2 cycles per hour). The manufacturing process involves making composite sheets using a twin-screw extruder in a hot melt state followed by compression molding. After that, test specimens are prepared following ASTM standards and then tested in a Universal Testing Machine (UTM) setup. Results revealed that the highest tensile strength of the reinforced polymer can be accomplished at 3% wt. NDPP and 6% wt. NTiO₂P. These filler loadings increased the tensile strength by 48% and 63% over the neat rPP, respectively. Moreover, the flexural strength of NDPP-based nanocomposite increased by 30% at 3% wt. while the strength of NTiO₂P-based composite was improved by 33% at 6% wt. over the neat polymer. Due to the soft nanofillers, both nanoparticles exhibited a slight decrease in Young’s modulus; 10.7% and 7.8% at 3% wt. NDPP and 6% wt. NTiO₂P, respectively. Similarly, the increase in elongation at break and flexural modulus for both nanocomposites contribute to improving the ductility of the neat polymer. The results from the morphological analysis using Field Emission Scanning Electron Microscope (FESEM) revealed that NTiO₂P with 6% wt. has better interlocking with the polymeric matrix and better filler distribution over 3% wt. NDPP. Results showed that the viscosity of NDPP-based nanocomposites exceeded that of NTiO₂P-based nanocomposites while the density of NDPP was less. This study indicates that nanocomposites produced from NDPP are economically feasible as natural fiber and ecologically friendly materials with a great potential for use in a variety of industrial applications.