Key Engineering Materials Vol. 856

Abstract: Palladium chloride impregnated on Al₂O₃-pillared clay (Pd/Al-PILC) was synthesized by intercalation of aluminium (III) chloride into clay interlayers and calcined at 500°C for 1 h. Subsequently, impregnated with PdCl₂ and calcination at 450°C for 4 h. The modified clay catalyst was characterized by X-ray diffraction (XRD) for investigated atomic spacing of catalysts and N₂ adsorption and desorption method (BET) for investigated surface area and pore volume of catalysts. The catalytic activities of Pd/Al-PILC was utilized for the reduction of nitrobenzene for synthesis aniline. The effect of various reaction factors, such as reaction time, reaction temperature, solvent system and the amount of catalyst were studied in order to optimize the reaction conditions. Aniline was prepared conveniently and efficiently via the reduction of nitrobenzene in the presence of a catalytic amount 40%Pd/Al-PILC of substrate in reflux temperature at 70°C for 4 h under extremely mild conditions.

Abstract: The efficiency of the modify natural rubber (NR) combination with methyl methacrylate (MMA) monomer for pavement surface was studied. The modified coating for pavement surface consisted of MMA resin and natural rubber compound (NRC) at the weight ratio of 70:30, 60:40, 50:50, 40:60 and 30:70, respectively. The effect of rubber in MMA was studied in terms of hardness (shore A and pencil tests), adhesive, abrasion and shear strength. The results showed that hardness (shore A) and adhesion of the compound coating slightly decreased with addition of NRC. Abrasion, hardness pencil tests and shear strength notably reduced as decreasing MMA and increasing NRC concentration. The most optimum sample satisfing the pavement surface standard is M7N3 consisting of MMA:NRC of 70:30.

Abstract: The plastics from municipal solid waste (MSW) were modified to improve cleanness for adding value. The stir and sonication were performed as cleaning processes. Xylene, tetrachloroethylene, chloroform, acetone and toluene were used as solvent cleaning. The most suitable cleaning process was sonication method with cleaning time of 5 min and the appropriate solvent was xylene for washing the plastic wastes for further study in terms of thermo-mechanical and rheological properties. The cleaning process was successful as evidence in thermogravimetric analysis (TGA) results. The properties of new plastics, cleaned plastic wastes and plastic wastes were compared and analyzed. Tensile strength of the specimens from plastic wastes was slightly decreased; however, elongation and impact strength of cleaned plastic wastes and plastic wastes sharply dropped as compared to new plastics. Tensile modulus of cleaned plastic wastes was slightly better than that of new plastics. Thermal stability of plastic waste was slightly lower than that of new plastic. Shear storage modulus (Gʹ), shear loss modulus (Gʺ) and shear viscosity (η) of new plastics showed the maximum value; on the other hand, those properties of cleaned plastic wastes and plastic wastes were similar. The cleaning method with solvent did not destroy thermo-mechanical and rheological properties of the cleaned plastic wastes.

Abstract: In situ forming matrix (ISM) is an injectable drug delivery system containing a drug-loaded polymeric solution. It was applied for local drug administration such as into a periodontal pocket for periodontitis treatment with an antimicrobial agent. ISM can transform with phase inversion into the solid-like matrix after contact an aqueous environment by solvent exchange mechanism. This study aims to develop ISM which various concentrations of rosin (R) as matrix former dissolved in organic biocompatible and biodegradable solvents such as N-methyl-2-pyrrolidone, dimethyl sulfoxide and 2-pyrrolidone. Physicochemical characterization and matrix formation behavior owing to phase inversion of R ISM were evaluated including pH, density, viscosity, contact angles, surface tension, expelling force through a syringe, matrix formation behavior and morphological change. The density of all R ISM exhibited in the range of 1.03-1.11 g/cm³ and contact angles (9.04-44.13°) indicated a good wetting property. Higher R concentration decreased pH of ISM owing to increased amount of abietic and pimaric acid from R while the viscosity, contact angles and force for expelling a syringe were increased. The viscosity of R ISM in dimethyl sulfoxide was less than that in 2-pyrrolidone; thus, ISM using dimethyl sulfoxide as a solvent exhibited good injectability. ISM comprising R concentration > 30%w/w promoted a faster matrix growth in which the amount of occurred R matrix was enhanced with time and the rate of matrix formation was lower with time. Doxycycline Hyclate (Dx)-loaded 40%w/w ISM in dimethyl sulfoxide (Dx-DR) had pH of 3.70, density of 1.1084 ± 0.0005 g/ml, viscosity of 35.72 ± 0.00 cPs, contact angles of 26.87 ± 2.40°, surface tension of 37.11 ± 0.11 mN/m and expelling force of 23.98 ± 0.18 N. It showed the sustainable Dx release in simulated crevicular fluid and the efficient antimicrobial activity against Staphylococcus aureus and Porphyromonas gingivalis. Thus, this phase inversion induced R ISM using dimethyl sulfoxide as a solvent showed potential as an antimicrobial agent-loaded drug delivery system for periodontitis treatment.

Abstract: In this study, the disintegration of poly(butylene succinate)(PBS) and poly(lactic acid) (PLA) under landfill conditions was investigated. Both polymers were melted, injected into a dumbbell-shape, and buried under the soil for 20 weeks. The morphology of the polymer from the scanning electron microscope (SEM) revealed that, after 6 weeks of the burial, the PBS polymer produced many micro-voids in the bulk of polymer. The amount of the voids increased with time. While the morphology of PLA showed a few voids and some cracks during the degradation process. Moreover, the mechanical properties of the PLA were decreased after 2 weeks following with PBS after 4 weeks of the burial times. The weight loss and the water uptake of PBS and PLA were slightly increased. From the result, it was found that the degradation of PBS and PLA proceeds via random chain scission of the ester bond through bulk erosion mechanism. The degradation of PLA degraded faster than the PBS due to the low crystallinity in the polymer chain. This result can be applied to the design waste management of biodegradable polymer products.

Abstract: Polyurethane (PU) gel was synthesized based on methylene diphenyl diisocyanate (MDI) and polyols corporation with 1,1,1-Tris(hydroxymethyl)propane (TMP) as a crosslinking agent. The chemical structure of synthesized polyurethane gel was investigated using Fourier-transform infrared spectroscopy (FTIR). The effects of curing temperature, curing time, and crosslinking concentration on the degree of swelling, gel content and hardness of polyurethane gel are investigated. In addition, the crosslink density and average molecular weight between crosslinking points were determined using the Flory-Rehner equation. The results revealed that the curing temperature had more pronounced effect on degree of swelling and gel content than curing time. As the curing temperature increased the degree of swelling and gel content in polyurethane gel increased. Curing time seem to have a complicated effect on crosslink density and average molecular weight between crosslinking points. The hardness of polyurethane gel tends to increase with increasing crosslinking concentration and curing time.

Abstract: The fillers from agriculture and industrial wastes filled natural rubber (NR) have been prepared to clarify their properties and develop to be the eco-friendly composites. This research aims to study the composites namely rice husk ash (RHA)/NR, clay/NR and crumb rubber/NR composites on the curing characteristics, mechanical and morphological properties. The results indicated that depending on a chemical composition of fillers, the properties of the composites are varied. For clay/NR composite, the occurrence of vulcanization was delayed comparing to the others. In term of mechanical properties, crumb/NR composite shows a toughest characteristic, for examples, it has the highest tensile strength, elongation at break and tear resistance, whereas hysteresis loss was found to be lowest among the composites. The toughness of crumb/NR composite can be influenced by a better interfacial interaction between filler and matrix comparing to the others as revealed by SEM. The clay/NR composite, on the other hand, has the highest hardness among the composites due to the hardness of clay itself and its uniformity of particle size. In the case of RHA/NR composite, from morphological observation by SEM shows that RHA particles have very poor dispersion in NR matrix which resulted in poor mechanical properties. However, the presence of RHA agglomerates was found to be beneficial for loading a high stress under a small deformation, for example, at 25% elongation. Therefore, these three difference composites from wasted materials were found to have unique characteristics which can be chosen and applied for some specific applications.

Abstract: In this research, jute fiber reinforced polypropylene and poly (lactic acid) composites were fabricated, respectively by Direct Fiber Feeding Injection molding (DFFIM) process. Jute spun yarns were directly fed into the barrel of molding process in order to eliminate the fiber breakage during extrusion compounding process. Mechanical properties of both composites were investigated by tensile testing and morphological properties were characterized by scanning electron microscopy (SEM). For jute reinforced polypropylene (PP) composites, tensile strength of composite decreased but modulus increased, compared with neat PP. The using maleic anhydride grafted polypropylene (MaPP) can improve interfacial bonding between jute fiber and PP matrix as observed by SEM, which resulted in the increasing of tensile strength. Therefore, in the case of jute/PLA composites, jute fibers surface treated with sodium hydroxide (NaOH) and silane coupling agent to improve interfacial adhesion. The tensile strength of untreated-jute/PLA composites are not different with PLA matrix but tensile modulus of untreated composites are higher than PLA matrix. In addition it is found that the tensile properties of NaOH-treated jute/PLA and NaOH+Silane-treated jute/PLA composites were improved, compared with untreated composites.

Abstract: In our time with the growing cooling demand in electronics and energy industries, new thermally conductive materials are in high demand. Thermal gasket and thermal interface materials (TIM) are applications acquiring the characteristics of the thermally conductive materials. They are used to offer bonding strength and efficient heat dissipation for heat dissipating device applications. These materials are inserted between two components in order to increase the thermal coupling between them. Elastomeric materials are promising as the thermal gasket and TIM. They are, however, limited for thermal conductivity causing a thermal insulator behaviour. In this framework, the major challenge is to create suitable elastomeric composites for enhancing thermal conductivity, whereas remaining a good elastic behavior. This article presents the effects of thermally conductive fillers (aluminum nitrile and zinc oxide) on thermal properties and flexibility of recycled thermoplastic elastomer vulcanizate composites and reclaimed rubber composites, while the analysis of composite morphology is scrutinized. The objective of this research is to perceive the characteristics of recycled elastomeric composites in order to deduce a fundamental notion to develop the gaskets or TIMs from recycled materials. New flexible composites are capable to provide approximately 0.4 W/m-K of thermal conductivity. The result indicates that the composites are conceivable to be applied for thermally conductive tape or adhesive applications which required the thermal conductivity in the range of 0.4-0.5 W/m-K.

Abstract: This research has focused on the fabrication of a urea biosensor based on electrically conducting poly (pyrrole-co-para-phenylenediamine) (PPy-co-PPD). High amount of free amino groups (-NH₂), originating from PPD, in the PPy-co-PPD structures made them suitable for chemical immobilization of urease. The PPy-co-PPD films were prepared by one-step electrodeposition of the mixture of pyrrole and PPD. It was found that the morphology and conductivity of the PPy-co-PPD films were influenced by amount of PPD in the copolymer. Increasing amount of PPD in the copolymer led to decreasing electrical conductivity. Greater particle size and less packing were observed for the copolymer with high PPD content. XPS revealed the existence of free amino groups (-NH₂) on the surface of PPy-co-PPD films. The PPy-co-PPD films were further subjected for covalent immobilization of urease, selective catalytic enzyme for urea. Potentiometric responses of the PPy-co-PPD films showed the highest sensitivity of 47.3-54.2 mV/pUrea (r² > 0.99) over the urea concentration ranging from 0.5-10.0 mM (pUrea 2.0-3.3). Detection limits and response linearity were in the normal range of urea level. Response time was approximately 10 seconds. Leaching test revealed that the PPy-co-PPD film showed 83% reduction of urease leaching out of the PPy-co-PPD film during measurement, compared to the PPy film.