Solid State Phenomena Vol. 317

Abstract: The aim of this research is to investigate the removal behavior of iron and manganese that naturally exist as divalent ions in groundwater by using nanofiltration membranes. The main focus of this study is to better understand the effect of applied pressures during the rejection of these metallic ions from synthetic groundwater in order to achieve drinking water standard. Polyamide and polypiperazine amide nanofiltration membranes denoted as PA-NF and PPA-NF were selected to investigate the iron and manganese rejection at low applied pressures (1-5 bar). In single solute solution with feed concentration at 10 mg/L and initial pH of 6.8 ± 0.5, the rejection of iron was ≥96% by PA-NF membrane at applied pressure of 2 bar. However, the rejection percentage by PPA-NF was 86.6% whereby this membrane unable to remove iron to the allowable drinking water standard. The rejection of manganese with single solute at concentration of 1 mg/L with initial pH of 6.8 ± 0.5 by using the PA-NF membrane was ≥98% and almost all of dissolved manganese were rejected at 5 bar. However, manganese removal by PPA-NF membrane was found less than 70% for all of the applied pressures. Findings from this work showed that the removal of iron and manganese were dependent on the applied pressures. PA-NF membrane able to remove both metallic ions that comply with the drinking water standard. The increased of applied pressure contributed to concentration polarization effect on the membrane surfaces leading to a decrease in solute rejection by decreasing the charge effect mainly for the iron removal from synthetic groundwater.

Abstract: Fatigue crack growth in NR/BR compound and the effect of two different types of recycled rubber powder (RRP) i.e. micronized cryo-ground 74 μm and ambient-ground 400 μm were studied using fracture mechanics approach. Absolute and relative hysteresis losses using single-edge notch tensile (SENT) specimens were determined with a displacement-controlled strain compensating for permanent set of the samples throughout the Fatigue Crack Growth (FCG) experiments. Results indicated a correlation between absolute/relative hysteresis loss and fatigue crack growth rate under specific dynamic strain amplitudes. Differences in relative hysteresis loss showed that additional energy dissipation, due to multiple new crack surfaces at the crack tip, contributes to the FCG of the RRP compounds. At higher tearing energy, beside other factors affecting the FCG performance of the RRP compounds, both higher absolute and relative hysteresis loss are slightly detrimental to the crack growth rates.

Abstract: In recent years, automotive hose and belt specifications have changed, requiring longer product life in terms of swelling, wear and heat ageing. Diene-based rubbers, such as natural rubber (NR) and styrene-butadiene rubber (SBR), have been widely used in diverse industries. However, some apparent defects such as limited ageing resistance and large compression set, have been demonstrated in some rubbers cured by sulfur or peroxides. In the making of general and industrial rubber goods, short production and sufficient scorch time is crucial especially by using an injection moulding. In this work, blend of Epoxidised Natural Rubber (ENR 25) and Butadiene was developed with two types of curing systems namely Conventional and Efficient Vulcanisation system. The aim of the study is to produce a satisfactory heat resistance rubber compounds and adequate process safety for rubber manufacturing. Results showed that curing system applied significantly affected thermal stability property of the compounds. Modulus and hardness of the blends appeared to decrease progressively with ageing. However, greater thermal stability especially ageing at 100°C for 200h was observed with compound containing efficient curing system compared to conventional curing system which corresponded to the cross link density attributed by the torque value and dynamic mechanical analysis. The results on stiffness however was effected by the curing system applied. The influence of cure temperature on the chemical crosslink density on both cure systems are being investigated. The network results will be correlated with the technical properties.

Abstract: Cellulose nitrate has attracted great interest amongst researchers due to its uses in wide range of products including paint and gun propellant. Therefore, this work focuses on the synthesis of cellulose nitrate from two different sources of cellulose; plant and bacterial, in order to obtain high percentage of nitrogen content hence suitable for propellant application. The synthesis of cellulose nitrate was carried out via nitration method using nata de coco and kapok (Ceiba pentadra L) as a raw materials of cellulose. The samples were then characterized by elemental analysis, fourier transform infrared (FTIR) spectroscopy, x-ray diffraction and surface electron morphology (SEM). FTIR analysis showed the presence of NO₂ groups in both nitrocellulose proving that nitrocellulose was successfully synthesized by nitration method even though it was produced from different sources of cellulose. It is also showed nitrocellulose with high percentage of nitrogen content was obtained from bacterial cellulose, 12.69% rather than plant cellulose.

Abstract: Nitrogen content is a paramount significance in predicting nitrocellulose. Nitrocellulose with high nitrogen content (>12.5%) can be used for propellant, while low nitrogen content (<12.5%) can be applied for the production of ink, paint and leather finishes. In this preliminary study, the effect of mole ratio of sulphuric acid to nitric acid, reaction temperature and time towards nitrogen content in nitrocellulose was investigated. Nitrocellulose was synthesized using nata de coco as bacterial cellulose source via nitration method. Nitrocellulose with percentage of nitrogen content of 11.74% to 12.75% was obtained when 2 to 4 mole ratio of sulphuric to nitric acid was used with operating temperature and time ranging 20°C to 40°C and 20 minutes to 40 minutes respectively. Analysis of Fourier transform infrared (FTIR) displayed the reduction of hydroxyl group in nitrocellulose proving that several hydroxyl group in cellulose was successfully replaced by nitryl group. Other characterizations such as elemental analyser, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were evaluated to support the result.

Abstract: The effect of fabrication methods on polysiloxane (POS) composites were studied by analysing both method of casting (CA) and compression (CO). The POS composites were reinforced with 2-12 wt% of natural derived silica from rice husk (RHA SiO₂) as a filler which incinerated at 700°C. The composites behaviour were analysed through tensile testing (ASTM D412). Through comparison study on both CA and CO composites’s tensile behaviour it shows that both composites strength keep increasing with 2wt% - 10wt% RHA SiO₂ addition but strength decreased at 12wt% due to agglomeration of RHA SiO₂. Moreover, it was found that the tensile strength of CO composites had offer 23.56% higher compared to CA composites. The difference were influenced by the distribution of RHA SiO₂ as filler. The surface morphology of CO composites had showed that the most of RHA SiO₂ were embedded and less agglomeration, compared to CA composites that had lots of agglomeration which lead to higher tendency of crack propagation. The arrangement of filler due to the CO method that helps RHA SiO₂ to distributed homogenously and embedded in a matrix of POS to avoid agglomeration and lead better adhesion respectively. Thus, CO method had potential to offer in enhancing tensile behaviour compared to CA method by influencing filler distribution arrangement for vibration absorber application.

Abstract: Purification on kappa (ƙ) carrageenan was performed by dissolving ƙ-carrageenan powder in distilled water and re-precipitated with ethanol and n-hexane separately during re-precipitation process. The purified kappa carrageenan was analyzed by using Fourier transform infrared (FTIR) spectroscopy and carbon, hydrogen, nitrogen, and sulfur (CHNS) elemental analysis. The outcomes from FTIR showed there are physical changes due to intermolecular interactions which lead to decrease and lower intensity of hydroxyl band at 3345 cm^-1 after re-precipitated with n-hexane, compared to re-precipitation with ethanol and unpurified ƙ-carrageenan. There were variations observed in the percentages of C, H and S in the CHNS analysis between unpurified and purified ƙ-carrageenan. The successfully purified ƙ-carrageenan are suitable to be used for further application.

Abstract: Poly (lactic acid) (PLA) is a useful alternative to petrochemical commodity material used in such as in food packaging industries. Due to its inherent brittleness, low thermal stability, and poor crystallization, it needs to improve its properties, namely in terms of thermal and mechanical performance. The plasticized PLA composites reinforced with nanofiller were prepared by solvent casting and hot press methods. Thermal and mechanical properties, as well as the crystallinity study of these nanocomposites, were investigated to study the effect of tributyl citrate (TBC) and TiO₂ on the PLA composites. The addition of TBC improved the flexibility and crystallinity of the composites. Reinforcement of TiO₂ was found as a practical approach to improve the mechanical properties, thermal stability, and enhanced crystalline ability for plasticized PLA nanocomposites. Based on the results achieved in this study, the composite with 3.5% nanofiller (pPLATi3.5) presented the optimum set of mechanical properties and improved thermal stability.

Abstract: The reinforcement effect of nanofiller in polymer enhanced the thermal stability, physical and mechanical properties of poly (lactic acid) (PLA) composites with good reinforcing capabilities for bio-based polymers. In this paper, the effect of reinforcement of titanium dioxide (TiO₂) nanofiller on the mechanical properties and thermal behavior of PLA matrix are reported. PLA/TiO₂ nanocomposites with different percentages of 2.0, 3.5, 5.0 and 7.0 %∙w/w were prepared by using solvent casting method and hot press machine. TiO₂ were dispersed in PLA matrix using mechanical mixer and ultrasonication technique. The mechanical properties and thermal behavior of PLA nanocomposites were characterized using dynamic mechanical analysis (DMA) and differential scanning calorimeter (DSC). The increased in storage modulus by the addition of nanofiller with the highest increment provided by 2.0 %·w/w TiO₂ indicated a strong influence and better interfacial bonding between nanofiller and PLA matrix. An increased in storage modulus started at 100 °C that linked to the cold crystallization (T_cc) of PLA composites is in agreement with DSC result. The T_cc shifted to higher temperature as the content of nanofiller increased and this result were observed at 2.0 %·w/w of the nanofiller content. Reinforcement of nanofiller increased the melting temperature from lower filler loading until 5.0 %·w/w. The incorporation of TiO₂ nanofiller as the reinforcement agent for PLA has a potential in biopolymer medical engineering and packaging industry, a highly competitive application with a great demand of cost and performance.

Abstract: The incorporation of filler and plasticizer provides effective nucleation and mechanical reinforcement in polymer composites to impart flexibility, toughness, thermal stability and tensile strength of PLA composites that can be used in the development of packaging applications. In this paper, the inclusion of plasticizer and reinforcement of nanofiller in PLA matrix prepared using solvent casting method aims to improve the thermomechanical properties that consequently alter the crystallization and melting behavior of PLA composites. Plasticized PLA with different percentages of TiO₂ at 2.0, 3.5, 5.0 and 7.0 % w/w were dispersed in PLA solution using mechanical mixer and ultrasonication technique to introduce a matrix reinforcing nanophase within the composite. The thermomechanical properties and thermal behavior of PLA nanocomposites were characterized using dynamic mechanical analysis (DMA) and differential scanning calorimeter (DSC). DSC cooling curves at low scanning rate of 2.0 K·min^-1 proved that the presence of TBC in PLA matrix increased the crystallinity of plasticized PLA nanocomposites that initiated the formation of perfect spherulites. TBC increased the crystallization activity during cooling, which in turn reduced the recrystallization effect on heating, in parallel with DMA results that revealed small peak of cold-crystallization activity on PLA nanocomposites with the addition of plasticizer observed at temperature range of 80 °C to 100 °C. Nanofiller induced nucleation for crystallization of PLA matrix and plasticizer accelerated the overall crystallization process. Considerable adjustments of plasticizer and nanofiller in PLA matrix in having a good balance of stiffness and flexibility are a practical strategy that has a potential in biopolymer medical engineering and in the development of packaging applications.