Applied Mechanics and Materials Vols. 754-755

Abstract: The thermal degradation of linear low density polyethylene (LLDPE)/ recycled acrylonitrile butadiene rubber (NBRr)/ rice husk powder (RHP) composites with and without epoxidized nature rubber (ENR-50) were studied. The thermal degradation of this composite was evaluated for 30 days using oven ageing. The NBRr content was manipulated in this work and the particle size for the rice husk powder was 150-300 μm. The composites were prepared by using two-roll mills at 180 °C and then were compressed at 180 °C to produce a 1 mm thin sheets. The dumbbell samples then were analysed by using universal testing machine and field emission screening electron microscopy for tensile and morphological properties. The results obtained showed that tensile strength was decreased with the increasing of NBRr content for both oven ageing and control composites. However the oven ageing composites recorded much lower tensile properties. This may possibly due to the chain session of LDPPE matrix at longer heat exposure duration. This finding is supported by the morphological micrograph with less ductile features of the respective specimens.

Abstract: The compatibilizer effect of ENR-50 on the tensile properties and morphology of linear low density polyethylene (LLDPE)/ recycled acrylonitrile butadiene rubber (NBRr)/ rice husk powder (RHP) composites has been studied. The RHP size utilize in this work is 150 – 300 μm. LLDPE/NBRr/RHP composites were prepared by melt mixing technique at 180 °C for 9 minutes at 50 rpm rotor speed using heated two roll mill. The series of composites investigated were 100/0/5, 80/20/5, 70/30/5, 60/40/5, 50/50/5, and 40/60/5. The composites were analysed by using tensile test and morphology examination. The result showed that the tensile strength of composite was decreased with the increasing of recycled acrylonitrile butadiene rubber (NBRr) content while elongation at break (E_b) were increased. However, the tensile strength and elongation at break result for composites with ENR-50 as compatibilizer showed higher values. The morphological finding supports the tensile properties which indicate better interaction between the RHP filler and LLDPE/NBRr matrix in the presence of ENR-50 compatibilizer.

Abstract: Wollastonite is one type of inorganic filler. The effects of wollastonite loading on tensile properties of wollastonite (WS) filled high density polyethylene (HDPE)/Natural Rubber (NR) composites was studied. The HDPE/NR/WS composites were prepared by using Brabender EC Plus at a temperature of 180 °C with rotor speed of 50 rpm for 10 min. It was found that the increasing of wollastonite loading had decreased the tensile strength and elongation at break, whereas the Young’s modulus of the HDPE/NR/WS composites had increased with the increasing of wollastonite loading.

Abstract: The present work aimed to study the effects of kaolin-based geopolymers in epoxy-layered silicate nanocomposites using a compressive test. A series of nanocomposites with kaolin-based geopolymers containing 1-7 phr content were prepared. A qualitative evaluation of the three-dimensional shape of a kaolin-based geopolymer surface and origin was characterised using the scanning electron microscopy (SEM). It was discovered that the addition of kaolin based geopolymer at the beginning, in low phr content, displayed a lower compressive strength than nanocomposites without kaolin based geopolymer filled. However, the compressive properties unexpectedly increased at 3phr of kaolin geopolymer content compared to nanocomposites without kaolin. This illustrated that the incorporation of kaolin geopolymers in the nanocomposite system can potentially improved the mechanical properties of the epoxy resin, thereby needs further exploration.

Abstract: Several epoxy nanocomposites incorporating layered silicates and fly ash based geopolymer were analysed by utilising the wide angle X-Ray diffraction (XRD) to characterise the nanoscale dispersion of the layered silicates. The morphological study of the nanocomposites using X-ray diffraction was an operative method to identify exfoliated and intercalated structures in the nanocomposite. It was discovered that the exfoliated structure was observed in the nanocomposites filled with montmorillonite (MMT) and fly ash-based geopolymers; while the intercalated structure was found in the nanocomposites with 3wt% of MMT. The results suggest that that the addition of fly ash-based geopolymers into epoxy/MMT mixture may contribute to superior compressive properties, in comparison to those nanocomposites without geopolymer filler addition.

Abstract: Fresh field natural rubber was coagulated by acetic acid, soaked in water at room temperature (WRT) or 70°C (W70) for 1 hr, and then dried in an oven at 40°C. Non-soaked natural rubber samples (NoW) served as a control. Two grades of natural rubber, namely air-dry sheet (ADS) and ribbed smoked sheet No.3 (RSS3) derived from the same latex, were also investigated. All dry rubber samples were characterized with Lovibond colorimeter according to ASTM D3157, as well as with a HunterLab spectrophotometer. Furthermore, all the dry rubber samples were dissolved in a chloroform:methanol mixture (4:1 v:v). The rubber was then precipitated out of the solution with methanol, and the remaining solution was quantitatively analyzed for total phenolic content (TPC). The plasticity retention index (PRI) was determined for all the dried rubber samples according to ASTM D3194. It was found that WRT, W70 and ADS were similar in lightness L*, while RSS3 had the lowest L*. W70 had the lowest redness a*, which increased in the order WRT, NoW, RSS3 and ADS. W70 also had the lowest yellowness b*, which increased in the order RSS3, NoW and WRT and ADS. Moreover, TPC was the lowest for the W70 sample, increasing in the order ADS, WRT, NoW and RSS3. The PRI was highest for W70, and decreased in the order WRT, RSS3, NoW and ADS. All of the PRI values observed were comparatively high relative to blocked standard Thai rubber 20 (STR20).

Abstract: The use of natural fiber as reinforcement in polymer composites has gained importance recently due to environmental concern and its abundance availability from agricultural crops and wood industry [1]. Many advantages offered by natural fibers over synthetic fibers include low density, greater deformability, low cost per unit volume, recyclability and biodegradability [2-3]. In addition, the mechanical properties of natural fibers such as flax, hemp, jute, sisal and kenaf are comparable with glass fiber in respect of strength and modulus [4]. Hence, many studies have been carried out to replace the synthetic fiber for composite preparation.

Abstract: Microwave sintering is new sintering technology method to produce Al alloys. The advantages of this method because of very short sintering time and less production cost compare to conventional sintering. However, the main problems in microwave sintering are required to be controlled sintering time due to rapid sintering mechanism. Therefore the effect of microwave sintering time to PM Aluminium will be studied. The compacted and sintered aluminium powder is placed in a microwave oven at a different period of 5 minutes, 10 minutes, 15 minutes and 20 minutes. Compression of 150 MPa is applied on aluminium powder to form pellets. Palette is shaped to 1cm in diameter and weighs 1g. SiC is placed together with aluminium samples in the microwave for the purpose of absorbing electromagnetic energy and is converted to heat. Results of different period sintering of aluminium pallet production altered physical properties of each sample. For a rapid sintering time, aluminium pallet does not show any binding reaction between powder particles. Whereas, for long microwave sintering period, solid particles phase change into solid-liquid phase caused by the movement and the formation of bonds between particles. Hence, this will be affecting the mechanical properties of the sample material.

Abstract: Palm oil boiler ash (BA) has been synthesis with alkaline activator to produce boiler ash based geopolymer. The ratio of BA/alkaline activator and Na₂SiO₃/NaOH was fixed for the entire experiment, where six different of NaOH concentration (6 M, 8 M, 10 M, 12 M, 14 M, 16 M) was used to produce geopolymer paste. The compressive strength of geopolymer paste with NaOH concentration 14 M showed the maximum strength which is 13.9 MPa. The strength reduce when geopolymer paste used NaOH concentration more than 14 M. In term of molar oxides SiO₂/Al₂O₃ , Na₂O/SiO₂ and H₂O/Na₂O with the increasing of NaOH concentration Na₂O/SiO₂ ratio also increased but H₂O/Na₂O ratio decreased. Meanwhile SiO₂/Al₂O₃ ratio remain constant because the BA/alkaline activator and Na₂SiO₃/NaOH ratio were constant in this study. The XRD analysis illustrated that the value of 2θ for all geopolymer samples were approximately the same which is 27° with major components of quartz and minor component of cristobalite.

Abstract: We has synthesized hyperbranched polyamides (HPI) series containing s-triazine rings derived from melamine in the main chain, according to A3 + B2 approach which involving the emulsion polymerization reactions of melamine in hydrochloric acid and stepwise thermal imidization. The effect of curing temperature on the degree of imidization (DI) films of Melamine-BPADA (4,4'-(4,4'-Isopropylidenediphenoxy) bis (phthalic anhydride) has been examined by using the techniques of FTIR (Fourier transform infrared) and SEM-EDX (Scanning Electron Microscope-Electron Diffaction X-Ray). The DI varied significantly with annealing temperature before the films were fully cured. The Melamine-BPADA film was nearly fully cured when annealed at 180 °C, while the same was revealed for SEM-EDX. The morphology of the Melamine-BPADA film did not vary with annealing at temperatures and the FTIR experiment fairly match those from the SEM-EDX.