Papers by Author: H. Kamarudin

Abstract: The effect of rambutan peels flour (RPF) content on the tensile properties of linear low density polyethylene filled with rambutan peel flour was studied. RPF was melt blended with linear low–density polyethylene (LLDPE). LLDPE/RPF blends were prepared by using twin screw extruder at 150°C with the flour content ranged from 0 to 25 wt%. The tensile properties were tested by using a universal testing machine (UTM) according to ASTM D638. The highest tensile strength was pure LLDPE meanwhile the tensile strength LLDPE/RPF decreased gradually with the addition of rambutan peels flour. Young’s modulus of rambutan peels flour filled LLDPE increased with increasing fiber loading. The crystallinity of the blends was significantly reduced with increasing RPF content. Instead, the water absorption increased with the addition of RPF content.

Abstract: The effects of different particle sizes of recycled nitrile glove (rNBRg) on curing characteristics and physical properties of natural rubber/styrene butadiene rubber/recycled nitrile glove (NR/SBR/rNBRg) blends were investigated. The particle sizes of rNBRg were differentiated by the method of sizing. S1 was obtained by cutting the rNBRg into smaller sheets; S2 was obtained by passing rNBRg through 2 rolls mill for 10 times; and S3 was obtained by passing rNBRg through 2 rolls mill for 10 times and then mechanically grinded. NR/SBR/rNBRg blends were prepared at 50/30/20 composition using two roll mill at room temperature, with different particle sizes, rNBRg (S1), rNBRg (S2) and rNBRg (S3). Curing characteristics (scorch time, cure time, minimum torque and maximum torque), tensile properties and physical properties (crosslink density, resilience and hardness) of the blends were investigated. Results indicated that scorch time, cure time and minimum torque decreased as the rNBRg particle size decreased, while maximum torque and crosslink density increased. Tensile strength of the blends decreased as the rNBRg particle size reduced, which explained the formation of holes on the surfaces of tensile fracture, observed by scanning electron microscope. The rigidity of NR/SBR/rNBRg blends increased when smaller rNBRg particles were used, which explained the increased in hardness and decreased in resilience of the blends.

Abstract: Natural fiber reinforced polylactic acid based biocomposites are broadly considered by the researchers to compete with non-renewable petroleum based products. In this study, the biodegradable composites which are the polylactic acid, PLA and rice straw, RS were prepared by using heated two roll-mill at 180°C. Mechanical properties showed that the tensile strength and elongation at break, E_b decreased with the increasing of RS while the Young’s modulus had increased. The TGA results confirmed that thermal stability of PLA with RS composites decreased when the RS fiber loading increased.

Abstract: Cure characteristics and physical properties of EPDM/rNBR filled bamboo fillers were studied. Results indicated that the addition of bamboo fillers has significant effects on EPDM/rNBR blends. The scorch time, t₂ decreased up to 25 phr fillers loading but increased further to 50 phr fillers loading. Cure time, t₉₀ increases as the increase in bamboo fillers in the blends. At a similar blend ratio fine sizes bamboo fillers in EPDM/rNBR (S1: ≤125μm) exhibited higher value of t₂ ad t₉₀ compared to EPDM/rNBR (S2: 125-250μm & S3: 250-500μm). The minimum torque, M_L also increases with increasing bamboo fillers in the blend. Meanwhile, the maximum torque, M_H of the EPDM/rNBR filled bamboo fillers were in contrast. The hardness and degree of crosslink density of the blends increased with the increase in bamboo fillers and reduce percentage of resilience at all blends. The fine sizes of bamboo fillers contributed to the better properties compared to the coarse sizes and medium sizes.

Abstract: The properties of blends made from low density polyethylene (LDPE) with various concentration of jackfruit seeds flour (JSF) with the presence of citric acid (CA) were investigated. The JSF content was varied from 0 to 20 wt%. The JSF were blended with LDPE by using an internal mixer (Brabender) at a temperature of 150°C. The test was carried out by using differential scanning calorimetry (DSC), with heating temperature of 100C/min. The crystallinity had improved with the presence of CA. However, the crystallinity slightly reduced with the increasing JSF content and further increased with the presence of CA.

Abstract: The effects of adding hexanedioic acid (HA) into low density polyethylene (LDPE)/jackfruit seeds (JSF) blends on the properties were investigated by using differential scanning calorimetry (DSC). The influence of the crystallinity and thermal properties of HA on LDPE at various compositions was investigated. JSF was blended with LDPE by using internal mixer (Brabender) at temperature 150°C. JSF content was varied from 0 to 20 wt%. Crystallinity of the blends was significantly reduced with increasing JSF content and further increased with the presence of HA. Therefore, the crystallinity of the blends was improved with the presence of HA.

Abstract: The reaction of limestone in the slaking process has been studied under different conditions of parameters such as calcination times, soaking times and particle sizes. The reactivity of quicklime was determined by recording temperature rise and the rate of temperature rise during the slaking process. The obtained ‘milk of lime’ is characterized using instrumental measurements such as X-ray fluorescence (XRF) to identify the chemical composition that exists in the sample. In this paper, the quicklime used during slaking test indicates the differential of temperature pattern which influences by quicklime particle sizes, calcination temperatures and soaking times. Results indicate that the optimum and efficient distribution of heat transfer and thermal decomposition onto quicklime can be obtained by calcining at 1100 °C with 60 minutes of soaking time samples which produced a highly porous structure towards higher reactivity of quicklime.

Abstract: This paper presents an experimental study of the relationship between water absorption and porosity for geopolymer paste. In order to reduce the carbon dioxide (CO₂) emissions to the environment, alternatively fly ash was used as binders in making concrete paste. Fly ash is a waste materials produced by combustion of coal at power plant. Geopolymer paste prepared from class F fly ash was obtained from coal power plant and mixed with an alkaline activator. The combination of sodium silicate (Na₂SiO₃) solution and sodium hydroxide (NaOH) solution were used as alkaline activator. The alkaline activator was prepared 24 hrs prior to use with the ratio of the mixture of Na₂SiO₃/NaOH is 2.5. Mixed fly ash and alkaline activator placed in moulds and compacted. The samples were kept at ambient temperature in the moulds until it hardened. All the samples were removed from the moulds after 24 hrs. Then, the samples were cured at 60 °C in the oven for 24 hrs. All twelve samples were prepared for water absorption and porosity measurement. The samples were examined after 7, 14, 28 and 90 days in terms of water absorption test and porosity test. It was observed that after day 90 the sample had the lowest water absorption of 3.81% and porosity 3.77%. The sample had the highest water absorption and porosity of 4.65% and 11.95% respectively at day 7. The pore size decreases and the structures became denser. The morphological structure of geopolymer paste pores can be observed by Scanning Electron Microscope (SEM). The porosity and permeability also decreased hence the durability potentially improved. Keywords: Water absorption, porosity, geopolymer, fly ash

Abstract: This paper presents a study on the relationship between porosity and compressive strength for geopolymer paste. In this research, geopolymer paste was made from fly ash class F based geopolymer mixed with alkaline activator; sodium hydroxide solution and sodium silicate solution. Twelve mixes were cast in 50mm x 50mm x 50mm moulds and the samples were cured for 24 hrs at 60 °C in the oven. The samples were examined after 7, 14, 28 and 90 days in terms of porosity test, pulse velocity test and compressive strength test. It was concluded that the sample at day 90 had the highest compressive strength of 56.50 N/mm² had porosity 3.77%. Thus, the sample with lowest porosity had highest pulse velocity 3303 m/s during ultrasonic testing with lowest transmission time 15.17 μs. Keywords: porosity, compression strength, geopolymer, pulse velocity

Abstract: This paper reports the fire resistance property of a lightweight aggregate geopolymer concrete (LWAGC) material synthesized by the alkali-activation of locally source fly ash (FA) after exposed to elevated temperatures ranged of 100 °C to 800 °C. The results illustrates that the concrete gained a compressive strength after exposing to elevated temperatures of 100, 200 and 300 °C. Afterward, the strength of the LWAGC is started to deteriorate after exposing to elevated temperatures ranged of 400 °C to 800 °C, due to the difference in thermal expansion between the geopolymeric paste and LWA as well as to the evaporation of the structural water which increased the thermal shrinkage.