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This work explores the feasibility of fused deposition modelling (FDM) to produce kenaf fiber/thermoplastic polyurethane (TPU) composites. Internal mixer was used for mixing different weight percentage (0, 5 and 10 wt %) of kenaf fiber with TPU before being extruded to produce filament for FDM feed stock. Addition of kenaf fiber was found to give benefits on dimensional stability of the printed samples which is importance for its implementation in FDM. TPU filled with 10wt% of kenaf fibre showed improvements in hardness and Young modulus of 15% and 49%. However, the tensile strength, elongation at break and density of the printed samples decreased with increasing kenaf fiber loading. This could be explained due to increase of voids and porosity within the material and poor wettability between TPU matrix and kenaf fiber which is evidenced by SEM observation.

Microplastic is classified as fragmented polymeric particles up to 500 microns in diameter. In an aqueous system, microplastic does not always present as a single particle, and these microparticles tend to aggregate and subsequently causing severe ecological risks. The exploration of the underlying mechanisms on how microplastics aggregate in seawater and freshwater enables the prediction of their diffusivity, distribution, and bioavailability in the water environment. In this study microplastic model systems of polypropylene (PP) and poly(vinyl chloride) (PVC) were used to investigate the interactions and aggregation size between microplastics in seawater and with the response anionic sodium dioctyl sulfosuccinate (AOT) surfactant dosages via electrophoretic mobility and Dynamic Light Scattering (DLS) measurements, supported by the UV-Vis spectrum analysis. This investigation revealed that mobile ions present in water ecosystems played a vital role in the surface interactions between microplastics and their aggregation behaviour. The surface charge of both PP and PVC microplastics were switched to a positive value at 5 wt.% of AOT and continued in the negative regime with increasing AOT concentration. Upon the addition of surfactant, surface charge neutralization and aggregation of PP and PVC microplastics were detected; however, the restabilization of microplastic was observed with increasing concentration of surfactant.

This study used water as the physical blowing agent as well as microwave heating (MH) and convection heating (CH) to simultaneously foam and cure natural rubber foam (NRF). Various processing methods and parameters, such as single heating and sequential heating using a mix of CH and MH; were investigated. The correlation between these processing methods as well as different water loadings was then evaluated and compared in terms of physical appearance, density, and morphology. The NRF samples produced using sequential MH and CH (SMC) heating exhibited better shape and structure than samples produced using single heating of either CH or MH only as well as sequential CH and MH (SCM) heating at all water loadings. NRF samples with water loadings of 1.5 and 2.0 phr had a density of less than 0.1 g/cm3. The potential heating mechanism of all the heating methods explored in this study was proposed and discussed to further understand the microwave heating process. The findings of this study proved that water could be utilized as a physical blowing agent in the production of NRF products with microwave-assisted foaming.

A massive demand for rubber-based goods, particularly gloves, was sparked by the emergence of the COVID-19 epidemic worldwide. This resulted in thousands of tons of gloves being scrapped due to the constant demand for the items, endangering our environment in a grave way. In this work, we aimed to focus on the utilization of waste nitrile gloves (r-NBR) as a component blended with natural rubber (NR). The life span and other related properties of the blend can be improved by proper control of the chemical recipe. This study assessed three types of crosslinking systems, namely sulfur (S), peroxide (DCP), and mixed sulfur/peroxide (S/DCP) systems. The results indicate that choosing S/DCP strongly affected the tensile strength of the blend, especially at relatively high contents of r-NBR, improving the strength by 40–60% for cases with 25–35 phr of r-NBR. The improvement depended on the crosslink types induced in the blends. It is interesting to highlight that the thermal resistance of the blends was significantly improved by using the S/DCP system. This indicates that the life span of this blend can be prolonged by using a proper curing system. Overall, the S/DCP showed the best results, superior to those with S and DCP crosslinking systems.

In this work, thermal and rheological properties of self-fabricated polylactic acid (PLA) filaments without and with 10-wt% polyethylene glycol (PLA/0PEG and PLA/10PEG, respectively) were investigated, and the properties were compared with a commercial PLA filament used for fused deposition modeling (FDM). The result showed that the melt flow index for self-fabricated filaments was comparable with commercial filaments at approximately 10 g/10 min at 190°C, suggesting suitability to be used as filament for FDM with well-wetted layers. Variation in thermal properties was found in PLA/10PEG with 20°C higher cold crystallization temperature ( T cc) after FDM in which disruption of the molecular arrangement reduced the ability for chain alignment and folding. The result also revealed that addition of PEG decreased the storage modulus ( G′), loss modulus ( G″), and complex viscosity ( η*), resulting in slow crystallization behavior, and however, the properties did not induce degradation of the filaments and printing products.

In this work, magnetorheological elastomers (MRE) based on nickel zinc ferrite and natural rubber were prepared. Self-healing capability was employed to the MRE by peroxide induced graft polymerization between zinc thiolate and natural rubber to produce reversible ionic crosslinks that can recover the properties of the fracture materials. Evidence that reversible ionic crosslinks occurred was determined by tensile test of original and healed sample. The results revealed that the tensile strength of the MRE recovered 56% in a minute and almost 100% in 10 minutes at room temperature. The morphology of the fractured surface also showed the fracture area was recovered after the healing processed. The dynamic mechanical analysis of the MREs under cyclic loading were also examined with parallel plate rheometer.

Self-healing fabrics have garnered a lot of attention due to their recovering functionality upon damage. This work describes a facile technique for developing a novel self-healing coating with the goal of producing autonomous intrinsic self-healing fabrics that can recover from damage at room temperature without the use of external stimuli. The coating was developed using natural rubber latex (NRL) and consisted of a dynamic reversible metal thiolate ionic network. The formation of the reversible ionic network was assessed by Differential Scanning Calorimetry (DSC), Ultraviolet-visible spectroscopy (UV-vis), Fourier Transform Infrared (FTIR) and zeta potential analysis. Scanning electron microscope (SEM) images revealed that the coating impregnated the fibres of the fabric and improved their structural integrity. The morphology of the punctured area revealed that intermolecular diffusion had occurred during the recovery and the sample had completely healed. The results also showed that the tensile strength, tear strength and puncture strength of the fabric achieved 100% healing efficiency when the damaged fabrics were brought into contact with each other and allowed to be healed at room temperature. This technology is expected to open up a new avenue in the textile industry.

In this work, a novel self-healing natural rubber was developed, and the concepts of mixing both covalent and reversible ionic crosslinks bonds were proposed. The developed materials have the capability of repairing themselves and recovering functionality when they are damaged without the need for detection. Evidence that covalent and reversible ionic crosslinks bonds had occurred was determined by the equilibrium swelling test. The tensile properties of the cured rubbers before and after the healing process were measured using a universal tensile tester to obtain healing efficiency of the materials. The results revealed that the developed self-healing natural rubber was able to recover 60% of its initial mechanical properties in a minute and almost 100% in 10 min at room temperature without the aid of any external resources. Scanning electron microscopy (SEM) showed that the fracture area recuperated with a scar mark after the healing process. Some of the potential products that could benefit from the advantages of these materials include tires, industrial rubber good, cable, hoses, belting, bearing, mounting and foot-wares.

Magnetorheological elastomers (MREs) based on waste nickel zinc ferrite and natural rubber were prepared. The amount of waste nickel zinc ferrite was varied at five levels (20, 40, 60, 80, and 100 phr) to assess the optimum amount of waste nickel zinc ferrite content for highest dynamic mechanical and tensile performance. Curing characteristics of the MREs were determined by moving disk rheometer (MDR 2000), and thermal properties were evaluated by thermogravimetric analysis (TGA). Tan δ was measured through parallel and plate rheometer over a frequency range of 0.1–100 Hz and a strain amplitude range of 0.1–6%. Tensile properties were measured with a universal tensile tester. The results revealed that tan δ, tensile properties, and thermal stability of the MREs increased with increase of waste nickel zinc ferrite contents. Anisotropic MREs, which had chain-like columnar structures of magnetic particles in the matrix as a consequence of an applied magnetic field during curing, were found to produce higher dynamic mechanical performance compared with isotropic MREs cured in the absence of a magnetic field.

Pre-structuring of magnetic particles during fabrication of magnetorheological elastomer (MRE) is a crucial step, which results in the formation of chain-like columnar structures in the rubber matrix. In this study, MRE based on natural rubber and carbonyl iron particles were prepared. The Taguchi method was utilized to study the effect of several dominating factors during the fabrication process such as pre-curing time, pre-curing temperature and applied magnetic field during curing on the loss tangent (tan δ) and tensile properties. Tan δ was measured through parallel-plate rheometer over a frequency range of 1–100 Hz and a strain amplitude range of 0.1–6%. Tensile properties were measured with a universal tensile testing machine. The obtained data were statistically analyzed using S/N ratios and ANOVA in order to predict the optimal combination of factors, and then further experiments were conducted for verification purpose. Results indicated that the magnetic field had the greatest influence on tan δ when measured over a range of frequency and elongation at break. Furthermore, pre-curing time and magnetic field were found to influence tan d when measured over a range of strain amplitude. However, none of the factors exhibited significant influence on tensile strength. In addition, the morphology of MRE was examined using scanning electron microscopy (SEM).

Natural rubber latex foam (NRLF) based on kenaf core and bast were prepared by using the Dunlop method. Mechanical properties, foam density, compression, hardness, thermal aging, and microstructural characteristics of kenaf-filled NRLF with different loadings of kenaf core and bast were analysed. The tensile strength, elongation at break, and compressive strength of kenaf bast filled NRLF samples decreased as the content of kenaf was increased. However, the modulus at 100%, hardness, and density of NRLF increased with increasing kenaf contents. The addition of kenaf core into NRLF increased the swelling percentage and aging of the foam compared to the bast. Scanning electron microscopy (SEM) results indicated that the fibrous kenaf bast had a stronger adhesion compared to the particulate kenaf core, resulting in higher tensile strength, elongation at break, and compression strength.

This research aims to investigate the influence of bed temperatures on various acrylonitrile butadiene styrene copolymer (ABS) parts produced from Fused Deposition Modeling (FDM). The Printing process was conducted at a fixed nozzle temperature of 240°C while bed temperatures were varied from 90°C, 100°C and 110°C. Part shapes were varied accordingly to examine warpage, shrinkage and density due to variation of part thicknesses separately. Changes in the glass transition temperature of ABS printed parts with different bed temperatures were examined using Differential Scanning Calorimetry (DSC). It was found that the warpage and shrinkage reduced with increasing bed temperature due to the reduction of thermal stress with a higher glass transition temperature of printed samples compared with its filament. The thin sample indicated pronounced shrinkage compared with thick sample due to lower thermal contraction in the thicker sample but the former was less affected by the variation of bed temperature. Samples of different heights with fixed infill density indicated variations of the trend of density with different bed temperatures.

Conventional asphalt binder is widely used as the crack sealing material. Crack sealing is one of the most frequent pavement maintenance methods. The level of performance during service life has a close relationship with the properties of asphalt binder used in the pavement or as crack sealant material. As for the pavement crack mechanism, there are two different working mechanisms that occur within the pavement crack, which is horizontal and vertical movement. Horizontal movements are caused by shrinkage and expansion of pavement due to the thermal changes in pavement material. While, the moisture related changes causes vertical movement. This study aims to introduce an alternative testing protocol that can simulate the real failure mechanism of pavement crack. This is due to limited approaches that had been taken by previous researchers to evaluate the performance of pavement-crack sealant. The tensile strength and resistance to shear stress had been chosen as the main performance evaluations in pavement crack sealant material. Prior to that, the bond test and Layer Parallel Direct Shear Test had been used to evaluate the tensile strength and shear resistance of crack sealant material, respectively. This testing protocols could be adopted by other researchers for further studies and also by the asphalt industry.

Geopolymerization had been discussed and concluded by previous researches as an exothermic reaction in which mostly had been determined by using calorimetric method. Calorimetric method enables to detect the amount of heat released or heat absorbed during a reaction and the peaks formed in its data also determine either the reaction is exothermic or endothermic. Researches on heat evolved during geopolymerization were usually being carried out for kinetic studies purpose. However, correlation on the heat evolved during the process to the properties of geopolymers are rarely reported. This study is conducted to determine the effect of heat evolved of geopolymerization during setting with various solid-to-liquid ratios (1.5,2.0,2.5) applied and correlate the heat evolved calculated with compressive strength of class C fly ash geopolymers. In this study, class C fly ash was used as a raw materials and alkali activator used was combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The amount of heat evolved and the peaks observation were determined by using Differential Scanning Calorimeter. The compressive strength was carried out for age of 1-day and 3-days using 50mmx50mmx50mm cubes of geopolymers as this study focused on early strength of geopolymers. The geopolymerization was resulted as an exothermic reaction and the exothermic peaks formation were varied with variation in solid-to-liquid ratio. The optimum ratio of solid-to-liquid ratio obtained in this study in which gave the highest amount of heat evolved (-96.2871 J/g) and highest compressive strength for 1-day age (26.825 MPa) was 2.0. The heat evolved was concluded as significantly affect the early strength of geopolymers for age of 1-day as it has a positive correlation and best fitted when plotted on a graph.Geopolymerization had been discussed and concluded by previous researches as an exothermic reaction in which mostly had been determined by using calorimetric method. Calorimetric method enables to detect the amount of heat released or heat absorbed during a reaction and the peaks formed in its data also determine either the reaction is exothermic or endothermic. Researches on heat evolved during geopolymerization were usually being carried out for kinetic studies purpose. However, correlation on the heat evolved during the process to the properties of geopolymers are rarely reported. This study is conducted to determine the effect of heat evolved of geopolymerization during setting with various solid-to-liquid ratios (1.5,2.0,2.5) applied and correlate the heat evolved calculated with compressive strength of class C fly ash geopolymers. In this study, class C fly ash was used as a raw materials and alkali activator used was combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The amount o...

The main objective in this study is to elucidate the geopolymerization of Class C fly ash at different solid-to-liquid ratio (1.0-3.0) by using heat evolution analysis. Differential Scanning Calorimeter was used to monitor heat evolution. The calculated heat evolved was utilized to analyze the reaction kinetics using Johnson-Mehl-Avrami-Kolmogrov Model and correlate with the compressive strength and microstructural properties encompassing morphology, functional group, phase analysis, and elemental distribution. The heat evolution was found to increase with increasing solid-to-liquid ratios. The nucleation mechanism of geopolymerization of Class C fly ash was governed by instantaneous heterogeneous nucleation with rod-like growth. Solid-to-liquid ratio of 2.5 was concluded as optimal ratio due to its great performance for strength development. Meanwhile the contribution of calcium (Ca) and iron (Fe) was confirmed due to the presence of Si-O-Ca and Si-O-Fe bonds in the functional group analysis, which was further confirmed by phase analysis and elemental distribution mapping.

An intrinsic self-healing natural rubber featuring reversible metal-thiolate ion networks was fabricated and the corresponding healing mechanism and mechanical properties were presented. The developed materials were able to repair themselves at room temperature upon damage without any external stimuli. Reversible metal-thiolate ion networks were proven to form within the rubber material. These networks dominated the cross-linking system and were identified by Differential Scanning Calorimetry (DSC) and Fourier-transform Infrared Spectroscopy (FTIR). Meanwhile, the quantitative amount of metal-thiolate ion networks and covalent crosslinks was determined by swelling testing. Scanning Electron Microscopy (SEM) results revealed that intermolecular diffusion had occurred at the fracture area of the self-healing samples. The results revealed that the mechanical properties could be 100% regenerated after the broken samples were brought into contact with each other. It was also found that self-healing increased by 60% of the material lifespan. This new material is expected to open up promising avenues for the manufacturing of sustainable rubber products.

The heat evolved during setting of class C fly ash geopolymers with different molarity of sodium hydroxide are discussed. The reaction kinetics and microstructure properties of geopolymers are studied towards the early strength development. Differential Scanning Calorimeter was applied to determine the heat evolved and Johnson-Mehl-Avrami-Kolmogrov Model was used to analyse the reaction kinetics during setting of the geopolymers. Morphology and strength development were monitored. The results revealed that the heat evolved increased proportionally with increasing molarity of sodium hydroxide. This indicated rapid reaction of geopolymerization due to the increasing of hydroxide ion content thus mainly affect dissolution process. It was also found that the geopolymerization during setting was governed by one-dimensional growth with instantaneous heterogeneous nucleation and this was supported by the morphology of the geopolymers observed. Among the activator molarities, the molarity of 12 (12M) was observed to be most influential based on its highest compressive strength (up to 46MPa at 7-days) and supported by the morphology properties results.

The objective of this study was to compare the physical and mechanical performance of poly(lactic acid) (PLA), acrylonitrile butadiene styrene (ABS), and nylon 6 fabricated using fused deposition modeling (FDM) and conventional injection molding. It is found that different processing methods did not affect the viscosity of the samples, and the percentage difference for the density measurement is less than 4%. Water absorption of FDM samples is approximately 108% higher compared to those fabricated using the injection molding. The results also revealed that the FDM method did not strongly affect the degree of crystallinity of ABS, but it increased the degree of crystallinity of PLA and nylon 6. The tensile strength, Young's modulus, elongation at break, and impact strength of FDM samples were approximately 48%, 50%, 48%, and 78%, lower compared with the injection molded samples. The results presented can provide a guide to manufacturing the final products using FDM with the desired performance.

This research focuses on the physical, chemical and morphological characterisation of the coconut shell activated carbon (CSAC) with different milling hours. It will be compared with carbon black, N220 in order to access the potential of CSAC as replacement filler for carbon black. Coconut shell activated carbon was produced through the process of pyrolysis at 850°C and impregnated chemically using potassium hydroxide, KOH. Milling process was conducted with different milling hours (0 h, 4 h, 24h and 36 h). Particle size analysis, surface area, x-ray diffraction (XRD), Scanning Electron Microscopic with Energy Dispersive X-ray Spectroscopy (SEM-EDS) and Fourier Transform Infrared Spectroscopy (FTIR) were performed in order to compare physical, chemical and morphological characteristic of carbon black, N220. Based on the results, utilization of the milling process of all CSAC samples were successful in decreasing the particle size, surface area, and pore volume but the average pore size increased.

Geopolymerization consists of several chemical reactions that has been reported widely as an exothermic reaction. Previous studies on heat released during geopolymerization used metakaolin and fly ash of F class as a precursor for geopolymer. Meanwhile, in this study, fly ash of C class is used and a preliminary study has been conducted on determining the exothermic reaction of the geopolymerization with various ratios of solid-to-liquid ranging from 1.5 to 2.5. The amount of heat released was determined by using Differential Scanning Calorimeter. It was proven that different solid-to-liquid ratio affected the amount of heat released during geopolymerization as the highest amount of the heat released were recorded at the optimum solid-to-liquid ratio of 2.0.

Damping in MREs is considered to be ascribed to viscous flow of the rubber matrix, interfacial damping at the interface between the magnetic particles and the matrix and magnetism induced damping. In this study, individual components in MREs that contribute to material damping were investigated. A model was developed to include viscous flow of the rubber matrix, interfacial damping and magnetism induced damping to give the total damping capacity of MREs ψMRE( ψMRE)It was found that ψMRE depends on frequency, iron sand content, strain amplitude and ψMRE is independent of the applied magnetic field over saturation magnetization. The proposed model was assessed experimentally using a series of isotropic and anisotropic MREs. Comparison between tan δ with ψMRE showed that ψMRE matched the experimental trends with average percentage difference of 8.1% and 21.8% for MREs with modified iron sand unmodified iron sand, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43247.

In this study, magnetorheological elastomers (MREs) based on iron sand and natural rubber were prepared. The Taguchi method was employed to investigate the effect of a number of factors, namely, the iron sand content, iron sand particle size, and applied magnetic field during curing on the loss tangent (tan δ) and energy dissipated during cyclic loading. Tan δ was measured through dynamic mechanical analysis over a range of frequency (0.01–130 Hz), strain amplitude (0.1–4.5%), and temperature (−100 to 50°C). The energy dissipated was measured with a universal tester under cyclic tensile loading. The data were then statistically analyzed to predict the optimal combination of factors, and finally, experiments were conducted for verification. It was found that the iron sand content had the greatest influence on tan δ when measured over a range of frequency, and the energy dissipated during hysteresis tests. However, none of the factors showed a significant influence on tan δ when measured over a range of strain amplitude. Furthermore, the iron sand content and magnetic field were also found to influence the width of the peak in tan δ as a function of the temperature. The morphological characteristics of the MREs were also examined with scanning electron microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41506.