Kamal Yusoh

Synthesis and physicochemical behaviour of polyurethane-multiwalled carbon nanotubes nanocomposites based on renewable castor oil polyols

Polyurethanes (PUs) are high performance materials, with vast industrial and engineering applications. In this research, effects of Multiwalled Carbon Nanotubes (MWCNTs) on physicochemical properties of Castor Oil based Polyurethanes (COPUs) were studied. MWCNTs were added in different weight percentages (0% to 1% wt) in a castor oil based polyurethane (COPUs-MWCNTs) nanocomposites. The composition, structure, and morphology of polyurethanes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), and element detection by energy dispersive spectroscopy (EDX) analysis, respectively. Thermal stability was studied by thermogravimetric analysis (TGA). Barrier properties and surface area studies were investigated by nitrogen permeability machine and BET technique. Mechanical properties were calculated by tensile universal testing machine. Results showed well dispersed MWCNTs in polyurethane matrix at different weight percentages. The best results were obtained with 0.3 wt% of MWCNTs in the composite. Surface area studies revealed presence of very few pores which is in a good agreement with barrier permeability, reduced up to ∼68% in 1wt% and ∼70% in 0.5 wt% of MWCNTs in polymer matrix, with respect to pure COPUs samples.

Dissolution/reprecipitation technique for waste polyolefin recycling using new pure and blend organic solvents

Abstract Restoration of waste polymer based on low-density polyethylene (LDPE), high-density polyethylene (HDPE) and polypropylene (PP) is studied using the dissolution/reprecipitation method. In this technique, pure turpentine, turpentine/petroleum ether (PetE) and turpentine/benzene as solvents with different fractions and PetE and n-hexane as non-solvents were examined. Commercial polymer products (packaging food, bags, laboratory plastic materials, detergent containers) used as raw materials were optimized with model polymers. Polymer recoveries in every case were <94%. Fourier transform infrared (FTIR) spectra and tensile mechanical properties of the samples before and after recycling were measured. Potential recycling-based degradation of the polymer was further investigated by measuring the thermal properties (melting point and crystallinity), before and after recycling, using differential scanning calorimetry (DSC). The blend solvents were seen as good solvents for all polyolefins used and the dissolution temperature was less than the pure solvent at the same time. High reconditioning was observed in most recycled samples, with no significant difference from the virgin materials. The studied technique seems to be viable for waste polyolefin polymer recycling.

Supercritical carbon dioxide-assisted process in synthesis of polymer/clay melt

Nanocomposites are currently being used in a number of fields, and new applications are continuously being developed including mechanical and biomaterial devices, as well as various in solar and fuel cells applications. Generally, the synthesis of polymer nanocomposites are done using solution chemistry, and this may raise serious concerns regarding air and water pollutions. Immediately, the ‘green’ method using supercritical carbon dioxide (scCO2) has grabbed the attention of researchers who are responsible to synthesize polymer composites by non-hazardous routes. Extrusion processes would benefit from the use of scCO2 since the rationale of the extrusion process is to formulate, provide texture and shape molten polymers by forcing them through a die. ScCO2 has been used in several studies as a medium of clay dispersion in polymer matrix by providing a solvent-free fabrication route for nanocomposites. Furthermore, it has more favorable interactions with polymers compared to other inert gases and has the ability to be dissolve in large quantities. It acts as a plasticizer, which modifies viscosity and interfacial properties of the polymer drastically. In this paper, experimental and theoretical studies of solubility and viscosity of several polymer melts in clay are discussed in detail. The assistance of scCO2 in clay dispersion and as a foaming agent has been reviewed extensively.

Enhanced performance of alkylated graphene reinforced polybutylene succinate nanocomposite

Polybutylene succinate (PBS) was being grafted with octadecylamine-functionalized graphene oxide (GO-ODA) to produce novel PBS/GO-ODA nanocomposites by solution blending technique. Alkylated graphene oxide has superhydrophobic surface thus improved the affinity of the filler with low polar polymer such as PBS. The structure and compatibility of the filler and nanocomposites were being characterized using Fourier transform infrared spectroscopy (FTIR), Universal tensile machine (UTM) and thermogravimetric analysis (TGA). Enhancement of tensile strength and Young’s modulus by 30% and 165% respectively was achieved with cooperation of 0.5% GO-ODA loading. The functionalization of GO-ODA in PBS matrix leads to the improvement in the nanocomposites properties.

Modification of pristine nanoclay and its application in wood-plastic composite

Abstract The modification of pristine nanoclay and its application in wood plastic composite (WPC) have been investigated in this paper. Pristine nanoclay was modified using transition metal ion (TMI) which was copper (II) chloride to achieve good dispersion and to improve properties of WPC. The morphology, composition, structure, and thermal stability of TMI-modified nanoclay were studied by field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) analysis. The pristine (WPC/MMT) and TMI-modified (WPC/MMT Cu) nanoclay based WPC were made from polypropylene (PP), wood flour (WF), and maleic anhydride grafted polypropylene (MAPP) coupling agent. Pristine and modified nanoclay with different concentration (1 wt%, 2.5 wt%, 4 wt% and 5 wt%) were used as a reinforcing filler for WPC. Mechanical, physical, morphological, and thermal properties of the prepared composites were evaluated. Result exhibit that at 1 wt% nanoclay content, the tensile, flexural, and impact strength of WPC/MMT improved by approximately 6%, 4%, and 8%, respectively, compared to WPC without nanoclay. For the WPC/MMT Cu, the improvements in these properties were about 2.6, 2.1 and 3 times higher than the WPC/MMT. The physical and thermal properties also improved by incorporating modified nanoclay in WPC.

Facile method for liquid-exfoliated graphene size prediction by UV-visible spectroscopy

In this work, an application of UV spectroscopy for facile prediction of liquid –exfoliated graphene size is discussed. Dynamic light scattering method was used to estimate the graphene flake size ( whilst UV spectroscopy measurement was carried out for extinction coefficient value (e) determination. It was found that the value of (e) decreased gradually as the graphene size was further reduced after intense sonication time (7h). This observation showed the influence of sonication time on electronic structure of graphene. A mathematical equation was derived from log-log graph for correlation between ( ) and (e) value. Both values can be expressed in a single equation as ( = (3.4 × 10−2) e1.2).

Sub-surface mechanical properties and sub-surface creep behavior of wood-plastic composites reinforced by organoclay

Abstract Wood-plastic composites (WPC) were manufactured from polypropylene, wood flour, maleic anhydride grafted polypropylene and organoclay. The sub-surface mechanical properties and the sub-surface creep behavior of the organoclay-based WPC were examined by the nanoindentation technique. The results showed that the hardness, elastic modulus and creep resistance of the WPC enhanced with the loading of C20 organoclay. This enhancement was subject to the organoclay content and the dispersion of organoclay in the polymer matrix. The hardness, elastic modulus and creep resistance of WPC with 1 wt% organoclay content enhanced by approximately 36%, 41% and 17%, respectively, in contrast with WPC without organoclay. To study the impact of organoclay content on the creep performance of WPC, a viscoelastic model was actualized. The results demonstrated that the model was in good agreement with the experimental information. Reinforcement of organoclay prompts expansion in elastic deformation and instigates a higher initial displacement at the early stage of creep.

Mechanical and Thermal Properties of the Waste Low and High Density Polyethylene-Nanoclay Composites

In extension with the previous work, recycling of the waste polyolefins by dissolution/ reprecipitation method, has been investigated. The goal of study was to explore the influence of organo-modified/ unmodified sodium montmorillonite clays, on the behaviours of waste polyolefins inclusive low density polyethylene (LDPE) and high density polyethylene (HDPE). 1-5 wt % of unmodified (MMT) and Organo-modified clay (OMMT) were added to the polyolefins, to prepare polyolefin-clay nanocomposites by melt intercalation method. X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM) were used to estimate the dispersion of clay in the polymer matrices and the morphology of nanocomposites. Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) were used to analyse the change in the thermic properties of the waste polyolefins nanocomposites. The XRD and FESEM results showed an intercalated structure in the HDPE and LDPE with Organo-clay nanocomposites, whereas no exfoliation was observed with unmodified clay in both waste HDPE and LDPE, respectively. DSC and TGA, showed an improved thermal behaviours in the HDPE/Organo-clay nanocomposites (3 wt%) clay loading. Melting temperature and crystallization percentage were observed to increase in 1, 2, and 3 wt% loadings. In waste LDPE/ clay nanocomposites, no improvement was established in the thermal stability.

Production of functional graphene by kitchen mixer: mechanism and metric development for in situ measurement of sheet size

It has been reported that the production of defect free graphene is possible by the application of a kitchen mixer. Yet, we note that the natural-surfactant role in the exfoliation mechanism by a kitchen mixer has rarely been discussed. To investigate the possibility of graphene exfoliation in a bio-surfactant medium, we have produced graphene from the co-mixing of graphite and gum Arabic. Through the modelling of bulky graphite as a single composite disc, we have shown that the exfoliation of graphite crystal may be possible through rotational motion of graphite surface. In this paper, we also have developed two simple metric systems that were designed from the application of UV spectroscopy for in situ measurement of graphene sheet size after exfoliation step.

Prediction of Experimental Measurement Data for High Density Polyethylene and Polypropylene Solubility in Organic Solvents

Abstract High density polyethylene (HDPE) and polypropylene (PP) solubility in several pure and blend non-polar organic solvents was measured at 365–430 K temperature at atmospheric pressure, with polymer concentration of 0.5–25 g in 100 ml of solvent. The activity coefficients were estimated depending on the experimental solubility results for all the polymer-solvent systems. A non-ideal equation combined with activity coefficient was developed based on the crystallinity. A new correlation equation was attained, which is based on the melting temperature and heat of fusion using SSPS software. These two equations were used to predict the solid-liquid experimental data for the binary system polymer-solvent. The distinction between the experimental and model data was assessed by using mean absolute deviation percentage (MAD %). The non-ideal equation based on crystallinity and the new correlations showed low MAD %, displaying a close match with the experimental data.