Azlin Fazlina Osman

In vitro biostability and biocompatibility of ethyl vinyl acetate (EVA) nanocomposites for biomedical applications

The in vitro biostability and biocompatibility of ethyl vinyl acetate (EVA) nanocomposites incorporating organically modified montmorillonite (organo-MMT) were investigated as new candidate material for biomedical applications. The in vitro treatment of neat EVA and EVA nanocomposites was performed by immersing the materials in oxidizing and hydrolytic agents, at a temperature of 37 °C, for 4 weeks. The in vitro mechanical properties of the materials under these environmentally challenging conditions were assessed. Based on morphology studies, the degree of MMT dispersion and exfoliation decreased as the nanofiller loading increased. The EVA containing 1 wt% organo-MMT exhibited the best nanofiller dispersion and exfoliation characteristics. The surface degradation features of this nanocomposite were seen to be smoother than those of neat EVA and other EVA nanocomposites. Furthermore, the EVA nanocomposites have improved mechanical properties in comparison with the neat EVA, and these properties were less affected by the in vitro conditions. The best in vitro mechanical properties were achieved when 1 wt% of organo-MMT was added into the EVA. It was postulated that the presence of a better dispersed and exfoliated organo-MMT layered structure introduced a more tortuous path for the diffusion of oxidants and water molecules, thereby decreasing their permeation towards the EVA molecular chains. Therefore, the degradation kinetics within the EVA molecular chains were at a lower rate, which resulted in enhanced biostability. Furthermore, the toughness of the hydrated EVA (exposed to PBS at 37 °C) was greatly enhanced with the addition of the 1 wt% organo-MMT. The biocompatibility assessment suggests that the EVA nanocomposites are not cytotoxic, and thus have fulfilled the prerequisite to be further developed as a biomedical material.

Pre-dispersed organo-montmorillonite (organo-MMT) nanofiller: Morphology, cytocompatibility and impact on flexibility, toughness and biostability of biomedical ethyl vinyl acetate (EVA) copolymer

Polymer-clay based nanocomposites are among the attractive materials to be applied for various applications, including biomedical. The incorporation of the nano sized clay (nanoclay) into polymer matrices can result in their remarkable improvement in mechanical, thermal and barrier properties as long as the nanofillers are well exfoliated and dispersed throughout the matrix. In this work, exfoliation strategy through pre-dispersing process of the organically modified montmorillonite (organo-MMT) nanofiller was done to obtain ethyl vinyl acetate (EVA) nanocomposite with improved flexibility, toughness, thermal stability and biostability. Our results indicated that the degree of organo-MMT exfoliation affects its cytotoxicity level and the properties of the resulting EVA nanocomposite. The pre-dispersed organo-MMT by ultrasonication in water possesses higher degree of exfoliation as compared to its origin condition and significantly performed reduced cytotoxicity level. Beneficially, this nanofiller also enhanced the EVA flexibility, thermal stability and biostability upon the in vitro exposure. We postulated that these were due to plasticizing effect and enhanced EVA-nanofiller interactions contributing to more stable chemical bonds in the main copolymer chains. Improvement in copolymer flexibility is beneficial for close contact with human soft tissue, while enhancement in toughness and biostability is crucial to extend its life expectancy as insulation material for implantable device.

Epoxy Layered Silicates with Fly Ash-Based Geopolymer: Flexural Properties

The effect of fly ash-based geopolymer in epoxy-layered silicates nanocomposites was studied through flexural properties and morphological characterization. In this study, a series of nanocomposites with fly ash-based geopolymer containing 1-7% wt were prepared. It was found that the addition of fly ash with lower content in the beginning showed lower flexural strength than nanocomposites without fly ash. However, flexural properties suddenly increased at 3% wt of fly ash geopolymer content in comparison to origin. This indicates the blending of fly ash geopolymer in nanocomposites systems have the ability for further studied.

In Vitro Mechanical Properties of Metallocene Linear Low Density Polyethylene (mLLDPE) Nanocomposites Incorporating Montmorillonite (MMT)

The viability of metallocene linear low density polyethylene (mLLDPE) nanocomposites is being investigated as a new material for biomedical application. The effect of filler loadings on the ambient and in vitro (after being exposed in oxidizing condition, 37°C) mechanical properties was studied. We observed that, the mLLDPE nanocomposites have higher mechanical property values as compared to the neat mLLDPE. Furthermore, these properties were less affected by the in vitro conditions. The best ambient and in vitro mechanical properties were achived when 3wt% of organically modified MMT (organo-MMT) was added into the mLLDPE. It was postulated that the presence of MMT layered structure introduced a more tortous path for the diffusing of oxidant molecules, thereby decreasing their permeability towards mLLDPE molecular chains. The smaller amount of oxidants entering the molecular chains resulted in greater retention of mechanical properties when tested in vitro. This preliminary biostability studies show promising properties of the mLLDPE nanocomposite which possess the potential to be further developed for biomedical devices.

The Effects of Melt Compounding Method on the Ambient and In Vitro Mechanical Properties of EVA/MMT Nanocomposites

The in vitro biostability of ethyl vinyl acetate (EVA) nanocomposite incorporating the organically modified montmorillonite (organo-MMT) was investgated as a new material for biomedical applications. The effects of compounding process and filler loadings on the ambient and in vitro (exposed in oxidizing condition, 37°C) mechanical properties were studied. We have observed that, the melt compounded EVA copolymer by internal mixer (Brabender plasticoder) achieved the highest ambient and in vitro mechanical properties at low nanofiller content (1wt% organo-MMT). In contrast, the melt compounded EVA copolymer by twin screw extruder achieved the highest ambient and in vitro mechanical properties at high nanofiller content (5wt% organo-MMT). We suggest that this was due to the capability of the twin screw extruder to provide greater shear force for the exfoliation and dispersion of the high content organo-MMT as compared to internal mixer (Brabender plasticoder). However, compounding by twin screw extruder caused more severe reduction in tensile toughness of the EVA containing 5 wt% organo-MMT, after this material was exposed to oxidative agent, 37°C. These studies show that the melt compounding method may bring significant effect to both the ambient and in vitro mechanical performance of the EVA nanocomposites, and hence further investigation towards optimization should be pursued.

Mechanical Properties and Morphology of Epoxy/Graphene Nanocomposite Using Bath Sonication and Tip Sonication

There are different graphene loadings (0, 0.2, 0.4, 0.6, 0.8, and 1.0 vol%) were used in order to study the effect graphene loading using different type of ultrasonication. Two types of ultrasonication: bath and tip sonication were applied in the preparation of epoxy/graphene nanocomposites. Effect of different ultrasonication applied on the mechanical properties and morphology of nanocomposites were investigated. By using tip sonication, epoxy/graphene shown better improvement in the mechanical properties due to direct ultrasonication that generates higher sound pressures and intensity compared to bath sonication which is indirect ultrasonication. Besides, epoxy/graphene nanocomposites prepared using tip sonication exhibits greater fracture toughness where lower intensity and non-uniform sonication effect failed to achieve optimum dispersion of graphene nanoplatelets and also its distribution using bath sonication. Rougher surface with increased deflected crack lines was observed on the samples that prepared using tip sonication further proven that more fracture energy was dissipated which inhibits the propagation of cracks and hence delayed the failure of nanocomposites.

Destabilization of Natural and Commercial Bentonite Interlayers by Ultrasonication, pH Control and Salt Addition

Natural and commercial bentonites can act as efficient fillers to reinforce a polymer matrix if their strong interlayer binding forces are weakened to reduce tactoid formation. In this research, interlayers destabilization process was applied to gain a loosely packed, swelled and disorganized clay layered structure for better polymer intercalation and filler dispersion during the polymer/clay composite fabrication. Three different destabilization methods were applied to the natural and commercial bentonites and their effects on swelling and platelets ordering/stacking of the clays were observed. The pristine and destabilized natural and commercial bentonites were characterized and compared based on their chemical component (XRF), chemical structure (XRD) and morphology (FESEM). Chemical analysis revealed that alumina content in the natural bentonite is less than in the commercial bentonite while silica content in natural bentonite is more than in the commercial bentonite. XRD results suggest that basal spacing (d001) of both natural and commercial bentonites reduced when single destabilization process (by salt addition) was applied but increased when destabilization was done by the combination of pH control and salt addition processes. These show that the destabilization process through combination of pH control and salt addition is more efficient in swelling both natural and commercial bentonite clays. This is supported by FESEM analysis where smaller, more loosely packed and uniform platelets were observed due to swelling and weakening of the interlayer binding forces of both natural and commercial bentonite clays.

Mechanical Properties and X-Ray Diffraction of Oil Palm Empty Fruit Bunch All-Nanocellulose Composite Films

The all-nanocellulose composite films were prepared using cellulose solvent system N-dimethylacetamide/lithium chloride (DMAc/LiCl). The process includes partial dissolution of oil palm empty fruit bunch (OPEFB) and microcrystalline cellulose (MCC) in the N-dimethylacetamide/lithium chloride (DMAc/LiCl) solution followed by the regeneration process. The regeneration process also includes the removal of the N-dimethylacetamide/lithium chloride (DMAc/LiCl) solvent by using distilled water and drying of the films. The all-nanocellulose composite films with OPEFB contents in the range of 1–4 wt% were prepared and analyzed for their mechanical properties and crystallinity. The all-nanocellulose composite film with 1 wt% of OPEFB content showed the best tensile strength and modulus of elasticity with the value of 7.95 and 179.77 MPa, respectively. This could be due to a good dispersion of the cellulose particles in the films. However, the elongation at break for the composite film with 1 wt% of OPEFB content showed lower value than the ones contained higher percentage of OPEFB contents. As the content of OPEFB increases the tensile strength decreases especially at 4 wt% of OPEFB content of the composite film. The X-ray diffraction (XRD) analysis suggests that the all-nanocellulose composite film with 1 wt% of OPEFB content has higher crystallinity compared to the all-nanocellulose composite film with 4 wt% of OPEFB content. This could explain why this particular all-nanocellulose-based composite system performed greater tensile strength and modulus at low OPEFB content (1 wt%).

Effect of ferric chloride on the electrical conductivity and characterization of polyethylene oxide/polyvinyl chloride/polyaniline conductive films

In this work, we present an exclusive study on the effect of Ferric chloride (FeCl3) on the electrical conductivity and characterizations of polyethylene oxide (PEO)/polyvinyl chloride (PVC)/polyaniline (PAni) conductive films. The objective of this paper is to improve the electrical conductivity of PEO/PVC/PAni conductive films with the addition of ferric chloride (FeCl3) as oxidants. PEO/PVC/PAni conductive films and PEO/PVC/PAni-FeCl3 conductive films were examined based on electrical conductivity, scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). It is shown that the electrical conductivity of PEO/PVC/PAni conductive films increased with increasing PAni loading and further increased with the introduction of FeCl3. The SEM images reveal PAni agglomerations in the PEO/PVC matrix at higher PAni loadings. Lastly, the structures of the conductive films with the effect of PAni, FeCl3 were revealed by the FTIR study.In this work, we present an exclusive study on the effect of Ferric chloride (FeCl3) on the electrical conductivity and characterizations of polyethylene oxide (PEO)/polyvinyl chloride (PVC)/polyaniline (PAni) conductive films. The objective of this paper is to improve the electrical conductivity of PEO/PVC/PAni conductive films with the addition of ferric chloride (FeCl3) as oxidants. PEO/PVC/PAni conductive films and PEO/PVC/PAni-FeCl3 conductive films were examined based on electrical conductivity, scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). It is shown that the electrical conductivity of PEO/PVC/PAni conductive films increased with increasing PAni loading and further increased with the introduction of FeCl3. The SEM images reveal PAni agglomerations in the PEO/PVC matrix at higher PAni loadings. Lastly, the structures of the conductive films with the effect of PAni, FeCl3 were revealed by the FTIR study.

Enhancement of Electrical Conductivity and Tensile Properties of Conductive Poly(vinyl Chloride)/Poly(ethylene Oxide)/Polyaniline Conductive Composite Films: Effect of Polyaniline Loading and Ethylene Dimethacrylate

The effect of ethylene dimethacrylate (EDMA) as a surface modifier and polyaniline (PAni) loading on poly(vinyl chloride) (PVC)/poly(ethylene oxide) (PEO) matrix was investigated. PVC/PEO conductive composite films with different PAni loading were fabricated using solution casting technique. The inclusion of EDMA exhibited higher tensile strength, modulus of elasticity and electrical properties for all filler loadings of PVC/PEO/PAni conductive composite films. The scanning electron microscopy (SEM) morphology indicated that the inclusion of EDMA in conductive films provided decent fillers dispersion in the PVC/PEO phases. The structural modifications, if occurred, will be interpreted with the assistance of FTIR spectroscopy.