Abdulkader M. Alakrach

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.

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.

Cure Characteristics, Tensile and Physical Properties of Recycled Natural Rubber Latex Glove (NRL-G) Filled Acrylonitrile Butadiene Rubber

The use of recycled natural latex rubber glove (NRL-G) as a reinforced material filled acrylonitrile butadiene rubber (NBR) was studied. The compounds of different NRL-G loading (0, 10, 20 and 30 phr) were prepared by using two roll mills at room temperature. Two different size ranges of NRL-G such as 300μm-700μm (fine) and 2cm-4cm (coarser) were used. The properties such as cure characteristics, tensile and physical properties were determined. The NBR/NRL-G compound with the fine size of NRL-G exhibits overall good cure characteristics and physical properties compared with coarser size. The addition of the of 20 phr content NRL-G (fine) contributed to the optimum tensile properties than coarser size.

Recycled Natural Rubber Latex Gloves Filled Chloroprene Rubber: Effects of Compatibilizers

In this study, the effects of the compatibilizers; trans-polyoctylene (TOR) and epoxidized natural rubber (ENR-50), on the cure characteristics and tensile properties of recycled natural rubber latex gloves (rNR-G) filled chloroprene rubber (CR) were investigated. Blends consisting of rNR-G in a weight ratio 20 phr in CR and The compatibilizers TOR and ENR-50 at different concentrations, i.e. 2, 4, 6, 8 and 10 phr, were prepared using a two roll mill. Incorporation of TOR resulted in a reducing of the cure characteristics, meanwhile ENR-50 increased them. On the other hand, both of TOR and ENR-50 were improved tensile properties. These effects are attributed to the enhanced interfacial adhesion between rNR-G and phases through the compatibilizing effect induced by TOR and ENR-50, and the good dispersion of the rNR-G phase in the CR matrix. The results confirmed that TOR and ENR-50 could potentially be used as compatibilizers for the recycled natural rubber latex gloves filled chloroprene rubber.

Studies on Tensile Properties of Compatibilized and Uncompatibilized Low-Density Polyethylene/Jackfruit Seed Flour (LDPE/JFSF) Blends at Different JFSF Content

Currently, natural fillers seem to be the suitable materials in polymer industry, which have emerged as a viable and abundant replacement for the relatively high-cost and non-renewable conventional fillers. However, the direct introduction of natural fillers into polymer matrix could effect negatively on some properties. Therefore, the aim of this work is to evaluate the influence of jackfruit seed flour (JFSF) (before and after compatibilization) on the tensile properties of (LDPE/JFSF) blends. Different JFSF content (5, 10, 15 and 20 wt.%) with (63-100 ) particle size were prepared in this work. Twin-screw extruder at 150°C and 50rpm screw speed followed by hot-compress machine at 150°C and 10MPa pressure were used respectively to produce (LDPE/JFSF) blends. Adipic acid (AA) solution was added as a compatibilizer into all blends equally (25wt% AA into 75wt% JFSf). The changes of tensile and morphological properties were investigated. Results shown decreasing on tensile strength and elongation at break of LDPE/JFSF and LDPE/JFSF/AA as JFSF increased. In contrast, Young’s modulus increased up to 10 wt.% of JFSF and then decreased. However, the addition of Adipic acid, particularly for JFSF 5wt.% has improved the tensile properties of LDPE/JFSF blends. The SEM micrographs showed the agglomeration at high JFSF content (20 wt%) which in turn effected negatively on the tensile properties. However, the blends show homogeneous surfaces as AA added.