Mat Uzir Wahit

Toughening of Polylactic Acid Nanocomposites: A Short Review

Polylactic acid (PLA) is a thermoplastic derived from renewable resources, which degrades to nontoxic compounds in landfills. With current advances in the field of nanotechnology, development of layered silicate-based PLA nanocomposites successfully created a sustainable material with enhanced physical, thermal and chemical properties, holding the future as an alternative to petroleum-based materials. However, the toughness of PLA in its pristine state and nanocomposites is often insufficient. As such, there has been tremendous effort in developing ways to improve this with incorporation of plasticizers and impact modifiers. In this review, we summarize approaches in toughening of PLA and its nanocomposites.

Mechanical and morphological properties of PP/NR/LLDPE ternary blend - Effect of HVA-2

Improvements in impact strength of polypropylene can be sought by melt blending with rubbers. In this study, blends of PP, natural rubber and linear low density polyethylene (PP/NR/LLDPE) were prepared in a laboratory scale extruder. The rubber content in the ternary blend was at 10 and 20% with LLDPE content fixed at 25% of the overall plastics content. After mixing and pelletising, the samples were injection moulded and tested for mechanical properties. The study showed that the mechanical properties were modified significantly with the addition of HVA-2. The incorporation of HVA-2 into the ternary blend improved the elongation at break, but no significant change was observed in the yield strength values. At both testing temperatures of 0 and 27 °C, the impact properties of 64/20/16 PP/NR/LLDPE ternary blends improve significantly as HVA-2 increases from 0 to 7.5%. However, the 72/10/18 PP/NR/LLDPE shows an optimum value at 0.5% HVA-2 concentration. SEM study shows that the number of holes due to the extraction of NR particles reduced significantly upon the addition of HVA-2. This observation indicates that the HVA-2 has crosslinked the rubber phases. The crosslinking of the rubber particles will increase the cohesive strength of natural rubber allowing it to undergo greater deformation before cohesive failure. It is also notable that the crosslinking can prevent the elastomer domain from re-aggregation and breakdown at shear stresses prevailing during the molding process and maintains mechanical properties effectively. In this study, the HVA-2 was also shown to be an effective compatibilizer by reducing the interfacial tension and improving adhesion between immiscible polymers, thus increasing the compatibility of the blend.

Mechanical, Thermal, and Morphological Properties of Polylactic Acid/Linear Low Density Polyethylene Blends

Melt blending of polylactic acid (PLA) and linear low density polyethylene (LLDPE) was performed to investigate the effects of LLDPE loadings on the morphology, mechanical and thermal properties of PLA/LLDPE blends. LLDPE was blended with PLA from 5—15 wt% and prepared by counterrotating twin-screw extruder followed by injection molding into test samples. The mechanical properties of the blends were assessed through tensile, flexural and impact testings while thermal properties were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis. Scanning electron microscope was used to study the dispersion and particle size of LLDPE in PLA matrix. The impact strength of PLA improved by 53% with addition of 10 wt% LLDPE. However, the tensile modulus and strength, and elongation at break of PLA/LLDPE blends decreased with increasing weight ratio of LLDPE. Similarly, flexural modulus and strength also dropped with addition of LLDPE. DSC results showed that glass transition temperature (Tg) and crystallinity (X c) of PLA increased with blending of LLDPE. The LLDPE particles size was seen to increase with increasing loadings of LLDPE which explains the unexpected decrease of impact strength after 10 wt%.

Development of regenerated cellulose/halloysite nanotube bionanocomposite films with ionic liquid

In this study, novel nanocomposite films based on regenerated cellulose/halloysite nanotube (RC/HNT) have been prepared using an environmentally friendly ionic liquid 1-butyl-3-methylimidazolium chloride (BMIMCl) through a simple green method. The structural, morphological, thermal and mechanical properties of the RC/HNT nanocomposites were investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM), thermal analysis and tensile strength measurements. The results obtained revealed interactions between the halloysite nanotubes and regenerated cellulose matrix. The thermal stability and mechanical properties of the nanocomposite films, compared with pure regenerated cellulose film, were significantly improved When the halloysite nanotube (HNT) loading was only 2 wt.%, the 20% weight loss temperature (T20) increased 20°C. The Youngs modulus increased from 1.8 to 4.1 GPa, while tensile strength increased from 35.30 to 60.50 MPa when 8 wt.% halloysite nanotube (HNT) was incorporated, interestingly without loss of ductility. The nanocomposite films exhibited improved oxygen barrier properties and water absorption resistance compared to regenerated cellulose.

Effect of Organoclay and Ethylene-Octene Copolymer Inclusion on the Morphology and Mechanical Properties of Polyamide/Polypropylene Blends

A series of compatibilized polyamide 6/polypropylene (PA6/PP) blends, of composition 70/30, 50/50, and 30/70 have been prepared in a twin screw extruder followed by injection molding. The four types of PA6/PP blends involved are the neat PA6/PP blends, PA6/PP/ethylene-octene copolymer (polyolefin elastomer, POE), PA6/PP/organoclay, and PA6/PP/POE/organoclay. Tensile, flexural, and Izod impact test are performed on these blends. The morphology of the blends is characterized by scanning electron microscopy (SEM). The mechanical properties of the blends are found to be strongly dependent on the PA6/PP blend ratio. For any blend system, with the increase in PP concentration, the strength and stiffness decreases, while the toughness increases. The incorporation of 4 wt% organoclay into PA6/PP blends significantly increases the modulus and strength but with corresponding reductions in impact strength. Conversely, the incorporation of POE increases the toughness, while the strength and stiffness decrease. However, PA6/PP blends containing both organoclay and POE elastomer are shown to have the potential to be more rigid and tougher than the neat PA6/PP itself. Blend ratio and presence of organoclay are found to influence the morphology (e.g., POE particle size and distribution) of POE toughened nanocomposites systems. A finer particle size and better distribution of POE elastomer has been observed in high PP concentration PA6/PP blends and organoclay filled PA6/PP blends.

Morphology, thermal, and mechanical behavior of ethylene octene copolymer toughened polyamide 6/polypropylene nanocomposites

Polyamide 6/polypropylene (PA6/PP = 70/30 parts) blends containing 10 wt% of ethylene octene copolymer (POE) and different loading (2–6 wt%) of organophilic modified monmorillonite (MMT, organocaly) are prepared using a twin screw extruder followed by injection molding. Polypropylene grafted maleic anhydride (PP-g-MAH) of 5 wt% is also incorporated as a compatibilizer. The mechanical properties of blended nanocomposites are studied through tensile, flexural, and impact tests. The morphology, essentially comprised of PP and POE particles dispersed in the PA6 matrix, is characterized by scanning electron microscopy (SEM). Wide angle X-ray diffraction (XRD) is used to characterize the formation of nanocomposites. The thermal properties are characterized by using differential scanning calorimeter (DSC) and thermogravimetry analysis (TGA). The dynamic mechanical properties of the PA6/PP blend and PA6/PP/POE nanocomposites are analyzed by using a dynamic mechanical thermal analyzer (DMTA). The incorporation of organoclay does not influence the melting temperature or crystallinity of PA6 or PP. However, the thermal stability of the nanocomposites improved by about 20 C with the incorporation of 2–4 wt% organoclay. The PA6/PP nanocomposites containing 4 wt% of organoclay and 10 wt% of POE exhibit good toughness retention without significant loss of stiffness and strength properties.

Biomechanical and bioactivity concepts of polyetheretherketone composites for use in orthopedic implants : a review

The use of polyetheretherketone (PEEK) composites in the trauma plating system, total replacement implants, and tissue scaffolds has found great interest among researchers. In recent years (2008 afterward), this type of composites has been examined for suitability as substitute material over stainless steel, titanium alloys, ultra high molecular weight polyethylene, or even biodegradable materials in orthopedic implant applications. Biomechanical and bioactivity concepts were contemplated for the development of PEEK orthopedic implants and a few primary clinical studies reported the clinical outcomes of PEEK-based orthopedic implants. This study aims to review and discuss the recent concepts and contribute further concepts in terms of biomechanical and bioactivity challenges for the development of PEEK and PEEK composites in orthopedic implants.

Development of regenerated cellulose/halloysites nanocomposites via ionic liquids.

In this study, regenerated cellulose/halloysites (RC/HNT) nanocomposites with different nanofillers loading were fabricated by dissolving the cellulose in 1-ethyl-3-methylimidazolium chloride (EMIMCl) ionic liquid. The films were prepared via solution casting method and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanical properties were investigated by tensile testing. It clearly displayed a good enhancement of both tensile strength and Youngs modulus with HNT loading up to 5 wt%. As the HNT loadings increased to 5 wt%, the thermal behaviour and water resistance rate was also increased. The TEM and SEM images also depicted even dispersion of the HNT and a good intertubular interaction between the HNT and the cellulose matrix.

Bionanocomposites of regenerated cellulose/zeolite prepared using environmentally benign ionic liquid solvent

Bionanocomposite films based on regenerated cellulose (RC) and incorporated with zeolite at different concentrations were fabricated by dissolving cellulose in 1-ethyl-3-methylimidazolium chloride (EMIMCl) ionic liquid using a simple green method. The interactions between the zeolite and the cellulose matrix were confirmed by Fourier transform infrared spectra. Mechanical properties of the nanocomposite films significantly improved as compared with the pure regenerated cellulose film, without the loss of extensibility. Zeolite incorporation enhanced the thermal stability and char yield of the nanocomposites. The scanning electron microscopy and transmission electron microscopy showed that zeolite was uniformly dispersed in the regenerated cellulose matrix. In vitro cytotoxicity test demonstrated that both RC and RC/zeolite nanocomposite films are cytocompatible. These results indicate that the prepared nanocomposites have potential applications in biodegradable packaging, membranes and biomedical areas.

The effect of polyethylene-octene elastomer on the morphological and mechanical properties of polyamide 6/polypropylene nanocomposites

Rubber-toughened nanocomposites (RTNC) consisting of ternary blends of polyamide 6 (PA6), polypropylene (PP) and polyethylene-octene elastomer (POE) containing 4 wt% of organophilic modified montmorillonite were produced by melt compounding followed by injection moulding. The blend composition was kept constant (PA6/PP=70/30 parts by weight) while the POE content was varied between 5 and 20 wt%. Maleated PP (PP-g-MA) was used as compatibilizer. The morphology of the RTNC was studied by scanning electron microscopy and X-ray diffraction (XRD). The mechanical properties of RTNC were studied through tensile, flexural, Izod impact and fracture toughness properties. While the tensile and flexural properties were found to decrease with the increasing concentration of POE, the toughness was significantly enhanced as compared to the neat PA6/PP blends. In general, the blends containing 10-15 wt% of POE had the best balance of stiffness, strength and toughness. The addition of 30 wt% of PP in the PA6 matrix improved the compatibility between PA6 and the rubber phase. XRD established that the organoclay was well dispersed (exfoliated) and preferentially embedded in the PA6 phase.