Natural fibers, as replacement of engineered fibers, have been one of the most researched topics over the past years. This is due to their inherent properties, such as biodegradability, renewability ...and their abundant availability when compared to synthetic fibers. Synthetic fibers derived from finite resources (fossil fuels) and are thus, affected mainly by volatility oil prices and their accumulation in the environment and/or landfill sites as main drawbacks their mechanical properties and thermal properties surpass that of natural fibers. A combination of these fibers/fillers, as reinforcement of various polymeric materials, offers new opportunities to produce multifunctional materials and structures for advanced applications. This article intends to cover recent developments from 2013-up to date on hybrid composites, based on natural fibers with other fillers. Hybrid composites preparation and characterization towards their applicability in advanced applications and the current challenges are also presented.
► Polystyrene microcapsules containing about 30wt% soft paraffin wax were successfully prepared. ► The presence of microcapsules in polypropylene influenced the morphology and properties of the ...matrix. ► The SEBS modifier had little influence on the interaction between polypropylene and microcapsules.
The study deals with the preparation and characterization of polystyrene (PS) capsules containing Fischer–Tropsch paraffin wax (PS:wax) as phase change material (PCM) for thermal energy storage embedded in a polypropylene (PP) matrix. Blends of PP/PS:wax were prepared without and with polystyrene–block–poly(ethylene-ran-butylene)-block-polystyrene (SEBS) as a modifier. The influence of PS:wax microcapsules on the morphology, as well as thermal and mechanical properties of the PP was investigated. The scanning electron microscopy (SEM) images of the microencapsulated PCM show that the capsules were grouped in irregular spherical agglomerates of size 16–24μm. However, after melt-blending with PP smaller, perfectly spherical microcapsules were well dispersed in the PP matrix. There was fairly good interaction between the microcapsules and the matrix, even in the absence of SEBS modification. The FTIR spectrum of the microcapsules is almost exactly the same as that of polystyrene, which indicates that the microcapsules were mostly intact and that the FTIR only detected the polystyrene shell. The amount of wax in the PS:wax microcapsules was determined as 20–30% by weight. An increase in PS:wax content resulted in a decrease in the melting peak temperatures of PP. The thermal stability of the blends decreased with an increase in PS:wax microcapsules content as a consequence of the lower thermal stability of both the wax and PS. There was a drop in storage modulus with increasing PS:wax microcapsules content.
Over the past decades, research has escalated on the use of polylactic acid (PLA) as a replacement for petroleum-based polymers. This is due to its valuable properties, such as renewability, ...biodegradability, biocompatibility and good thermomechanical properties. Despite possessing good mechanical properties comparable to conventional petroleum-based polymers, PLA suffers from some shortcomings such as low thermal resistance, heat distortion temperature and rate of crystallization, thus different fillers have been used to overcome these limitations. In the framework of environmentally friendly processes and products, there has been growing interest on the use of cellulose nanomaterials viz. cellulose nanocrystals (CNC) and nanofibers (CNF) as natural fillers for PLA towards advanced applications other than short-term packaging and biomedical. Cellulosic nanomaterials are renewable in nature, biodegradable, eco-friendly and they possess high strength and stiffness. In the case of eco-friendly processes, various conventional processing techniques, such as melt extrusion, melt-spinning, and compression molding, have been used to produce PLA composites. This review addresses the critical factors in the manufacturing of PLA-cellulosic nanomaterials by using conventional techniques and recent advances needed to promote and improve the dispersion of the cellulosic nanomaterials. Different aspects, including morphology, mechanical behavior and thermal properties, as well as comparisons of CNC- and CNF-reinforced PLA, are also discussed.
The influence of the introduction of expanded graphite (EG), as well as combinations of EG with Cloisite 15A clay and diammonium phosphate (DAP), into EVA and an EVA/wax blend on the thermal ...stability and flammability of the polymer and blend was investigated. In the presence of EG + Cloisite 15A, the material formed a dense and stable char layer (carbonized ceramic) which significantly improved the flame resistance of the materials, while the presence of EG and EG + DAP much less uniform char layers were formed and the improvement in flame resistance was not so significant. X-ray diffractometry investigations showed intercalation of EVA into the organoclay, which became more effective in the presence of wax. It was, however, found that there was little separation of the EG platelets, although the presence of wax caused a decrease in the sizes of the EG agglomerates. The thermal stability of EVA and the EVA/wax blend improved in the presence of EG and its combination with Cloisite 15A and DAP.
Wood-plastic composites (WPCs) are a group of emerging and a sustainable class of high-performance materials, consisting of polymers reinforced with wood particulates, having a wide range of ...applications in the field of building, infrastructure, and transportation. However, the main drawback of the WPCs is their high flammability. Fire retardants usually enhance WPCs' flame retardancy but at the expense of mechanical properties. This paper reviews the available literature on flame retardant WPCs in developing an optimum condition between the flammability and mechanical properties, i.e., the addition of wood-flour and flame retardant (FR) in order to find a balance between the flammability resistance and their mechanical properties. It concentrates on the recent advances in the mechanical properties and flammability studies of wood flour-polymer composite products. The applications and durability of these flame retardant WPCs with future remarks are also highlighted.
The study reports on the flammability, thermal stability, impact properties and thermal conductivity of shape-stabilized phase change materials based on a soft Fischer–Tropsch paraffin wax blended ...with polypropylene (PP). The blends were melt-mixed with expanded graphite (EG) up to 9 wt% to improve the thermal conductivity and flammability resistance of the material. The thermal stability and flammability results show an increase in thermal stability and flame resistance of PP in the presence of EG, with the flammability further increasing in the presence of wax, probably because of the smaller and better dispersed EG particles in the PP/wax/EG composite that gave rise to a more compact char layer. Although the thermal degradation mechanism did not change in the presence of EG, the EG particles retarded the evolution of the volatile degradation products. The storage modulus of the PP/wax/EG composite was lower than those of PP and PP/EG, and decreased with increasing in wax content because of the softening effect of the wax. The impact strength of the PP/wax/EG composites increased with increasing EG content in all the samples, but decreased with increasing wax content.
In the past, polymer materials have been used in electronic devices; however, the major drawback with polymers is their low thermal conductivity, i.e., 0.1-0.5 W/(m·K). Hence, researchers came up ...with the idea of incorporating conductive fillers into the polymer matrix in order to increase their thermal conductivity. Different conductive materials classified as carbon, metallic, and ceramic-based fillers have been used for this task. However, the drawback with carbon and metalbased fillers is that they reduce the intrinsic insulating properties of polymer materials. Recently, boron nitride (BN), a ceramic-based filler was selected as the conductive filler of choice due to its combined excellent thermal conductivity and electrical insulation as well as high breakdown strength. Due to differences in polarities, boron nitride and polymer matrices form a weak interfacial bond. Therefore, the weak interfacial bond is commonly improved by surface chemical modification of the boron nitride fillers. Furthermore, most of the theoretical models are used to predict the thermal conductivities of boron nitride-polymers composites fitted well with experimental data. This proved that the models could be used to predict the properties of boron nitride composites before their experimental data. The review paper discusses the effect of boron nitride orientation, nanostructures, modification, and its synergy with other conductive fillers on the thermal conductivity and mechanical properties of the polymer matrices.
•Carbon nanofibres fabricated with electrospinning technique.•Factors influencing textural properties of electrospun carbon nanofibres (E-CNFs)•Review the application of E-CNFs and its ...(nano)composites for water and air purification.•Highlight potential of electrospun nanofibres for emerging pollutants and propose future trends.
Electrospun carbon nanofibres (E-CNFs) are attractive materials with a huge potential to be applied in different fields such as water remediation, air purification, sensing, and healthcare. These fibres can be employed as adsorbents for different pollutants such carbon oxides, nitrogen oxides, methane, metal ions, dyes, drugs, and antibiotics due to their unique properties such as abundant available pore size, large surface area, high adsorption capacity, fast adsorption rate for various analytes, ease to prepare and rapid regeneration. This review discusses the fabrication of novel carbon nanofibres and their composites using electrospinning technique for water and air purification. We conclude with recent trends and challenges with regard to application of electrospun carbon nanofibres in water and air purifications.
The contamination of the water sources and the environment degradation by the organic dyes from different industries has become a serious problem. A wide variety of chemical, physical and biological ...treatments have been explored for decontamination of dye-laden wastewater. Among these treatments, adsorption received tremendous interest because of its efficiency, possible recyclability and inexpensiveness. Electrospun nanofibers adsorbents emerged as the preferred candidates in treating the dye-impacted wastewater satisfactorily because of their inherent and intrinsic features, such as large surface area, high surface-to-volume ratio and ease functionalization for specificity. The modification of PVA nanofibers, adsorbent dosage, dye concentration, pH value and temperature are found to be equally essential to achieve desired efficiency. As a result, the present review aims to provide an overview on the preparation of the PVA nanofibers and the factors influencing the dye removal efficacy. Most importantly, the literature search over the last decade on the performance of the electrospun PVA-based nanofibers as adsorbent for the removal of azo dyes from wastewater is also discussed. In light of their improved adsorption capacity, the PVA-based nanofibers will finally find their way in industrial dye-impacted water treatment and other appropriate applications in the near future.
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