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Melt electrospinning has been developed in the last decade as an eco-friendly and solvent-free process to fill the gap between the advantages of solution electrospinning and the need of a cost-effective technique for industrial applications. Although the benefits of using melt electrospinning compared to solution electrospinning are impressive, there are still challenges that should be solved. These mainly concern to the improvement of polymer melt processability with reduction of polymer degradation and enhancement of fiber stability; and the achievement of a good control over the fiber size and especially for the production of large scale ultrafine fibers. This review is focused in the last research works discussing the different melt processing techniques, the most significant melt processing parameters, the incorporation of different additives (e.g., viscosity and conductivity modifiers), the development of polymer blends and nanocomposites, the new potential applications and the use of drug-loaded melt electrospun scaffolds for biomedical applications.

There has been much effort to provide eco-friendly and biodegradable materials for the next generation of composite products owing to global environmental concerns and increased awareness of renewable green resources. This review article uniquely highlights the use of green composites from natural fiber, particularly with regard to the development and characterization of chitosan, natural-fiber-reinforced chitosan biopolymer, chitosan blends, and chitosan nanocomposites. Natural fiber composites have a number of advantages such as durability, low cost, low weight, high specific strength, non-abrasiveness, equitably good mechanical properties, environmental friendliness, and biodegradability. Findings revealed that chitosan is a natural fiber that falls to the animal fiber category. As it has a biomaterial form, chitosan can be presented as hydrogels, sponges, film, and porous membrane. There are different processing methods in the preparation of chitosan composites such as solution and solvent casting, dipping and spray coating, freeze casting and drying, layer-by-layer preparation, and extrusion. It was also reported that the developed chitosan-based composites possess high thermal stability, as well as good chemical and physical properties. In these regards, chitosan-based “green” composites have wide applicability and potential in the industry of biomedicine, cosmetology, papermaking, wastewater treatment, agriculture, and pharmaceuticals.

This paper reports a study of composite blends of polysulfone (PS) and polyvinylpyrrolidone (PVP) that were prepared in different wt% composition using carbon nanotubes (CNT), milled carbon fibers (MCF), graphene oxide (GO), and chopped carbon fibers (CCF) as nanofillers. The permeability measurements of the composites showed that the PS/PVP blends with different nanofillers demonstrated higher permeability for hydrogen gas than that of the pristine polymers, either singly or the polymer blend. The gases used for the permeation measurements were H 2 , CO 2 , N 2 , O 2 , and CH 4 . Selectivity was calculated for H 2 /CO 2 , H 2 /N 2 , and H 2 /CH 4 gas pairs. The results of the selectivity were plotted to show Robeson's 2008 upper bound and compared with reported data. The permeability of all gases increased for modified composite polymer membranes. We noted that O 2 gas solubility follows a trend similar to other gases, but gives a higher value than H 2 gas. The selectivity measurements showed that the MCF and CCF composite with the PS/PVP blend membranes demonstrated the highest selectivity for hydrogen gas among all different gas pairs. This indicates that PS/PVP composite membranes with MCF and CCF can be used for hydrogen purification and production of green hydrogen. There is a trade-off between permeability and selectivity parameters; GO and CNT nanofillers showed constant selectivity as permeability increased, which can be explained by the nanogap theory. The structural and morphological properties of these prepared composite membranes were characterized by field-emission scanning electron microscopy (FE-SEM), thermal properties by differential scanning calorimetry (DSC), and mechanical properties using a universal testing machine (UTM) for tensile strength, and Fourier transform infrared (FTIR) spectroscopy was carried out to identify the possible bond between polymers and nanofillers of the blend composite membranes. Blends modified with CNT, MCF, and GO exhibited increased viscosity, with an increase in the ∆b value at increasing concentrations, suggesting a favorable interaction between the phases. The water flux studies indicated that the highest pure water flux was obtained by the PS + PVP + CCF membrane. The highest rejection of Na 2 SO 4 and of MgSO 4 was for the PS + PVP + CNT membrane.

Natural fibers play a significant role in the polymer nanocomposites due to its biodegradability, sustainability, ease of disposal and minimal energy required during processing. The utilization of sustainable materials in developing usable products is making a tremendous impact in the society by mitigating the problems caused by hazardous plastics. Recent research studies have focused on identifying promising natural fibres with superior mechanical properties. In this study, we explore the reinforcing ability of extracted pure plant-based nanocellulose fibres in PVA/PEC nanocomposite films. The produced nanocellulose was characterized using a combination of techniques, including 13 C NMR, XRD, FTIR, DLS, and morphological examination via AFM and TEM, along with thermal analysis. The synthesized AgO/ZnO nano structures were used as inorganic filler. The nano structures were confirmed by using XRD, TEM and XPS analysis. The reinforcing effect of nanocellulose was investigated by incorporating varying concentrations of CNF into PVA/PEC films, followed by characterization using XRD and FTIR. The physical properties of the films were evaluated through TGA, WVTR and water contact angle measurements. Reduction in microbial viability results in the promising antibacterial activity. Biodegradability was assessed through a soil burial test, where the observed weight loss indicated good biodegradation behavior with a controlled degradation rate. The overall study provides a comprehensive analysis of nanocellulose extraction and its effective use as a reinforcing agent in polymer blends. In conclusion, the extracted nanocellulose demonstrates significant potential for enhancing the structural and functional properties of nanocomposite films for sustainable applications.

Biodegradable composites consisting of Poly-(butylene adipate-co-terephthalate) (PBAT), thermoplastic starch, hydrophobically modified nanofibrillated cellulose (HMNC), and green surfactant (sucrose fatty acid ester) were prepared via the melt-mixing and film-blowing process (PBAT-HMNC). The composites were characterized using the Fourier transform infrared spectroscope (FT-IR), scanning electron microscope (SEM), and thermogravimetric analyzer (TGA). The mechanical and barrier properties were systematically studied. The results indicated that PBAT-HMNC composites exhibited excellent mechanical and barrier properties. The tensile strength reached the maximum value (over 13 MPa) when the HMNC content was 0.6% and the thermal decomposition temperature decreased by 1 to 2 °C. The lowest values of the water vapor transmission rate (WVTR) and the oxygen transmission rate (OTR) were obtained from the composite with 0.6 wt% HMNC, prepared via the film-bowing process with the values of 389 g/(m2·day) and 782 cc/(m2·day), which decreased by 51.3% and 42.1%, respectively. The Agaricus mushrooms still had a commodity value after 11 days of preservation using the film with 0.6 wt% HMNC. PBAT-HMNC composites have been proven to be promising nanocomposite materials for packaging.

The present work reports the influence of Polyvinylpyrrolidone (PVP) and hematite ( α -Fe 2 O 3 ) nanorods (NRs) on the physicochemical properties of chitosan (Cs), as an approach to broaden its medical and technological applications. Hematite NRs of 11.4 nm diameter and 87.9 nm crystallite size were prepared by a free-template chemical method. Cs, PVP/Cs and blend loaded with hematite NRs were prepared by solution casting. Significant changes in the films’ surface were clarified using the scanning electron microscope (SEM). Fourier transformation infrared spectroscopy (FT-IR) confirmed the interaction between the NRs and the NH 2 and OH functional groups of Cs. DSC measurements showed one endothermic peak assigned to the water elimination, and an exothermic one, in the range 268–287 °C, attributed to the decomposition of saccharine structure in Cs. The swelling properties of the films were sensitive to the pH of the solution. PVP/Cs film showed ~ 85 % transmittance in the visible region and its optical band gap narrowed from 5.4 eV to 4.05 eV after loading with 2.0  wt.% hematite. The influence of NRs content on the optical constants of the films is discussed. The dielectric properties depend on the film’ structure. The large Polaron tunneling (LPT) model is the best suitable mechanism for the electric conduction. Due to their high thermal stability and decomposition temperature, transmittance and high conductivity, the prepared films are a candidate for the packaging industry, for use in some medical applications such as treating some chronic wounds, and optical windows and fibers.

The purpose of this work was to investigate the effect of cellulose nanocrystals (CNC) from bamboo fiber on the properties of poly (lactic acid) (PLA)/poly (butylene succinate) (PBS) composites fabricated by melt mixing at 175 °C and then hot pressing at 180 °C. PBS and CNC (0.5, 0.75, 1, 1.5 wt.%) were added to improvise the properties of PLA. The morphological, physiochemical and crystallinity properties of nanocomposites were analysed by field emission scanning electron microscope (FESEM), Fourier-transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD), respectively. The thermal and tensile properties were analysed by thermogravimetic analysis (TGA), Differential scanning calorimetry (DSC) and Universal testing machine (UTM). PLA-PBS blend shows homogeneous morphology while the composite shows rod-like CNC particles, which are embedded in the polymer matrix. The uniform distribution of CNC particles in the nanocomposites improves their thermal stability, tensile strength and tensile modulus up to 1 wt.%; however, their elongation at break decreases. Thus, CNC addition in PLA-PBS matrix improves structural and thermal properties of the composite. The composite, thus developed, using CNC (a natural fiber) and PLA-PBS (biodegradable polymers) could be of immense importance as they could allow complete degradation in soil, making it a potential alternative material to existing packaging materials in the market that could be environment friendly.

Structural analyses of glass fiber reinforced epoxy polymer (GFRP) composites dispersed with rutile (TiO 2 ) nanoparticles using compression molding were studied to reveal the effects of filler addition. Ball milling is performed for nanoparticles and reduces the particle size from 3 to 67.64 nm to enhance the blending of dispersions in the resin. The nanoparticles were added to the resin at weight percentages of 0%, 5%, 10%, and 15% prior to fabrication using an ultrasonic liquid processor. Flexural strength, tensile strength, hardness, and toughness were measured to study the mechanical behavior of the composite. The addition of filler showed improvement in the mechanical properties of the GFRP dispersion-strengthened composite. 15 wt.% rutile particles have tensile strengths of 228 MPa, tensile moduli of 4123 MPa, flexural strengths of 317 MPa, and flexural moduli of 10,010 MPa, respectively. These values are 58.33%, 16.8%, 77.15%, and 92.5% greater than the values of 0 wt. % rutile inclusion. In comparison with the pristine specimen, the shore “D” hardness of materials with 10 wt. % TiO 2 is 8.43% higher, while that of materials with 15 wt.% TiO 2 is 3.6% higher. The impact strength of the composite sample with 5 wt. % TiO 2 is 72.12% greater than that of the pure sample. Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were carried out to analyze the morphological behavior, percentages of different elemental distributions, and crystalline size and structure of nanoparticles in the composite. FESEM was used to reveal the pullout of fiber, damaged interfaces, filler dispersion, and voids in specimens. The aim of this research is to investigate the incorporation of rutile (TiO 2 ) filler inclusion and E-glass fiber reinforcement in epoxy nanocomposite materials, exclusively for airplane structural applications. Hence, this method improves the mechanical and structural qualities of the GFRP composites.

Polymer-processing operations with dominating elongational flow have a great relevance, especially in several relevant industrial applications. Film blowing, fiber spinning and foaming are some examples in which the polymer melt is subjected to elongational flow during processing. To gain a thorough knowledge of the material-processing behavior, the evaluation of the rheological properties of the polymers experiencing this kind of flow is fundamental. This paper reviews the main achievements regarding the processing-structure-properties relationships of polymer-based materials processed through different operations with dominating elongational flow. In particular, after a brief discussion on the theoretical features associated with the elongational flow and the differences with other flow regimes, the attention is focused on the rheological properties in elongation of the most industrially relevant polymers. Finally, the evolution of the morphology of homogeneous polymers, as well as of multiphase polymer-based systems, such as blends and micro- and nano-composites, subjected to the elongational flow is discussed, highlighting the potential and the unique characteristics of the processing operations based on elongation flow, as compared to their shear-dominated counterparts.

Light-weight and high-strength polymer composites have attracted the special attention of automotive and aerospace sectors since they offer advantages such as less fuel consumption and higher fuel efficiency. In the present study, an effort has been made to prepare such polymer composites using natural fiber and very low-density hollow inorganic particles. The use of hollow glass microspheres (HGM) as a potential filler particle for making light-weight hybrid polymer composites was investigated. Polypropylene (PP) and maleic anhydride-grafted-polypropylene (in 9:1 ratio) constituted the base matrix (BM). For strength reinforcement, alkali-treated short bamboo fibers (SBF) were employed, while for making the composite material light in weight, HGM were incorporated. Silane treatment of HGM by (3-aminopropyl)triethoxysilane was performed to enhance interfacial adhesion with BM. Adequate wetting of HGM and SBF was evident from the SEM images of cryo-fractured samples. A 14% increase in tensile strength was observed in comparison to virgin PP for the composite with 5 wt.% HGM, and a desirable decrease in density was observed for all the composite samples with increasing HGM content. Improvement in hardness but a marginal decrease in impact strength due to HGM fillers was observed. Rheological analysis of the composite melt samples showed an apparent increase in the complex modulus with increasing HGM content. Thermal analysis of the composites revealed a significant impact of hybrid fillers on the crystallinity, with SBF showing a minimal effect while HGM reducing it significantly. Wide-angle x-ray diffraction spectra showed changes in the crystal structure of the composite with noticeable β -form peaks.