In this study, pure cellulose was isolated from Algerian date palm fronds (DPF) using three different delignification processes (acidified NaClO 2 , totally chlorine free (TCF) and their combination). Then, microcrystalline cellulose (MCCs) particles have been successfully produced via direct acid hydrolysis of the different celluloses. All samples were characterized using infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TGA) and differential scanning calorimeter (DSC). From the FTIR analysis, most of hemicellulose and lignin were effectively removed throughout the extraction processes. The XRD spectra revealed that all MCCs belong to cellulose I type, and showed a highly crystallinity index than that of pure celluloses. According to DSC and TGA/DTG analyses, the MCC samples presented a higher decomposition temperature. The obtained results showed that the extracted MCC samples exhibited similar properties than those of commercial MCC. Furthermore, the employment of a combined process allowed obtaining MCC with higher crystallinity and better thermal stability. Thus, according to these results, date palm fronds can be considered as a potential low-cost material for MCC production and the combined process is promising to isolate high purity MCC from cellulosic substrate.

Esparto grass, known as alfa, is a renewable biomass widely distributed in southern and western Mediterranean basin. The present work focused on the isolation of pure cellulose from alfa stems, via different approaches, i.e., acidified sodium chlorite (NaClO 2), totally chlorine free (TCF) or their combination, followed by the preparation of microcrystalline cellulose (MCC) using acid hydrolysis method. The obtained samples were characterized using infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TGA) and differential scanning calorimeter (DSC). The FTIR spectroscopy exhibited the removal of lignin and hemicellulose after the delignification and alkaline treatments. The XRD data showed that all of the MCCs have higher crystallinity indexes (Alfa-MCC 73-82%) and belong to cellulose I type. From SEM images, it is clear that the different MCC particles presented rough surface and micro-sized particles. The DSC/ TGA analyses revealed that MCC samples present better thermal stability than their respective cellulose ones, with higher temperature of decomposition (more than 350 °C). Moreover, the use of a combined process yields to MCC with higher crystallinity and better thermal stability. Consequently, based on these findings, the delignification with combined method can be considered as a promising approach to extract MCC from alfa fibers with outstanding features.

High performance thermosetting resins are targeted in many exigent applications, such as aerospace and marine fields, for the development of lightweight structural composites. Till now, these industries only rely on petroleum-based materials for their supposedly better performances. However, the latest developments in the field suggest otherwise. In fact, many reports confirmed that sustainable and ecofriendly thermosetting polymers can display similar or even better performances. Additionally, exploring alternative renewable feedstock’s to meet the ever increasing demands of these industries is an essential step towards sustainable development. Aiming to unravel the potential of these materials, the present review summarizes the most relevant chemical routes allowing the preparation of fully or partially bio-based thermosetting resins. Meanwhile, the overall performances of these exceptional materials are also compared with their petroleum-based counterparts.

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By following the rules of green chemistry, a novel composite is developed from a renewable and ecofriendly resource, namely, vanillin. The latter was used as a phenolic precursor for the microwave synthesis of a bio-based benzoxazine resin (Va-BZ). Afterward, high-performance green composites were developed by reinforcing Va-BZ with various amounts of chopped silane surface modified carbon fibers (CFs). The chemical structure of the Va-BZ monomers was confirmed by 1H NMR and Fourier transform infrared spectroscopy. The grafting of the silane moiety on the CF surface was assessed by FTIR and TGA analyses. The autocatalytic ring opening polymerization of the Va-BZ monomers was confirmed by DSC analysis. The mechanical performances of the developed green composites were studied by flexural and tensile investigations. The findings suggested that the maximum amount of 20 wt. CFs afforded the best results, with flexural and tensile strengths of 450 and 462 MPa, respectively. The SEM was used to study the fractured tensile surfaces and elucidated the toughening mechanism. Meanwhile, the TGA showed that the introduction of the CFs markedly improved the thermal stability of the benzoxazine matrix. Overall, this study confirmed that greener approaches can also result in high-performance composites satisfying the needs of exigent applications.

In this study, a new kind of hybrid material was prepared from various amounts of silane surface modified alumina nanoparticles, oxidized ultra high molecular weight polyethylene (UHMWPE) fibers, and epoxy resin. The reinforcing phases were selectively treated to achieve a fully connected network aiming an effective stress transfer between the constituents. The efficiency of the grafting mechanisms was confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The developed hybrid materials were tested for their mechanical, thermomechanical, and ballistic performances. The mechanical results, namely tensile and bending, confirmed the positive effects of increasing the nanofillers amounts up to 5 wt%. The thermochemical properties analyzed by dynamic mechanical analysis (DMA) revealed consequent improvements in the storage modulus and glass transition temperature upon the addition of the nanophase. In the meantime, the ballistic tests evaluated under the National Institute of Justice standard (NIJ standard-0101.06-IIA) also highlighted an improved kinetic energy absorption following the increase in the amounts of the discontinuous phase. Subsequent experimentations precisely quantified the required number of plies for an effective projectile stopping under the chosen standard. Overall, this study unraveled for the first time ever the benefits obtained from a fully connected hybrid network under both static and dynamic loads.

In this study, new high-performance composite laminates were prepared from epoxy resin and surface modified ultrahigh-molecular-weight polyethylene (UHMWPE) fibers. The UHMWPE fibers underwent two types of chemical modifications, namely through chromic acid and potassium permanganate oxidations. The adopted chemical procedure aimed the grafting of polar groups on the outer surface of fibers for an improved chemical and physical compatibility with the polymeric matrix. The efficiency of the grafting methodology was confirmed by vibrational, thermal, and morphological analyses, and the grafting mechanism was thoroughly discussed. Furthermore, composite laminates were prepared to study the effects of chemical treatments on the mechanical and morphological properties of the resulting composites. The grafting techniques allowed consequent improvements in the tensile and bending properties, up to 34% and 23% for the tensile and flexural strengths, respectively. The study of the fractured surfaces confirmed the exceptional compatibility between the fillers and the polymeric matrix and further corroborated the mechanical findings. Finally, the adopted modification techniques can be regarded as cost-effective and highly suitable for the manufacturing of structural composites for advanced applications.

In this study, a new high-performance hybrid material was designed targeting an efficient ballistic and nuclear shielding protection. To achieve this goal, a typical highly performant thermosetting resin, namely the phthalonitrile (PN) resin, was reinforced with Kevlar fibers (KF-29), as continuous phase, and erbium oxide (Er2O3) nanoparticles, as discontinuous phase. The reinforcing phases underwent a silane surface modification to create a fully connected network aiming an improved stress transfer between the constituents. The mechanical investigations through tensile and bending testing confirmed the positive effect of the addition of an increasing amount (up to 20 wt%) of the Er2O3 nanoparticles. The hybrids also provided excellent gamma rays shielding performances with a screening ratio of about 33% for a 3 cm thick sample. In the meantime, the ballistic tests evaluated under the National Institute of Justice standard (NIJ standard-0101.06-IIA) also highlighted an improved kinetic energy absorption following the increase in the amounts of the discontinuous phase. Overall, this study unraveled for the first time ever the benefits obtained from a fully connected hybrid network in the field of ballistic and radiation protection.