Nanocellulose/Nanodiamond Hybrids: A Review

Nanocellulose can be obtained from low-cost sources and has been extensively studied in the last decades due to its biodegradability, biocompatibility, low weight, large specific surface area, and good mechanical and optical properties. The nanocellulose properties palette can be greatly expanded by incorporating different metals, metal oxides or carbon nanomaterials, with the formation of multifunctional hybrids. Nanocellulose–nanocarbon hybrids are emerging nanomaterials that can respond to many current challenges in areas such as water purification, energy storage and conversion, or biomedicine for drug delivery, tissue engineering, antitumor and antimicrobial therapies, and many others. Although nanocellulose–nanodiamonds hybrids are still in their infancy, these nanomaterials are extremely promising for applications requiring good thermal conductivity and mechanical strength along with optical transparency. A strong increase in the thermal conductivity of a nanocellulose film of about 150 times was obtained after the addition of 90 wt% single-crystal nanodiamonds and a 70% increase in the Young’s modulus of nanocellulose films was produced by the addition of 5 wt% nanodiamonds. Therefore, in this review, data related to the manufacturing routes, main properties, and applications of nanocellulose–nanodiamonds hybrids are presented and discussed. This review paves the way for new methods and procedures to obtain nanocellulose–nanodiamonds hybrids better adapted to practical needs

Complex Effects of Hemp Fibers and Impact Modifiers in Multiphase Polypropylene Systems

Natural fibers-reinforced polymer composites have progressed rapidly due to their undeniable advantages. Most of the commercial polypropylene (PP)-based materials are characterized by either high impact toughness or high stiffness, while the manufacture of PP composites with both good toughness and stiffness is challenging at present. In this work, poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) and poly(styrene-b-butadiene-b-styrene) (SBS) copolymers were used in different amounts as modifiers in PP/hemp fibers (HF) composites, with the aim to use them for electrical vehicle parts. The interface in these multiphase systems was controlled by the addition of maleated polypropylene (MAPP). SEBS and SBS showed different effects on the elongation at break of the blends and the corresponding composites due to the HF that stiffened the multiphase systems. Similarly, a different action of MAPP was observed in the composites containing SEBS or SBS: higher Young’s and storage moduli were obtained for the composite containing SBS, while greater elongation at break and impact strength values were recorded for the SEBS-containing system. In addition, a remarkable dispersion in the MAPP-containing composite and two times smaller average particle size were revealed by the SEM analysis for the SEBS particles compared to the SBS ones. The higher affinity of SEBS for PP compared to that for SBS and the different morphological characteristics of the systems containing SEBS and SBS may explain the different effects of these impact modifiers on the mechanical properties of the composites. The composites developed in this work were designed as substitutes for the fully synthetic polymeric materials or metal components used in the manufacturing of automotive parts

Opposite Roles of Bacterial Cellulose Nanofibers and Foaming Agent in Polyhydroxyalkanoate-Based Materials

In this work, an economically feasible procedure was employed to produce poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-based foams. Thermally expandable microspheres (TESs) were used as a blowing agent, while bacterial cellulose (BC) nanofibers served both as a reinforcing agent and as a means of improving biocompatibility. PHBV was plasticized with acetyltributylcitrate to reduce the processing temperature and ensure the maximum efficiency of the TES agent. The morphological investigation results for plasticized PHBV foams showed well-organized porous structures characterized by a porosity of 65% and the presence of both large pores (>100 µm) and finer ones, with a higher proportion of pores larger than 100 µm being observed in the PHBV nanocomposite containing TESs and BC. The foamed structure allowed an increase in the water absorption capacity of up to 650% as compared to the unfoamed samples. TESs and BC had opposite effects on the thermal stability of the plasticized PHBV, with TESs decreasing the degradation temperature by about 17 °C and BC raising it by 3–4 °C. A similar effect was observed for the melting temperature. Regarding the mechanical properties, the TESs had a flexibilizing effect on plasticized PHBV, while BC nanofibers showed a stiffening effect. An in vitro cytotoxicity test showed that all PHBV compounds exhibited high cell viability. The addition of TESs and BC nanofibers to PHBV biocomposites enabled balanced properties, along with lower costs, making PHBV a more attractive biomaterial for engineering, packaging, or medical device applications

Contribution of the Surface Treatment of Nanofibrillated Cellulose on the Properties of Bio-Based Epoxy Nanocomposites Intended for Flexible Electronics

The growing interest in materials derived from biomass has generated a multitude of solutions for the development of new sustainable materials with low environmental impact. We report here, for the first time, a strategy to obtain bio-based nanocomposites from epoxidized linseed oil (ELO), itaconic acid (IA), and surface-treated nanofibrillated cellulose (NC). The effect of nanofibrillated cellulose functionalized with silane (NC/S) and then grafted with methacrylic acid (NC/SM) on the properties of the resulted bio-based epoxy systems was thoroughly investigated. The differential scanning calorimetry (DSC) results showed that the addition of NCs did not influence the curing process and had a slight impact on the maximum peak temperature. Moreover, the NCs improved the onset degradation temperature of the epoxy-based nanocomposites by more than 30 °C, regardless of their treatment. The most important effect on the mechanical properties of bio-based epoxy nanocomposites, i.e., an increase in the storage modulus by more than 60% at room temperature was observed in the case of NC/SM addition. Therefore, NC’s treatment with silane and methacrylic acid improved the epoxy–nanofiber interface and led to a very good dispersion of the NC/SM in the epoxy network, as observed by the SEM investigation. The dielectric results proved the suitability of the obtained bio-based epoxy/NCs materials as substitutes for petroleum-based thermosets in the fabrication of flexible electronic devices

Bio-Based Poly(lactic acid)/Poly(butylene sebacate) Blends with Improved Toughness

A series of poly(butylene sebacate) (PBSe) aliphatic polyesters were successfully synthesized by the melt polycondensation of sebacic acid (Se) and 1,4-butanediol (BDO), two monomers manufactured on an industrial scale from biomass. The number average molecular weight (Mn) in the range from 6116 to 10,779 g/mol and the glass transition temperature (Tg) of the PBSe polyesters were tuned by adjusting the feed ratio between the two monomers. Polylactic acid (PLA)/PBSe blends with PBSe concentrations between 2.5 to 20 wt% were obtained by melt compounding. For the first time, PBSe’s effect on the flexibility and toughness of PLA was studied. As shown by the torque and melt flow index (MFI) values, the addition of PBSe endowed PLA with both enhanced melt processability and flexibility. The tensile tests and thermogravimetric analysis showed that PLA/PBSe blends containing 20 wt% PBSe obtained using a BDO molar excess of 50% reached an increase in elongation at break from 2.9 to 108%, with a negligible decrease in Young’s modulus from 2186 MPa to 1843 MPa, and a slight decrease in thermal performances. These results demonstrated the plasticizing efficiency of the synthesized bio-derived polyesters in overcoming PLA’s brittleness. Moreover, the tunable properties of the resulting PBSe can be of great industrial interest in the context of circular bioeconomy