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Between 1955 and 1960, theories about lignin configuration were vacillating between random-coil and crosslinked “microgel” representations for macromolecular lignin chains. Light scattering was important in these early studies, but it was difficult to deal adequately with lignin fluorescence at the 546 nm incident wavelength being used. Crosslinkin...
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... Limiting trends were encountered not only when the lignin derivatives were covalently cross-linked 14 with a difunctional reactant (Figure 4) but also when they were blended noncovalently 15 with a compatible polymeric compo- nent ( Figure 5). A list of tensile properties for some common engineering plastics is relevant in this context (Table 1). A range of polymeric-material behavior between polyethylene (30 MPa strength, 9% elongation-at-break) and polystyrene (46 MPa strength, 2% elongation-at-break) reveals that polyur- ethanes produced from hydroxypropyl kraft lignin and hexamethylene diisocyanate (Figure 4) exhibited acceptable tensile behavior only when the kraft lignin content remained below 40 wt %. ...
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Over the last ten years a new trend of research activities regarding the flame retardancy of polymeric materials has arisen. Indeed, the continuous search for new flame retardant systems able to replace the traditional approaches has encouraged alternative solutions, mainly centred on nanotechnology. In this context, the deposition of nanostructure...
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... Despite of the extensive processing required for such refined materials, only few applications require such levels of high strength. Most synthetic rigid plastics, for instance, hardly reach ca. 100 MPa of ultimate tensile strength and more than 7 % elongation at break (Sarkanen, Chen, & Wang, 2016). In addition, biodegradable polyesters, either synthetic or bio-based, very rarely exceed ultimate strengths of 60 MPa (Manavitehrani et al., 2016), not to mention that water-soluble cellulose derivative films present ultimate tensile strength values below 55 MPa (Rincon-Iglesias, Lizundia, & Lanceros-Mendez, 2019). ...
The deconstruction and valorization of chitinous biomass from crustaceans is a promising route for sustainable bioproduct development alternative to petroleum-based materials. However, chitin nanocrystal and chitin nanofibril isolation from crustacean shells is often subjected to extensive processing, compromising their environmental and cost sustainability. To address the sustainability challenge that chitin valorization presents, herein we introduce a mild fibrillation route to generate “chitin pulp”; where a careful control of the macro- and micro-fibrillated chitin with protein and mineral components yields tailored properties. Films produced from protein-rich chitin pulp showed ultimate strength of up to 93 ± 7 MPa. The surface energy and wetting behavior, going from hydrophilic to nearly-hydrophobic, could be tailored as a function of pulp composition. Life cycle assessment of the protein-rich chitin pulps demonstrated that the global warming potential of chitin pulp is reduced by 2 to 3 times when compared to chitin nanocrystals. Overall, this work presents a new and potentially scalable route for the generation of chitin-based materials having a reduced environmental footprint compared to nanochitins and chitosan, thus opening a new route for the valorization of chitin beyond nanochitin for the development of environmentally and economically sustainable materials.
... Firstly, the surface treatment weakened the intermolecular tion of CGs. Secondly, alkali treatment disrupted the interparticle adhesion of C promoted their migration [48]. In comparison with the PBAT/CG composite, the strength and elongation at break of PBAT/CG-OH-TA composite increased by 47. 53.6%, respectively. ...
... Firstly, the surface treatment weakened the intermolecular interaction of CGs. Secondly, alkali treatment disrupted the interparticle adhesion of CGs and promoted their migration [48]. In comparison with the PBAT/CG composite, the tensile strength and elongation at break of PBAT/CG-OH-TA composite increased by 47.0% and 53.6%, respectively. ...
Preparing composites from gricultural waste with biodegradable polymers is one of the strategies used to ensure the long-term sustainability of such materials. However, due to the differences in their chemical properties, biomass fillers often exhibit poor interfacial adhesion with polymer matrices. Inspired by mussel foot silk, this work focused on the surface modification of coffee grounds (CGs) using a combination of tannic acid (TA) and alkali treatment. CGs were used as a biomass filler to prepare polybutylene adipate terephthalate (PBAT)/CG composites. The modification of CGs was demonstrated by Fourier transform infrared spectroscopy (FTIR), the water contact angle, and scanning electron microscopy (SEM). The effect of CGs on the rheological, tensile, and thermal properties of the PBAT/CG composites was investigated. The results showed that the addition of CGs increased the complex viscosity, and the surface modification enhanced the matrix–filler adhesion. Compared with unmodified CG composites, the tensile strength and the elongation at break of the composite with TA-modified alkali-treated CGs increased by 47.0% and 53.6%, respectively. Although the addition of CGs slightly decreased the thermal stability of PBAT composites, this did not affect the melting processing of PBAT, which often occurs under 200 °C. This approach could provide a novel method for effectively using biomass waste, such as coffee grounds, as fillers for the preparation of polymer composites.
... However, the properties of the protein/starch bioplastic are highly affected by the processing method. The physical and mechanical properties of various bioplastic compositions [103][104][105][106] are summarised in Table 2. ...
Starch-based biopolymers occupy a significant place in polymer world for replacing plastics derived from petrochemicals. Their non-toxicity, bio-compatible nature and comparable mechanical and degradation properties make them suitable candidates for various applications, including packaging sector. Starch derived from a variety of agricultural waste is converted to bio-composites by chemical modification in the presence of plasticisers and other chemical moieties. These bio-polymers are biodegradable in nature; however, they are associated with certain disadvantages, such as brittleness, moisture sensitivity, and poor thermal and mechanical properties. Efforts are being made by researchers to overcome these challenges by various strategies in order to make it at par to the conventional plastic. Few companies have initiated using starch-based biopolymers for producing commercial products, but scientific world definitely demands significant studies that can enhance the properties of this material to an appreciable extent. This will also help in reducing the production cost and improving the overall economy of biopolymers’ segment.
... In addition to the size reduction of the lignin agglomerates in the PBAT/ML composites as observed in the SEM micrographs (Figure 2), the mobility of lignin was improved due to the disruption of the strong hydrogen bonds between −OH groups. 33 Similarly, the P/MP 3 /L composites also possessed better tensile performances than P/L composites ( Table 5). The results were attributed to MAH-g-PBAT, which acted as a bridge connecting the lignin agglomerates to the PBAT matrix. ...
In the past 70 years, over 8 billion tons of plastics have been produced, the majority of which cannot be fully biodegraded, causing their fragments to be found everywhere in the biosphere, including living organisms. Herein, a group of biodegradable composites were produced by blending poly(butylene adipate-co-terephthalate) (PBAT) with technical lignin through a twin-screw extrusion method. Two strategies were developed to improve the mechanical properties of PBAT/lignin composites: 1) modifying lignin via methylation to reduce hydrogen bonding between -OH groups; and 2) enhancing the intermolecular interactions between PBAT and lignin by adding maleic anhydride-graft-PBAT as a compatibilizer. The composites obtained from the two strategies with 60 wt% lignin contents exhibited ideal tensile performance which could meet the requirement of the Chinese National Standard for packaging. The interactions between different composite components were investigated by morphological and thermal analyses. The results showed that when the lignin used as filler in the composites, the molecular mobility of lignin and the size of its agglomerates remarkably impacted the ductility and mechanical strength of the PBAT/lignin films. A simple cost comparison between neat PBAT film and PBAT/lignin composite films indicated that the latter was economically competitive, and the production costs could significantly reduce by 36%.
... In 2016, a softwood ball-milled lignin, on its own, was found to be capable of forming a plastic with tensile strength above that of polyethylene [3]. In the present work, softwood kraft lignin (Indulin), when blended with just 5 wt% 1,8-dinitroanthraquinone, is shown to form another lignin-based polymeric material with tensile strength greater than polyethylene. ...
... The X-ray powder diffraction patterns of unblended BML-and MBML-based materials consist of two overlapping Lorentzian peaks [3] reflecting (primarily) the distributions of separation distances between cofacially-offset and edge-on aromatic rings in the lignin components ( Figure 5). The respective peak maxima occur at 4.0-4.2 ...
... A noteworthy example of an other-lignin blend component may be found in maple γvalerolactone (GVL) lignin which, when cast on its own, forms a plastic with tensile strength (33 MPa) greater than that of polyethylene ( Figure 11). Its tensile behavior is very similar to that of the softwood ball-milled lignin [3] shown in Figure 4. Presumably, this arises from the fact that GVL lignins are not far removed from the corresponding native lignins in structure [30] except that their molecular weights have been reduced because of inter-unit (predominantly) β-O-4 cleavage. Industrial softwood kraft lignin alone forms a material with tensile strength (9.5 MPa) about 3-fold lower than that of polyethylene. ...
Functional polymeric materials composed solely of lignin preparations appeared only very recently. A gradual paradigm shift spanning 56 years has revealed how lignin–lignin blends can upgrade the performance of 100 wt% lignin-based plastics. The view, first espoused in 1960, that lignin macromolecules are crosslinked reduces the plausibility of creating functional polymeric materials that are composed only of lignin preparations. Lignin-based materials would be much weaker mechanically if interstices remain in significant numbers between adjoining macromolecular structures that consist of rigid crosslinked chains. In 1982, random-coil features in the hydrodynamic character of kraft lignin (KL) components were evident from ultracentrifugal sedimentation equilibrium studies of their SEC behavior. In 1997, it was recognized that the macromolecular species in plastics with 85 wt% levels of KL are associated complexes rather than individual components. Finally, in 2016, the first polymeric material composed entirely of ball-milled softwood lignin (BML) was found to support a tensile strength above polyethylene. Except in its molecular weight, the BML was similar in structure to the native biopolymer. It was composed of associated lignin complexes, each with aromatic rings arranged in two domains. The inner domain maintains structural integrity largely through noncovalent interactions between cofacially-offset aromatic rings; the peripheral domain contains a higher proportion of edge-on aromatic-ring arrangements. Interdigitation between peripheral domains in adjoining complexes creates material continuity during casting. By interacting at low concentrations with the peripheral domains, non-lignin blend components can improve the tensile strengths of BML-based plastics to values well beyond those seen in polystyrene. The KL-based plastics are weaker because the peripheral domains of adjoining complexes are less capable of interdigitation than those of BML. Blending with 5 wt% 1,8-dinitroanthraquinone results in a tensile strength above that of polyethylene. Analogous effects can be achieved with 10 wt% maple γ-valerolactone (GVL) lignin which, with a structure close to the native biopolymer, imparts some native character to the peripheral domains of the KL complexes. Comparable enhancements in the behavior of BML complexes upon blending with 10 wt% ball-milled corn-stover lignin (BMCSL) result in lignin-only polymeric materials with tensile strengths well beyond polystyrene.
... Sarkanen et al. also found that the tensile properties of the polymeric materials prepared solely with methylated or acetylated lignin were similar to polystyrene (Fig. 5), and although the materials were very fragile, they could be plasticized through forming miscible blends with aliphatic polyesters [92,93]. When the methylene/ Application of Lignin in Thermoplastic Materials, Fig. 3 The effect of lignin content on crystallite size and crystallinity with increasing lignin content. ...
... Through the preferential interactions with peripheral domains, miscible blend components modulate strength and ductility in these quite original lignin-based plastics [98]. The nonlignin miscible blend components preferentially interact with these peripheral components, which subsequently affects the viscoelastic behavior of ligninbased polymer materials [93]. ...
... Furthermore, the properties of the materials also depend on the composition and casting conditions of the blend, as shown in Fig. 5. After casting the solution at 150 C, the tensile properties of the materials composed solely of ball-milled softwood lignin are comparable to those of polystyrene [93]. When the solution is cast at 150 C and then annealed at 180 C, the tensile properties of the blends containing 85% w/w levels of methylated ball-milled softwood lignin can surpass those of polystyrene [99]. ...
Vitrimers are promising reprocessable materials. To tune their properties, microphase separated block copolymers as backbones play an essential role in the thermal and mechanical properties of the resulting nanostructured networks. In this study, various narrow disperse di‐ and triblock copolymers containing a hydroxyethyl methacrylate block and, for comparison, random copolymers of the same comonomers are synthesized in a controlled manner by photoiniferter reversible addition‐fragmentation chain transfer (photoRAFT) polymerization. Subsequently, the copolymers are modified by acetoacetate groups and cross‐linked with diamines. After curing, the di‐ and triblock copolymer‐based vitrimers exhibit excellent thermal and mechanical properties compared to random ones; moreover, their characteristic properties can be adjusted by different types and amounts of diamines. As the transamination reaction is a thermoreversible exchange reaction the resulting vitrimers are reprocessible and therefore are recyclable materials. The combinion of two these classes of soft materials, namely vitrimers and block copolymers, leads to materials with a broad spectrum of adjustable mechanical properties for various applications with an improved end‐of‐life management, when compared to permanently crosslinked thermosets. This article is protected by copyright. All rights reserved
EU Academy of Sciences
Universal Journal of Renewable Energy 10 (2022)
Profitability in producing liquid biofuels or commodity organic chemicals from lignocellulosic plant polysaccharides depends, in part, on the value that the co‐product lignins may concomitantly gain. Compelling demonstrations of potential lignin valorization had been developed by 2020 through the creation of thermoplastics with 95–98 wt% levels of underivatized kraft lignin from a traditional pulp mill. These homogeneous biodegradable blends could readily surpass polystyrene in tensile behavior, and their production costs were estimated to be less than the 2021 polystyrene selling price, which was expected to rise. Such formulations are not limited to co‐product lignins from the kraft process, which was established in 1890 for delignifying wood chips to make paper. These compositions can be modified to create functional blends with high levels of other lignin preparations, including those from some emerging biorefinery processes. Actually, the idea of developing plastics with very high lignin contents had been initially greeted with almost universal disbelief. Isolated lignin preparations differ in a fundamental way from other polymers used in common plastics. They are largely composed of well‐defined associated complexes rather than individual macromolecular chains or cross‐linked networks. Lignin complexes consist of compact inner domains and penetrable peripheral domains. Because they interact preferentially with the latter, miscible non‐lignin components have a heightened impact on the mechanical properties of the resulting blends. When exposed to the environment, the biodegradability of these new plastics depends on a sugar requirement displayed by white‐rot fungi as they cleave lignins on a pathway leading to complete mineralization.
