Regenerated Cellulose Materials Research Articles

Progress in application of medical absorbable haemostatic materials for haemostasis in orthopaedic surgery

The application progress of medical absorbable haemostatic material (MAHM) in hemostasis during orthoapedic surgery was reviewed, in order to provide reference for clinical hemostasis program. The domestic and foreign literature on the application of MAHM for hemostasis in orthopedic surgery was extensively reviewed and summarized. According to biocompatibility, MAHM can be divided into oxidized cellulose/oxidized regenerated cellulose materials, chitosan and its derivatives materials, starch materials, collagen and gelatin materials, and fibrin glue materials, etc., which can effectively reduce blood loss when used in orthopedic surgery for hemostasis. Each hemostatic material has different coagulation mechanism and suitable population. Oxidized cellulose/oxidized regenerated cellulose, chitosan and its derivatives, starch hemostatic material mainly stops bleeding by stimulating blood vessel contraction and gathering blood cells, which is suitable for people with abnormal coagulation function. Collagen, gelatin and fibrin glue hemostatic materials mainly affect the physiological coagulation mechanism of the human body to stop bleeding, suitable for people with normal coagulation function. Reasonable selection of MAHM can effectively reduce perioperative blood loss and reduce the risk of postoperative complications, but at present, single hemostatic material can not meet clinical needs, and a new composite hemostatic material with higher hemostatic efficiency needs to be developed.

Enhancing the Mechanical Properties of Regenerated Cellulose through High-Temperature Pre-Gelation

This paper investigates the effects of pre-gelation on cellulose dissolved in LiCl/DMAc solutions to enhance the properties of regenerated cellulose materials. This study focuses on characterizing the crystallinity, molecular orientation, and mechanical performance of cellulose fibers and hydrogels prepared with and without pre-gelation treatment. X-ray diffraction (XRD) analysis reveals that crystallinity improvement from 55% in untreated fibers to 59% in fibers pre-gelled for 3 and 7 days, indicating a more ordered arrangement of cellulose chains post-regeneration. Additionally, XRD patterns show improved chain alignment in pre-gelled fibers, as indicated by reduced full width at half the maximum of Azimuthal scans. Mechanical testing demonstrates a 30% increase in tensile strength and a doubling of the compression modulus for pre-gelled fibers compared to untreated fibers. These findings underscore the role of pre-gelation in optimizing cellulose material properties for applications ranging from advanced textiles to biomaterials and sustainable packaging. Future research directions include further exploration of the structural and functional benefits of pre-gelation in cellulose processing and its broader implications in material science and engineering.

High-speed shear-induced micro regenerated cellulose materials preparation: A promising solution for highly efficient and low pressure drop air filtration using agricultural waste

Cellulose has attracted much attention in application of air filtration for the excellent ability of degradability and biocompatibility. However, limited by the strength of natural structure, air filters based on native cellulose usually have high pressure drop (ΔP) or thick volume. In this study, an efficient air filter was produced with low ΔP (6.8 Pa) using a low amount of dry material (9 ∼ 12 mg/cm3) through simple preparation process with high-speed shear induced. Analysis showed the chains of regenerated cellulose (RC) were stretched and arranged orderly due to the shear induced during the entire coagulation process, letting to an increasing of crystalline of RC. Furthermore, RC filter exhibited a high PM2.5 capture efficiency (over 99.65 %) with high-quality factor (0.853 Pa−1) under high PM concentration conditions. This work gave a novel sight on the potential of air filtration produced by agricultural waste bioresources furthermore, offered an interesting and simple avenue for daily respiratory protective media.

Molar masses and molar mass distributions of commercial regenerated cellulose materials and softwood dissolving pulp determined by SEC/MALLS

The molar masses and molar mass distributions of three commercial regenerated cellulose samples, viscose rayon, Tencel, and Bemliese (or cuprammonium nonwoven), have been determined by dissolution in 8% (w/w) lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) and subsequent size-exclusion chromatography with multi-angle laser-light scattering detection (SEC/MALLS). Before dissolution in LiCl/DMAc, the regenerated cellulose samples were pretreated by the following three methods: (1) soaking in ethylene diamine (EDA) and subsequent solvent exchange to N,N-dimethylacetamide (DMAc) through methanol, (2) soaking in water and subsequent solvent exchange to DMAc through ethanol, and (3) soaking in water and subsequent solvent exchange to tert-butyl alcohol through ethanol and freeze dying. The pretreated samples were dissolved in 8% (w/w) LiCl/DMAc by stirring the cellulose/LiCl/DMAc mixtures for 1–3 weeks followed by dilution to 1% (w/v) LiCl/DMAc for SEC/MALLS analysis. The EDA- and water-pretreated samples gave almost the same SEC-elution pattens and molar mass plots, resulting in similar number- and mass-average molar masses. However, the freeze-dried samples gave 10%‒20% lower mass recovery ratios than those obtained for the EDA- or water-pretreated samples, probably because of incomplete dissolution of the freeze-dried samples in 8% (w/w) LiCl/DMAc. The average mass-average degree of polymerization values of viscose rayon, Tencel, and Bemliese were 340, 530, and 880, respectively. The slopes of the conformation plots were 0.58–0.62, showing that all of the molecules in the three regenerated cellulose samples were dissolved in 1% (w/v) LiCl/DMAc, forming linear random-coil conformations.Graphical abstract

Aligned regenerated cellulose films with enhanced mechanical and optical properties for light management

The dissolution of cellulose endows the green and environmentally friendly cellulosic material with a wide range of processing properties, further enhancing its advantages as a basic material. However, its unsatisfactory mechanical performance and functionality severely limited its practical application. Herein, a facile molecular orientation strategy was developed to orient the aggregated structure of the dissolved cellulose in the lithium chloride/N,N-dimethylacetamide system and to obtain high-performance films. During the preparation process, cross-linking, stretching, and hot pressing were utilized to anchor, orient, and fix the orientated structure of the cellulose molecular chains. Morphological analysis confirmed that the present process can produce an oriented microstructure of cellulose films with remarkable mechanical and optical properties. The optimal film obtained with a stretching ratio of 50 % exhibited a high mechanical strength of 145.9 MPa, and a high light transmittance of 86.2 %. Compared to the unstretched sample, the stretched films showed higher thermal stability, much higher mechanical strength (up to 169 % of the pure cellulose film), and stronger light polarization and scattering response. The present strategy, based on the regulation of cellulose aggregate structure, provides a promising approach for the development of advanced regenerated cellulose materials with excellent performance and multifunctional properties.

Tough and Strong All-Biomass Plastics from Agricultural and Forest Wastes via Constructing an Aggregate of Hydrogen-Bonding Networks

The development of all-biomass materials to replace conventional plastics has been gradually becoming a focus. However, all-biomass plastics, especially those fabricated from agricultural and forestry wastes, have the obstacles of poor formability and/or low toughness. Herein, we demonstrated a facile, efficient, and easy-to-scale method to significantly improve the formability and toughness of biomass materials via constructing an aggregate of hydrogen-bonding networks, where the relatively weak hydrogen bonding could be sacrificed during stretching. After a continuous preparation process that combined a paper-making process with an in situ welding process, the regenerated cellulose material with a layered microstructure was spontaneously formed. The interlayer hydrogen-bonding interactions could dissipate energy during stretching. As a result, the cellulose plastics were tough and strong. The tensile strength, strain, and toughness reached 154.9 MPa, 57.7%, and 81.76 MJ/m3, respectively, which were markedly higher than those of previous cellulose-based materials. The corresponding cellulose hydrogel exhibited an excellent strength of 9.5 MPa and a high strain of 171.4% also. During this scalable process, a 1-ethyl-3-methylimidazolium acetate (EmimAc) aqueous solution worked as a dispersant and a solvent, and a high solid content of cellulose/EmimAc (20 wt %) was used. Based on such an effective method, various agricultural and forestry wastes, including corn straw, wheat straw, grass, and wood powder, could be directly processed into high-tough all-biomass films, indicating a huge potential in ecofriendly materials, environmental protection, and bioresource utilization.

One-Step Treatment for Upgrading Bleached Bamboo Pulp to Dissolving Pulp High Solvency in Green Alkali/Urea Aqueous Solution.

Bleached bamboo pulp, as a kind of natural cellulose, has received significant attention in the field of biomass materials due to its advantages of environmental protection and the abundance of raw materials. Low-temperature alkali/urea aqueous system is a green dissolution technology for cellulose, which has promising application prospects in the field of regenerated cellulose materials. However, bleached bamboo pulp, with high viscosity average molecular weight (Mη) and high crystallinity, is difficult to dissolve in an alkaline urea solvent system, restraining its practical application in the textile field. Herein, based on commercial bleached bamboo pulp with high Mη, a series of dissolvable bamboo pulps with suitable Mη was prepared using a method of adjusting the ratio of sodium hydroxide and hydrogen peroxide in the pulping process. Due to the hydroxyl radicals being able to react with hydroxyls of cellulose, molecular chains are cut down. Moreover, several regenerated cellulose hydrogels and films were fabricated in an ethanol coagulation bath or a citric acid coagulation bath, and the relationship between the properties of the regenerated materials and the Mη of the bamboo cellulose was systematically studied. The results showed that hydrogel/film had good mechanical properties, as the Mη is 8.3 × 104 and the tensile strength of a regenerated film and the film have values up to 101 MPa and 3.19 MPa, respectively. In this contribution, a simple method of a one-step oxidation of hydroxyl radicals to prepare bamboo cellulose with diversified Mη is presented, providing an avenue for a preparation of dissolving pulp with different Mη in an alkali/urea dissolution system and expanding the practical applications of bamboo pulp in biomass-based materials, textiles, and biomedical materials.

Effect of pulp prehydrolysis conditions on dissolution and regenerated cellulose pore structure

When producing regenerated cellulose materials, e.g., fibers and films, pulp fibers are first dissolved in a solvent and then regenerated in an antisolvent. The pulp properties have a significant impact on the dissolution. This study examines the effect of pulp prehydrolysis conditions on pulp structure, subsequent dissolution in cold aqueous NaOH/ZnO solvent, and regenerated cellulose film properties. The fiber and regenerated cellulose swelling and pore structure is addressed. Once-dried kraft pulp was activated in acid hydrolysis at two temperatures, 60 and 80 °C. The hydrolysis primarily affected the cellulose degree of polymerization (DP), and its reduction dramatically improved the pulp dissolution. Surprisingly, higher hydrolysis temperature did not increase the fiber hornification. DP reduction marginally effected the pulp swelling properties but had a significant effect on the regenerated film swelling. The regenerated films contained cellulose II, and their wet porosity correlated inversely with the DP. Low hydrolysis temperature films remained more porous after critical point drying.

Self-assembling hierarchical flexible cellulose films assisted by electrostatic field for passive daytime radiative cooling

Natural cellulose materials possess hierarchical microstructures and high crystallinity, which gives the possibility to develop high-performance cellulose structural materials. However, the hierarchical microstructures of natural cellulose materials will be disappeared in regenerated cellulose materials owing to the dissolution process. Achieving hierarchical microstructures and high crystallinity as natural cellulose materials in flexible regenerated cellulose materials is an arduous challenge. Herein, a simple electrostatic-field-assisted self-assembly strategy is proposed to greatly boost the crystallization of regenerated cellulose materials and obtain hierarchical flexible fibrous cellulose film. Large areas of cellulose crystallites with the lattice spacing close to monoclinic cellulose II are presented, and crystallinity as high as 71.0 % is achieved for the self-assembled fibrous cellulose film. Moreover, the self-assembled cellulose film has a bioinspired fibrous morphology with anisotropic hierarchical microstructures, and therefore can be used as flexible passive daytime radiative cooling materials with subambient cooling up to 11.3 °C in hot summer. It is the first time to realize high crystallinity and hierarchical microstructures in regenerated cellulose materials by the self-assembly of cellulose macromolecules at the molecular level. This strategy provides new perspectives for the development of advanced flexible cellulose materials with hierarchical microstructures and high crystallization from natural cellulose resources.

Regenerative Textiles: A Framework for Future Materials Circularity in the Textile Value Chain

Materials science breakthroughs have regenerated high value fibres from end-of-life cellulose-based textiles that can be introduced into existing textile fabrication processes from raw material to textile product in established textile value chains. Scientific developments with regenerated cellulose fibres obtained from waste textiles suggest their potential to replace virgin resources. The current scale-up of regeneration technologies for end-of-life cellulose-based textiles towards pilot and commercial scales can potentially achieve a future materials circularity, but there is a lack of a long-term view of the properties of materials after consecutive recycling stages take place. Cellulose-based materials cannot be infinitely recycled and maintain the same quality, a factor which may provide new challenges for future textile processes in the context of the circular bioeconomy. This paper maps collaborative design and materials science projects that use regenerated cellulose obtained from waste feedstock according to materials in the value chain they seek to substitute. It also presents four new processes that use regenerated cellulose materials in relation to their intervention in the value chain (as determined in a PhD investigation). A framework is presented to demonstrate how these circular material design processes take place at earlier stages of the textile value chain after subsequent regeneration stages.

Lignin enhances cellulose dissolution in cold alkali

Aqueous sodium hydroxide solutions are extensively used as solvents for lignin in kraft pulping. These are also appealing systems for cellulose dissolution due to their inexpensiveness, ease to recycle and low toxicity. Cellulose dissolution occurs in a narrow concentration region and at low temperatures. Dissolution is often incomplete but additives, such as zinc oxide or urea, have been found to significantly improve cellulose dissolution. In this work, lignin was explored as a possible beneficial additive for cellulose dissolution. Lignin was found to improve cellulose dissolution in cold alkali, extending the NaOH concentration range to lower values. The regenerated cellulose material from the NaOH-lignin solvents was found to have a lower crystallinity and crystallite size than the samples prepared in the neat NaOH and NaOH-urea solvents. Beneficial lignin-cellulose interactions in solution state appear to be preserved under coagulation and regeneration, reducing the tendency of crystallization of cellulose.

Biocompatible and biodegradable super-toughness regenerated cellulose via water molecule-assisted molding

• Double cross-linked regenerated cellulose (DCRC) exhibited excellent mechanical properties. • DC structure and pressure-induced orientation distribution improved the toughness of DCRCs. • The reversible hydrogen bond interaction makes the DCRCs capable of 3D mouldability. • The DCRCs exhibted excellent biocompatibility and biodegradability. Most of the commonly used plastics are derived from petrochemicals and produce severe environmental problems. The development of cost-effective bio-based and biodegradable materials with excellent mechanical properties, high thermal and chemical stability, excellent biocompatibility, good processability, and ability to be reshaped remains a challenge. Herein, we report a double cross-linking strategy, combining plane hot-pressing and water molecule-assisted molding processes, to fabricate 3D structured double-cross-linked regenerated cellulose (DCRC). The incorporation of chemical and physical crosslinking domains and the pressure-induced orientation distribution remarkably improved the toughness of the DCRCs. Moreover, the reversible hydrogen bond interaction between cellulose chains could be simply regulated by water molecule, making the DCRCs capable of three-dimensional mouldability. The novel strategy used in this study will be helpful in preparing regenerated cellulose materials with excellent mechanical properties, good moldability and excellent biocompatibility and biodegradability as alternatives to petrochemical plastics for the development of sustainable materials.

Unique CO2-switched cellulose solution properties in the CO2/DBU/DMSO solvent system and the preparation of regenerated materials

Taking advantage of the unique CO2-switched cellulose solution properties in CO2/DBU/DMSO solvent system, the thermal-induced CO2 release provides an alternative approach to prepare regenerated cellulose materials with IVI crystalline structure.

Recent Progress in High-Strength and Robust Regenerated Cellulose Materials.

High-strength petroleum-based materials like plastics have been widely used in various fields, but their nonbiodegradability has caused serious pollution problems. Cellulose, as the most abundant sustainable polymer, has a great chance to act as the ideal substitute for plastics due to its low cost, wide availability, biodegradability, etc. Herein, the recent achievements for developing cellulose "green" solvents and regenerated cellulose materials with high strength via the "bottom-up" route are presented. Cellulose can be regenerated to produce films/membranes, hydrogels/aerogels, filaments/fibers, microspheres/beads, bioplastics, etc., which show potential applications in textiles, biomedicine, energy storage, packaging, etc. Importantly, these cellulose-based materials can be biodegraded in soil and oceans, reducing environmental pollution. The cellulose solvents, dissolving mechanism, and strategies for constructing the regenerated cellulose functional materials with high strength and performances, together with the current achievements and urgent challenges are summarized, and some perspectives are also proposed. The near future will be an exciting era for high-strength biodegradable and renewable materials. The hope is that many environmentally friendly materials with good properties and low cost will be produced for commercial use, which will be beneficial for sustainable development in the world.

Macro- and Microstructural Evolution during Drying of Regenerated Cellulose Beads.

The macro- and microstructural evolution of water swollen and ethanol swollen regenerated cellulose gel beads have been determined during drying by optical microscopy combined with analytical balance measurements, small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS). Two characteristic length scales, which are related to the molecular dimension of cellulose monomer and elongated aggregates of these monomers, could be identified for both types of beads by SAXS. For ethanol swollen beads, only small changes to the structures were detected in both the SAXS and WAXS measurements during the entire drying process. However, the drying of cellulose from water follows a more complex process when compared to drying from ethanol. As water swollen beads dried, they went through a structural transition where elongated structures changed to spherical structures and their dimensions increased from 3.6 to 13.5 nm. After complete drying from water, the nanostructures were characterized as a combination of rodlike structures with an approximate size of cellulose monomers (0.5 nm), and spherical aggregates (13.5 nm) without any indication of heterogeneous meso- or microporosity. In addition, WAXS shows that cellulose II hydrate structure appears and transforms to cellulose II during water evaporation, however it is not possible to determine the degree of crystallinity of the beads from the present measurements. This work sheds lights on the structural changes that occur within regenerated cellulose materials during drying and can aid in the design and application of cellulosic materials as fibers, adhesives, and membranes.

Microcrystalline cellulose treated by steam explosion and used for thermo-mechanical improvement of polypropylene

The use of cellulose fibers derived from renewable resources as reinforcement in polymeric composites provides positive environmental benefits with respect to disposal and raw material savings. Microcrystalline cellulose is a regenerated cellulose material that is free of lignin and hemicellulose, widely used in various applications. Recently, there has been enormous interest in producing polymer nanocomposites using cellulose nanofibers as reinforcement. Moreover, the steam explosion process is an ecofriendly method to modify cellulose fibers by inducing fibrillation, allowing the production of nanofibers. Fibrillation of microcrystalline cellulose using steam explosion process as the only cellulose treatment process was not yet studied in the literature. In the present work, steam explosion process was applied to commercial microcrystalline cellulose and the obtained fibers were characterized and employed in composites with polypropylene for evaluation of the thermal, mechanical, and morphological properties in relation to the matrix. The results showed that this process promoted partial fibrillation to nanosized diameter, and an increase in crystalline degree and thermal stability of the original fiber. As for the polypropylene/cellulose composites in the absence of compatibilizer, there was an increase of thermal degradation temperature and mechanical properties measured by dynamic-mechanical analysis in comparison with pure polypropylene.

Strong, transparent cellulose film as gas barrier constructed via water evaporation induced dense packing

A simple strategy of water evaporation induced dense packing is used to construct regenerate cellulose film (CF) with high strength and transparency. Cellulose solution was cast and exposed to atmosphere at room temperature to conduct water evaporation, and it was concentrated and undergoes a sol-gel transition to form a physically cross-linked network with high packing density. CFs were obtained after removing the residue solvent. The dense packing led to homogeneous structure and decreased pore size, as well as enhanced mechanical, optical and gas barrier property. The highest tensile strength reached 158.2 and 11.7 MPa in the dry and hydrogel state, respectively, stronger than regenerated cellulose films of same kind, while the visible light transmittance at 550 nm reached 89.94 and 95.05% in the dry and hydrogel state. O2 and CO2 permeability at 40% relative humidity reached 1.37 × 10−17 and 1.08 × 10−17 cm3 cm cm−2 s−1 Pa−1, respectively, lower than literatures in the same condition. Moreover, cellulose/silver nanocomposite was fabricated by taking advantage of the mechanical and optical property of CF, demonstrating a considerably low detection limit and high sensitivity as optical sensing platform. The present work supplies a simple pathway to improve the structure and property of regenerated cellulose materials, demonstrating great potentials.

Preparation of high-performance cellulose composite membranes from LiOH/urea solvent system

New green solvent system alkali (such as NaOH and LiOH)/urea which could rapidly dissolve cellulose could be potentially used to prepare high-performance regenerated cellulose materials with low cost. Pure regenerated cellulose materials have relatively low strength inherent effects. In this work, we choose TEMPO-oxide cellulose nanofiber (CNF) and graphene oxide (GO) as fillers to prepare isotropic regenerated cellulose membrane (RCM) with significantly enhanced mechanical properties. Dynamic mechanical analyzer (DMA) test shows that RCM with content of 5 wt% CNF has the maximum enhancement value of 32.5% improvement comparing with pure RCM. And RCM with 0.4 wt% GO has the maximum improvement of 17.9%. Mechanical properties decrease with further increasing filler contents. We employ transmission electron microscopy to confirm the structure of fillers in solution and scanning electron microscopy to observe the microstructures of these RCMs. The results are consistent with DMA tests. In addition, XRD results confirm that the crystal structure of RCMs is the same with RCMs without filler. Thermogravimetric analyses results indicate that RCMs keep great thermal stability below 300 °C. Transmittance (Tr) property is carried out by UV–Vis spectroscopy. Pure RCMs and CNF/RCMs keep high transparency at the wavelength of 800 nm. Transparency of RCMs with GO decrease quickly when the content of GO increases. In conclusion, the enhancement mechanism is proposed as the addition of fillers makes up the defects in RCMs. Furthermore, CNF illustrates large aspect ratio which is beneficial for stress transfer. As for GO, polar groups on surface provide strong interaction with the matrix. This is the first time that the enhancement effects of different fillers are systematically analyzed and compared for RCMs system. Our work could benefit the selection of appropriate fillers for such green solvent system and expand its range of applications.

Dissolution of cellulose in novel carboxylate-based ionic liquids and dimethyl sulfoxide mixed solvents

A series of substituted piperazinium, piperidinium, and pyrrolidinium acetates were synthesized. Highly effective cellulose solvents have been designed by mixing an aprotic polar solvent, dimethyl sulfoxide (DMSO), with synthesized ionic liquids (ILs). Different weight ratios of corresponding IL/DMSO mixed solvents were prepared to investigate the effect of cosolvent on cellulose solubility. Cellulose solubility in IL/DMSO solvent systems was measured at 25, 50 and, 80 °C. The effect of factors such as solvent composition, process temperature, type of IL’s cation, and alkyl chain length of IL’s cation on cellulose solubility was investigated. Amongst all tested solvents, N,N’-dimethyl-N-ethylpiperazinium acetate ([DMEPpz][Ac]/DMSO) mixed solvent exhibits the best performance in the dissolution of cellulose, reaching up to 13.5 wt% at 80 °C. The dissolved cellulose was regenerated using water as an antisolvent. The structure and morphology of the regenerated cellulose material were characterized by SEM, XRD, and FTIR, respectively.

Functionalized Imidazalium Carboxylates for Enhancing Practical Applicability in Cellulose Processing

Developing cellulose-based products is highly important because of their low-cost, reproducibility, and biodegradability. However, extensive application for cellulose has been actually hindered due to its well-known insolubility. Herein, some 22 novel functionalized imidazalium carboxylates exhibit tremendously enhanced dissolution capacity for cellulose even without extra energy consumption and are much superior to the previously reported solvents so far. Systematic investigations reveal that the powerful dissolution capacity for cellulose mainly results from the contribution of the imidazolium skeleton cation, not replacing acidic H atoms in imidazolium skeleton by alkyl, binding more allyl in N atoms of imidazolium cation, and binding an electron-donating group in carboxylate anion. Of particular importance, porous cellulose materials with varying micromorphology, for the first time, are reported by tuning the anionic and/or cationic structures of an IL. Moreover, the regenerated cellulose material ret...