Microfibrillar Structure Research Articles

Unconventional strategies for liver tissue engineering: plant, paper, silk and nanomaterial-based scaffolds.

The paper highlights how significant characteristics of liver can be modeled in tissue-engineered constructs using unconventional scaffolds. Hepatic lobular organization and metabolic zonation can be mimicked with decellularized plant structures with vasculature resembling a native-hepatic lobule vascular arrangement or silk blend scaffolds meticulously designed for guided cellular arrangement as hepatic patches or metabolic activities. The functionality of hepatocytes can be enhanced and maintained for long periods in naturally fibrous structures paving way for bioartificial liver development. The phase I enzymatic activity in hepatic models can be raised exploiting the microfibrillar structure of paper to allow cellular stacking creating hypoxic conditions to induce in vivo-like xenobiotic metabolism. Lastly, the paper introduces amalgamation of carbon-based nanomaterials into existing scaffolds in liver tissue engineering.

Valorization of Grass Clipping Waste: A Sustainable Approach to Cellulose Extraction and Paper Manufacturing

This study investigates the physical, mechanical, and structural characteristics of handmade paper samples derived from cellulose extracted from grass clippings using two distinct methods as follows: (1) alkali treatment and (2) alkali treatment followed by bleaching, coupled with the incorporation of barium sulfate as a mineral filler. Our investigation revealed that the handmade paper samples’ densities, moisture contents, and thicknesses varied within the ranges of 0.436 to 0.549 g/cm3, 5.60 to 2.51%, and 0.41 to 0.50 mm, respectively. The tensile strength and folding endurance of the papers produced through alkali treatment with barium sulfate were notably superior to those produced from bleached pulp and barium sulfate. Our analysis indicates that several critical factors, including paper density, thickness, the crystallinity index, and the microfibrillar structure of cellulose, intricately influence the mechanical and strength properties of the samples. Using Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) techniques, we identified characteristic cellulose bonds and examined cellulose’s crystalline and amorphous phases. Additionally, the crystallinity index of the samples was determined using both the Segal and peak deconvolution methods. Scanning electron microscopy (SEM) micrographs revealed interconnected networks of cellulose fibers with varying thicknesses and lengths, along with incorporated mineral filler within the cellulose fiber structure. Variations in mineral particle retention were attributed to the presence or absence of cellulose microfibrils. These findings contribute to our understanding of the observed strength characteristics of the paper samples and underscore the potential applications of cellulose derived from grass clippings, especially when combined with barium sulfate as a mineral filler in paper production.

Specific temperature-modulated crab shell-derived porous carbon as a typical recycling material for nitrofurazone electrochemical sensor

Nitrofurazone (NFZ), a nitroimidazole antibiotic, can cause serious toxicity when overused, its quantification is crucial for human health. Herein, crab shell waste is converted into porous biochar at a high temperature, which can be employed for the establishment of an electrochemical sensor for the quantitative detection of NFZ. The morphological and structural properties of the crab shell carbon at different temperatures were characterized by SEM, XRD, FT-IR and N2 adsorption-desorption analyses. The crab shell carbon prepared at 500 °C (C-CS-500) and 700 °C (C-CS-700) is calcite-based and contains micro-fibrillar similar to chitin structure, while the crab shell carbon prepared at 900 °C (C-CS-900) is lime-based and lacks the similar structure. And the synergistic influence of calcite-based composition and micro-fibrillar structure of crab shell carbon offered strong electron-transport properties and a large electrode active at a higher carbonized temperature. The electrochemical signals demonstrated that the crab shell carbon prepared at 700 °C provided enhanced sensing capability for rapid NFZ detection with a wide linear range of 0.40–80 μM, a high sensitivity of 0.55 μA μM−1 and a low detection limit of 0.11 μM (S/N = 3), as compared to the crab shell carbon prepared at 500 °C and 900 °C. In addition, the sensor can also be utilized to quantify nitrofurazone in the real drug (compound cod liver oil ointment) with satisfactory recovery.

Effect of swelling degree on structural evolution and orientation behavior of Poly(vinyl alcohol) films during stretching

For the preparation of polarizing film, the initial condensed structure of the PVA film is the key factor to determine the subsequent process conditions such as dyeing and stretching of PVA film. In the present work, the difference of the initial condensed structure of Poly (vinyl alcohol) (PVA) films with different swelling degrees and their influence on the orientation behavior and morphological structure evolution during stretching were investigated in detail. The results showed that the PVA film with a higher swelling degree possessed a lower content of microfibril structure at the same strain and the higher critical strain εs, revealing that the undissolved lamellae could act as the precursor for the formation of oriented microfibrillar structures. Furthermore, in order to investigate the influence of different swelling degrees on the lamellar orientation and the formation of microfiber structure during the stretching of PVA films, the long period of lamellae (Lp), the period of nanofibrils (Lf), and the Full Width at Half Maxima (FWHM) of Lf were calculated. It was found that the Lp and the Lf of the microfibrillar structure in the equatorial and meridional directions were larger and the FWHM of Lf was smaller for PVA films with higher swelling degree, indicating that the PVA film with a higher swelling degree could form a more relaxed and uniform periodically folded microfibrillar network, resulting in a higher light transmission in the visible region. Therefore, on the premise of ensuring the mechanical strength, the PVA film with a relatively higher swelling degree can be used to obtain commercial polarizing films with excellent light transmittance.

Development of sustainable cellulose‐based composite of polypropylene reinforced by recycled microfibrillar poly (ethylene terephthalate)

AbstractSustainable composites based on blends from polypropylene (PP) and recycled polyethylene terephthalate (RPET) and wood flour (WF) were prepared under industry‐relevant conditions by melt extrusion, followed by continuous drawing through spinnerets. Maleic anhydride grafted polypropylene (PP‐g‐MA) was employed to improve the compatibility between matrix and WF. The effects of incorporation of WF and RPET microstructure on the morphological features, rheological measurements, and mechanical properties were investigated. The drawing process converted elliptical RPET phase into highly oriented microfibrillar structure, as characterized by means of scanning electron microscopy (SEM). The highly oriented blend (HOB) represented nonterminal behavior due to the presence of physical networks and enhanced surface area of microfibers for chemical interactions. The tensile strength of neat PP increased by the addition of WF and the existence of microfibrillar RPET phase, whereas the microstructure of RPET had more pronounce effect. The tensile strength and elastic modulus of PP reinforced by WF and oriented RPET improved by 65% and 92%, respectively, demonstrating the high potential of this environmental‐friendly reinforcement method to intensify the mechanical properties of PP.

Implication of Freeze-Thaw Erosion and Mechanism Analysis of High-Performance Aromatic Liquid Crystal Fibers.

According to the demand for high-performance fibers for high-latitude ocean exploration and development, this paper selects representative products of high-performance liquid crystal fibers: thermotropic liquid crystal polymer fibers (TLCP) and poly p-phenylene terephthalamide (PPTA) fibers. Through a series of freeze-thaw (F-T) experiments for simulating a real, cold marine environment, we then measure the retention of mechanical properties of these two kinds of fibers. Before that, due to the difference in their chemical structures, we tested their Yang-Laplace contact angle (YLCA) and water absorption; the results suggested that PPTA fibers would absorb more moisture. Surprisingly, then, compared with thermotropic liquid crystal polymer (TLCP) fibers, the retention of the mechanical properties of poly p-phenylene terephthalamide (PPTA) fibers decreased by around 25% after the F-T experiments. The Fourier-transformed infrared (FT-IR) analysis, the attenuated total reflection (ATR) accessory analysis and the degree of crystal orientation measured by two-dimensional wide-angle X-ray diffraction (2D-WAXD) confirm that no changes in the chemical and the orientation structure of the crystal region of the fibers occurred after they underwent the F-T cycles. However, as observed by scanning electron microscopy (SEM), there are microcracks of various extents on the surface of the PPTA fibers, but they do not appear on the surface of TLCP fibers. It is obvious that these microcracks will lead to the loss of mechanical properties; we infer that the moisture absorbed by the PPTA fibers freezes below the freezing point, and the volume expansion of the ice causes the collapse of the microfibrillar structure. The two sorts of fibers subjected to the F-T experiments are immersed in a sodium chloride solution, and the amount of water infiltrated into the PPTA microfibrillar structure is evaluated according to the content of sodium ions in the fiber surface and subsurface layers through X-ray spectroscopy (EDS) elemental analysis. From the above analysis, we found that TLCP fibers can more effectively meet the operating standards of the severe and cold marine environment.

In situ‐induced epiphytic crystallization of MC PA6 by self‐assembled nucleator and reinforcing effect

AbstractMonomer casting nylon‐6 (MC PA6), as a high‐performance engineering plastic, replaces metals to be widely applied, while further improving the mechanical properties of MC PA6 is significant for its withstanding heavy loads and increasing its range of applications. In this work, amide nucleating agent (NUDA) with good compatibility and crystal matching relationship with PA6 was firstly dissolved in ε‐caprolactam monomer, and MC PA6‐NUDA was synthesized in situ. NUDA self‐assembled into special frameworks and induced epiphytic crystallization of PA6 to form an enhanced sheaf‐like crystal on its surface with microfibrillar structure during the parallel polymerization–crystallization process. Incorporation of appropriate content of NUDA improved the melting/crystallization point and crystallinity with decreasing grain size obviously, and advanced the crystallization process of MC PA6 mainly via reducing the nucleation potential energy and inducing the formation of crystal nuclei. As a result, the glass transition temperature increased, the tensile strength exhibited a significant 22% increase and the fracture toughness was nearly three times that of neat MC PA6. Meanwhile, deformation with many yield folds as well as stress‐whitening phenomena were observed on the impact‐fractured surfaces, presenting a ductile fracture feature, indicating reinforcing and toughening effect of NUDA on the PA6 matrix. © 2023 Society of Industrial Chemistry.

Short aramid fiber reinforced thermotropic liquid crystalline polyester composites: Fabrication, thermal, and mechanical properties

We conducted a study to analyze the impact of short aramid fibers (AFs) on the melt-rheological behavior, thermal transition, thermal stability, and mechanical durability of thermotropic liquid crystal polyesters (TLCPs). By using different AF loading contents ranging from 3–15 wt%, we produced TLCP matrix composites through masterbatch-based melt-compounding and injection-molding. The SEM images and FT-IR spectra demonstrate that the AFs are dispersed in the TLCP matrix with a microfibrillar structure through good interfacial adhesion caused by specific intermolecular interactions between the TLCP and AFs. As a result, the complex viscosity, shear storage/loss moduli, and thermal transition (melt-crystallization, glass transition, and melting) temperatures of the composites increase with increasing AF filler content. However, the melt-crystallization and melting enthalpies increase only at low AF loading contents of 3–5 wt%. At high AF contents of 7–15wt%, the enthalpies decrease owing to the partial aggregation of AF fillers. The thermogravimetric analysis proves that the thermal stability of TLCP/AF composites improves when the AF filler is introduced. The dynamic mechanical analysis using the stepped isothermal method shows that the addition of 5 wt% AF to the TLCP leads to an approximately 150% improvement in elastic moduli and long-term mechanical durability at elevated temperatures.

Fabrication of highly electrically conductive polypropylene/polyolefin elastomer/multiwalled carbon nanotubes composites via constructing ordered conductive network assisted by die‐drawing process

AbstractIn this work, a facile strategy is proposed to prepare highly electrically conductive polypropylene (PP)/polyolefin elastomer (POE)/multiwalled carbon nanotubes (MWCNTs) composites with ordered conductive networks using a house‐made die‐drawing apparatus. Results showed that increasing either die‐drawing speed or drawing ratio led to an increase of crystallinity by 10% and orientation factor by 0.15 for PP, respectively, which played an important role in tuning the electrical conductivity and mechanical properties. Prior to die‐drawing process, MWCNTs were selectively distributed in POE domains, resulting in a remarkable increase of electrical conductivity. The prevailing high‐stress field during die‐drawing process was able to deform MWCNTs‐enriched POE domains to ordered microfibrillar structure, as confirmed by morphology observations. This resulted in a further increase of electrical conductivity for die‐drawn PP/POE/MWCNTs composites when compared with that of MWCNTs‐containing counterparts without die‐drawing. Moreover, both the tensile strength and elongation at break for die‐drawn PPCNTE30 composites were increased by 20% and 127% as compared with their counterparts without die‐drawing treatment.

All-cellulose-based high-rate performance solid-state supercapacitor enabled by nitrogen doping and porosity tuning

Renewable cellulose-based papers are considered as a good resource for energy storage devices owing to their interlaced microfibrillar structure and high electrolyte absorptivity. Herein, an all-cellulose-based solid-state high-rate supercapacitor assembled with cellulose paper-derived self-supporting porous carbon electrodes and filter paper separator is designed. Benefiting from ingenious surface chemistry and pore structure engineering, the electrodes possess interconnected network structure, hierarchical pores, and appropriate N/O doping levels. The electrode demonstrates high specific capacitance (222.2 F g−1 at 0.2 A g−1), prominent rate capability (120.1 F g−1 at 100 A g−1), and outstanding cyclic stability (98.7 % capacitance retention after 20,000 cycles at 80 A g−1), which surpass most of cellulose-based self-supporting carbon electrodes ever reported. By integrating the well-designed electrodes with a piece of filter paper separator, the assembled symmetric solid-state supercapacitor (1.2 V) achieves an encouraging specific capacitance of 115.0 F g−1 along with an impressive energy density of 22.9 Wh kg−1 and a maximum power density of 15.9 kW kg−1. Moreover, the symmetric supercapacitor with 1 M Et4NBF4 organic electrolyte (3 V) delivered a maximum energy density and power density of 62.5 Wh kg−1 and 54.9 kW kg−1, respectively. This study proposes a design concept of all-cellulose-based solid-state supercapacitors, which presents a promising direction toward environmentally friendly and sustainable energy storage technology.

Biocompatibility improvement and controlled in vitro degradation of poly (lactic acid)-b-poly(lactide-co-caprolactone) by formation of highly oriented structure for orthopedic application.

Poly (lactic acid) (PLA) has been proposed as a promising orthopedic implant material, whereas insufficient mechanical strength, unsatisfied biocompatibility and inappropriate degradation rate restrict its further application. In this work, self-reinforced poly (lactic acid)-b-poly(lactide-co-caprolactone) (PLA-b-PLCL) block copolymer with long-chain branches was fabricated through two-stage orientation. Compared with smooth and hydrophobic PLA surface, the surface of PLA-b-PLCL presented micro-phase separated structure with improved hydrophilicity, and cells seeded on it showed improved adhesion/proliferation and high alkaline phosphatase (ALP) activity. After the 1st stage orientation at temperature higher than Tg1 (glass transition temperature of PLA phase), the amount of CH3 and CO groups on surface of PLA-b-PLCL increased, while "groove-ridge" structure formed, resulting in enhancement of surface hydrophobicity. After the 2nd stage orientation at Tg1 ~ Tg2 (glass transition temperature of PLCL phase), surface hydrophobicity/amount of CO groups further increased and "groove-ridge" structure became more significant. Due to suitable wettability and enhanced material-cell mechanical interlocking, cell proliferation/ALP activity were improved and a continuous cell layer formed on sample surface. During in vitro degradation in phosphate buffered saline solution, by introduction of PLCL segments, the crystallinity decreased and solution absorption increased, resulting in a rapid deterioration of mechanical properties. After the 1st stage orientation, a dense microfibrillar structure with high crystallinity formed, which hindered diffusion of solution and delay hydrolytic degradation. After the 2nd stage orientation, PLCL segments were arranged more closely, resulting in a further inhibition of degradation, which was helpful for controlling the strength decay rate of PLA as bone fixation materials.

Extraction and Characterization of Natural Cellulosic Fiber from Taraxacum Sect. Ruderalia

ABSTRACT The aim is to explore the utilization of cellulosic fibers extracted from the Taraxacum Sect. Ruderalia, which is also known as dandelion, introduces a potential reinforcement for the green composite industry. This research is focused on the analysis of chemical, physical, thermal, and morphological properties of the Taraxacum Sect. Ruderalia fibers. Its lightweight (1.397 g/cm3) with the presence of an acceptable cellulose ratio (52.7%) and high crystallinity (69.59%) provide comparable tensile strength (57.36 MPa) and Young’s modulus (2.96 GPa) for Taraxacum Sect. Ruderalia fibers. The fibers are experimentally thermal resistant to 272°C according to TGA that may be profitable in extrusion processes in polymeric composite manufacturing. The average fiber diameter and wall thickness were optically 233 µm and 1.5 µm, respectively. Taraxacum Sect. Ruderalia fibers have a rough surface character with some irregularities such as porosities, particles, indentations, protrusions, and also the microfibrillar structure which can support mechanical interlocking with polymer in a composite system. With all these encouraging properties, Taraxacum Sect. Ruderalia fibers can be good alternative reinforcement for common cellulosic bast fibers in the development of ecologically friendly and sustainable polymeric-based materials.

Novel Tissue-Engineered Multimodular Hyaluronic Acid-Polylactic Acid Conduits for the Regeneration of Sciatic Nerve Defect.

The gold standard for the treatment of peripheral nerve injuries, the autograft, presents several drawbacks, and engineered constructs are currently suitable only for short gaps or small diameter nerves. Here, we study a novel tissue-engineered multimodular nerve guidance conduit for the treatment of large nerve damages based in a polylactic acid (PLA) microfibrillar structure inserted inside several co-linear hyaluronic acid (HA) conduits. The highly aligned PLA microfibers provide a topographical cue that guides axonal growth, and the HA conduits play the role of an epineurium and retain the pre-seeded auxiliary cells. The multimodular design increases the flexibility of the device. Its performance for the regeneration of a critical-size (15 mm) rabbit sciatic nerve defect was studied and, after six months, very good nerve regeneration was observed. The multimodular approach contributed to a better vascularization through the micrometrical gaps between HA conduits, and the pre-seeded Schwann cells increased axonal growth. Six months after surgery, a cross-sectional available area occupied by myelinated nerve fibers above 65% at the central and distal portions was obtained when the multimodular device with pre-seeded Schwann cells was employed. The results validate the multi-module approach for the regeneration of large nerve defects and open new possibilities for surgical solutions in this field.

Influence of deproteinization and demineralization process sequences on the physicochemical and structural characteristics of chitin isolated from Deep-sea mud shrimp (Solenocera hextii)

Isolation of chitin from shrimp shell waste using chemical process is a well-adopted industrial practice due to its short process time and efficiency in removing both minerals and proteins from the shell. This study aims to compare the physicochemical, functional, and structural characteristics of chitin obtained from Deep-sea mud shrimp shells using two chemical process sequences: (i) initial deproteinization followed by demineralization (DPM) and (ii) initial demineralization followed by deproteinization (DMP). Characteristics of the extracted chitin, namely degree of acetylation, whiteness index, purity, crystallinity index and surface morphology were evaluated and compared with those of commercial chitin. The high levels of deproteinization and demineralization observed for both DPM and DMP processes suggest the effectiveness of the processes. The Mw of 436.59 ± 1.00 kDa, DA of 81.56 ± 1.10% and WI of 71.39 ± 0.72 for chitin prepared by DMP were higher than those of chitin prepared by DPM, which had Mw of 429.34 ± 1.21 kDa, DA of 75.91 ± 0.99% and WI of 45.03 ± 1.39. The CrI values for DPM and DMP chitins were 68.7% and 72%, respectively. SEM analysis revealed a microfibrillar structure with porosity for the isolated chitin.

Thermally and organomodified montmorillonite as effective regulators of the structure formation process in polypropylene/polystyrene blends

The influence of the concentration of thermally and organomodified montmorillonite on the processes of structure formation in a blend of polypropylene/polystyrene (PP/PS) was studied. It is established that in nanofilled compositions, as well as in the original, is formed a microfibrillar structure, the dimensional characteristics of which depend on the content of the additive and the method of its modification. The investigated clays by content (0.2–2.0) wt. % by weight of polypropylene have a compatibilizing effect in the blend of PP/PS, which reduces the average diameter of microfibers by 1.6 times and increases the homogeneity of their distribution by diameter: statistical indicators decrease (standard deviation, variance, coefficient of variation). The modifying effect of thermally modified clay is higher—the improvement of the dimensional characteristics of PP microfibers is achieved at its minimum content in the blend (0.2 wt. %). The formation of anisotropic PP structures in the PS matrix and the relaxation of the accumulated stresses at the exit of the molding hole is the main factor that causes high values of the coefficient of swelling of the extrudates (4.0–7.7). The change in the microstructure of the extrudates of nanofilled systems during spinning depends on the composition of the blend and the method of modification of montmorillonite. The average diameters of microfibers decrease from 2.2 μm (in the original blend) to (1.3–2.0) μm (in three-component) depending on the content of additives. The ability to regulate the microstructure of incompatible polymer blends by introducing additives of thermally and organomodified montmorillonite will contribute to the creation of nanocomposites with controlled morphology, as well as new fine-fiber materials with improved filtering characteristics.

In Ukrainian

There were PP- and iron-containing, fibrous, carbon- and nanodispersed-addition-based composite fibers prepared. There were addition content equals of 5.0%mass. There were blend of isotactic PP and addition homogenized in melt with one-screw lab extruder. There were zonal temperature on extruder equals of 230-250 o C. There were strangs receiving in bath of water and threated with knife granulation. Then, there were granules drying on air during 5h, and, then in thermal vacuum oven at 80±5 o C during 3h. Then, there are monofiber of 1 mm’s diameter formed on lab stand. Then, from one formed those others monofibers of different values of spinneret drawing (Фв, %). There were Фв for monofibers equals of 300 and 500%. Then, there were formed monofibers threated with thermoorientational drawing process at 150 oC. Then, there were monofibers of Фв value, which equals of 300%, drawn till draw degree λ=6, but, those others of Фв value, which equals of 500% - to λ=4. It is succeed, for composite monofibers, that orientational drawing process has had realized, until to the same value, as well as for one of virgin PP. But, when at formation and thermoorientational drawing processes, there were placing much number of breaks, as compared with monofiber of pure PP. When studying the structure with SEM technique, there was revealed microfibrillar structure of composite monofiber. When using optical microscopy, then there was determined irregularity for distribution of addition’s particles, leading to disproportional distribution of tension values at loading. It is revealed, for composite monofiber, at given value for content of addition, that electrical conductivity phenomenon is absent here. There are real ε’and imaginal ε’’ parts of complex dielectrical permittivity phenomenon, on frequency of 9 GHz, equals of 2.1 and 0.2, accordingly. It is established, that pure, non-drawn and composite monofiber itrinsically have satisfactory magnetic properties (σs=0.5 Gs∙cm3/g, Hc= 695 E). There are real μ’ and imaginal μ’’ parts of complex magnetical permittivity phenomenon equals of 1.1 and 0.02, accordingly.

РЕГУЛЮВАННЯ СТІЙКОСТІ РІДКИХ МІКРОСТРУМЕНІВ ПОЛІПРОПІЛЕНУ В МАТРИЦІ СПІВПОЛІАМІДУ ЗА РАХУНОК НАНОДОБАВОК

Goal. Investigation of the effect of the concentration of nanoparticles of aluminum oxide (Al2O3) and alumina modified with silver (Ag/Al2O3) on the decomposition kinetics of liquid microjets of polypropylene (PP) in a copolyamide (CPA) matrix and the possibility of controlling the microfibrillar morphology of the PP/CPA blend.Methodology. The components of the blend were mixed on a screw-disk extruder. The kinetics of the disintegration of liquid microjets was studied using a technique based on the theory of destabilization of a liquid cylinder under the action of capillary waves. The degree of dispersion of polypropylene in the matrix was evaluated by photomicrographs of cross sections of the extrudates of the blends.Results. Nanoadditives of the original and silver-modified aluminum oxide with a content of (0.1 ÷ 3.0) wt.% In the blend increase the compatibility of the components: the surface tension (γαβ) in the compositions of all compositions decreases. Ag/Al2O3 nanoparticles are more effective than aluminum oxide nanoparticles - the γαβ value decreases by 9.6 and 5.3 times, respectively, which ensures a high degree of dispersion of the dispersed phase component in the matrix. The disintegration resistance of polypropylene microjets is increasing, as evidenced by a decrease in the instability coefficient (q) and an increase in the microjet lifetime (tl). The curves of q and tl dependence on the additive content have an extreme character. The minimum values of the instability coefficient of microjets and the maximum values of their lifetime are achieved at a nanoparticle concentration corresponding to the lowest interfacial tension.Scientific novelty. The positive effect of the investigated nanoadditives on the kinetics of the decomposition of liquid microjets of polypropylene in the copolyamide matrix has been established. The highest modifying effect in the presence of Ag/Al2O3 nanoparticles is due to their amphiphilic nature, which ensures the predominant localization of nanoparticles at the interface and a synergistic increase in the degree of compatibility in the PP/CPA system.Practical significance. The regularities of increasing the stability of liquid microjets to disintegration in polymer blends filled with nanoparticles have been established, which will make it possible to determine the parameters of the processes of mixing and forming fibers and films, in which the microfibrillar structure arising during the flow of the melt will remain unchanged in the products.

Enhanced thermal stability and long-term mechanical durability at elevated temperatures of thermotropic liquid crystal polyester/glass fiber composites

We herein report the influences of glass fibers (GFs) on the thermal stability and long-term mechanical performance at elevated temperatures of thermotropic liquid crystal polyester (TLCP) composites for advanced applications in the industrial sectors of automotive, electric/electronics, aerospace, and construction. For this purpose, TLCP-based composites with 10–40 wt% GF loadings are fabricated by facile melt-mixing and injection-molding. The scanning electron microscopy (SEM) images and X-ray diffraction patterns demonstrate that the GFs are dispersed in the TLCP matrix with a microfibrillar structure. The specific interactions between TLCP and GFs in the composites are identified by ATR FT-IR spectroscopic analyses. The thermal degradation temperatures of the composites increase slightly with the increment of GFs with high thermal stability and heat capacity. The long-term mechanical durability of TLCP/GF composites at 150 °C is analyzed by obtaining time-dependent storage modulus master curves based on the stepped isothermal method and time–temperature superposition principle. The dynamic mechanical moduli, activation energy, and long-term mechanical durability are found to be highly enhanced for TLCP composites with higher GF loadings, which is owing to the efficient stress transfer from the TLCP matrix to reinforcing GF fillers via specific interactions at the composite interface.

Extruded-Calendered Sheets of Fully Recycled PP/Opaque PET Blends: Mechanical and Fracture Behaviour.

This work presents the experimental results of the mechanical and fracture behaviour of three polymeric blends prepared from two recycled plastics, namely polypropylene and opaque poly (ethylene terephthalate), where the second one acted as a reinforcement phase. The raw materials were two commercial degrees of recycled post-consumer waste, i.e., rPP and rPET-O. Sheets were manufactured by a semi-industrial extrusion-calendering process. The mechanical and fracture behaviours of manufactured sheets were analyzed via tensile tests and the essential work of fracture approach. SEM micrographics of cryofractured sheets revelated the development of in situ rPP/rPET-O microfibrillar composites when 30 wt.% of rPET-O was added. It was observed that the yield stress was not affected with the addition of rPET-O. However, the microfibrillar structure increased the Young’s modulus by more than a third compared with rPP, fulfilling the longitudinal value predicted by the additive rule of mixtures. Regarding the EWF analysis, the resistance to crack initiation was highly influenced by the resistance to its propagation owing to morphology-related instabilities during tearing. To analyze the initiation stage, a partition energy method was successfully applied by splitting the total work of fracture into two specific energetic contributions, namely initiation and propagation. The results revelated that the specific essential initiation-related work of fracture was mainly affected by rPET-O phase. Remarkably, its value was significantly improved by a factor of three with the microfibrillar structure of rPET-O phase. The results allowed the exploration of the potential ability of manufacturing in situ MFCs without a “precursor” morphology, providing an economical way to promote the recycling rate of PET-O, as this material is being discarded from current recycling processes.

A study elucidating the relation between cellulose dissolution and crystallinity after cellulase treatment at different doses

Cellulose is the most abundant renewable resource which has found a diverse range of applications. Cellulose dissolution is a significant property for manufacturing man-made cellulosic fiber through viscose process. Crystalline microfibrillar structure and relatively high ordered packing of polymeric chains contribute to recalcitrance and poor reactivity of cellulose. One of the most common methods to improve cellulose dissolution is cellulase treatment. Herein, cellulase treatment at different doses was studied to explore the correlation of cellulose dissolution with crystallinity. Pulp showed improvement in Fock reactivity and other properties related to viscose application. But contrary to previous studies, cellulose crystallinity as determined by XRD and FTIR did not correlate with Fock reactivity at a higher dose of cellulase. The results indicated some complex mechanism to be involved between the cellulose dissolution and crystallinity than a simple negative correlation. Cellulase treatment at 150 HCU/g resulted in the upgraded pulp suitable for viscose application.