Wide-angle X-ray Diffraction Patterns Research Articles

Analysis of the turbostratic structures in PAN-based carbon fibers with wide-angle x-ray diffraction

Carbon fiber (CF) is a versatile material renowned for its excellent mechanical, thermal, and electrical properties. Polyacrylonitrile (PAN)-based CFs dominate the market in part due to their high tensile strength, rendering them suitable for structural applications in a wide variety of applications ranging from sporting goods to aerospace. Over five decades of commercial development of PAN-based CF has resulted in a range of varieties with different tensile moduli and tensile strengths. The microstructures, nanostructures, and crystal structures of PAN-based CF all play pivotal roles in the macroscale properties of this material. In particular, the crystal structure and crystallite orientation in CF is closely related to the mechanical properties. The crystal structure of PAN-based CF generally consists of turbostratic carbon, a disordered form of graphite, the characteristics of which can be effectively characterized in a bulk format through wide-angle x-ray diffraction (WAXD). In this work, we employed a three-part approach to the analysis of WAXD patterns collected from four intermediate modulus PAN-based CFs. The approach incorporates a Scherrer analysis, a Debye analysis, and an orientational analysis to provide precise estimates of crystallite sizes, crystallite distributions, and crystallite orientations with the fiber axis. The results presented here suggest that intermediate modulus PAN-based CF mostly consists of small turbostratic crystallites (<4 nm), with larger crystallites having increased orientation with the fiber axis. The results here imply the presence of curvature and/or wrinkling of the turbostratic layers within the CF structure.

Studies of the Physical Structure of Cured Epoxy Resin Composite Modified with Silicon-Containing Additives

Abstract The possibility of regulating the structure and reducing its defectiveness opens great possibilities for controlling the properties of epoxy composite materials. This article reports the results of investigation by X-ray scattering and nuclear magnetic resonance methods and the microstructural changes that occur when silicon-containing additives such as polydimethyl siloxane (PDMS-5) and pyrogenic silica (HDK) are introduced into epoxy resin ED-20. The mechanism of formation of the structure of epoxy binder ED-20 with L-20 curing agent in the presence of complex additives is found. The modifying additive (PDMS-5 + HDK) is located in the epoxy binder because of the chemical interaction of functional polar groups and the developed surface. The additives increase the mobility of the reaction mixture and also facilitate and regulate the spatial orientation of macromolecules during polymerization. This contributes to the formation of a more regular and less defective spatial structure. The epoxy binder is a heterogeneous two-component system, one of which corresponds to a pseudo-crystalline region in which the movement of molecules is suppressed, and the second is found at lower volume fractions and is amorphous. The only maximum in the wide-angle X-ray diffraction pattern of the binder without additives is attributable to the distribution of molecular chains in the para-crystalline lattice. The addition of the HDK additive leads to ordering of the supramolecular structure, in which linear clusters consisting of 5–7 spheres appear. The average size of the spheres is from 8 to 26 nm. The addition of additives in the samples leads to the formation of a more regular and less defective spatial structure because of the interaction of functional polar groups and the surface, which regulate the spatial orientation of macromolecules during polymerization.

Atomistically informed hierarchical modeling for revisiting the constituent structures from heredity and nano-micro mechanics of sheath-core carbon fiber.

To better understand the heterogeneous anisotropic nanocomposite features and provide reliable underlying constitutive parameters of carbon fiber for continuum-level simulations, hierarchical modeling approaches combining quantum chemistry, molecular dynamics, numerical and analytical micromechanics are employed for studying the structure-performance relationships of the precursor-inherited sheath-core carbon fiber layers. A robust debonding force field is derived from energy matching protocols, including bond dissociation enthalpy calculations and rigid-constraint potential energy surface scan. Logistic long range bond stretching curves with exponential parameters and shifted force vdW curves are designed to diminish energy perturbations. The pseudo-crystalline microstructure is proposed and validated using virtual wide angle X-ray diffraction patterns and bond-orientational order parameters. The distribution or alignment features of the nanocomposite microstructures are collected from quantum chemical topology analysis and normal vector extractions. Non-equilibrium tensile loading simulation predicts the decomposed strain energy contributions, principal-axis modulus, strength limit, localized stress, and fracture morphologies of the model. Finally, an atomistically-informed stiffness prediction model combining numerical homogenization and analytical self-consistent Eshelby-Mori-Tanaka-type effective mean field micromechanics theory is proposed, giving a successful estimation of the overall stiffness matrix of the sheath-core carbon fiber system. The hierarchical models in combination with the carbonization reaction template will help in providing efficient and feasible schemes for the synergistic process-performance control of distinct types of carbon fiber.

Influence of compatibility in the EVA/starch/organoclay biodegradable nanocomposite on thermal properties and flame self-extinguishing behavior

ABSTRACT Thermal and flammability properties of ethylene vinyl acetate/starch/organoclay (EVA/S/C20A) nanocomposites are shown in this work. Wide-angle X-ray diffraction (WAXD) patterns and micrographs obtained by field emission scanning electron microscopy (FE-SEM) show the formation of nanostructured systems. The organoclay layers were preferably intercalated-exfoliated with the EVA polymer. Even so, the vinyl acetate group in EVA interacted with both the C20A clay and the starch macromolecules, achieving compatibility between the three components. The intercalated layers of clay provided protection against thermal degradation of the EVA. However, based on the kinetic study, the Ea of the nanocomposite degradation was lower than that of pure EVA. The flammability tests demonstrated the absence of dripping during burning and the self-extinguishing capacity of the flame (HB in the UL-94 test) in the EVA/C20A and EVA/S/C20A nanocomposites. The results are related to the nanointercalation of the clay and the compatibility between the three components with different properties. Thus, the flame self-extinguishing potential of ternary nanocomposites, previously studied as biodegradable, is demonstrated.

Photocatalytic Systems Based on ZnO Produced by Supercritical Antisolvent for Ceftriaxone Degradation

Emerging contaminants are a significant issue in the environment. Photocatalysis is proposed as a solution for the degradation of pollutants contained in wastewater. In this work, ZnO-based photocatalysts have been produced and tested for the photocatalytic degradation of an antibiotic; specifically, ceftriaxone has been used as a model contaminant. Moreover, there is particular interest in combining small-size ZnO particles and β-cyclodextrin (β-CD), creating a hybrid photocatalyst. Zinc acetate (ZnAc) (subsequently calcinated into ZnO) and β-CD particles with a mean diameter of 0.086 and 0.38 µm, respectively, were obtained using the supercritical antisolvent process (SAS). The produced photocatalysts include combinations of commercial and micronized particles of ZnO and β-CD and commercial and micronized ZnO. All the samples were characterized through UV–Vis diffuse reflectance spectroscopy (DRS), and the band gap values were calculated. Raman and FT-IR measurements confirmed the presence of ZnO and the existence of functional groups due to the β-cyclodextrin and ZnO combination in the hybrid photocatalysts. Wide-angle X-ray diffraction patterns proved that wurtzite is the main crystalline phase for all hybrid photocatalytic systems. In the photocatalytic degradation tests, it was observed that all the photocatalytic systems exhibited 100% removal efficiency within a few minutes. However, the commercial ZnO/micronized β-CD hybrid system is the photocatalyst that shows the best performance; in fact, when using this hybrid system, ceftriaxone was entirely degraded in 1 min.

Salicylic Acid Release from Syndiotactic Polystyrene Staple Fibers

Films and fibers of syndiotactic polystyrene (sPS), being amorphous or exhibiting nanoporous crystalline (NC) or dense crystalline phases, were loaded with salicylic acid (SA), a relevant non-volatile antimicrobial molecule. In the first section of the paper, sPS/SA co-crystalline (CC) δ form is characterized, mainly by wide angle X-ray diffraction (WAXD) patterns and polarized Fourier transform infrared (FTIR) spectra. The formation of sPS/SA δ CC phases allows the preparation of sPS fibers even with a high content of the antibacterial guest, which is also retained after repeated washing procedures at 65 °C. A preparation procedure starting from amorphous fibers is particularly appropriate because involves a direct formation of the CC δ form and a simultaneous axial orientation. The possibility of tuning drug amount and release kinetics, by simply selecting suitable crystalline phases of a commercially available polymer, makes sPS fibers possibly useful for many applications. In particular, fibers with δ CC forms, which retain SA molecules in their crystalline phases, could be useful for antimicrobial textiles and fabrics. Fibers with the dense γ form which easily release SA molecules, because they are only included in their amorphous phases, could be used for promising SA-based preparations for antibacterial purposes in food processing and preservation and public health. Finally, using a cell-based assay system and antibacterial tests, we investigated the cellular activity, toxicity and antimicrobial properties of amorphous, δ CC forms and dense γ form of sPS fibers loaded with different contents of SA.

Photocatalytic performance assessment of Fe-N co-doped TiO2/β-cyclodextrin hybrid systems prepared by supercritical antisolvent micronization for organic dyes removal

This work aims to demonstrate that micronized β-cyclodextrin (β-CD) improves the photocatalytic activity of Fe-N-TiO2. Fe-N-TiO2/β-CD hybrid systems were employed in the photocatalytic removal of Acid Orange7 (AO7) and Methylene Blue (MB). The supercritical antisolvent process (SAS) was used to micronize β-CD at different pressures. The chemical-physical properties of the hybrid photocatalysts were detected through various characterization methods. Wide angle X-ray diffraction patterns evidenced the anatase as the typical TiO2 crystalline phase. FT-IR spectra showed interactions between β-CD and Fe-N-TiO2. The activity of photocatalysts in the degradation of AO7 and MB dyes was analyzed under UV and visible light irradiation. Fe-N-TiO2/β-CD120 photocatalyst led to the total UV light-driven discoloration of the AO7 aqueous solution. Instead, the Fe-N-TiO2/β-CD120 system allowed for achieving an MB discoloration kinetic constant under visible light higher than the AO7 discoloration kinetic constant. Reuse cycle tests proved that the Fe-N-TiO2/β-CD120 sample is a stable photocatalytic material.

Synthesis and gas separation performance of Tröger's base-containing polyimides derived from 9,9-Bis(trifluoromethyl)-2,3,6,7-xanthenetetracarboxylic dianhydride

Two imide-containing diamine monomers were prepared using 9,9-bis(trifluoromethyl)-2,3,6,7-xanthenetetracarboxylic dianhydride (6FcDA) and 2,6-dimethylaniline or 2,6-diisopropylaniline as the starting materials. Two polyimides of intrinsic microporosity (PIM-PIs), i.e., 6FcDA-Me2NH2-TB and 6FcDA-iPr2NH2-TB, were then synthesized via TB polymerization of imide-containing diamines and dimethoxymethane in trifluoroacetic acid. The surface areas, fractional free volumes, and interchain distances of the PIM-PIs were in the range of 555–569 m2 g−1, 0.16–0.20, and 0.60–0.67 nm, respectively. These values followed the order of 6FcDA-Me2NH2-TB < 6FcDA-iPr2NH2-TB owing to the larger size of isopropyl substituents relative to methyl groups. Furthermore, 6FcDA-Me2NH2-TB exhibited obvious π-π stacking interactions as evidenced by the diffraction peaks at ∼ 26 ° in wide angle X-ray diffraction patterns. Consequently, 6FcDA-Me2NH2-TB showed higher perm-selectivity but lower gas permeability as compared to 6FcDA-iPr2NH2-TB. Particularly, both polymers had a CO2 permeability of > 2900 Barrer and a CO2/CH4 selectivity of > 10, located between the 1991 and 2008 Robeson’s upper bound for CO2/CH4 separation.

Polymerization of Allyltrimethylisilane and 4-Methyl-1-Pentene by Using Metallocene Catalysts.

Polymers of higher olefin, obtained by Ziegler-type polymerization, have been used in some critical fields, e.g., as the membrane for extracorporeal membrane oxygenation (ECMO), which plays an important role in the treatment of patients with severe COVID-19. The polymer obtained by a single-site catalyst, e.g., metallocene catalysts, demonstrated a higher performance. The homo- and co-polymerization of allyltrimethylisilane (ATMS) and 4-methyl-1-pentene (4M1P) were conducted using syndiospecific (cat 1) and isospecific (cat 2) metallocene catalysts. Cat 1 showed low conversions and provided a polymer with a higher molecular weight, while cat 2 behaved oppositely. 13C-NMR spectra certified the stereotacticity of the resultant polymer, and the resonance of the carbon atom of CH2 (αα') between the two tertiary carbon atoms of the ATMS and 4M1P units were observed. This could be the evidence of the formation of a true copolymer. The crystallization of the polymer was explored using a differential scanning calorimeter (DSC) and wide angle X-ray diffraction (WAXD). All homopolymers and some of the copolymers showed high melting temperatures and low melting enthalpies. The WAXD patterns of the syndiotactic polymer and isotactic homopolymer or the ATMS-rich copolymer were consistent with the reported literature, but the isotactic 4M1P-rich copolymer provided the crystal form I, which is unusual for a 4M1P polymer without any pretreatment.

Enhancing Mechanical Properties of Poly(p-phenylene sulfide) by Biaxial Deformation Using Cross-Rolling and Subsequent Annealing

The effect of thermal treatment on the mechanical performance of biaxially oriented poly(p-phenylene sulfide) by cold roll milling was studied. It was found that the ductility of the cross-rolled material could be further enhanced by annealing at temperatures above Tg and the yield strength could be enhanced by annealing at temperatures below Tg with a partial loss in ductility. Two-dimensional wide-angle X-ray diffraction patterns suggested a reduced crystallinity in the rolled material and showed that the crystal structure of the unrolled material could be partially recovered by annealing above Tg; however, scattering patterns adjacent to the crystalline reflections persisted with heat treatment. Modulated differential scanning calorimetry (MDSC) and broadband dielectric spectroscopy indicated that cross-rolling altered the kinetics of the cold-crystallization process. MDSC and dynamic mechanical analysis measured a reduction in Tg suggesting enhanced molecular mobility as an outcome of cross-rolling. After annealing at temperatures well beyond Tg, a large reduction in elongation to failure was observed, and the material could not cold draw. These results suggest that a two-stage process involving plastic deformation by roll milling followed by annealing treatment may be used to commercially produce high toughness and yield strength sheet products from commercially available resins.

Antimicrobial and Antiviral Activity of Silver-Containing Nanocomposites Formed by 3D Printing Technology

Silver nanoparticles have become the focus of numerous researchers to create efficient antimicrobial and antiviral agents due to their pronounced pharmacological effects, low toxicity to the human body and the environment, and high stability in extreme conditions. To create antimicrobial drugs with silver nanoparticles, matrices from polymers of both synthetic and natural origin are used. Biopolymer polylactide (PLA) is one of the most promising materials for 3D printing (additive production) due to its physicochemical and technological properties. The aim of the work was to study the antimicrobial and antiviral activity of silver-containing nanocomposites formed on the basis of PLA with the addition of chitosan or polyethyleneimine (PEI) by 3D printing technology. Methods. Peculiarities of the structural organization of silver-containing materials were investigated by the method of wide-angle radiography on an XRD-7000 diffractometer. The morphology of the samples was studied by transmission electron microscopy on a JEM-1230 instrument. Filament formation proceeded through melting PLA-AgPalm-PEI or PLA-AgPalm-chitosan films in an extruder at a temperature of T=160±1°С. Samples were formed from the obtained filaments using a 3D printer. Th e antimicrobial activity of silvercontaining nanocomposites was determined by the disk diffusion method against opportunistic pathogens S. aureus and E. coli. Cytotoxicity and antiviral activity were investigated using the MTT method and staining by gentian violet. Results. Analysis of wide-angle X-ray diffraction patterns of products formed by 3D printing technology at 160°C showed that PLA-Ag-PEI and PLA-Ag-chitosan materials contain metallic silver. Analysis of microphotographs of PLA-4%Ag-PEI and PLA-4%Ag-chitosan products formed by 3D printing technology showed that silver nanoparticles formed by adding chitosan as a reducing agent and stabilizer to the polymer matrix of PLA are much smaller than when using PEI. Silver-containing nanocomposite samples, such as filaments and products formed from PLA-4%Ag-PEI and PLA-4%Agchitosan films subjected to heat treatment and without heat treatment, show antimicrobial activity against test cultures of S. aureus and E. coli. It was found that nanocomposites based on PEI and chitosan do not show cytotoxic effects in MDCK and HEP-2 cultures. Nanocomposites of both types show a weak antiviral effect against adenovirus serotype 2; the reduction of infectious titer was 0.5 lgTCID50/mL. None of the studied nanocomposites showed antiviral action on the influenza virus model. Conclusions. The investigated silver-containing nanocomposites with a silver concentration of 4% by weight, formed by 3D printing technology from PLA-4%Ag-PEI and PLA-4%Ag-chitosan films, show antimicrobial activity against S. aureus and E. coli test cultures and antiviral activity on influenza A virus and human adenovirus and do not show a cytotoxic effect on cells. The obtained data allow us to state that the studied silver-containing nanocomposites are promising antimicrobial agents for use in various fields of medicine and the food industry.

Exploration of disentangled UHMWPE tape as a soft body armour material

Disentangled ultrahigh molecular weight polyethylene (UHMWPE) is a very promising material with extremely high tenacity and modulus. In this work, the effect of drawing on the morphological, physical, and mechanical properties of disentangled UHMWPE tapes was studied. The tapes were characterised by using the density gradient column method , wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), polarised optical microscopy and scanning electron microscopy (SEM). The density and crystallinity of tape improved after each stage of drawing. The unoriented crystalline structure of the as-prepared UHMWPE tape gradually transformed into an oriented crystalline structure on drawing as confirmed by WAXD patterns. As the draw ratio increased, concomitant increase in birefringence, and tensile properties were also noticed. The tape obtained after the final stage of drawing had tensile properties similar to that of gel spun UHMWPE fibres. Hence, this tape was used to make prototype of soft armour panel (SAP) that stopped all the bullets fired when subjected to ballistic test and yielded very low back face signature (BFS) justifying the potential of disentangled UHMWPE tape as a ballistic material.

Facile Preparation and Characterization of Silica Nanoparticles from South Africa Fly Ash Using a Sol–Gel Hydrothermal Method

Silica nanoparticles (SNPs) consist of several applications which include lightweight aggregates, energy storage, and drug delivery. Nevertheless, the silica reagents used in SNP synthesis are both costly and hazardous. As a result, it is critical to look for other sources of silica. For this research, a simple sol–gel hydrothermal approach is used to make SNPs from South African fly ash (SAFA). SAFA is classified as fly ash class F according to X-ray fluorescence (XRF) analysis. The wide-angle X-ray diffraction (XRD) pattern reveals the structural composition of SAFA and the amorphous phase of extracted SNPs, while Fourier transform infrared (FTIR) examination reveals the presence of silanol and siloxane groups. Basic SNPs were generally spherical with diameters of about 60 nm, according to scanning electron microscopy (SEM) and transition electron microscope (TEM) studies. The presence of SiO2 is confirmed by energy-dispersive X-ray spectroscopy (EDX) spectrum analysis. Particle size assessment indicates particle sizes ranging from 48 nm to 87 nm in diameter, with a mean diameter of 67 nm. The application of SNPs in wastewater treatment demonstrated that they can be used to remove Cd2+ from an aqueous solution. This research offers new ideas for using South African fly ash in SNP manufacturing.

Linear hydrogen bonded aggregates of carboxylic acids in crystalline channels of syndiotactic polystyrene

Sorption of long aliphatic carboxylic acids (lauric with 12 C atoms and stearic with 18 C atoms) and of an aliphatic dicarboxylic acid (adipic), by amorphous and nanoporous-crystalline δ-form and ε-form films of syndiotactic polystyrene (sPS), is reported. Fourier Transform Infrared (FTIR), Polarized FTIR and Wide Angle X-ray diffraction (WAXD) patterns show that the empty crystalline channels of the ε form are able to host long carboxylic acids as well as dicarboxylic acids. These acids are instead absorbed much more slowly and only from the amorphous phase for δ form sPS films, which exhibit crystalline cavities rather than crystalline channels. This selective and fast uptake of carboxylic acids in the crystalline channels of the sPS ε form is due the formation of hydrogen bonded linear dimers and linear polymers, for monocarboxylic and dicarboxylic acid guests, respectively.

Keratin Modified and Functionalized as a Reinforcement and Nucleation Agent of β-Polypropylene Composites

ABSTRACT A new green β nucleating agent has been obtained from industrial waste. This way, pimelic acid (PA) was chemically supported on treated keratin fibers to promote the β polymorph into a polypropylene matrix using several percentages of reinforcement (0.5, 1.0, and 5.0% w/w). IR spectra suggest a successful functionalization showing the presence of a new band at 1571 cm−1, indicating a bond between PA and the keratin surface. According to the scanning electron spectroscopy, the nucleating agent was homogeneously distributed on the keratin surface. Wide angle X-ray diffraction (WAXD) patterns and differential scanning calorimetry (DSC) curves demonstrate that the functionalized keratin fibers were able to promote a high percentage of β-crystal into the polypropylene matrix (79% and 60%, respectively). The thermomechanical properties were characterized by dynamic mechanical analysis (DMA). At −30°C, the new reinforcement provides an important increase of 25% in the storage modulus compared with the raw polypropylene. The new reinforcement seems to strongly influence the mobility of the amorphous phase, shifting the Tg to higher temperatures.

Structural evolution and related physical properties of machine direction oriented poly(butylene succinate-co-adipate) films

This study sheds light on the microstructural change of uniaxially oriented poly(butylene succinate-co-adipate) (PBSA) copolymer, and the consequent gas permeabilities, as well as tensile and optical properties. Uniaxial stretching at 62 °C takes place by means of a machine direction orientation (MDO) with varied draw ratios and annealing near the melting temperature. The PBSA precursor sheet favorably melt-crystallizes in the form of α-PBS crystals with isotropic in-plane orientation. MDO-PBSA films with and without annealing exhibit preferential orientation of the α-PBS crystal parallel to the stretching direction (MD), with an increased degree of crystallinity according to the increased draw ratio and applied annealing. This was evident from two-dimensional wide-angle X-ray diffraction patterns and X-ray diffraction profiles. Additionally, MDO stretching above the crystallization temperature simultaneously induces rigid amorphous fraction, in particular, by a high draw ratio (5 × ) and chain relaxation during annealing near the melting temperature. From the determined Herman's orientation function, the c-axis of the α-PBS crystal is parallel to the MD, thereby resulting in decreased diffusion path tortuosity. Consequently, oxygen and water vapor permeation are promoted. Furthermore, Young's modulus and tensile strength of MDO-PBSA films drastically increase with high ductility, and are approximately two and four times higher than those of non-oriented PBSA, respectively. MDO-PBSA films exhibit high clarities above 94% while yielding low haze values.

In-Situ X-Ray Analyses of Structural Change During Drawing and Shrinking of Linear Low-Density Polyethylene Film

Structural changes during the drawing and shrinking of linear low-density polyethylene (LLDPE) film are analyzed through in-situ X-ray measurements. A synchrotron radiation source enables simultaneous analyses combining small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD). During drawing, the original unoriented SAXS and WAXD patterns transformed into line and spot patterns, indicating the orientation of both lamellar stacking and the molecular axis along the drawing direction. During the subsequent shrinking these patterns are retained, suggesting the tilted lamellar and molecular chains. A possible model for structural changes indicates that tie molecules between lamellae effectively transmit drawing and shrinking stresses, which contributes to desirable actuation properties.

Alkali-activation of cellulose nanofibrils to facilitate surface chemical modification under aqueous conditions

In this study, we developed a surface-activation technique for cellulose nanofibrils (CNFs) using mild-alkali and aqueous conditions. CNFs were initially processed using the aqueous counter collision (ACC) method to produce Janus-type amphiphilic CNFs with both hydrophilic and hydrophobic faces on the surface of a single nanofibril (ACC-CNF). Selective functionalization of the hydroxy groups on the hydrophilic faces creates an opportunity to develop novel nano-building blocks that introduce heterogeneous and tailored surface characteristics into the design of nanomaterials. In this study, alkaline conditions were used to activate the hydroxy groups on the surface of ACC-CNFs as a pre-treatment for the partial crystalline transformation from cellulose I to cellulose II. We found that alkali treatment with sodium hydroxide (NaOH) solutions (concentration range 1–7 wt%) did not fully transform the structure of ACC-CNFs into cellulose II, nor change the morphology of nanofibrils, as seen from their wide-angle X-ray diffraction patterns and atomic force microscopy images. We also found that the hydroxy groups at the surface region of the ACC-CNFs were sufficiently reactive under the moderate alkali and aqueous conditions to undergo subsequent carboxymethylation. Therefore, alkali treatment of ACC-CNFs with a 1–7 wt% NaOH solution rendered the surface of the ACC-CNFs as sufficiently reactive for chemical modification without morphological changes. This simple method for surface activation of CNFs can be useful in the development of future sustainable and novel materials for a variety of applications.

Aromatic Polyesters Containing Ether and a Kinked Aromatic Amide Structure in the Main Chain: Synthesis and Characterisation

A novel bisphenol containing preformed multiple ether and amide linkages, N, N′-Bis (4-hydroxyphenoxyphenylene) isophthalamide (IPCD), was prepared and analysed by spectroscopic methods. New aromatic polyesters were prepared by polycondensation of IPCD with 1, 3-benzene diacidchloride and/or 1, 4-benzene diacidchloride. These obtained polyesters were structurally analysed by infra-red spectroscopy, measurements of inherent viscosity, wide-angle X-ray diffraction patterns, and thermal techniques such as differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and solubility tests in organic solvents. The synthesised polyesters had high molecular weights, as indicated by their inherent viscosities from 0.67 to 0.78 dL/g in N-methyl-2-pyrrolidone. The incorporation of ether and kinked aromatic amide moieties in the main polyester chains greatly affected the properties of these aromatic polyesters. The prepared polyesters readily dissolved in amide-type polar aprotic solvents and pyridine, indicating their solution processability. The DSC curves above the polyesters showed glass transition temperatures of 194 to 269 °C. TGA indicated that these newly obtained polyesters were stable up to 301 °C and retained a 39 to 48% weight at 900 °C. W-XRD analyses showed that the newly synthesised polyesters were amorphous, which is reflected in their solubility behaviour.

Morphological, crystallinity and thermal stability characterization of poly(3-hydroxybutyrate-Co-3-hydroxyhexanoate)/zinc oxide nanoparticles bionanocomposites: Effect of filler content

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx)/ZnO-NP nanoparticles bionanocomposites were elaborated by melt compounding in a twin-screw extruder at content ratio of 1.5, 3 and 6 wt.%. Morphology, crystallinity and thermal stability of the PHBHHx-based bionanocomposite samples were investigated by scanning electron microscopy (SEM), wide angle X-ray Diffraction (WAXD) and thermogravimetric analysis (TGA) aiming at evaluating the structure-properties relationships with respect to filler content and to neat PHBHHx. Morphological observations by SEM of the fractured surface of the bionanocomposite samples showed that ZnO-NP was randomly dispersed in PHBHHx matrix, with however a noticeable presence of filler aggregates at 6 wt.%. WAXD patterns displayed an increase in crystallinity of PHBHHx bionanocomposites with increasing ZnO-NP content, whereas TGA data indicated a decrease in thermal stability in comparison with the neat polymer. This result showed that the addition of ZnO-NP promoted the thermal degradation of PHBHHx through a random chain scission mechanism. Moreover, it was found that beyond 3 wt.% of filler content, no significant change was observed in the properties of PHBHHx/ZnO-NP bionanocomposites. The study highlighted the potential use of ZnO-NP at low content, as reinforcement in PHBHHx without necessarily carrying out any filler surface treatment nor solvent casting process.