Polymers

This research focused on the development of biomaterials based on cassava starch and corn starch and on the effect of the incorporation of polycaprolactone (PCL) on the thermal and thermomechanical properties of the blends. The results indicated partial compatibility in the blends, especially with cassava starch at a content of 20 wt% as reflected by the maintenance of tensile strength and elongation. In addition, the changes in the crystal quality of PCL and the displacement of the absorption bands of the carbonyl groups of PCL in the infrared (989–1000 cm⁻¹), attributed to the formation of hydrogen bonds between these groups and the hydroxyl groups of starches, were also associated with compatibility. It was observed that the crystallinity of PLC in the presence of cassava and corn starch was 38% and 62%, respectively; a crystallinity greater than that of PCL was related to an improved nucleation at the interface. Based on these properties, the blends are expected to be functional for the manufacture of short-term use products by conventional thermoplastic processing methods. Full article

Biocompatible smart interfaces play a crucial role in biomedical or tissue engineering applications, where their ability to actively change their conformation or physico-chemical properties permits finely tuning their surface attributes. Polyelectrolytes, such as acrylic acid, are a particular type of smart polymers that present pH responsiveness. This work aims to fabricate stable hydrogel films with reversible pH responsiveness that could spontaneously form wrinkled surface patterns. For this purpose, the photosensitive reaction mixtures were deposited via spin-coating over functionalized glasses. Following vacuum, UV, or either plasma treatments, it is possible to spontaneously form wrinkles, which could increase cell adherence. The pH responsiveness of the material was evaluated, observing an abrupt variation in the film thickness as a function of the environmental pH. Moreover, the presence of the carboxylic acid functional groups at the interface was evidenced by analyzing the adsorption/desorption capacity using methylene blue as a cationic dye model. The results demonstrated that increasing the acrylic acid in the microwrinkled hydrogel effectively improved the adsorption and release capacity and the ability of the carboxylic groups to establish ionic interactions with methylene blue. Finally, the role of the acrylic acid groups and the surface topography (smooth or wrinkled) on the final antibacterial properties were investigated, demonstrating their efficacy against both gram-positive and gram-negative bacteria model strains (E. coli and S. Aureus). According to our findings, microwrinkled hydrogels presented excellent antibacterial properties improving the results obtained for planar (smooth) hydrogels. Full article

Mixing soil with waste tire rubber granules or fibres is a practical and promising solution to the problem of global scrap tire pollution. Before successful applications, the mechanical behaviour of the soil–rubber mixture must be thoroughly investigated. Comprehensive laboratory studies (compaction, permeability, oedometer and triaxial tests) were conducted on the completely decomposed granite (CDG)–rubber mixtures, considering the effects of rubber type (rubber granules GR1 and rubber fibre FR2) and rubber content (0–30%). Results show that, for the CDG–rubber mixture, as the rubber content increases, the compaction curves become more rubber-like with less obvious optimum moisture content. The effect on permeability becomes clearer only when the rubber content is greater than 30%. The shape effect of rubber particles in compression is minimal. In triaxial shearing, the inclusion of rubber particles tends to reduce the stiffness of the mixtures. After adding GR1, the peak stress decreases with the increasing rubber content due to the participation of soft rubber particles in the force transmission, while the FR2 results in higher peak stress especially at higher rubber contents because of the reinforcement effect. For the CDG–GR1 mixture, the friction angle at the critical state (φ’_cs) decreases with the increasing rubber content, mainly due to the lower inter-particle friction of the CDG–rubber interface compared to the pure CDG interface, while for the CDG–FR2 mixture, the φ’_cs increases with the increasing rubber content, again mainly due to the reinforcement effect. Full article

Wood–plastic composites (WPC) with good mechanical and physical properties are desirable products for manufacturers and customers, and interfacial bond strength is one of the most critical factors affecting WPC performance. To verify that a higher interfacial bond strength between wood and thermoplastics improves WPC performance, wood veneer–thermoplastic composites (VPC) and oriented strand–thermoplastic composites (OSPC) were fabricated using hot pressing. The effects of the coupling agent (KH550 or MDI) and the thermoplastic (LDPE, HDPE, PP, or PVC) on the interfacial bond strength of VPC, and the mechanical and physical properties of OSPC, were investigated. The results showed that coupling agents KH550 and MDI improved the interfacial bond strength between wood and thermoplastics under dry conditions. MDI was better than KH550 at improving the interfacial bond strength and the mechanical properties of OSPC. Better interfacial bonding between plastic and wood improved the OSPC performance. The OSPC fabricated using PVC film as the thermoplastic and MDI as the coupling agent displayed the highest mechanical properties, with a modulus of rupture of 91.9 MPa, a modulus of elasticity of 10.9 GPa, and a thickness swelling of 2.4%. PVC and MDI are recommended to fabricate WPCs with desirable performance for general applications. Full article

Polydimethylsiloxane (PDMS) is one of the most promising elastomers due its remarkable proprieties such as good thermal stability, biocompatibility, corrosion resistance, flexibility, low cost, ease of use, chemically inertia, hyperplastic characteristics, and gas permeability. Thus, it can be used in areas such as microfluidic systems, biomedical devices, electronic components, membranes for filtering and pervaporation, sensors, and coatings. Although pure PDMS has low mechanical properties, such as low modulus of elasticity and strength, it can be improved by mixing the PDMS with other polymers and by adding particles or reinforcements. Fiber-reinforced PDMS has proved to be a good alternative to manufacturing flexible displays, batteries, wearable devices, tactile sensors, and energy harvesting systems. PDMS and particulates are often used in the separation of liquids from wastewater by means of porosity followed by hydrophobicity. Waxes such as beeswax and paraffin have proved to be materials capable of improving properties such as the hydrophobic, corrosion-resistant, thermal, and optical properties of PDMS. Finally, when blended with polymers such as poly (vinyl chloride-co-vinyl acetate), PDMS becomes a highly efficient alternative for membrane separation applications. However, to the best of our knowledge there are few works dedicated to the review and comparison of different PDMS composites. Hence, this review will be focused on PDMS composites, their respective applications, and properties. Generally, the combination of elastomer with fibers, particles, waxes, polymers, and others it will be discussed, with the aim of producing a review that demonstrates the wide applications of this material and how tailored characteristics can be reached for custom applications. Full article

Hydrogels are spatially organized hydrophilic polymeric systems that exhibit unique features in hydrated conditions. Among the hydrogel family, composite hydrogels are a special class that are defined as filler-containing systems with some tailor-made properties. The composite hydrogel family includes magnetic-nanoparticle-integrated hydrogels. Magnetic hydrogels (MHGs) show magneto-responsiveness, which is observed when they are placed in a magnetic field (static or oscillating). Because of their tunable porosity and internal morphology they can be used in several biomedical applications, especially diffusion-related smart devices. External stimuli may influence physical and chemical changes in these hydrogels, particularly in terms of volume and shape morphing. One of the most significant external stimuli for hydrogels is a magnetic field. This review embraces a brief overview of the fabrication of MHGs and two of their usages in the biomedical area: drug delivery and hyperthermia-based anti-cancer activity. As for the saturation magnetization imposed on composite MHGs, they are easily heated in the presence of an alternating magnetic field and the temperature increment is dependent on the magnetic nanoparticle concentration and exposure time. Herein, we also discuss the mode of different therapies based on non-contact hyperthermia heating. Full article

Having the advantage of eco-friendly decomposition, bioplastics could be used to replace petroleum-based plastics. In particular, poly(3-hydroxybutyrate) (PHB) is one of the most commercialized bioplastics, however, necessitating the introduction of PHB-degrading bacteria for its effective disposal. In this study, Microbulbifer sp. SOL66 (94.18% 16S rRNA with similarity to Microbulbifer hydrolyticus) demonstrated the highest degradation activity among five newly screened Microbulbifer genus strains. Microbulbifer sp. SOL66 showed a rapid degradation yield, reaching 98% in 4 days, as monitored by laboratory scale, gas chromatography-mass spectrometry, scanning electron microscopy, gel permeation chromatography, and Fourier transform infrared spectroscopy. The PHB film was completely degraded within 7 days at 37 °C in the presence of 3% NaCl. When 1% xylose and 0.4% ammonium sulfate were added, the degradation activity increased by 17% and 24%, respectively. In addition, this strain showed biodegradability on pellets of poly(3-hydroxybutyrate-co-4-hydroxybutyrate), as confirmed by weight loss and physical property changes. We confirmed that Microbulbifer sp. SOL66 has a great ability to degrade PHB, and has rarely been reported to date. Full article

Organic–inorganic xerogel networks were synthesized from bacterial poly (3-hydroxybutyrate) (PHB) for potential biomedical applications. Since silane-based networks usually demonstrate increased biocompatibility and mechanical properties, siloxane groups have been added onto polyurethane (PU) architectures. In this work, a diol oligomer (oligoPHB-diol) was first prepared from bacterial poly(3-hydroxybutyrate) (PHB) with an environmentally friendly method. Then, hexamethylene diisocyanate or biobased dimeryl diisocyanate was used as diisocyanate to react with the short oligoPHB-diol for the synthesis of different NCO-terminated PU systems in a bulk process and without catalyst. Various PU systems containing increasing NCO/OH molar ratios were prepared. Siloxane precursors were then obtained after reaction of the NCO-terminated PUs with (3-aminopropyl)triethoxysilane, resulting in silane-terminated polymers. These structures were confirmed by different analytical techniques. Finally, four series of xerogels were prepared via a sol–gel process from the siloxane precursors, and their properties were evaluated depending on varying parameters such as the inorganic network crosslinking density. The final xerogels exhibited adequate properties in connection with biomedical applications such as a high in vitro degradation up to 15 wt% after 12 weeks. Full article

Dual transient networks were prepared by mixing highly charged long wormlike micelles of surfactants with polysaccharide chains of hydroxypropyl guar above the entanglement concentration for each of the components. The wormlike micelles were composed of two oppositely charged surfactants potassium oleate and n-octyltrimethylammonium bromide with a large excess of anionic surfactant. The system is macroscopically homogeneous over a wide range of polymer and surfactant concentrations, which is attributed to a stabilizing effect of surfactants counterions that try to occupy as much volume as possible in order to gain in translational entropy. At the same time, by small-angle neutron scattering (SANS) combined with ultrasmall-angle neutron scattering (USANS), a microphase separation with the formation of polymer-rich and surfactant-rich domains was detected. Rheological studies in the linear viscoelastic regime revealed a synergistic 180-fold enhancement of viscosity and 65-fold increase of the longest relaxation time in comparison with the individual components. This effect was attributed to the local increase in concentration of both components trying to avoid contact with each other, which makes the micelles longer and increases the number of intermicellar and interpolymer entanglements. The enhanced rheological properties of this novel system based on industrially important polymer hold great potential for applications in personal care products, oil recovery and many other fields. Full article

Novel stiff, tough, highly transparent and ultra-extensible self-assembled nanocomposite elastomers based on poly(2-methoxyethylacrylate) (polyMEA) were synthesized. The materials are physically crosslinked by small in-situ-formed silica nanospheres, sized 3–5 nm, which proved to be a very efficient macro-crosslinker in the self-assembled network architecture. Very high values of yield stress (2.3 MPa), tensile strength (3.0 MPa), and modulus (typically 10 MPa), were achieved in combination with ultra-extensibility: the stiffest sample was breaking at 1610% of elongation. Related nanocomposites doubly filled with nano-silica and clay nano-platelets were also prepared, which displayed interesting synergy effects of the fillers at some compositions. All the nanocomposites exhibit ‘plasto-elastic’ tensile behaviour in the ‘as prepared’ state: they display considerable energy absorption (and also ‘necking’ like plastics), but at the same time a large but not complete (50%) retraction of deformation. However, after the first large tensile deformation, the materials irreversibly switch to ‘real elastomeric’ tensile behaviour (with some creep). The initial ‘plasto-elastic’ stretching thus causes an internal rearrangement. The studied materials, which additionally are valuable due to their high transparency, could be of application interest as advanced structural materials in soft robotics, in implant technology, or in regenerative medicine. The presented study focuses on structure-property relationships, and on their effects on physical properties, especially on the complex tensile, elastic and viscoelastic behaviour of the polyMEA nanocomposites. Full article

Fused filament fabrication is a technology of additive manufacturing that uses molten thermoplastics for building parts. Due to the convenient shape of the raw material, a simple filament, the market offers a great variety of materials from simple to blends of compatible materials. However, finding a material with the desired properties can be difficult. Making it in-house or using a material manufacturer can be costly and time-consuming, especially when the optimum blend ratios are unknown or new design perspectives are tested. This paper presents an accessible method of producing core-shell filaments using material extrusion 3D printing. The printed filaments are characterised by a polycarbonate (PC) core and acryl butadiene styrene (ABS) shell with three material ratios. Their performance was investigated through printed samples. Additionally, the material mixing degree was studied by varying the extrusion temperature, nozzle feeding geometry, and layer thickness. The influence of all four factors was evaluated using a graphical representation of the main effects. The results showed that a core-shell filament can be processed using a 3D printer with a dual extrusion configuration and that the mechanical properties of the samples can be improved by varying the PC–ABS ratio. This research provides an accessible method for developing new hybrid filaments with a predesigned structure using a 3D printer. Full article

The development of edible films and coatings in the food packaging industry presents one of the modern strategies for protecting food products and ensuring their freshness and quality during their shelf lives. The application of microbial polysaccharides to the development of food package materials, as an alternative option to the commonly used plastic materials, is both economic and environmentally favorable. New edible films were developed using dextran from lactic acid bacterium Leuconostoc mesenteroides T3, and additionally plasticized by different concentrations of polyglycerol. The best tensile strength of the films was obtained using a formulation that contained 10 wt% of polyglycerol, which corresponded to a value of 4.6 MPa. The most flexible formulation, with elongation at break of 602%, was obtained with 30 wt% of polyglycerol. Water vapor permeability values of the films synthesized in this study were in the range of (3.45–8.81) ∗ 10⁻¹² g/m s Pa. Such low values indicated that they could be efficient in preventing fruit from drying out during storage. Thus, the film formulations were used to coat blueberries in order to assess their quality during a storage time of 21 days at 8 °C. The results showed that dextran/polyglycerol films could be efficient in extending the shelf life of blueberries, which was evidenced by lower weight loss and total sugar solids values, as well as a delay in titratable acidity, in comparison to the uncoated blueberries. Full article

Malva parviflora L. is an edible and medicinal herb containing mucilaginous cells in its leaves. Mucilage obtained from M. parviflora leaves (MLM) was extracted in distilled water (1:10 w/v) at 70 °C followed by precipitation with alcohol. Preliminary phytochemical tests were performed to assess the purity of the extracted mucilage. Results showed that the yield of mucilage was 7.50%, and it was free from starch, alkaloids, glycosides, saponins, steroids, lipids and heavy metals. MLM had 16.19% carbohydrates, 13.55% proteins and 4.76% amino acids, which indicate its high nutritional value. Physicochemical investigations showed that MLM is neutral and water-soluble, having 5.84% moisture content, 15.60% ash content, 12.33 swelling index, 2.57 g/g water-holding capacity and 2.03 g/g oil-binding capacity. The functional properties, including emulsion capacity, emulsion stability, foaming capacity and stability increased with increased concentrations. Micromeritic properties, such as bulk density, tapped density, Carr’s index, Hausner ratio, and angle of repose, were found to be 0.69 g/cm³, 0.84 g/cm³, 17.86%, 1.22 and 28.5, respectively. Scanning electron microscopy (SEM) showed that MLM is an amorphous powder possessing particles of varying size and shape; meanwhile, rheological studies revealed the pseudoplastic behavior of MLM. The thermal transition process of MLM revealed by a differential scanning calorimetry (DSC) thermogram, occurring at a reasonable enthalpy change (∆H), reflects its good thermal stability. The presence of functional groups characteristic of polysaccharides was ascertained by the infrared (IR) and gas chromatography/mass spectrometry (GC/MS) analyses. GC revealed the presence of five neutral monosaccharides; namely, galactose, rhamnose, arabinose, glucose and mannose, showing 51.09, 10.24, 8.90, 1.80 and 0.90 mg/g of MLM, respectively. Meanwhile, galacturonic acid is the only detected acidic monosaccharide, forming 15.06 mg/g of MLM. It showed noticeable antioxidant activity against the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical with an IC₅₀ value of 154.27 µg/mL. It also prevented oxidative damage to DNA caused by the Fenton reagent, as visualized in gel documentation system. The sun protection factor was found to be 10.93 ± 0.15 at 400 µg/mL. Thus, MLM can be used in food, cosmetic and pharmaceutical industry and as a therapeutic agent due to its unique properties. Full article

Moisture is detrimental to the performance of epoxy resin material for electrical equipment in long-term operation and insulation. Therefore, moisture absorption is one of the critical indicators for insulation of the material. However, some relevant test methods, e.g., the direct weighing method, are time-consuming, and it usually takes months to complete a test. For this, it is necessary to have some modification to save the test time. Firstly, the study analyzes the present prediction method (according to ISO 62:2008). Under the same accuracy, the time required is reduced from 104 days to 71 days. Subsequently, the Langmuir curve-fitting method for water absorption of epoxy resin is analyzed, and the initial values of diffusion coefficient, bonding coefficient, and de-bonding coefficient are determined based on the results of molecular simulation, relevant experiment, and literature review. With the optimized prediction model, it takes only 1.5 days (reduced by 98% as compared with the standard prediction method) to determine the moisture absorbability. Then, the factors influencing the prediction accuracy are discussed. The results have shown that the fluctuation of balance at the initial stage will affect the test precision significantly. Accordingly, this study proposes a quantitative characterization method for initial trace moisture based on the terahertz method, by which the trace moisture in epoxy resin is represented precisely through the established terahertz time-domain spectroscopy system. When this method is used to predict the moisture absorbability, the experimental time may be further shortened by 33% to 1 day. For the whole water absorption cycle curve, the error is less than 5%. Full article

Producing parts by 3D printing based on the material extrusion process determines the formation of air gaps within layers even at full infill density, while external pores can appear between adjacent layers making prints permeable. For the 3D-printed medical devices, this open porosity leads to the infiltration of disinfectant solutions and body fluids, which might pose safety issues. In this context, this research purpose is threefold. It investigates which 3D printing parameter settings are able to block or reduce permeation, and it experimentally analyzes if the disinfectants and the medical decontamination procedure degrade the mechanical properties of 3D-printed parts. Then, it studies acetone surface treatment as a solution to avoid disinfectants infiltration. The absorption tests results indicate the necessity of applying post-processing operations for the reusable 3D-printed medical devices as no manufacturing settings can ensure enough protection against fluid intake. However, some parameter settings were proven to enhance the sealing, in this sense the layer thickness being the most important factor. The experimental outcomes also show a decrease in the mechanical performance of 3D-printed ABS (acrylonitrile butadiene styrene) instruments treated by acetone cold vapors and then medical decontaminated (disinfected, cleaned, and sterilized by hydrogen peroxide gas plasma sterilization) in comparison to the control prints. These results should be acknowledged when designing and 3D printing medical instruments. Full article

We found the logical way to prove the existence of the mechanism that maintains the rates of biodegradation and regeneration of cervical spine cartilage. We demonstrate, that after we restore access to arterial blood flow through cervical vertebral arteries to rhomboid fossa it causes the prevalence of regeneration over biodegradation. This is in the frames of consideration of the human body as a dissipative structure. Then the recovery of the body should be considered as a reduction of the relative rates of decay below the regeneration ones. Then the recovery of cervical spine cartilage through redirecting of inner dissipative flow depends on the information about oxygen availability that is provided from oxygen detectors in the rhomboid fossa to the cerebellum. Our proposed approach explains already collected data, which satisfies all the scientific requirements. This allows us to draw conclusions that permit reconsidering the way of dealing with multiple chronic diseases. Full article

Ni_0.5Zn_0.5Fe₂O₄ nanofibers with an average diameter of 133.56 ± 12.73 nm were fabricated by electrospinning and calcination. According to our thermogravimetric—differential thermal analysis and X-ray diffraction results, the calcination temperature was 650 °C. The microstructure, crystal structure, and chemical composition of the nanofibers were observed using field-emission scanning electron, X-ray diffraction, and energy-dispersive X-ray spectroscopy. Commercial particle samples and samples containing 10 wt% and 20 wt% nanofibers were fabricated, and the electromagnetic properties were analyzed with a vector network analyzer and a 7.00 mm coaxial waveguide. Regardless of the nanofiber content, Ni_0.5Zn_0.5Fe₂O₄ was dominantly affected by the magnetic loss mechanism. Calculation of the return loss based on the transmission line theory confirmed that the electromagnetic wave return loss was improved up to −59.66 dB at 2.75 GHz as the nanofiber content increased. The absorber of mixed compositions with Ni_0.5Zn_0.5Fe₂O₄ nanofibers showed better microwave absorption performance. It will be able to enhance the performance of commercial electromagnetic wave absorbers of various types such as paints and panels. Full article

In this study, polycaprolactone (PCL)- and poly(acrylic acid) (PAA)-based electrospun nanofibers were prepared for the carriers of antimicrobials and designed composite nanofiber mats for chronic wound care. The PCL- and PAA-based electrospun nanofibers were prepared through in situ polymerization starting from PCL and acrylic acid (AA). Different amounts of AA were introduced to improve the hydrophilicity of the PCL electrospun nanofibers. A compatibilizer and a photoinitiator were then added to the electrospinning solution to form a grafted structure composed of PCL and PAA (PCL-g-PAA). The grafted PAA was mainly located on the surface of a PCL nanofiber. The optimization of the composition of PCL, AA, compatibilizer, and photoinitiator was studied, and the PCL-g-PAA electrospun nanofibers were characterized through scanning electron microscopy and ¹H-NMR spectroscopy. Results showed that the addition of AA to PCL improved the hydrophilicity of the electrospun PCL nanofibers, and a PCL/AA ratio of 80/20 presented the best composition and had smooth nanofiber morphology. Moreover, poly[2 -(tert-butylaminoethyl) methacrylate]-grafted graphene oxide nanosheets (GO-g-PTA) functioned as an antimicrobial agent and was used as filler for PCL-g-PAA nanofibers in the preparation of composite nanofiber mats, which exerted synergistic effects promoted by the antibacterial properties of GO-g-PTA and the hydrophilicity of PCL-g-PAA electrospun nanofibers. Thus, the composite nanofiber mats had antibacterial properties and absorbed body fluids in the wound healing process, thereby promoting cell proliferation. The biodegradation of the PCL-g-PAA electrospun nanofibers also demonstrated an encouraging result of three-fold weight reduction compared to the neat PCL nanofiber. Our findings may serve as guidelines for the fabrication of electrospun nanofiber composites that can be used mats for chronic wound care. Full article

Cigarette smoking is a popular habit that has negative health consequences for populations. In this study, we developed a gallic acid-containing, gelatin-based nonwoven mat with photodegradation and photoindication functions. This could react with sidestream cigarette smoke and simultaneously inhibit the activity of the microbe growth in the air. The results of a fluorescence emission spectrum evidenced this photoindication function. Neither the nicotine nor gallic acid showed a redshift emission spectrum. However, the emission spectrum of the nonwoven mat exhibited the redshift and increased in intensity after absorbing the sidestream cigarette smoke. In this spectral evidence, the natural polymer played a key role in the photoindication function’s display because it could dissolve the nicotine of the sidestream cigarette smoke and cause it to react with the gelatin structure. The high performance liquid chromatography–mass spectroscopy results indicated that the gallic acid and ultraviolet (UV) light enhanced the absorption of nicotine and nicotine-like derivatives, which were dissolved by the Tween 80 of nonwoven mat. The liquid paraffin and Tween 80 could oxidize, dehydrogenate, and demethylate the nicotine that was absorbed by the gelatin nonwoven mat. In conclusion, the nonwoven mat developed in this study provided the functions to filter the nicotine of sidestream smoke and activate the photoindication property by absorbing 365-nm UV light. Full article