Denisa Nicoleta Airinei, Cristina Modrogan, Oanamari Daniela Orbuleț
et al.
Non-degradable plastic bags are a major contributor to marine and soil pollution. They represent a significant percentage of the generated solid waste and can last for hundreds of years in the environment. The aim of the present study was to find alternatives to conventional non-degradable plastic bags by obtaining biodegradable and compostable bags starting from simple materials like starch, poly(lactic acid) (PLA), and glycerol. Increasing the strength and hardness of the polymer was achieved by adding a mineral (talcum). The preliminary studies indicated that two compositions are suitable for advanced testing to produce the initial granular material. These materials were tested for the determination of melt flow index (MFI), Fourier Transform Infrared Spectroscopy (FTIR), and the polymers response to heating (thermogravimetric analysis, TGA and differential scanning calorimetry, DSC). The polymer biodegradability was evaluated by burial in two types of soil. The obtained results were compared with the same set of experiments performed on conventional polyethylene bags. After three months in the soil, only the materials synthesized in this study show signs of accentuated degradation while polyethylene bags are still intact. The surface morphology was explored by scanning electron microscopy (SEM). The results indicated that the biodegradable thermoplastic material meets the requirements of the European standard EN13432/2002 regarding compostable and biodegradable packaging.
This study proposes an advanced analytical method for evaluating the morphology and chemical states of polymer alloys using low-loss spectral imaging in scanning transmission electron microscopy. This approach involves extracting spectral features through Gaussian fitting, as established in our previous study, followed by statistical cluster analysis of 12 extracted spectral features. This technique enables the assessment of component distribution and the detection of reaction layers within polymer alloys. Furthermore, by comparing these feature plots with those of the standard samples, significant spectral shifts were observed, indicating chemical modifications such as conjugated double bond formation and crosslinking. In particular, thermoplastic polyurethane elastomer and Styrene-ethylene butylene-styrene block copolymer exhibited increases in the relative peak fractions of conjugated double bonds (NG2) and unsaturated C=C bonds (NG3), along with a red shift in the former peak position (μG2), consistent with known thermal degradation mechanisms. In contrast, low-density polyethylene showed a blue shift of μG2 with minimal change in NG2, suggesting limited conjugated bond formation. A supervised classification model using these features achieved over 99 % accuracy using support vector machine and random forest algorithms. Permutation importance analysis identified μG2, NG5 (G5: bulk plasmon), and NG2 as the most influential features for classification, underscoring the role of π–π∗ transitions and bulk plasmon features in polymer identification. This method addresses the common limitations of conventional spectral decomposition techniques concerning ambiguity in determining the number of components. This approach offers insights into the chemical state changes induced by alloying, serving as a powerful tool for nanoscale analysis.
Great Iruoghene Edo, Alice Njolke Mafe, Nawar. F. Razooqi
et al.
This review paper analyzes recent advancements in bio-polymer coatings for probiotic microencapsulation, with a particular emphasis on chitosan and its synergistic combinations with other materials. Probiotic microencapsulation is essential for protecting probiotics from environmental stresses, enhancing their stability, and ensuring effective delivery to the gut. The review begins with an overview of probiotic microencapsulation, highlighting its significance in safeguarding probiotics through processing, storage, and gastrointestinal transit. Advances in chitosan-based encapsulation are explored, including the integration of chitosan with other bio-polymers such as alginate, gelatin, and pectin, as well as the application of nanotechnology and innovative encapsulation techniques like spray drying and layer-by-layer assembly. Detailed mechanistic insights are integrated, illustrating how chitosan influences gut microbiota by promoting beneficial bacteria and suppressing pathogens, thus enhancing its role as a prebiotic or synbiotic. Furthermore, the review delves into chitosan’s immunomodulatory effects, particularly in the context of inflammatory bowel disease (IBD) and autoimmune diseases, describing the immune signaling pathways influenced by chitosan and linking gut microbiota changes to improvements in systemic immunity. Recent clinical trials and human studies assessing the efficacy of chitosan-coated probiotics are presented, alongside a discussion of practical applications and a comparison of in vitro and in vivo findings to highlight real-world relevance. The sustainability of chitosan sources and their environmental impact are addressed, along with the novel concept of chitosan’s role in the gut-brain axis. Finally, the review emphasizes future research needs, including the development of personalized probiotic therapies and the exploration of novel bio-polymers and encapsulation techniques.
The 10 kV switchgear is widely utilized in power systems due to its convenience and reliability. However, in high-humidity environments, switchgear is susceptible to condensation, which can severely damage its internal insulation components. To address this issue, this study modifies epoxy resin (EP) by incorporating nano-MgO to improve its hydrophobic properties. Initially, molecular dynamics simulations were conducted to determine the optimal doping ratio of nano-MgO by evaluating modified materials with varying concentrations. MgO/EP composites were then synthesized with nano-MgO doping levels of 1, 5, 10, and 15 wt%, and their hydrophobic and electrothermal properties were assessed. Following this, a thermal aging test was performed to evaluate the long-term performance of the composites. The findings demonstrate that the addition of nano-MgO enhances the hydrophobicity, thermal conductivity, and insulating properties of the EP. Specifically, as the concentration of nano-MgO increases, both the contact angle and thermal conductivity of the composites improve, while the volume resistivity first increases and then decreases with higher nano-MgO content. Nonetheless, all composites consistently outperform pure EP. Throughout each aging stage, the contact angle, thermal conductivity, and volume resistivity of the nano-MgO-modified EP remain superior to those of the unmodified EP.
Enhancing the hydrophobicity of chitosan through acylation enables the encapsulation of water-insoluble drugs within the polymeric carrier cores. In this study, hydrophobically modified chitosan was synthesized by reacting low-molecular-weight chitosan with acyl chloride (C18–C24) using an agitation method under mild conditions. The structure of acylated chitosan was analyzed using FTIR and 1H-NMR spectroscopy. The degree of substitution (DS) varied between 56% and 69% for different long-chain N-acylated chitosan, with N-stearoyl chitosan (ChC18) exhibiting the highest DS. The incorporation of capecitabine (CAP) into extended acylated chitosan increased particle size and decreased zeta potential. N-lignoceroyl chitosan (ChC24) exhibited the highest zeta potential value of −27 mV for 0.2 mg of CAP, indicating that the most extended acyl group was the most stable in the suspension. Transmission electron microscope images revealed that all acylated chitosan particles were spherical, with sizes ranging from 100 to 200 nm, and existed as stand-alone entities, indicating excellent stability in suspension. The loading of CAP increased in particle size but did not alter particle shape, except for ChC24, which exhibited agglomeration. SEM images revealed that the individual arrangement of particles in CAP-ChC18 made it more stable than other acylated chitosan. In contrast, the formation of clusters in CAP-ChC24 can be attributed to strong hydrophobic interactions. X-ray photoelectron spectroscopy results show that there is no nitrogen atom in ChC18, which means that the acyl group is oriented inward and bound to the stearoyl group via van der Waals forces. At different drug weight-to-carrier ratios, the encapsulation efficiency (EE) of CAP with varying acyl group lengths ranged from 85% to 97%. The drug loading (DL) capacity and EE increased as the amount of drug in the carrier increased. However, the length of the acyl group did not significantly affect DL and EE, even when the carrier-to-drug ratio was consistently maintained. Sustained release was observed in CAP-loaded ChC24, indicating a significant influence of the extended chain on chitosan. Consequently, extended N-acylated chitosan possesses enormous potential as a drug delivery system for CAP.
Hadi Muhamad Al-Haqqem Abdul, Rahim Nor Azura Abdul, Leng Teh Pei
et al.
Homogenization of pigment is the key to coloring a plastic product evenly. In this article, the tensile properties of recovered carbon black merge with low molecular weight lubricants and other compounding ingredients in the form of pigment masterbatch (PM) added in a recycled low-density polyethylene (rLDPE) resin were evaluated. The prepared masterbatch with the varying amount and types of processing aids (A and B) was first compounded using the heated two-roll mill. Subsequently, the manually mixed masterbatch in rLDPE was put through an injection molding machine for the shaping process to produce an rLDPE pigment masterbatch composite (PMC). The tensile test was performed on the samples to evaluate the mechanical properties of the PMC. Meanwhile, the melt flow index test was executed to justify the composite flow characteristics. Fourier-transform infrared spectroscopy analysis and scanning electron microscopy were also carried out to analyze the PM and PMC chemical properties and their constructed surface morphology. Besides, X-ray diffraction analysis was performed to determine the changes in degree of crystallinity before and after the water absorption test. The addition of PM in rLDPE has slightly increased the rLDPE matrix tensile properties. While, the usage of more processing aid B in the PMC has turned out to secure better tensile properties compared to the addition of higher amount of processing aid A in the PMC. Interestingly, the tensile properties of all composites after the water absorption test were enhanced, suggesting that a stronger bond was formed during the immersion period.
Abbas Mohammadi, Zahra Shahsanaei Goneirani, Alireza Fatahi
Today, the specialists’ attention on polyurethanes is increasing day by day due to easy synthesis, available raw materials, favorable mechanical properties, biocompatibility, and the possibility of providing different products, such as water-based polyurethanes, foams, hydrogels and glues. Chitosan is a natural polymer that is extracted from the deacetylation of chitin and contains glucosamine and N-acetyl glucosamine units. This non-toxic natural polymer has very useful properties such as antimicrobial activity, biocompatibility, biodegradability, and tissue repair and regeneration effects. One of the weaknesses of chitosan is its poor solubility and processability due to its strong intra- and intermolecular hydrogen bonding. Therefore, chitosan has been used mainly in modified form or in combination with other polymers in various applications. The combination of synthetic polymers with natural polymers is of particular importance because natural polymers such as chitosan can show some properties such as biocompatibility, biodegradability, low toxicity, high cell viability, and internal tissue growth; while the synthetic polymers have other characteristics such as favorable processing, mechanical and physical properties, and appropriate chemical and thermal stability. Recently, chitosan has been used in combination with polyurethanes to improve its mechanical properties, thermal stability, biodegradability, antimicrobial properties and biological activity. During these studies, products in various forms such as composite, elastomer, fiber, foam, scaffold, and hydrogel have been prepared for different applications. In this review, polyurethanes containing chitosan and their synthesis methods for various applications are discussed. The products prepared in these studies have been suggested for various applications such as antibacterial coating, wound dressing, tissue engineering scaffold, fabric modification, fibers, hydrogels and foams.
Polymer semiconductors have been experiencing a remarkable improvement in electronic and optoelectronic properties, which are largely related to the recent development of a vast library of high‐performance, donor–acceptor copolymers showing alternation of chemical moieties with different electronic affinities along their backbones. Such steady improvement is making conjugated polymers even more appealing for large‐area and flexible electronic applications, from distributed and portable electronics to healthcare devices, where cost‐effective manufacturing, light weight, and ease of integration represent key benefits. Recently, a strong boost to charge carrier mobility in polymer‐based field‐effect transistors, consistently achieving the range from 1.0 to 10 cm2 V−1 s−1 for both holes and electrons, has been given by uniaxial backbone alignment of polymers in thin films, inducing strong transport anisotropy and favoring enhanced transport properties along the alignment direction. Herein, an overview on this topic is provided with a focus on the processing–structure–property relationships that enable the controlled and uniform alignment of polymer films over large areas with scalable processes. The key aspects are specific molecular structures, such as planarized backbones with a reduced degree of conformational disorder, solution formulation with controlled aggregation, and deposition techniques inducing suitable directional flow.
Niamh Willis‐Fox, Etienne Rognin, Talal A. Aljohani
et al.
Summary Polymer mechanochemistry is an exciting, rapidly developing field; however, it lacks detailed studies on the link between lab-scale mechanical activation and how the chemistry will translate to the complex flows and forces experienced during fluid-based molding and additive manufacturing techniques. This is especially important for polymers, which are the functional material of choice for applications such as organic electronics, biological scaffolds, and drug-delivery coatings, because there is the highest likelihood of mechanical activation. This review examines the most recent development in force-sensitive molecules known as mechanophores by re-categorizing them by material phase and method of activation and discussing the forces involved in such flow systems and where activation may occur in relevant manufacturing processes. The overall finding of this review is that for real, practical, and scalable industrial applications of these exciting mechanochemical materials, there must be a concurrent study of the forces experienced and their effect on the detailed chemistry.
Fused Filament Fabrication is a 3D Printing technology that uses molten thermoplastic material forced through a nozzle to manufacture parts additively. This technology can use many thermoplastic grades and can produce single or multi-material parts depending on printer configuration. However, when printing a component with multiple materials, their compatibility must be considered to ensure proper bonding. The main issue of using non-compatible or low compatible material is that material will not fuse, resulting in poor mechanical properties. This study aimed to investigate if the mechanical properties of standard polymers, Polylactic Acid and Polyethylene Terephthalate can be improved using reinforcing strings of engineering-grades polymers, Polyamide 645 and Polyamide with 20% short carbon fiber reinforcement. The reinforcements were designed as simple strings cores, enveloped by a standard polymer material. The investigation was planned using a Taguchi L8 matrix. The results showed that the mechanical properties and specimens' integrity made of standard polymers could be improved by adding reinforcing strings of engineering-grade polymers.
Expanding the application field of epoxy resins is absolutely required to improve their flame retardant performance. Reactive-type silicon-phosphorus-nitrogen contained flame retardants can improve the flame retardancy of epoxy resins, while suppress the migration of retardants from the interior to the surface of the matrix. Therefore, a novel reactive multi-element flame retardant, N-((4-hydroxyphenyl)- (9,10-dihydro-9-oxa-10-phosphaphenanthene-10–yl) methyl) amino propyl heptaisobutyl silsesquioxane (PmDOH) was designed and synthesized. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) results show that the maximum mass loss rate of the PmDOH modified epoxy resin (EP) decreases, while the char residue increases gradually with the increase of PmDOH. Moreover, the limiting oxygen index (LOI) value of PmDOH/EP thermosets with 10 wt% of PmDOH (EP-10%) increases to 30.4%, and vertical burning test (UL-94) arrives to V-0 grade. Micro combustion calorimeter (MCC) results show that the PHRR and the THR of PmDOH/EP reduce gradually with the increase of PmDOH. FT-IR and SEM results demonstrate that the PmDOH modified EP is more easily carbonized and a more compact and continuous structure char layer is generated during the combustion process in comparison with the pure EP.
G. Pier Villegas, A.G. Alvarado Mendoza, L.G. Guerrero Ramírez
et al.
The polymerization of aniline hydrochloride by inverse microemulsion in a batch process and the semicontinuous process was studied as a function of the surfactant ionic and nonionic. Polymerizations were carried out at 60°C for 4 h with a yield polymer of circa 67 and 27% wt. for ionic and nonionic surfactants. The conductivity of synthesized polyaniline by the semicontinuous process is higher up to three orders of magnitude than that of the batch process for both surfactants. The calculating degree of oxidation by UV-Vis showed the relative intensities of the quinoid to benzenoid unit around one. The morphology was determined by Scanning Electron Microscopy (SEM) and observed that the formation of the different morphologies is due to the self-assembly behavior of surfactant. The diameter z-average particle size (Dz) was studied by Transmission Electron Microscopy (TEM), which determined that the diameter particle in a semicontinuous state is larger than the one produced in a batch; this is due to the control of monomer addition in the system. These findings suggest that the polymerization process and the type of surfactant influence the properties of polyaniline.