Hasil untuk "Polymers and polymer manufacture"

M. Belgacem, A. Gandini

J. Lunt

M. F. Moradali, B. Rehm

Bacteria are prime cell factories that can efficiently convert carbon and nitrogen sources into a large diversity of intracellular and extracellular biopolymers, such as polysaccharides, polyamides, polyesters, polyphosphates, extracellular DNA and proteinaceous components. Bacterial polymers have important roles in pathogenicity, and their varied chemical and material properties make them suitable for medical and industrial applications. The same biopolymers when produced by pathogenic bacteria function as major virulence factors, whereas when they are produced by non-pathogenic bacteria, they become food ingredients or biomaterials. Interdisciplinary research has shed light on the molecular mechanisms of bacterial polymer synthesis, identified new targets for antibacterial drugs and informed synthetic biology approaches to design and manufacture innovative materials. This Review summarizes the role of bacterial polymers in pathogenesis, their synthesis and their material properties as well as approaches to design cell factories for production of tailor-made bio-based materials suitable for high-value applications. Bacteria produce diverse polymers, such as polysaccharides, polyesters, polyphosphates and extracellular DNA. In this Review, Moradali and Rehm discuss the types of bacterial polymers and their role in bacterial physiology and pathogenesis as well as their production and use as novel biomaterials.

A. Leon, Qiyi Chen, Napolabel B. Palaganas et al.

C. DelRe, Yufeng Jiang, Philjun Kang et al.

A. Goyanes, Fabrizio Fina, Annalisa Martorana et al.

Hippolyte Houisse, Renaud Bouchet, Christian Carrot et al.

Lithium metal has been seen for long as the key to develop next generation of high energy batteries but suffers from the formation of lithium dendrites during cycling which is hardly hindered by liquid electrolytes. Polymer electrolytes based on poly (ethylene oxide) doped by lithium salts provide good interfaces but suffer from poor ionic conductivity at room temperature and lack of mechanical properties above the melting temperature. Composite electrolytes are considered as a possible way to overcome these issues. This study experimented melt-extrusion without added solvent as a way to elaborate such an electrolyte using a model NaSICON type Li1.3Al0.3Ti1.7(PO4)3 lithium-ion conductive filler, dispersed in a doped polymer matrix. Morphological, physical and resulting electrochemical properties of various compositions were investigated. 55 vol% of filler was shown to be the maximum that can be incorporated due to excessive viscosity and jamming. Below this limit, the extruded electrolytes display homogeneously dispersed particles and reduced tuneable porosity that enable to get soft elastic membranes at room temperature. Limitation of the ionic conductivity was observed and attributed to tortuosity and transport resistance at interfaces.

Fengtao Li, Jing Wang, Xuelian He

In this study, a titanium-based constrained geometry catalyst, [t-BuNSiMe2(Me4Cp)]TiMe2, was synthesized and activated with methylaluminoxane for ethylene-propylene random and block copolymerization. The catalyst exhibited optimal activity at 70°C, yielding random copolymer chains with trace amounts of long polyethylene crystalline segments. When the ethylene content fell below 35%, random copolymers failed to crystallize. The block copolymerization system achieved maximum catalytic activity at a reaction temperature of 50°C and an ethylene block duration of 10 minutes. Shorter ethylene block durations correlated inversely with enhanced catalytic activity, increased molecular weight (peaking at 2.88 × 105 g/mol), and a narrower molecular weight distribution. The predominant component comprised extended PPP segments, constituting over 50% of the total copolymer composition. Within the polymer chains, propylene monomers were primarily incorporated as PPP and PPE structural motifs. Moreover, a progressive decrease in [PPP] content was observed with increasing ethylene block duration, whereas [PPE] content exhibited the opposite trend. This inverse relationship suggested that PPP segments gradually transform into PPE configurations via ethylene monomer insertion. These findings demonstrated that product structure and properties can be effectively tuned by adjusting initial monomer feed ratios or the timing of monomer block introduction.

Dejana Pejak Simunec, Johnson Jacob, Ahmad E.Z. Kandjani et al.

Yun Liu, Guangze Yang, Thejus Baby et al.

Poor solubility often leads to low drug efficacy. Encapsulation of water‐insoluble drugs in polymeric nanoparticles offers a solution. However, low drug loading remains a critical challenge. Here, we report a simple and robust sequential nanoprecipitation technology to produce stable drug‐core polymer‐shell nanoparticles with high drug loading (up to 58.5%) from a wide range of polymers and drugs. This technology is based on tuning the precipitation time of drugs and polymers using a solvent system comprising multiple organic solvents, which allows the formation of drug nanoparticles first followed by immediate precipitation of one or two polymers. This technology offers a new strategy to manufacture polymeric nanoparticles with high drug loading having good long‐term stability and programmed release, and opens a unique opportunity for drug delivery applications.

Yanju Liu, H. Lv, X. Lan et al.

Md. Masud Rana, Md. Hafezur Rahaman, G. M. Arifuzzaman Khan et al.

Abstract L‐ and D‐ form oligo(lactic acid)s (OLLA and ODLA) grafted α‐cellulose (OLLA‐g‐cellulose and ODLA‐g‐cellulose) were prepared by the graft polycondensation reaction in C6H5CH3 medium at 130°C and 380 mm of mercury pressure. Para‐toluene sulphonic acid (5 wt% of oligo(lactic acid)) was used as a catalyst whereas potassium persulfate (0.01 wt% of oligo(lactic acid)) was used as a co‐catalyst in the graft polycondensation reaction. OLLA and ODLA with a degree of polymerization (DP) 6–7 used in polycondensation reaction were also prepared by ring‐opening polymerization of L‐ and D‐lactides at 140°C for 10 h with stannous octoate (C16H30O4Sn) as a motivator, L, and D monomer of lactic acids as co‐motivators. FTIR analysis proved the bonding of OLLA and ODLA onto the α‐cellulose surface. The thermal properties of poly(L‐lactic) acid (PLLA) composites were explored by thermal analysis (TG, DTA, and DTG). Degradation, melting, and maximum weight loss temperature of the composites were increased with the increase of grafted cellulose up to 10% and then decreased. TG and DTA results showed that the incorporation of grafted α‐cellulose (grafted cellulose) can improve the thermal properties of PLLA composites. Highlights Synthesis of oligo(lactic acid)s from L‐ and D‐lactides by ring‐opening polymerization reactions. α‐cellulose extraction and graft modification with oligo(lactic acid)s. Preparation of grafted α‐cellulose composite with PLLA matrix. Evaluation of thermal properties of the grafted α‐cellulose‐reinforced composites.

Guoqi ZHANG, Di MENG, Bin XIA et al.

Plastic products are widely used in human daily life, while facilitating human life, plastics have also produced many negative effects due to the lack of effective recovery measures, plastic pollution has become an important environmental issue of global concern. Marine plastics can be degraded into smaller microplastics (MPs) through various ways under the influence of environmental factors. They can be ingested by marine organisms mixed with food sources, and then accumulated in the body, causing serious negative effects on marine lifes and marine ecology. Recently, it has been proved that the Changshan Islands sediments contain a certain amount of MPs, the content reached 133.14 to 499.82 n/kg. Changshan Islands is one of the eight major islands in China. It is located at the confluence of the Yellow Sea and the Bohai Sea, and has a unique geographical location. The fish community between the islands is rich in species, especially in many migratory species, and high in species diversity. The seasonal change of fish species composition and dominant species is obvious. It has been proved MPs can cause a certain degree of harm to marine organisms. Therefore, the distribution of MPs in organisms in the Changshan Islands sea area deserves to be studied. In this study, the MPs in the gastrointestinal tracts and muscles of wild fish were digested and separated after collecting them from the marine culture zone of Changshan Islands. The results showed that MPs were detected existing in the gastrointestinal tracts of all fish, but not in muscle tissues. The reason may be that MPs are too large to be endocytosed by intestinal epithelial cells, and thus can not participate in the blood circulation of fish. The abundance of MPs in the gastrointestinal tracts of seven species of marine wild fish ranged from 0.19 to 3.79 items/individual. The abundance of MPs in Coilia nasus is the highest among all fish, this phenomenon may be related to the living environment and predation habits of C. nasus, which living in the bottom of the sea. The MPs in sediments will undergo a cyclic process of suspension, sedimentation and resuspension under the flow of seawater, thus greatly increasing the exposure and intake risk of MPs by bottom organisms, such as C. nasus. The shape of MPs was dominated by the fiber, and the color was mostly transparent, which size is mainly less than 300 μm. The reason may be that the individual size of fish collected in this survey is small, and larger-sized MPs cannot enter into the gastrointestinal tract of fish through feeding. Large plastics in the environment are broken under the photooxidation, wave action, physical wear and alternating freeze-thaw. The different shapes of MPs detected in this study may be derived from the decomposition of these large plastics. Fibers are the predominant form of MPs encountered in global wildlife studies. It could also be because fibrous MPs are the most abundant in the marine environment. Additionally, MPs Fibers can be bended or intertwined with food, possibly due to long-term accumulation for the slower fibers excretion, increasing the chance of being ingested by organisms. The types of polymers detected were cellophane, cellulose and polyethylene, among which cellophane had the highest content. Cellophane is an organic cellulose-based polymer that has been used in food packaging and cigarette packaging. It is also used as a release agent in the manufacture of glass fiber and rubber products, or as a coating in combination with synthetic polymers. There was no obvious toxic effect on cellulose and cellulite. The polymer hazard index (PHI) is an important criterion for risk assessment of MPs, and is based primarily on the percentage content of a given polymer and the polymer's hazard fraction for ecological and health risk assessment. The potential risk of MPs to humans can be estimated by the polymer hazard index. The higher the polymer hazard index, the higher the ecological risk in the sea area. The toxicity coefficient of polyethylene is 10, the toxicity grade is grade II, the hazard index is low, and it belongs to the low risk polymer. Moreover, people usually discard the gastrointestinal tract of fish before eating, thus the MPs in the fishes of Changshan Islands, and the safety factor of fish products in Changshan Islands is higher. In this study, through the collection of wild fish in Changshan Islands, the MPs in gastrointestinal tract and muscle tissue were extracted, and the abundance and type of MPs were analyzed. The pollution status of MPs in fish in the adjacent waters of Changshan Islands was clarified, which provided basic data for exploring the impact of MPs on the ecological environment safety of Changshan Islands ecosystem. Further research on the distribution of MPs in other wild organisms, such as shellfish, and in other economically viable locations should be considered, which can provide a scientific basis for the analysis of MP pollution levels and the formulation of prevention and control strategies in the marine environment.

Salma Majidah, Lavita Nuraviana Rizalputri, Eduardus Ariasena et al.

Integration of gold nanoparticles onto electrochemical biosensor electrodes has been widely conducted to improve the performance of biosensors. Gold nanospikes (AuNS), as one of the gold nanoparticle morphologies, can be integrated into biosensors through electrodeposition and has the potential to immobilize bioreceptor on biosensors using the self-assembled monolayer (SAM) method. This paper examines the potential of AuNS-deposited Screen-Printed Carbon Electrodes (SPCEs) on immobilizing enzymes as label-based electrochemical biosensor by evaluating the optimum parameter for glucose oxidase (GOx) enzyme immobilization on the SPCE that consists of incubation time and concentration of SAM molecule—L-cysteine—and GOx enzyme, then reviews its performances. The developed biosensor exhibits excellent performance in detecting glucose (linear range of 0.2–15 mM and limit of detection (LOD) of 116 µM), with good selectivity against uric acid, urea, ascorbic acid, dopamine, and lactic acid, and superiority towards gold nanosphere modified biosensor.

Marthinus Brits, Martin J. M. van Velzen, Feride Öykü Sefiloglu et al.

Abstract The limited available data on human internal exposure poses a significant challenge in assessing the risks associated with micro and nanoplastics (MNPs) to human health. A contributing factor to this challenge is the scarcity of sensitive analytical methods to quantify the mass concentration of plastic polymers in human blood. In this study we present an improved and validated method for quantitatively analysing polyethylene (PE), polyethylene terephthalate (PET), poly(vinyl chloride) (PVC), poly(methyl methacrylate) (PMMA), polypropylene, and polystyrene in human whole blood samples. We introduce and apply stringent quality assurance and quality control procedures, including the validation of the method using quality control samples and continuous monitoring of batch analyses to ensure data reliability. Expanding upon prior pioneering work by Leslie et al. (2022), we optimised the pyrolysis-gas chromatography–mass spectrometry (Py-GC-MS) conditions to enhance method sensitivity and selectivity. Recovery experiments demonstrated a high level of accuracy and precision, with values ranging from 68 to 109% for quality control samples. Applying this method to whole blood samples (n = 68), we identified plastic polymers in 64 samples, with PE as the predominant polymer, followed by PVC, PET, and PMMA. In 17 blood samples, polymer concentrations were found to exceed the limit of quantitation, with a mean of 1070 ng/mL for the summed polymer concentrations, ranging between 170 and 2490 ng/mL. The mean of the sum of polymers across all blood samples (n = 68) was 268 ng/mL. These findings underscore the pressing need for further research aimed at comprehensive MNP quantification in human matrices, considering the potential health implications.

Sergiy Korniy, Mariia-Olena Danyliak, Ivan Zin

The article provides a brief overview of the use of zeolites as environmentally safe anticorrosion pigments for organic coatings on metals. The number of studies on zeolite-based inhibiting pigments has increased significantly in recent years, due to the need to replace chromates and reduce the content of phosphate corrosion inhibitors. Based on the results available in the literature, an assessment was conducted on the inhibitory properties of complex zeolite pigments obtained by various methods. Emphasis is placed on the advantages and disadvantages of ion exchange modification of zeolites with inhibitory substances and mechanochemical synthesis of pigments. Zeolites have a wide perspective in anticorrosion technologies due to their porous structure, large surface area, high pore volume, and the ability to accumulate inhibitory ions and molecules. Such properties of zeolites make possible their use for the development of self-healing or “smart” polymer coatings. Considering the environmental safety of zeolites and their excellent thermal and chemical stability, anti-corrosion polymer coatings inhibited by zeolite pigments could become an effective environmentally friendly alternative to chromate-based protective coatings. The main trends and prospects for the development of research in this domain are presented.

Elnaz Talebi, Golnoosh Abdeali, Ahmad Reza Bahramian

Hypothesis: Solid/liquid phase change materials (PCMs) are among the materials used to store thermal energy. By nanoencapsulating these materials, the problem of leakage during melting can be solved and the thermal efficiency of the system can be increased. In previous studies, researchers have used complex and expensive methods to prepare nanocapsules of PCM. In this work, in order to simplify and reduce the time and costs of the synthesis process, the difference in the solubility parameter of the core and shell materials at different temperatures and the sequence in phase separation have been used for the synthesis of PCM nanocapsules.Methods: In order to make the desired PCM nanocapsule, the difference in solubility parameters of polyethylene glycol, polystyrene and toluene at temperatures of 5, 25 and 80ºC has been used. In fact, this difference in the solubility parameter creates a homogeneous solution of these three substances at a temperature of 80ºC. By decreasing the temperature to 25°C, primary cores are formed and solid polyethylene glycol nanoparticles are completely separated. Further, by decreasing the temperature to 5ºC, polystyrene is separated from the solution and completely covers the nanoparticles of polyethylene glycol. In this way, using the sedimentation with temperature gradient method, polyethylene glycol nanoparticles were first synthesized, and polyethylene glycol nanoparticles were coated with polystyrene deposition. Also, to increase the thermal conductivity of the shell and the thermal efficiency of the PCM system, carbon nanoparticles have been used in polystyrene shells. Findings: Examining and evaluating the morphology of the synthesis PCM system in this work confirmed the creation of a polyethylene glycol/polystyrene core/shell nanocapsule. The thermal energy absorption efficiency of the heat transfer fluid prepared from these nanoparticles at the applied temperature of 55ºC is about 17% more than that of water.

Pilar Bernal-Ortega, Elfi Gaillard, Frances van Elburg et al.

The increasing demand on passenger car tires requires a continuous effort of tire manufacturers to improve their performance and safety. Achieving a balance between the three properties that form the “Magic Triangle of Tires” is one of the biggest challenges in this field. This work aims to improve this balance between wet grip, rolling and wear resistance by the use of performance hydrocarbon resins as an alternative to treated distillate aromatic extracted (TDAE) oil in tire tread compounds. In this framework, the effect on the in-rubber properties of five different hydrocarbon resins with different chemical nature, was studied in a styrene butadiene rubber (SBR)/polybutadiene rubber (BR) blend. The effect of the resins was analyzed by the use of different experimental techniques. All the compounds containing resin in their formulation, independently of their amount and chemical nature, showed an increase in the wet grip indicator and abrasion resistance indicator. However, it also was observed a deterioration in the rolling resistance indicator.

Al-Otaibi Wejdan, Alandis Naser M., Alam Manawwer

This article describes the synthesis of polyesteramide (PEA) resin from Leucaena leucocephala oil (LLO) obtained from seeds of L. leucocephala tree, locally grown in King Saud University Campus. LLO was transformed into amide diol by based catalyzed amidation reaction, followed by esterification reaction with malic acid (MA), that resulted in LLO-based PEA (LPEA). The synthesis was performed without using any solvent or catalyst. Fourier-transformation infrared spectroscopy and nuclear magnetic resonance confirmed the formation of LPEA by the introduction of amide and ester moieties. LPEA was further reinforced with nano graphene oxide (GO) and fabricated into nanocomposite corrosion protective coatings (LPEA/GO). LPEA/GO coatings obtained were tough, flexibility retentive and showed good corrosion resistance performance toward 3.5 w/w% NaCl medium. Thermogravimetric analysis confirmed good thermal stability of coatings with safe usage up to 200°C.

Parissa Khadivparsi, Morteza Rafiee-Tehrani, Farid Dorkoosh et al.

Metoprolol has been widely used for controlling high blood pressure, preventing myocardial reinfarction, setting rate changes, setting heart rhythm, treatment of chronic angina and preventing excessive bleeding during surgery. The purpose of this research is formulation and manufacture of extended release tablets of metoprolol succinate that conform to all the in vitro physicochemical US Pharmacopoeia national formulary (USP32). For preparing the tablets, the hydrophilic HPMC(K100M) polymer was used in direct compression method. Release of metoprolol in phosphate buffer having pH=6.8 (USP32) was measured by HPLC. Also, using experimental correlation of diffusivity in buffer medium and Gurney-Lurie charts during tablet enlargement with time, diffusion coefficients of drug and partition coefficients were obtained at different time steps. The rate of drug release depends on the type, viscosity and polymer concentration. Drug release results over 20 hours for polymers of HPMC(K100M), HPMC(K4M), HPMC(K15M), polyethylene oxide, ethyl cellulose, Eudragit (RL100) were investigated and compared. The results demonstrated that HPMC(K100M) met the standards of USP32 very well and was superior over the other polymers tested.