High-strength oriented PET products were prepared via the confined drawing process. The aggregation structure changes and orientation behavior of PET with different initial crystallinities (before and after drawing) were investigated by TMDSC, WAXD, and SAXS. Combined with the three-phase structure model, the generation and evolution process of highly-ordered rigid amorphous fraction (RAF) were further confirmed. Meanwhile, the effect of drawing temperature on the structure and properties of oriented PET was systematically explored. Consequently, below the cold crystallization temperature, limited mobility of crystalline regions results in two key evolutionary behaviors of PET during drawing: the transformation of the amorphous phase into highly-ordered RAF, and stress-induced crystallization under tensile force. Additionally, the annealing temperature is another key factor influencing the microstructural evolution of semi-crystalline PET. The temperature at which the crystalline phase forms, it directly determines the mobility of the crystalline regions. The characterization results from TMDSC and X-ray techniques quantitatively analyzed the composition and variation law of the aggregation structure, providing guidance for the structure-property regulation of high-strength oriented PET.
Jacem Zidani, Latifa Tajounte, Abdellah Benzaouak
et al.
The review highlights the advancements in flexible lead-free piezoelectric materials, emphasizing their potential for energy harvesting and sustainable energy. Although normal piezoelectric materials such as lead zirconate titanate (PZT) have great efficiency, their lead content causes environmental issues. This research focuses on replacement materials like biodegradable polymers and bismuth sodium titanate (BNT), which not only show interesting piezoelectric capabilities but also have advantages in terms of flexibility and biocompatibility. In order to increase piezoelectric performance while maintaining flexibility, it is advised to include inorganic fillers into polymer matrices, therefore qualifying these materials for usage in biomedical and wearable electronics applications. The evaluation also covers the issues resulting from the great usage of these resources, including e-waste and the need of sustainable solutions. The general message of the research underlines the need of developing new piezoelectric materials able to effectively gather mechanical energy from different sources, therefore promoting self-sustaining systems and reducing reliance on traditional power sources. The review also underlines how lead-free piezoelectric materials can boost power density and chemical oxygen demand (COD) removal rates in microbial fuel cells (MFCs), therefore promoting sustainable energy solutions that turn organic waste into bioelectricity.
Polymers and polymer manufacture, Engineering (General). Civil engineering (General)
The production of food packaging membranes with antibacterial activity is of great significance because it can inactivate bacteria in food and protect the human body from food-borne diseases. Herein, a novel polyacrylonitrile (PAN)/cellulose acetate (CA) composite nanofibers membrane with citral as an antibacterial agent was fabricated by utilizing electrospinning technology. Subsequently, the PAN/regenerated cellulose (RC)/citral composite nanofibers membrane was obtained through an alkaline hydrolysis process and citral grafting modification strategy. At the same time, the preservation efficacy of this membrane in refrigerated chicken breast was investigated. Results indicate that the PAN/RC/citral composite nanofibers membrane, modified by grafting citral, exhibits uniform fiber diameter, favorable morphology, and excellent mechanical properties. Moreover, citral crosslinks with RC components in fiber membranes significantly reduce the total bacterial count and total volatile basic nitrogen value in chicken breast during the packaging and storage process, thereby extending the shelf life of refrigerated chicken breast. This research provides a new approach to the production of antibacterial food packaging films and demonstrates their broad potential application value in the field of food packaging.
Mohammadmahdi Negaresh, Milad Karbalaei‐Bagher, Yousef Jahani
et al.
Abstract The investigation of chain branching in polypropylene (PP) holds significant importance for comprehending the impact of structural modifications on the properties of PP. The utilization of ethylene‐octene copolymer (EOC) presents a valuable opportunity to examine the influence of branching density on the ability of electron beam irradiation or a chemical agent in a PP blend. The introducing long chain branches (LCB) into PP can enhance its mechanical properties, particularly impact strength. This characteristic is of particular significance in applications where the material is subjected to mechanical stress, such as automotive components or packaging materials. Blends of PP/EOC were produced using 20 and 30 wt% of EOC and 0.5 phr trimethylolpropane trimethacrylate (TMPTMA) monomer. To evaluate the efficiency of branching in both solid and molten states, irradiated samples and samples mixed with dicumyl peroxide (DCP) were selected. The rheological properties of the molten blends in shear and extensional modes were assessed, and their morphology was examined using scanning electron microscopy. The existence of LCB in all samples was confirmed through dynamic viscoelastic measurements. It was concluded that although the irradiation promoted chain scission within the backbone, which resulted in long chain branching, DCP created LCB on the backbone chains of PP through chemical reaction in the melt state. Additionally, the strain hardening constant (n) was calculated, and its value for the irradiated sample PP/EOC 80/20 was 0.19, whereas its value for this blend when employing DCP was 0.14. While the complex viscosity of irradiated blend (8764 Pa.s) was greater than that of melt state branched blend (8377 Pa.s) at 0.1 rad/s, in the higher frequencies it became smaller due to the more effective creation of long chain branches through peroxide grafting in the molten state. The results of the study verified the presence of LCB in the materials by observing longer relaxation time and strain hardening behavior. Highlights The chain branching of PP/EOC blends was investigated in both the melt state and solid state through the presence of TMPTMA monomer. The effectiveness of TMPTMA monomer in grafting was mostly notable in the molten state. The steady state viscosity of LCB‐(PP/EOC) was higher in the presence of dicumyl peroxide compared to irradiated PP/EOC. The samples containing 80 wt% of PP exhibited longer side branches compared to the sample with 70 wt% of PP according to shear and extensional rheometry. The induced side chain branches resulting from irradiation and the use of dicumyl peroxide help increase the miscibility of the polymers to a similar extent.
A series of electromagnetic interference (EMI) shielding composites composed of an epoxy-based vitrimer matrix and stainless-steel fabric was prepared in this study. The polymer matrix presents tunable mechanical properties and chemical recyclability through adjustment of the content ratio of soft aliphatic sebacic acid (SA) to rigid crosslinker 3-(carboxymethyl)cyclopentane-1,2,4-tricarboxylic acid (TCAA). All the recycled vitrimers exhibit strengths comparable to the original materials, suggesting that similar cross-linking structures were reformulated successfully. Furthermore, a noticeable enhancement in the mechanical strength is observed for the combination of matrix and stainless-steel fabric, indicating that the combination of vitrimer material and fabric is excellent. However, a certain extent of decreased mechanical abilities was observed for the composites after reclaiming, while no apparent differences are noted in the results between multiple recycling processes. This tendency may be attributed to the complex fabric structure, which allows a distinct distribution for the reclaimed matrix that is repolymerized by evaporating the solvent compared to the original polymer. In addition, the original and repeatedly recycled composites reveal comparable EMI shielding abilities of around 70 dB, demonstrating the potential for high performance when applied as EMI shielding materials.
Water present in natural rubber was found to play a role in forming carbon-carbon crosslinking junctions before forming carbon-sulfur crosslinking junctions when its effect on the accelerated sulfur vulcanization was investigated by analyzing low–molecular weight products through various instrumental analytical techniques. Samples were prepared by mixing deproteinized natural rubber (DPNR) with various moisture contents with stearic acid, ZnO, sulfur, and N-tert-butylbenzothiazole-2-sulfenamide, and they were vulcanized at 150 °C for various cure times. Low–molecular weight products such as 2,2′-dibenzothiazole disulfide (MBTS), 2-mercaptobenzothiazole (MBT), ZnMBT, Zn2+ and sulfur linked to the rubber were extracted from the vulcanized natural rubbers using benzene and dioxane, and subsequently measured by high-performance liquid chromatography, UV–visible spectroscopy, inductively coupled plasma atomic emission spectroscopy, and combustion analysis. The water present in natural rubber was found to strongly affect the production and formation rate of the low–molecular weight products in the accelerated sulfur vulcanization of natural rubber. As the result it suggests that the water promotes the formation of the C-C linkages, and then it sequentially promotes the formation of the C-S linkages.
Abstract Despite global efforts to monitor, mitigate against, and prevent trash (mismanaged solid waste) pollution, no harmonized trash typology system has been widely adopted worldwide. This impedes the merging of datasets and comparative analyses. We addressed this problem by 1) assessing the state of trash typology and comparability, 2) developing a standardized and harmonized framework of relational tables and tools, and 3) informing practitioners about challenges and potential solutions. We analyzed 68 trash survey lists to assess similarities and differences in classification. We created comprehensive harmonized hierarchical tables and alias tables for item and material classes. On average, the 68 survey lists had 20.8% of item classes in common and 29.9% of material classes in common. Multiple correspondence analysis showed that the 68 surveys were not significantly different regarding organization type, ecosystem focus, or substrate focus. We built the Trash Taxonomy Tool (TTT) web-based application with query features and open access at openanalysis.org/trashtaxonomy. The TTT can be applied to improve, create, and compare trash surveys, and provides practitioners with tools to integrate datasets and maximize comparability. The use of TTT will ultimately facilitate improvements in assessing trends across space and time, identifying targets for mitigation, evaluating the effectiveness of prevention measures, informing policymaking, and holding producers responsible.
Environmental pollution, Polymers and polymer manufacture
Poly(lactic acid)/polyamide11 (PLA/PA11) blends were prepared by reactive blending with multifunctional epoxy oligomer as compatibilizer, and the compatibility of PLA and PA11 was improved. The compatibilization, toughness mechanisms, and rheological behavior of PLA/PA11 blends were studied. Positron annihilation lifetime spectroscopy (PALS) was used to study the free volume and interfacial compatibility of the compatibilized blends. Moreover, the influence of free volume and void volume on the barrier properties of the blend films was discussed. The glass-transition temperature and storage modulus of PLA in the compatibilized PLA/PA11 blends decreased, and the rheological behavior in the blends changed from liquid-like to solid-like at low-frequency. This finding showed that the interfacial compatibility between PLA and PA11 improved, and the material properties underwent a rigid-to-tough transition. PALS analysis further showed the improved interfacial compatibility of the multifunctional epoxy reactive compatibilizer reduced the free-volume pores and increased the number of free-volume pores. The entanglement degree of the molecular-chain segment in the compatibilized blend system increased, and the volume of free-volume pore decreased. The reactively compatibilized PLA/PA11 blend had excellent oxygen and water barrier properties, and its oxygen transmissibility and water-vapor diffusion coefficient greatly decreased. Therefore the reactive compatible PLA/PA11 blends had potential application and research value as packaging-barrier film materials.
The robotics design process can be complex with potentially multiple design iterations. The use of 3D printing is ideal for rapid prototyping and has conventionally been utilised in concept development and for exploring different design parameters that are ultimately used to meet an intended application or routine. During the initial stage of a robot development, exploiting 3D printing can provide design freedom, customisation and sustainability and ultimately lead to direct cost benefits. Traditionally, robot specifications are selected on the basis of being able to deliver a specific task. However, a robot that can be specified by design parameters linked to a distinctive task can be developed quickly, inexpensively, and with little overall risk utilising a 3D printing process. Numerous factors are inevitably important for the design of industrial robots using polymer-based additive manufacturing. However, with an extensive range of new polymer-based additive manufacturing techniques and materials, these could provide significant benefits for future robotics design and development.
One key issue restricting semi-crystalline polymers to be widely applied in powder bed fusion (PBF) of polymers is lack of good powder processability, especially a wide sintering window. In this work, a thermal treatment method with mixed dispersant system (TTMS) was developed to modify a common isotactic polypropylene (PP) powder to adapt for PBF. Both sintering window (SW) and particle morphology of the PP powder were improved by the TTMS process. The SW was expanded from 15 °C for the raw PP powder to 51 °C for the TTMS-PP powder, since the TTMS process facilitated the formation of α crystal with larger lamellar thickness as revealed by differential scanning calorimeter and X-ray diffraction measurements. Moreover, the particle size of the TTMS-PP powder was reduced to 60 μm, which was only a third of the raw PP's size. Consequently, the TTMS-PP powder exhibited a lower flow energy compared to the raw PP powder. These improvements contributed to a better laser processability of the TTMS-PP powder, as demonstrated by the single-layer component with reduced part deformation and better dimensional accuracy. This work is believed to provide a useful guideline for the development of semi-crystalline polymer powders for the PBF technology.
Aghil Asadi, Mohsen Najafi, Hossien Bouhnedi
et al.
Hypothesis: The volume of studies conducted on biopolymeric materials emphasizes the high-consumption of polymers in biomaterial fields, especially in cosmetics industry which must be resistant to different kinds of microorganisms and bacteria. Polymers in this category include acrylate polymers, which are generally made by precipitation polymerization. Carbopol is a brand of acrylic polymer, based on poly(acrylic acid). This polymer is highly used as thickening and gelling agents for its rheological features. By chemically induced antimicrobial agents into the carbopol structure, microgels of inherently antimicrobial properties are obtained with effective applications in personal and public health applications, including combating and controlling corona epidemics (Covid 19). Methods: In this study, it has been tried to improve the antibacterial nature of Carbopol by its bonding and surface modification with different amounts of cationic monomer acryloyl oxyethyl trimethyl ammonium chloride (A.Etac). In this work, for the first time, we attempted to modify the surface of carbopol by ultrasound. We also studied the swelling rate of the sample before and after surface modification in aqueous, alcoholic and salt solutions. Infrared spectroscopy (IR), scanning electron microscopy (SEM) with energy dispersive X-Ray analysis (SEM-EDX), antibacterial, rheometry and swelling tests were used to evaluate the chemical surface modification of Carbopol microparticles to achieve the stated goals. Antibacterial properties of the samples were evaluated by gram-negative bacteria (E. coli) and gram-positive bacteria (S. aureu) by plate count agar method. Findings: Experimental results showed that the modified carbopol was significantly resistant to the bacteria. It should be noted that the samples showed more resistance to gram-positive bacteria than gram-negative bacteria. The results of rheological analysis also showed that the gel strength significantly increased after surface chemical modification. In addition, modified samples showed higher swelling in water and biological media (0.9% brine)
Puerarin (Pue) is the most abundant isoflavonoid in kudzu root. It has been widely used as a therapeutic agent for the treatment of cardiovascular diseases. However, poor-bioavailability of puerarin is the main obstacle to its widespread clinical applications. In this paper, HA-ADH-PS nanomicelles were prepared by chemical modification, noncovalent modification and etc, and characterized by means of FT-IR, ultraviolet (UV) and thermogravimetric analysis (TG). The encapsulation efficiency and drug loading of Pue-loaded HA-ADH-PS nanomicelles were 45.1% and 19.89% by UV, respectively. It could be observed from the transmission electron microscopy (TEM) images that HA-ADH-PS micelles appeared obvious spherical structure in the water. The particle size of HA-ADH-PS nanomicelles and Pue-loaded HA-ADH-PS nanomicelles were about 136.8 nm and 119.5 nm with a PDI of 0.237 and 0.272, respectively. The fluorescence probe method was used to characterize the critical micelle concentration, the critical micelle concentration (CMC) value of the nanomicells was 0.002 g/L and the results met the requirements and ensured the stability of micelles after dilution. DPPH assay suggested that Pue-loaded HA-ADH-PS nanomicelles had an obvious radical scavenging effect in vitro. MTT test showed that Pue-loaded HA-ADH-PS nanomicelles was non-toxic and had good biocompatibility. Thus, Pue-loaded HA-ADH-PS nanomicelles could be used as a potential drug carrier for puerarin.
بیوپلیمر ازنظر بیوشیمی دان ها عبارت است از ماکرو مولکولهای بیولوژی که از تعداد زیادی زیر واحد کوچک و شبیه به هم که بااتصال کووالانسی به هم متصل شدهاند و یک زنجیره طولانی را ایجاد میکنند، ساختهشدهاند. با توجه به اینکه بیوپلیمرها از موجودات زنده از قبیل گیاهان، جانداران و میکروارگانیسمها بهطور طبیعی تولید میشوند و ازلحاظ زیستمحیطی نیز تجزیهپذیر هستند، بسیار مناسب میباشند. انواع بیوپلیمرها شامل اسیدهای نوکلوئیک، پروتئینها ، پلیساکاریدها، پلیهیدروکسی آلکانوات، پلی فنول، پلی فسفات و پلی سولفاتها هستند .بهمنظور استفاده از بیوپلیمرها در صنایع نیاز به تجاری کردن فرآیند تولید و همچنین بهینه کردن تولید آنها است با توجه به مطالعات انجامشده در خصوص بهینهسازی شرایط تولید بیوپلیمر مشخصشده است علاوه بر تأثیر عوامل تغذیهای مهم در فرآیند تولید بیوپلیمرها از قبیل منابع کربن، نیتروژن، فسفر، گوگرد و... عوامل فیزیکی و غیر تغذیهای نیز در فرآیند تولید بیوپلیمرها بسیار مؤثر میباشند. در این مطالعه به بررسی پارامترهایی نظیر شدت هوادهی، دور همزدن، دما و pH در تولید بهینه پلی ساکارید های میکروبی که یکی از مهمترین و پرکاربردترین بیوپلیمرها هستند، پرداختهشده است. با توجه به نتایج، در اکثر منابع بررسیشده مقادیر مناسب برای شدت هوادهی، دور همزدن، دما و pH به ترتیب vvm 3-0.5، rpm800-200 ، C°32-27 ، 8-5 در نظر گرفتهشده ، که بهینه مقدار پلی ساکارید تولید خواهد شد.
شعله کاظمی فرد, لیلا ناجی, فرامرز افشار طارمی
et al.
سلول خورشیدی دستگاهی است که قابلیت تبدیل انرژی خورشید را به انرژی الکتریکی با استفاده از اثر فوتوولتایی دارد. در سالهای اخیر، بهدلیل توسعه نسلهای مختلف سلولهای خورشیدی، انواع گوناگونی از آنها، شامل سلولهای خورشیدی سیلیکونی، حساس شده به رنگدانه، نقاط کوانتومی، آلی و نسلهای جدید ساخته شدهاند. در میان انواع مختلف این سلولها، نوع پلیمری آن به دلیل انعطافپذیری، وزن سبک، امکان طراحی مواد بهکار رفته در ساختار آنها، ضریب جذب زیاد، فرایندپذیری در حالت محلول و فنون ساخت ارزانقیمت توجه بسیاری را به خود جلب کردهاند. در این مقاله، سلولهای خورشیدی پلیمری و پلیمرهای رسانای مزدوج که در ساختار لایه فعال بهکار گرفته میشوند، همراه با ویژگیهای پلیمرهای مزدوج، معرفی میشوند. در ادامه نیز، به بررسی پیشرفتهای اخیر در معماری ساختار لایه فعال این دستگاهها، بهمنظور افزایش بازده تبدیل انرژی پرداخته میشود. در پایان، روشهای مشخصهیابی این دستگاهها و مهمترین پارامترهای آنها بیان میشوند.
فعالیت کاتالیزور از مهم ترین پارامترها در فرایندهای پلیمرشدن است. برای یک سامانه کاتالیزوریفعالیت ممکن است به شرایط پلیمرشدن از قبیل دما و فشار وابسته باشد. با این حال، برای شرایط ثابتپلیمرشدن، افزایش فعالیت به روش تغییر دما و فشار رضایت بخش نیست و صنعتگران مجبورند تا مقدارکاتالیزور در راکتور یا زمان انجام پلیمرشدن را افزایش دهند که این کار نیز از لحاظ اقتصادی مقرونبه صرفه نیست. در سال های اخیر، توجه پژوهشگران به استفاده از اصلاح کننده ها در کاتالیزورهایزیگلر-ناتا برای افزایش فعالیت یا بهبود فضاویژگی جلب شده است. این مواد، که اغلب از خانوادههالیدهای آلی، هالیدهای فلزی و شبه فلزی انتخاب می شوند، افزون بر اثرگذاری روی فعالیت کاتالیزور ومقدار کومونومرپذیری آن، روی خواص نهایی پلیمر از قبیل مقدار و نوع نظم فضایی )در پلیمرشدنپروپیلن(، متوسط های عددی و وزنی وزن مولکولی، دمای ذوب و بلورینگی، چگالی توده و اندازه ذراتآنها نیز اثر می گذارند که در این مقاله بدان پرداخته می شود.
Maryam Mansourirad, Mehdi Razzaghi Kashani, Seyed Mohammad Mousavi
Nowadays, due to environmental concerns, there has been great attention to recycling and reclaiming of tires. Different methods have been used for reclaiming or desulfurization of rubber. One of these methods, in which desulfurization of rubber happens with no damage to the polymer structure, is desulfurization by biological microorganisms. In this research the application and performance of thermophilic and sulfur oxidizing bacteria, Acidianus brierleyi for this purpose was investigated. Ground tire rubber was detoxified with organic solvents, and the optimum conditions for growing microorganisms in the existence of rubber powder in the shaker flasks were determined. In order to accelerate the process, the suitable conditions for growth of bacteria and desulfurization in the bioreactor were adopted. Fourier transfer infrared spectroscopy and scanning electron microscopy were employed to characterize desulfurization of bio-treated powder from bioreactor. The results indicated that morphological changes on powder surface and reduction of sulfur bonds have occurred. Samples from bioreactors, with and without bacteria and also untreated rubber powder were compounded with virgin styrene butadiene rubber. Tensile and dynamic properties were investigated using uni-direction tensile test and dynamic-mechanical-thermal analysis, respectively. Although some differences in dynamic-mechanical-thermal properties of samples pointed to stronger interaction between rubber matrix and treated rubber powder, no significant improvements in the mechanical properties of vulcanizates containing A.brierleyi-treated powder were observed. Low concentration of sulfur in rubber vulcanizates, chemical bonds of sulfur, and low efficiency of A. brierleyi in breaking sulfur bonds and reclaiming rubber were considered as the reasons for low efficiency of this treatment process.
Farhad Salimi, Mohsen Vafaie, Mehdi Razzaghi Kashani
et al.
A gel composite (based on polyacrylamide and crosslinker Cr(III) acetate) was prepared by solvent method (distillate and water formation) and nanoclay particle (kaolinite). Using XRD tests, d001 was evaluated for kaolinite nanoparticles in gel composite. Kaolinite modification using dimethyl-sulfoxide led to increase interlamellar spacing from 7.21 to 10.82 o A. Based on the results obtained for samples prepared from unmodified clay besides the pure clay, there is a wide peak at 2θ = 8o; which is a representative of polymer diffusion between the clay layers. For the sample prepared from modified clay, no increase in interlamellar space was observed. Addition of 15% clay (modified and unmodified) caused the syneresis to reduce by 20%. The gelation time for composites prepared from both types of clays increased due to increases in clay concentration, which this increase for the sample prepared from unmodified clay was greater. The viscosity of gel for samples prepared from modified clay increased due to increased clay concentration, which reached its maximum for 15% clay concentration. However for unmodified clay the maximum value of viscosity was observed for 30% clay concentration.