Polymers最新文献

{"title":"Impact of Runner Size, Gate Size, Polymer Viscosity, and Molding Process on Filling Imbalance in Geometrically Balanced Multi-Cavity Injection Molding.","authors":"Minyuan Chien, Yaotsung Lin, Chaotsai Huang, Shyhshin Hwang","doi":"10.3390/polym16202874","DOIUrl":"https://doi.org/10.3390/polym16202874","url":null,"abstract":"<p><p>The injection molding process is one of the most widely used methods for polymer processing in mass production. Three critical factors in this process include the type of polymer, injection molding machines, and processing molds. Polypropylene (PP) is a widely used semi-crystalline polymer due to its favorable flow characteristics, including a high melt flow index and the absence of a need for a mold temperature controller. Additionally, PP exhibits good elongation and toughness, making it suitable for applications such as box hinges. However, its tensile strength is a limitation; thus, glass fiber is added to enhance this property. It is important to note that the incorporation of glass fiber increases the viscosity of PP. Multi-cavity molds are commonly employed to achieve cost-effective and efficient mass production. The filling challenges associated with geometrically balanced layouts are well documented in the literature. These issues arise due to the varying shear rates of the melt in the runner. High shear rate melts lead to high melt temperatures, which decrease melt viscosity and facilitate easier flow. Consequently, this results in an imbalanced filling phenomenon. This study examines the impact of runner size, gate size, polymer viscosity, and molding process on the filling imbalanced problem in multi-cavity injection molds. Tensile bar injection molding was performed using conventional injection molding (CIM) and microcellular injection molding (MIM) techniques. The tensile properties of the imbalanced multi-cavity molds were analyzed. Flow length within the cavity served as an indicator of the filling imbalance. Additionally, computer simulations were conducted to assess the shear rate's effect on the runner's melt temperature. The results indicated that small runner and gate sizes exacerbate the filling imbalance. Conversely, glass fiber-filled polymer composites also contribute to increased filling imbalance. However, foamed polymers can mitigate the filling imbalance phenomenon.</p>","PeriodicalId":20416,"journal":{"name":"Polymers","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11511498/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142506582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic Light Scattering Microrheology of Phase-Separated Poly(vinyl) Alcohol-Phytagel Blends.","authors":"Richa Ghosh, Sarah A Bentil, Jaime J Juárez","doi":"10.3390/polym16202875","DOIUrl":"https://doi.org/10.3390/polym16202875","url":null,"abstract":"<p><p>In this investigation, we explored the microrheological characteristics of dilute hydrogels composed exclusively of Poly(vinyl) alcohol (PVA), Phytagel (PHY), and a blend of the two in varying concentrations. Each of these polymers has established applications in the biomedical field, such as drug delivery and lens drops. This study involved varying the sample concentrations from 0.15% to 0.3% (<i>w</i>/<i>w</i>) to assess how the concentration influenced the observed rheological response. Two probe sizes were employed to examine the impact of the size and verify the continuity hypothesis. The use of two polymer blends revealed their immiscibility and tendency to undergo phase separation, as supported by the existing literature. Exploring the microrheological structure is essential for a comprehensive understanding of the molecular scale. Dynamic light scattering (DLS) was chosen due to its wide frequency range and widespread availability. The selected dilute concentration range was hypothesized to fall within the transition from an ergodic to a non-ergodic medium. Properly identifying the sample's nature during an analysis-whether it is ergodic or not-is critical, as highlighted in the literature. The obtained results clearly demonstrate an overlap in the results for the storage (G') and loss moduli (G″) for the different probe particle sizes, confirming the fulfillment of the continuum hypothesis.</p>","PeriodicalId":20416,"journal":{"name":"Polymers","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11510749/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142506538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of PLA/LW-PLA Composite Materials Manufactured by Dual-Nozzle FDM 3D-Printing Processes.","authors":"Ye-Eun Park, Sunhee Lee","doi":"10.3390/polym16202852","DOIUrl":"https://doi.org/10.3390/polym16202852","url":null,"abstract":"<p><p>This study investigates the properties of 3D-printed composite structures made from polylactic acid (PLA) and lightweight-polylactic acid (LW-PLA) filaments using dual-nozzle fused-deposition modeling (FDM) 3D printing. Composite structures were modeled by creating three types of cubes: (i) ST4-built with a total of four alternating layers of the two filaments in the <i>z</i>-axis, (ii) ST8-eight alternating layers of the two filaments, and (iii) CH4-a checkered pattern with four alternating divisions along the <i>x</i>, <i>y</i>, and <i>z</i> axes. Each composite structure was analyzed for printing time and weight, morphology, and compressive properties under varying nozzle temperatures and infill densities. Results indicated that higher nozzle temperatures (230 °C and 240 °C) activate foaming, particularly in ST4 and ST8 at 100% infill density. These structures were 103.5% larger on one side than the modeled dimensions and up to 9.25% lighter. The 100% infill density of ST4-Com-PLA/LW-PLA-240 improved toughness by 246.5% due to better pore compression. The ST4 and ST8 cubes exhibited decreased stiffness with increasing temperatures, while CH4 maintained consistent compressive properties across different conditions. This study confirmed that the characteristics of LW-PLA become more pronounced as the material is printed continuously, with ST4 showing the strongest effect, followed by ST8 and CH4. It highlights the importance of adjusting nozzle temperature and infill density to control foaming, density, and mechanical properties. Overall optimal conditions are 230 °C and 50% infill density, which provide a balance of strength and toughness for applications.</p>","PeriodicalId":20416,"journal":{"name":"Polymers","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11511382/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142506553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Polypropylene Crystallinity Reduction through the Synergistic Effects of Cellulose and Silica Formed via Sol-Gel Synthesis.","authors":"Gulbarshin K Shambilova, Rinat M Iskakov, Aigul S Bukanova, Fazilat B Kairliyeva, Altynay S Kalauova, Mikhail S Kuzin, Egor M Novikov, Pavel S Gerasimenko, Igor S Makarov, Ivan Yu Skvortsov","doi":"10.3390/polym16202855","DOIUrl":"https://doi.org/10.3390/polym16202855","url":null,"abstract":"<p><p>This study focuses on the development of environmentally sustainable polypropylene (PP)-based composites with the potential for biodegradability by incorporating cellulose and the oligomeric siloxane ES-40. Targeting industrial applications such as fused deposition modeling (FDM) 3D printing, ES-40 was employed as a precursor for the in situ formation of silica particles via hydrolytic polycondensation (HPC). Two HPC approaches were investigated: a preliminary reaction in a mixture of cellulose, ethanol, and water, and a direct reaction within the molten PP matrix. The composites were thoroughly characterized using rotational rheometry, optical microscopy, differential scanning calorimetry, and dynamic mechanical analysis. Both methods resulted in composites with markedly reduced crystallinity and shrinkage compared to neat PP, with the lowest shrinkage observed in blends prepared directly in the extruder. The inclusion of cellulose not only enhances the environmental profile of these composites but also paves the way for the development of PP materials with improved biodegradability, highlighting the potential of this technique for fabricating more amorphous composites from crystalline or semi-crystalline polymers for enhancing the quality and dimensional stability of FDM-printed materials.</p>","PeriodicalId":20416,"journal":{"name":"Polymers","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11510954/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142506612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Avocado Seed Starch-Based Films Reinforced with Starch Nanocrystals.","authors":"Pedro Francisco Muñoz-Gimena, Alejandro Aragón-Gutiérrez, Enrique Blázquez-Blázquez, Marina Patricia Arrieta, Gema Rodríguez, Laura Peponi, Daniel López","doi":"10.3390/polym16202868","DOIUrl":"https://doi.org/10.3390/polym16202868","url":null,"abstract":"<p><p>Biopolymers derived from biomass can provide the advantages of both biodegradability and functional qualities from a circular economy point of view, where waste is transformed into raw material. In particular, avocado seeds can be considered an interesting residue for biobased packaging applications due to their high starch content. In this work, avocado seed starch (ASS)-based films containing different glycerol concentrations were prepared by solvent casting. Films were also reinforced with starch nanocrystals (SNCs) obtained through the acid hydrolysis of ASS. The characterization of the extracted starch and starch nanocrystals by scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis has been reported. Adding 1% of SNCs increased elastic modulus by 112% and decreased water vapor permeability by 30% with respect to neat matrix. Interestingly, the bioactive compounds from the avocado seed provided the films with high antioxidant capacity. Moreover, considering the long time required for traditional plastic packaging to degrade, all of the ASS-based films disintegrated within 48 h under lab-scale composting conditions. The results of this work support the valorization of food waste byproducts and the development of reinforced biodegradable materials for potential use as active food packaging.</p>","PeriodicalId":20416,"journal":{"name":"Polymers","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11511395/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142506549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chitin Extracted from Black Soldier Fly Larvae at Different Growth Stages.","authors":"Andrea Marangon, Geo Paul, Riccardo Zaghi, Leonardo Marchese, Giorgio Gatti","doi":"10.3390/polym16202861","DOIUrl":"https://doi.org/10.3390/polym16202861","url":null,"abstract":"<p><p>The black soldier fly (BSF) <i>Hermetia Illucens</i> can grow rapidly and on a wide variety of organic materials, and it is extensively used as a means of disposing of household organic waste. Different phases of the life cycle of BSF larvae (BSFL) are used in this work to extract chitin after the removal of lipids, mineral salts, and proteins. Multiple techniques, such as X-ray diffractometry, infrared spectroscopy, solid-state Nuclear Magnetic Resonance (¹³C ss-NMR) and thermogravimetric analysis, are used to investigate the chemical and physical characteristics of the extracted samples of chitin, which shows a high degree of acetylation (from 78% to 94%). The extracted chitin shows an increase of the thermal stability of 20 °C in the initial stage of life and 35 °C at the end of the life cycle if compared with a commercial standard. Moreover, the extracted chitin shows an increase in the crystallinity degree during the BSFL growth time (from 72% to 78%).</p>","PeriodicalId":20416,"journal":{"name":"Polymers","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11511002/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142506556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fused Filament Fabrication 3D Printing Parameters Affecting the Translucency of Polylactic Acid Parts.","authors":"Vladimír Vochozka, Pavel Černý, Karel Šramhauser, František Špalek, Pavel Kříž, Jiří Čech, Tomáš Zoubek, Petr Bartoš, Jan Kresan, Radim Stehlík","doi":"10.3390/polym16202862","DOIUrl":"https://doi.org/10.3390/polym16202862","url":null,"abstract":"<p><p>The effect of 3D printing parameters by Fused Filament Fabrication (FFF) on the translucency of polylactic acid (PLA) parts was investigated. Six different printing parameters were studied: object orientation, layer height, nozzle temperature, fan speed, extrusion multiplier, and printing speed. The commercially available Plasty Mladeč PLA filament and the Original Prusa MK4 3D printer were used for the experiments. The translucency of the printed samples of 50 × 25 × 1 mm dimensions was measured using a luxmeter in an integrating sphere. A total of 32 sample combinations were created. Each sample was printed ten times. The results show that all investigated parameters significantly affect the optical properties of PLA parts. The best measured translucency values were obtained when printing in portrait mode, with a layer height of 0.30 mm, nozzle temperature of 240 °C, fan speed of 100%, 0.75 set extrusion multiplier, and a speed of 40 mm/s. ANOVA was used to statistically evaluate the effect of each parameter on translucency, and statistically significant differences were found between different combinations of parameters (<i>p</i> < 0.05). Scanning Electron Microscope (SEM) analysis provided detailed images of the surface structure of the printed samples, allowing for a better discussion of the microscopic properties affecting the translucency. The best print setting has an efficiency of 88% compared to the default setting of 65%. The ability of visible light to pass through the print (translucency) improved by 23%.</p>","PeriodicalId":20416,"journal":{"name":"Polymers","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11511128/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142506567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of Silica Nanoparticles on the Piezoelectro-Elastic Response of PZT-7A-Polyimide Nanocomposites: Micromechanics Modeling Technique.","authors":"Usama Umer, Mustufa Haider Abidi, Syed Hammad Mian, Fahad Alasim, Mohammed K Aboudaif","doi":"10.3390/polym16202860","DOIUrl":"https://doi.org/10.3390/polym16202860","url":null,"abstract":"<p><p>By using piezoelectric materials, it is possible to convert clean and renewable energy sources into electrical energy. In this paper, the effect on the piezoelectro-elastic response of piezoelectric-fiber-reinforced nanocomposites by adding silica nanoparticles into the polyimide matrix is investigated by a micromechanical method. First, the Ji and Mori-Tanaka models are used to calculate the properties of the nanoscale silica-filled polymer. The nanoparticle agglomeration and silica-polymer interphase are considered in the micromechanical modeling. Then, considering the filled polymer as the matrix and the piezoelectric fiber as the reinforcement, the Mori-Tanaka model is used to estimate the elastic and piezoelectric constants of the piezoelectric fibrous nanocomposites. It was found that adding silica nanoparticles into the polymer improves the elastic and piezoelectric properties of the piezoelectric fibrous nanocomposites. When the fiber volume fraction is 60%, the nanocomposite with the 3% silica-filled polyimide exhibits 39%, 31.8%, and 37% improvements in the transverse Young's modulus ET, transverse shear modulus GTL, and piezoelectric coefficient e31 in comparison with the composite without nanoparticles. Furthermore, the piezoelectro-elastic properties such as ET, GTL, and e31 can be improved as the nanoparticle diameter decreases. However, the elastic and piezoelectric constants of the piezoelectric fibrous nanocomposites decrease once the nanoparticles are agglomerated in the polymer matrix. A thick interphase with a high stiffness enhances the nanocomposite's piezoelectro-elastic performance. Also, the influence of volume fractions of the silica nanoparticles and piezoelectric fibers on the nanocomposite properties is studied.</p>","PeriodicalId":20416,"journal":{"name":"Polymers","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11511313/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142506542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advances in Electrospun Poly(ε-caprolactone)-Based Nanofibrous Scaffolds for Tissue Engineering.","authors":"Karla N Robles, Fatima Tuz Zahra, Richard Mu, Todd Giorgio","doi":"10.3390/polym16202853","DOIUrl":"https://doi.org/10.3390/polym16202853","url":null,"abstract":"<p><p>Tissue engineering has great potential for the restoration of damaged tissue due to injury or disease. During tissue development, scaffolds provide structural support for cell growth. To grow healthy tissue, the principal components of such scaffolds must be biocompatible and nontoxic. Poly(ε-caprolactone) (PCL) is a biopolymer that has been used as a key component of composite scaffolds for tissue engineering applications due to its mechanical strength and biodegradability. However, PCL alone can have low cell adherence and wettability. Blends of biomaterials can be incorporated to achieve synergistic scaffold properties for tissue engineering. Electrospun PCL-based scaffolds consist of single or blended-composition nanofibers and nanofibers with multi-layered internal architectures (i.e., core-shell nanofibers or multi-layered nanofibers). Nanofiber diameter, composition, and mechanical properties, biocompatibility, and drug-loading capacity are among the tunable properties of electrospun PCL-based scaffolds. Scaffold properties including wettability, mechanical strength, and biocompatibility have been further enhanced with scaffold layering, surface modification, and coating techniques. In this article, we review nanofibrous electrospun PCL-based scaffold fabrication and the applications of PCL-based scaffolds in tissue engineering as reported in the recent literature.</p>","PeriodicalId":20416,"journal":{"name":"Polymers","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11511575/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142506529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bacterial Degradation of Low-Density Polyethylene Preferentially Targets the Amorphous Regions of the Polymer.","authors":"Trinh Nguyen, Jan Merna, Everett Kysor, Olaf Kohlmann, David Bernard Levin","doi":"10.3390/polym16202865","DOIUrl":"https://doi.org/10.3390/polym16202865","url":null,"abstract":"<p><p>Low-density polyethylene (LDPE) is among the most abundant synthetic plastics in the world, contributing significantly to the plastic waste accumulation problem. A variety of microorganisms, such as <i>Cupriavidus necator</i> H16, <i>Pseudomonas putida</i> LS46, and <i>Pseudomonas chlororaphis</i> PA2361, can form biofilms on the surface of LDPE polymers and cause damage to the exterior structure. However, the damage is not extensive and complete degradation has not been achieved. The changes in polymer structure were analyzed using Time-domain Nuclear Magnetic Resonance (TD-NMR), High-Temperature Size-Exclusion Chromatography (HT-SEC), Differential Scanning Calorimetry (DSC), and Gas Chromatography with a Flame Ionization Detector (GC-FID). Limited degradation of the LDPE powder was seen in the first 30 days of incubation with the bacteria. Degradation can be seen in the LDPE weight loss percentage, LDPE degradation products in the supernatant, and the decrease in the percentage of amorphous regions (from >47% to 40%). The changes in weight-average molar mass (Mw), number-average molar mass (Mn), and the dispersity ratio (Đ) indicate that the low-molar mass fractions of the LDPE were preferentially degraded. The results here confirmed that LDPE degradation is heavily dependent on the presence of amorphous content and that only the amorphous content was degraded via bacterial enzymatic action.</p>","PeriodicalId":20416,"journal":{"name":"Polymers","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11511126/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142506550","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}