Lower Elongation Research Articles

Modification of Glucose Metabolic Pathway to Enhance Polyhydroxyalkanoate Synthesis in Pseudomonas putida

Medium-chain-length polyhydroxyalkanoates (mcl-PHAs) are semi-crystalline elastomers with a low melting point and high elongation at break, allowing for a wide range of applications in domestic, agricultural, industrial, and mainly medical fields. Utilizing low-cost cellulose hydrolyzed sugar as a carbon source and metabolic engineering to enhance synthesis in Pseudomonas putida is a promising strategy for commercializing mcl-PHAs, but little has been attempted to improve the utilization of glucose for synthesizing mcl-PHAs. In this study, a multi-pathway modification was performed to improve the utilization of substrate glucose and the synthesis capacity of PHAs. To enhance glucose metabolism to flow to acetyl-CoA, which is an important precursor of mcl-PHA, multiple genes in glucose metabolism were inactive (branch pathway and negative regulatory) and overexpressed (positive regulatory) in this study. The two genes, gcd (encoding glucose dehydrogenase) and gltA (encoding citrate synthase), involved in glucose peripheral pathways and TCA cycles were separately and jointly knocked out in Pseudomonas putida QSRZ6 (ΔphaZΔhsdR), and the mcl-PHA synthesis was improved in the mutants; particularly, the mcl-PHA titer of QSRZ603 (ΔgcdΔgltA) was increased by 33.7%. Based on the glucose branch pathway truncation, mcl-PHA synthesis was further improved with hexR-inactivation (encoding a negative regulator in glucose metabolism). Compared with QSRZ603 and QSRZ6, the mcl-PHA titer of QSRZ607 (ΔgcdΔgltAΔhexR) was increased by 62.8% and 117.5%, respectively. The mutant QSRZ609 was constructed by replacing the endogenous promoter of gltB encoding a transcriptional activator of the two-component regulatory system GltR/GltS with the ribosome subunit promoter P33. The final mcl-PHA content and titers of QSRZ609 reached 57.3 wt% and 2.5 g/L, an increase of and 20.9% and 27.3% over that of the parent strain QSRZ605 and an increase of 110.4% and 159.9% higher as compared to QSRZ6, respectively. The fermentation was optimized with a feeding medium in shaker flacks; then, the mcl-PHA contents and titer of QSRZ609 were 59.1 wt% and 6.8 g/L, respectively. The results suggest that the regulation from glucose to acetyl-CoA by polygenic modification is an effective strategy for enhancing mcl-PHA synthesis, and the mutants obtained in this study can be used as chassis to further increase mcl-PHA production.

Examination of Microstructure, Mechanical Properties, and Fatigue Strength in a Wire Arc Additively Manufactured Material Comprising Dissimilar Materials: AISI 316L Stainless Steel and Carbon Steel

This study provides a comprehensive investigation into the microstructure, hardness, tensile strength, and bending fatigue behavior of a Wire Arc Additively Manufactured (WAAM) component composed of dissimilar materials—Carbon Steel (CS) and 316L stainless steel. Microscopic analysis reveals distinct microstructural characteristics, such as equiaxed ferrite grains in WAAM CS and a coarse columnar structure with delta-ferrite phases in WAAM 316L. A macroscopic phase map indicates a predominantly Body-Centered Cubic (BCC) structure near the interphase, suggesting element migration between CS and 316L due to high heat input. Higher magnification scans highlight martensitic structures on both sides of the interphase, with the CS side exhibiting larger grain sizes. Hardness assessment along the built direction shows a peak hardness of 407 HV near the interphase on the 316L side, contrasting with the CS side's average interphase hardness of 316 HV due to larger grain sizes. The yield strength of both WAAM CS and WAAM dissimilar material was consistently measured at 392 MPa. In comparison, WAAM 316L exhibited a slightly lower yield strength of 359 MPa. Notably, WAAM 316L demonstrated the highest tensile strength among the materials, reaching 656 MPa. Meanwhile, WAAM CS displayed a robust tensile strength of 503 MPa, and the WAAM dissimilar material exhibited a yield strength of 520 MPa. In terms of elongation, WAAM CS and WAAM 316L showcased values of 44.9% and 49.6%, respectively. On the other hand, WAAM dissimilar material exhibited a somewhat lower elongation of 20.4%, suggesting a different mechanical behavior in terms of ductility. Bending fatigue tests on WAAM 316L, WAAM CS, and the dissimilar material reveal a fatigue limit of approximately 225 MPa for WAAM 316L, 210 MPa for WAAM CS, and approximately 210 MPa for the dissimilar material. In the low-cycle and medium-cycle regimes, the dissimilar material exhibits slightly superior fatigue strength, potentially due to its marginally higher static strength. Notably, consistent fractures on the CS side during fatigue tests underscore a recurring behavior in the dissimilar material.

Quantitative Analysis of TPU Microstructure and Performance Optimization across Various Processing Conditions.

Thermoplastic polyurethane (TPU) is essential in resource exploration, healthcare, automotive, and high-end recreational sports. Despite extensive research on TPU's microstructures and their macroscopic properties, the impact of processing conditions like compression and injection molding remains underexplored. This study investigates the influence of processing conditions on TPU by preparing samples with varying hard segment contents using compression molding at 205 °C and injection molding at melt temperatures of 205, 210, 215, and 220 °C, followed by heat treatment at 120 °C for 12 h. Results indicate that injection-molded TPU at 205 °C exhibits lower hydrogen bonding, crystallinity, long period, interfacial thickness, and lamella thickness than compression-molded TPU, leading to higher Young's modulus but lower elongation at break. As melt temperatures increase, these microstructural parameters decrease, reducing Young's modulus and increasing elongation at break. Post heat treatment, microstructural parameters increase, aligning Young's modulus with that of compression-molded samples, while elongation at break surpasses them. This suggests that heat treatment enhances microphase separation by rearranging hard and soft segments. our research reveals a consistent pattern across TPUs with varying hard segment contents, indicating that adjusting processing parameters can effectively regulate microstructure and performance, offering valuable insights for developing high-performance polyurethanes.

A Brief Review of Hemp Fiber Length Measurement Techniques

Accurate fiber length measurement is essential for the processing and quality management of textile products. This article reviews the current methods used to measure fiber length, including manual, photoelectric, capacitive, and optical techniques. Existing sample preparation processes for natural fiber characterization have been primarily developed for cotton and wool fibers. However, hemp fibers present unique challenges due to their greater length variability, high strength, and low elongation, making some traditional sample preparation methods less effective. Image processing offers a promising approach for scalable and precise measurement of hemp fiber length. Nevertheless, current image processing techniques are limited by the inability to effectively handle overlapping fibers, which increases both the time and cost of testing. Continued research into developing more advanced segmentation algorithms could lead to more widely adopted commercial methods for fiber measurement.

Characterization of Chayotextle Starch Films Supplemented with Essential Oils and Their Effect as a Coating on the Shelf Life of Bread

AbstractStarch extracted from chayote root is a carbohydrate polymer ideal for producing edible films, especially when combined with essential oils. This study develops starch‐based edible films incorporating rosemary (E‐RO) or cinnamon (E‐CO) essential oil and assesses their effectiveness in extending bread's shelf life. Films with essential oils exhibit significantly higher (p < 0.05) water vapor permeability compared to control films without oil. Tensile strength and elongation tests show that films stored at low water activity (aw < 0.443) have greater strength and lower elongation (p < 0.05) than those stored at high water activity. Additionally, essential oils significantly enhance the films' antimicrobial and antifungal activity against selected microorganisms. Edible films with essential oils are fully degraded around day 18, while control films degraded by day 15. Bread coated with these films is stored at different temperatures to analyze effects on physicochemical properties and hardness. Sensory analyses reveal that coated bread receives overall acceptance scores (7.61–8.64) similar to control bread and show delayed mould growth during the 15‐day storage period. These findings suggest that chayote root starch‐based films with essential oils have strong potential as active food coatings, effectively extending the shelf life of stored bread.

Experimental study on seismic performance of bridge pier with new HRB650E high-strength steel bar

To facilitate the application of high-strength steel in reinforced concrete bridge structures, this study explores the seismic performance of full-scale HRB650E high-strength reinforced concrete bridge piers. Initially, monotonic tensile tests were conducted on HRB400 and HRB650E steel rebars with the same slenderness ratio to analyze the differences in their mechanical properties. Subsequently, quasi-static cyclic tests were carried out on four square full-scale RC bridge piers to examine the influence of new high-strength rebars, stirrup ratios, and axial load ratios on the seismic performance. Based on the experimental results, a hysteresis model suitable for HRB650E reinforced concrete columns was developed. The findings indicate that the HRB650E steel bar exhibited lower uniform elongation and fracture elongation compared to HRB400 steel bar. The displacement at which HRB650E piers reached crack damage was 36 % higher than that of HRB400 piers, and they also showed lower residual displacements at all load levels. The maximum lateral load capacity and the ductility coefficient of HRB650E piers increased significantly compared to HRB400 piers. While the initial secant stiffness of both types was comparable, HRB650E piers exhibited a slower rate of stiffness degradation, resulting in higher secant stiffness at the ultimate state. They also demonstrated 35 % higher cumulative energy dissipation at the ultimate state. When the stirrup ratio of HRB650E piers was increased from 1.1 % to 1.7 %, there was a slight reduction in residual displacement, a small increase of the yield strength, and a minor improvement in the maximum lateral load capacity. Furthermore, a higher stirrup ratio was observed to improve energy dissipation levels at all loading stages. Increasing the axial load ratio of HRB650E piers from 0.1 to 0.2 allowed the piers to withstand greater deformations at the same repairable ultimate state, with significant increases in yield strength, maximum lateral load capacity, initial secant stiffness, and secant stiffness at the ultimate state, but a small increase in the cumulative energy dissipation. The hysteresis model for HRB650E RC columns, based on experimental data, exhibited good computational accuracy.

Root traits of soybeans exposed to polyethylene films, polypropylene fragments, and biosolids

Biosolid use imports microplastics into the rhizosphere where they may interfere with root-soil-microbial interactions and cause morphological adaptations in crop root systems. Few studies have examined the response of crop roots to microplastics at documented soil concentrations, and many studies collect root traits using destructive techniques. Hence, there is little information on when and how microplastics effect the physical structure of root systems. Using the rhizobox method, soybeans (Glycine max) were grown in soil amended with biosolid microplastic mimics (polyethylene film or polypropylene fragments at 2,000 and 15,000 particles/kg dry soil) or biosolids and imaged weekly until maturity (11 weeks) using a custom scanner system. Plant biomass increased in the polyethylene treatments and decreased in the high concentration polypropylene treatment. Relative to the Control, polyethylene treatments had larger root length, reduced root diameters, reached maturity faster, had deeper root systems, and had a greater number of lateral roots. In contrast, polypropylene treatments had a mixed response, with high concentrations eliciting a lower root length, fewer laterals, and a more vertical root orientation. Segmented linear regression revealed that root growth in the Control and Biosolid treatments continued through the course of the experiment, while the microplastic treatments reached maturity up to two weeks earlier. Imagery revealed that microplastics elicited deeper rooting depth within the first week and differences in all root traits were evident by the development of the first trifoliate leaflets. Microplastic effects on root traits at early life stages suggest soil physiological drivers, while increased branching frequency and lower lateral elongation are suggestive of changes in soil nitrogen availability. The minimal difference in root traits in the biosolid treatment may be attributable to differences in microplastic properties or counteractive effects by other biosolid constituents.

Artificial Intelligence, Genuine Outcome: Analysis of 72 Consecutive Cases of Subfascial Augmentation Mastopexy With Smooth Round Implants Supported by P4HB Scaffold.

Ptosis recurrence often leads to unsatisfactory results after mastopexy, even more so when additional stress is provided by implants on compromised native tissue. The poly-4-hydroxybutyrate(P4HB) scaffold (GalaFLEX) with its favorable safety profile and proven long-term mechanical strength represents a preferred option for soft tissue support. The primary endpoint was assessment of lower pole stretch from the early postoperative period up to 3 years. Out of 151 patients who underwent surgery by G.B. from March 2020 to December 2023, a total of 72 with a 12-month-mininum follow-up who had primary (46) or secondary (26) augmentation mastopexy with subfascial round smooth implants and P4HB scaffold support were included in the study. Three-dimensional artificial intelligence software was utilized for all measurements. Further analysis included evaluation of ptosis recurrence and all complications. No recurrent ptosis, bottoming out, implant displacement, or capsular contracture was reported during follow-up (mean, 24.8 months). The lower pole arch's elongation was 8.04% and 9.44% at 1 and 3 years respectively, comparing favorably with previous reports. Statistically significant correlation (P < .05) between implant size and lower pole stretch was noted, this being greater for larger implants (> 400 cc; P = .0011) and primary cases (P = .1376). Progressive volume redistribution from upper to lower pole was observed in the first year, with substantial stability thereafter. This is the largest published series reporting long-term results (up to 45 months) in mastopexy augmentation with GalaFLEX, suggesting its supportive role in lower pole stability even in the setting of concurrent breast augmentation with smooth implants in a subfascial plane.

The impact of heat treatment process on the drilling characteristics of Al–5Si–1Cu–Mg alloy produced by sand casting

Aluminum–Silicon (Al–Si) based materials are commonly preferred in engineering studies requiring high mechanical performance as an alternative to steel materials. These alloys are especially preferred in the automotive industry, aerospace components and heavy machinery parts. In post-casting processes, machining operations are of great importance for high geometric precision, surface quality and longer fatigue life in mechanical environments. In this research, the microstructural, mechanical and machining characteristics of the Al–5Si–1Cu–Mg material produced by sand casting method in both as-cast (AC) and heat-treated (HTed) (Solid solution, quenching and aging-SQA) states were experimentally investigated. Microstructural examinations were carried out with optical microscope and SEM images. Mechanical properties were determined by tensile and hardness tests. Then, drilling experiments were performed in the CNC vertical machining center with 8 mm diameter uncoated HSS (High Speed Steel) cutting tools at constant cutting conditions (i.e., cutting speed-V: 125 m/min, feed rate-f: 0.05 mm/rev and depth of cut-DoC: 15 mm). In microstructural investigations, it was determined that the microstructure of the Al–5Si–1Cu–Mg material in AC state consists of α-Al, eutectic Si, β-Fe (β-Al5FeSi) and π-Fe (π-Al8Mg3FeSi6) intermetallics. After the SQA, the existing phases generally exhibited a spherical structure, and it was seen that the β phase in the microstructure transformed into the Ɵ (Al7FeCu2) phase. SQA improved the hardness, yield and tensile durability of the material, whereas decreasing the elongation to fracture. SQA process improved the machining characteristics of the material by decreasing thrust force, moment, surface roughness and built-up edge (BUE) formation. The machined subsurface structure of HTed alloy under constant cutting conditions was determined to be more stable and smooth and the machined surface microhardness of HTed alloy was higher compared to as-cast alloy due to the effect of solid precipitation hardening. In addition, shorter and more broken chips occurred in the machining of HTed alloys due to the effect of low elongation to fracture.

The Association Between the Structure of the Fatty Chain in Amides and Their Lubricating Performance in Acrylonitrile‐Butadiene‐Styrene (ABS) Resins

ABSTRACTThe exploitation of efficient lubricants for ABS resins is widely recognized as beneficial for industrial production. Fatty diamides are typically applied as the lubricants for ABS resins; however, the connection between fatty chain structures and the lubricating properties is still vague. In this work, a range of ethylenediamine‐based amide lubricants (EDA‐Cn) with different fatty chain structures were successfully prepared and chemical structures were characterized in detail by the Fourier transform infrared spectrometer and proton nuclear magnetic resonance. The rheological test results suggested that the complex viscosity and relaxation time were positively associated with the fatty chain lengths of EDA‐Cn. The dynamic mechanical analysis results confirmed that EDA‐Cn exhibited excellent compatibility with ABS resins. The lubricating effect of EDA‐Cn decreased with increasing fatty chain lengths, which was manifested by a higher glass transition temperature, and lower elongation at break of ABS resins. In comparison to EDA‐C22, the complex viscosity (angular frequency = 0.1 rad/s) and glass transition temperature of EDA‐C10 have decreased by 24.9% and 3.9%, respectively. The molecular dynamics simulations revealed the intrinsic mechanism of lubricant‐substrate interaction. The EDA‐Cn containing short fatty chain lengths reduced the interaction energy with the matrix, thereby promoting the diffusive movement of the chain segments, and resulted in the increase in the mean square displacement and improved flow properties. These findings provided sufficient theoretical basis for the rational design and preparation of lubricants for ABS resins.

Heterostructure-induced anisotropy of tensile property in laser directed energy deposition TC11 titanium alloy

Grain structure is generally considered as an important factor to influence the anisotropy of mechanical properties of the additive manufactured metallic component. In this work, we revisit the mechanical anisotropy of a TC11 alloy with heterogeneous grain structure fabricated by laser directed energy deposition(L-DED) technology, and fully unravel the plastic deformation behavior with different types of heterogeneous grain morphology. It is found that the 0-BD specimens and 45-BD specimens exhibit desirable strength-ductility synergy with considerable YS, high UTS and prominent ductility. The synergistic increase in strength and plasticity is induced by the hetero-deformation of equiaxed grain and columnar grain induced. Specially, the optimum hetero-deformation induced (HDI) strengthening is obtained in 45-BD specimen due to the symmetric constraint morphology of heterostructure. The lower strength and elongation of the 90-BD specimens are associated with the fracture of α phases at grain boundaries perpendicular to the loading direction.

The effects of cellulose nanocrystals (CNC) and halloysite nanotubes (HNT) on selected properties of crosslinked modified tapioca starch films

Abstract Crosslinked modified tapioca starch films with CNC and HNT have the potential to be good renewable and biodegradable food packaging. Starch, CNC, and HNT were used because of their availability and cheap cost. This study aimed to investigate the effect of varying concentrations of CNC and HNT on the morphology, mechanical and optical properties of crosslinked modified tapioca starch films as an initial step in developing an active food package. Both CNC and HNT have high crystallinity and a large amount of OH groups. The OH groups as well as the ion-dipole interaction in HNT increase the tensile strength of the films. The highest tensile strength and the lowest elongation were recorded in films containing 5% CNC and 5% HNT. Beyond 5%, the addition of these nanomaterials diminished the tensile strength due to agglomeration which is the weak point of the films. Below the 5%, the nanomaterials serve as good reinforcing agents which improve the tensile strength. In addition, all films have good transmission capacity for visible light, while films with HNT outperform films with CNC in UV blocking ability.

Morphological Analysis of River Characteristics in Musi Rawas Utara Regency

Effective watershed management requires the efficient collection, storage, and use of runoff water, as well as the recharge of groundwater. This study will employ morphometric analysis to determine the characteristics of the rivers flowing through one of the districts of the Province of South Sumatera, Musi Rawas Utara (Muratara). Using DEM data and GIS software, this study conducted a quantitative-descriptive analysis to obtain quantitative information about the watershed. The acquired numbers are interpreted descriptively to provide a description of the watershed's characteristics and their implications for rivers in Muratara.The eighth-order rivers of Muratara Regency are classified as major rivers. A mean bifurcation ratio (Rb) of 3.98 indicates that geological features have no effect on the typical flat drainage pattern. On average, the drainage density of the watersheds was moderate, but a few locations had a very high drainage density range, indicating their erodibility. The basins of rivers with low circularity and elongation ratios (0.19 and 0.48, respectively) are elongated and have a steep slope. The morphometric research reveals that the Muratara rivers have abundant water resources and are also predicted to experience numerous water-related disasters. Using morphometric knowledge, however, the local government could develop mitigation and planning systems for river management. Future measures must include ensuring that adequate drainage systems are in place and that all construction adheres to the principles of proper land management.

Effect of Raw Material and Process Conditions During the Dry Forming of CTMP Fibers for Molded Pulp Products

ABSTRACT This article provides a concise insight into the thermoforming of airlaid CTMP pulp. First, the airlaid process was studied, showing that fiber fractionation and the retention of fines occurred in the forming head. Then, the effect of temperature and pressure during thermoforming was investigated. Harsher conditions, i.e. higher temperature and pressure, yielded greater densification of the substrate and higher tensile strength. The maximum strength was found at the highest settings tested, that is, 100 MPa and 200°C. The screening of thermoforming conditions was also compared to previously published results on wetforming. Next, the effect of softwood CTMP pulp was delineated, which on average showed the best mechanical properties at elevated freeness and high degrees of bleaching. At last, a comparison between dry forming and wetforming was made for one selected pulp quality. Here, the dryformed substrates were stiffer at low elongation, yet the wetformed substrates yielded a greater extensibility and higher tensile strength. In conclusion, dryformed pulp mostly relies on temperature and pressure for bond formation during thermoforming, which produces materials that are distinctly different from wetformed molded pulp.

Microstructure evolution in laser powder bed fusion melted 2205 duplex stainless steel using in-situ EBSD during uniaxial tensile testing

Compared to duplex stainless steels (DSSs) prepared by traditional methods, specimens produced through laser powder bed fusion (LPBF) exhibit excellent yield strength but lower elongation. To improve elongation, understanding microstructure evolution during uniaxial tensile testing is crucial. This study investigates the slip behavior, grain boundary evolution, and phase transformation of LPBF 2205 duplex stainless steel during tensile deformation using in-situ electron backscatter diffraction (EBSD). Results show the formation of slip bands, which increase in number as loading stress rises. The primary slip systems activated are {110}<111> in ferrite and {111}<110> in austenite. In the ferrite phase, slip dislocations accumulate and generate low-angle grain boundaries (LAGBs), which evolve into high-angle grain boundaries (HAGBs), refining the grain structure. Numerous Σ3 annealing twins form in the austenite phase, but detwinning and twinning reduce Σ3 content as deformation processes. Ferrite and austenite exhibit good stability during the initial stages of tensile deformation. However, some austenite transforms into martensite through the transformation-induced plasticity (TRIP) effect at the final stages of deformation, which helps relieve stress concentration and delays material fracture. This study provides valuable insights for optimizing microstructure to improve the mechanical properties of LPBF materials.

Investigation on Tensile Properties of Polylactide-Nanoclay (PLA/ MMT) Surface Modification Nanocomposites

Polylactic acid (PLA) has gained significant attention as an environmentally friendly biopolymer, but its limited mechanical properties have hindered broader applications. Nanoparticles such as montmorillonite (MMT) offer a promising approach to address this limitation. The intercalation of MMT with polymer chains can significantly impact the mechanical properties of the nanocomposites. Hence, this paper investigated the effect of surface-modified montmorillonite (MMT) nanoparticles on the mechanical properties of polylactic acid (PLA) nanocomposites. The acetylation process of MMT was carried out followed by neutralisation process with NaOH. PLA granules and acetylated-modified MMT were mixed, crushed into granular form, and moulded. The effect of varying concentrations of modified MMTs on the tensile strength, elongation at break, and maximum force of PLA/MMT nanocomposites was evaluated using the ASTM D638 standard. FTIR results showed shifts in peak intensities in regions 2750 cm-1- 2810 cm-1 led to changes in the aliphatic and aromatic regions, which confirmed the presence of acetylation. Controlled surface modification improved interfacial interactions and load distribution, enhancing overall mechanical performance. The incorporation of surface-modified MMT in PLA/MMT nanocomposite increased the maximum force, Young's modulus, elongation at breaks and tensile strength. PLA/1wt% MMT and the PLA/7wt% MMT compositions exhibited good mechanical properties. However, the PLA/5 wt% MMT blendis deemed more suitable for food applications, such as disposable cups, plates, and cutleries, due to its lower elongation point. In conclusion, the hydrophilic properties of MMT and the hydrophobic properties of PLA are compatible due to the synergistic effects during surface modification which enhance the overall performance of the nanocomposites.

Microstructure, deformation and fracture mechanism of Mg-Gd-Y-Zn-Zr alloy with different rolling routes during tension

The microstructure, deformation and fracture mechanism of unidirectional rolling (UR) and cross rolling (CR) Mg-4.7Gd-3.4Y-1.2Zn-0.5Zr alloy during tension were studied. Both rolled alloys exhibit typical bimodal microstructures, with the difference being that UR alloy has elongated grains containing rod LPSO phase, while CR alloy has relatively rounded deformed grains containing lamellar LPSO phase. After tension until fracture, the LPSO phase morphology of the two alloys remains unchanged. CR alloy exhibits a higher yield strength and lower elongation than UR alloy. Although the higher average basal <a> slip Schmid factor result in the lower yield strength of UR alloy, the activation of the high proportion of non-basal slip is responsible for its higher elongation. UR alloy and CR alloy exhibit ductile fracture and quasi cleavage fracture characteristics, respectively. For UR alloy, a variety of dislocations accumulated near grain boundary and the weak slip transfer effects between grains both contributes to the propagation of grain boundary cracks. However, the effects of weak interfacial bonding between metastable lamellar LPSO phase and matrix, along with the similar orientation and higher geometric compatibility of CR alloy, lead to the rapid spread of transgranular cracks.

Tailoring Hydrogel Sheet Properties through Co-Monomer Selection in AMPS Copolymer Macromers.

This study investigates hydrogels based on 2-Acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS) copolymers, incorporating N-hydroxyethyl acrylamide (HEA) and 3-sulfopropyl acrylate potassium salt (SPA). The addition of HEA and SPA is designed to fine-tune the hydrogels' water absorption and mechanical properties, ultimately enhancing their characteristics and expanding their potential for biomedical applications. A copolymer of AMPS, 2-carboxyethyl acrylate (CEA) combined with methacrylic acid (MAA) as poly(AMPS-stat-CEA-stat-MAA, PACM), was preliminarily synthesized. CEA and MAA were modified with allyl glycidyl ether (AGE) through ring-opening, yielding macromers with pendant allyl groups (PACM-AGE). Copolymers poly(AMPS-stat-HEA-stat-CEA-stat-MAA) (PAHCM) and poly(AMPS-stat-SPA-stat-CEA-stat-MAA) (PASCM) were also synthesized and modified with AGE to produce PAHCM-AGE and PASCM-AGE macromers. These copolymers and macromers were characterized by 1H NMR, FT-IR, and GPC, confirming successful synthesis and functionalization. The macromers were then photocrosslinked into hydrogels and evaluated for swelling, water content, and mechanical properties. The results revealed that the PASCM-AGE hydrogels exhibited superior swelling ratios and water retention, achieving equilibrium water content (~92%) within 30 min. While the mechanical properties of HEA and SPA containing hydrogels show significant differences compared to PACM-AGE hydrogel (tensile strength 2.5 MPa, elongation 47%), HEA containing PAHCM-AGE has a higher tensile strength (5.8 MPa) but lower elongation (19%). In contrast, SPA in the PASCM-AGE hydrogels led to both higher tensile strength (3.7 MPa) and greater elongation (92%), allowing for a broader range of hydrogel properties. An initial study on drug delivery behavior was conducted using PACM-AGE hydrogels loaded with photosensitizers, showing effective absorption, release, and antibacterial activity under light exposure. These AMPS-based macromers with HEA and SPA modifications demonstrate enhanced properties, making them promising for wound management and drug delivery applications.

Effect of potassium salt type on physicochemical properties of carrageenan films and rehydrated hydrogels

This study focused on the effect of potassium salt type on the physicochemical properties of carrageenan (Car) films and rehydrated hydrogels, with the aim of developing a new method for the preparation of Car hydrogels. The addition of potassium salt decreased the tensile strength (TS) of Car films, especially those containing KI. After rehydration, the weight and thickness change ratios of the Car films decreased with salt addition, and the sequence was as follows: K2CO3 < KH2PO4 < CH3COOK < KCl < K2SO4 < KSCN < KI < C6H5K3O7. The effect of potassium salt type on the TS and thermal transition temperature of rehydrated hydrogels was opposite that on weight and thickness change ratios. The hydrogels with K2CO3, KH2PO4, CH3COOK, KCl, and K2SO4 exhibited lower transverse relaxation time (T2) and smaller pore size compared with the other hydrogels. On the other hand, the effect of potassium salt type on hydrogels prepared using Car films soaked in potassium salt solution (S-Car) was similar to that observed on hydrogels prepared using Car films with potassium salt soaked in ultrapure water (U-Car). Compared with U-Car hydrogels, the S-Car hydrogels had higher TS and thermal transition temperature and lower elongation at break, T2, pore size, and hydrogen bond intensity. In conclusion, the potassium salt type and soaking method can be used to regulate the properties of Car hydrogels and provide a theoretical basis for the design of Car hydrogels.

Strain rate dependence of mechanical behavior in an AlSi10Mg alloy with different states fabricated by laser powder bed fusion

The strain rate dependence of mechanical behavior in an AlSi10Mg alloy with different states fabricated by laser powder bed fusion (LPBF) was investigated systematically via thermodynamic calculations, microstructure characterization and mechanical characteristic evaluation in the present study. The results show that there is a close relationship among the material state, microstructure and dynamic mechanical behavior. Before tensile deformation, the as-built specimen possesses a fine equiaxed grain structure and a typical cellular structure surrounded by continuously distributed particles; the annealed specimen has coarser equiaxed grain structures and particles, but no cellular structure is present. Both the as-built and annealed specimens exhibit weak strain rate sensitivity, and the strain rate sensitivity parameters are 0.01 and 0.024, respectively. Under specific strain rate conditions, the as-built specimen has a higher strength and lower elongation than the annealed specimen. After tensile deformation, there is a significant increase in the dislocation density. Independent of the material state, the dislocation density increases with increasing strain rate. Compared with the as-built specimen, the annealed specimen has a stronger strain rate sensitivity because of the greater dislocation density variation.