Polymers最新文献

To compare them with PTFE-40# steel tribo-pairs, the tribological properties of textured PEEK-40# (AISI 1040) steel friction pairs were researched under full-film lubrication conditions by manufacturing micro-dimples with different dimensions on the contact surfaces of 1040 steel discs using laser surface texturing (LST). After repeated tribological tests, the coefficients of friction (COFs), wear losses, and wear morphologies of the PEEK-1040 steel friction pairs were measured and analyzed. The results show that micro-dimples do not significantly reduce the average COFs of PEEK-1040 steel friction pairs when lubricated with a sufficient amount of hydraulic oil, but they do reduce the wear losses of most groups. When the dimple diameter was 250 μm, the dimple depth was 5 μm, the area ratio was 6.6%, and the mass loss of the 1040 steel disc was reduced by 90% compared to the smooth reference. In comparison to the behavior of the PTFE-1040 steel tribo-pairs, PEEK-1040 steel friction pairs can provide better tribological performance, whether smooth or dimple-textured. This study offers important insights for the design of seals in machinery.

Damping material performance influences the efficacy of vibration and noise reduction. However, traditional damping materials often have low damping peaks or narrow damping temperature ranges. In this study, a series of polyurethane (PU)/poly(ethylene methacrylate) (PEMA) composites were synthesised, in which the PU hard segments were varied using toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate. The soft segments comprised tetrahydrofuran homopolymer glycol. The influence of the hard-segment structure on the properties of the PU/PEMA composites was investigated by infrared spectroscopy, thermogravimetric analysis, dynamic mechanical thermal analysis, and other experimental methods. The performance mechanism was explored from a molecular perspective via integration with molecular dynamics simulations. The PU/PEMA material with IPDI hard segments comprised numerous microphase-separated structures and exhibited greater free volume, fuller molecular-chain movement, and the highest damping performance, with a loss factor of 0.56. The PU/PEMA composites synthesised with TDI and MDI hard segments exhibited better compatibility, with the MDI-PU/PEMA system exhibiting a higher hydrogen-bonding force. This material also exhibited a higher thermal stability, with an initial breakdown temperature of 287.87 °C. This study provides a basis for regulating and optimising the performance of PU-based damping materials.

Reducing the ecological impact of dyes through wastewater discharge into the environment is a challenge that must be addressed in textile wastewater pollution prevention. Congo red (CR) dye is widely used in experimental studies for textile wastewater treatment due to its high organic loads used in its preparation. The degradation of organic dyes of the CR type was investigated using the photocatalytic activity of functionalized polymers. We have employed photodegradation procedures for both polymer-supported glycine groups (Code: AP2) and polymer-supported glycine-Zn(II) (Code: AP2-Zn(II)). A photocatalysis efficiency of 89.2% was achieved for glycine pendant groups grafted on styrene-6.7% divinylbenzene copolymer (AP2) and 95.4% for the AP2-Zn(II) sample by using an initial concentration of CR of 15 mg/L, a catalyst concentration of 1 g/L, and 240 min of photocatalysis. The findings provided here have shown that the two materials (AP2 and AP2-Zn(II)) may be effectively employed in the heterogeneous photocatalysis method to remove CR from water. From the perspective of the degradation mechanism of CR, the two photocatalysts act similarly.

The environmental challenges posed by laboratory plastic waste, particularly single-use items, underscore the urgent need for sustainable alternatives. This study investigated the development of reusable and biodegradable labware, addressing both functional and environmental demands. The content of the biodegradable additive in the polypropylene (PP) varied from 1% to 2% by weight via twin-screw extrusion, followed by injection molding to fabricate test specimens. Three different grades of PP were also compared. Optical, mechanical, and thermal properties were systematically assessed before and after repetitive autoclave sterilization for up to 10 cycles (121 °C, 15 min, 0.11 MPa). Additionally, cytotoxicity following electron beam irradiation (E-Beam 25 and 50 kGy) was evaluated in compliance with ISO 10993-5, alongside biodegradability studies conducted under ASTM D5511 conditions. The results demonstrate that the biodegradable additive stabilized the appearance and enhanced the flexural and impact strengths of PP without compromising thermal stability, particularly after five autoclave cycles. Cytotoxicity assays confirmed the biocompatibility of the additive-modified PP, while biodegradability tests indicated moderate degradation, with 12% biodegradation achieved over 6 months compared to negligible degradation in the negative control. These findings highlight the potential of additive-modified PP as a sustainable solution for reusable labware, balancing durability with improved environmental performance and providing a viable step toward more sustainable laboratory practices.

Sulfation of arabinogalactan (AG) from larch wood (Larix sibirica Ledeb.) in the melt of a sulfamic acid-urea mixture has been first examined. The impact of the AG sulfation temperature on the AG sulfate yield and the sulfur content has been established. The high sulfur content (11.3-11.6%) in sulfated AG has been obtained in the temperature range of 115-120 °C for a sulfation time of 0.5 h. The process effectively prevents molecular degradation under these conditions. The incorporation of sulfate groups into the arabinogalactan structure has been confirmed by the appearance of absorption bands in the FTIR spectrum that are typical of sulfate group vibrations. The ¹³C NMR spectroscopy study has proven that the AG sulfation in the melt of a sulfamic acid-urea mixture leads to the substitution of some free hydroxyl groups for C6, C4, and C2 carbon atoms of the AG β-D-galactopyranose units. The advantage of the proposed AG sulfation method is that the reaction occurs without solvent, and the reaction time is only 0.5 h. The kinetics of the thermal decomposition of the initial AG and sulfated AG samples have been studied. It has been found that the sulfated AG samples have a lower thermal resistance than the initial AG. The kinetic analysis has revealed a decrease in the activation energy of the thermal degradation of the sulfated samples as compared to the initial AG.

This research seeks to investigate the viability of using Tectona grandis wood powder as a reinforcement material in polymer matrix composites because of the increasing awareness of natural fibers that offer impressive characteristics and cost-effectiveness in addition to being biodegradable. The fibers were mixed with epoxy resin, and the mixture was passed through a filter to remove fiber bundles and then compression molded to form composites, which were cured in an oven. Different experiments were performed on the composite to measure its mechanical characteristics. The tests performed were a tensile test to measure the mechanical properties of the material like strength and elastic properties, a compression test for evaluating the behavior of the material under a compressive load, a hardness test for the rate of indentation resistivity, and an impact test for the material's ability to withstand shock loads. The results showed that fiber reinforcement caused a significant enhancement in the mechanical aspect of the composite, where the compression strength obtained was 249.83 MPa, and the tensile strength obtained was 17.98 MPa. SEM microstructural analysis and a moisture absorption test were performed, while an additional analysis was carried out using Ansys work bench software. This research proves that Tectona grandis wood powder improves the mechanical properties of polymer composites and represents a viable substitute for synthetic reinforcements.

Skin aging is a complex and multifactorial process influenced by both intrinsic and extrinsic factors. The periorbital area of the face is particularly susceptible to premature aging signs due to its delicate skin structure, and is a major concern for many individuals. While hyaluronic acid (HA)-based dermal filler products are commonly used for periorbital rejuvenation, novel approaches to effectively locally address the visible signs of aging are available. This study aimed to investigate Innovyal Regenerative Action (IRA), an injectable polynucleotide-HA (PN-HA) regenerative complex designed for periocular prejuvenation. Firstly, PN-HA was compared to other commercially available HA-based dermbooster products (Profhilo^®, Suisselle Cellbooster^® Glow, and NCTF^® 135 HA) in terms of rheological properties, in vitro antioxidant capacity, and total collagen production stimulation in human fibroblasts. Secondly, the clinical effects of the IRA PN-HA complex were evaluated in two case reports (monotherapy for periorbital prejuvenation). It was shown that the PN-HA complex outperformed its comparators in terms of relative rheological behavior (biophysical attributes normalized to polymer contents), intrinsic antioxidant activity (CUPRAC, FRAP, and ORAC assays), as well as total collagen level induction (72-h in vitro dermal fibroblast induction model). Generally, the results of this study provided mechanistic and preliminary clinical insights into the potential benefits of the IRA PN-HA complex for periocular cutaneous treatment. Overall, it was underscored that combining the structural support and regenerative properties of PN with the hydrating and volumizing effects of HA bares tangible potential for multifactorial skin quality enhancement and for periocular prejuvenation in particular.

The mechanical properties and envelope curve predictions of polyurethane-improved calcareous sand are significantly influenced by the magnitude and direction of principal stress. This study conducted a series of directional shearing tests with varying polyurethane contents (c = 2.5%, 5%, and 7.5%), stress Lode angles (θσ = -19.1°, 0°, 19.1°, and 30°), and major principal stress angles (α = 0°, 30°, 45°, 60°, and 90°) to investigate the strength and non-coaxial characteristics of calcareous sand improved by polyurethane foam adhesive (PFA). Key findings revealed that failure strength varied significantly with the major principal stress axis direction, initially decreasing to a minimum at α = 45° before increasing, with a 30% decrease and 25% increase observed at c = 5%. Non-coaxial characteristics between strain increment and stress directions became more pronounced, with angles varying up to 15°. Increasing polyurethane content from 2.5% to 7.5% enhanced sample strength by 20% at θσ = -19.1° and α = 60°. A generalized linear strength theory in the π-plane accurately described strength envelope variations, while a modified Lade criterion, incorporating polymer content, effectively predicted multiaxial strength characteristics with less than 10% deviation from experimental results. These contributions provide quantitative insights into failure strength and non-coaxial behavior, introduce a robust strength prediction framework, and enhance multiaxial strength prediction accuracy, advancing the understanding of polyurethane-improved calcareous sand for engineering applications.

Cisplatin, a frequently used chemotherapeutic for the treatment of cervical cancer, causes adverse effects that limit its use. Treatment with local therapy that limits toxicity remains a challenge. The aim of this study was to develop a local intravaginal cisplatin delivery system of polycaprolactone/polyvinylpyrrolidone sheath/core fibers by coaxial electrospinning. Physicochemical properties, degradation rate, mucoadhesion, release profile, and in vitro biosafety assays were characterized. Microscopy images confirmed the coaxial nature of the fibers and showed continuous morphology and diameters of 3-9 µm. The combination of polymers improved their mechanical properties. The contact angle < 85° indicated a hydrophilic surface, which would allow its dissolution in the vaginal environment. The release profile showed a rapid initial release followed by a slow and sustained release over eight days. The degradation test showed ~50% dissolution of the fibers on day 10. The adhesion of the fibrous device to the vaginal wall lasted for more than 15 days, which was sufficient time to allow the release of cisplatin. The biosafety tests showed great cytocompatibility and no hemolysis. The characteristics of the developed system open the possibility of its application as a localized therapy against cervical cancer, reducing adverse effects and improving the quality of life of patients.

Bioactive restorative materials are crucial for promoting remineralization and protecting dental tissues through ion release. This study examines how pH and temperature influence the short- and long-term ion (F^-, Ca²⁺, Sr²⁺, OH^-, Si, and PO₄^3-) release from seven commercial materials: Cention Forte Filling Material, Cention Primer, Stela Self Cure, Riva Light Cure HV, Riva Self Cure, Equia Forte HT Fil, and Fuji IX GP Fast. Disks were prepared according to the manufacturers' instructions; immersed in buffer solutions at pH 4.8, 6.8, and 8.8; and stored at 37 °C and 44 °C. Ion release was measured after 1, 7, and 28 days using ion chromatography and mass spectrometry. Results revealed that ion release was significantly affected by pH, temperature, and exposure time. The highest fluoride (40.14 ± 0.32 mg/L) and calcium (74.23 ± 0.37 mg/L) releases were observed in Riva Light Cure at pH 4.8 and 44 °C after 28 days, with the highest strontium release (5.87 ± 0.06 mg/L) occurring under the same conditions. In contrast, silicon release peaked in Cention Forte Filling (31.72 ± 0.68 mg/L) at pH 4.8 and 37 °C. These findings highlight the impact of environmental factors on material performance, assisting clinicians in selecting optimal restorative materials for long-term dental health.