Polymers最新文献

It is a great challenge to obtain an ideal hydrogel for the clinical treatment of intrauterine adhesion (IUA) disease. Here, a novel injectable chitosan-lignin/poloxamer hydrogel loaded with platelet-rich plasma (CL-PF127@PRP) was prepared by self-assembly at room temperature. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), rheological analysis, and injectable writing were used to characterize the structure of the hydrogel. The results confirmed that the amino group of chitosan and the sulfonic group of sodium lignosulfonate were ionic-crosslinked by electrostatic attraction, which stabilized the three-dimensional structure of the PF127 hydrogel loaded with PRP, and PRP made the porous structure gradually become tight. Moreover, the CL-PF127@PRP hydrogel displayed good injectability and a solid state. The soaking experiment showed that the CL-PF127@PRP hydrogel had suitable degradation at pH = 7 and a good PRP release rate (PRP release 70% at 96 h). Cell experiments in vitro demonstrated that the CL-PF127@PRP hydrogel possessed good biocompatibility, an anti-inflammatory function, and pro-angiogenic activity. Furthermore, an animal experiment of skin wound and IUA confirmed that the skin wound closure rate of the CL-PF127@PRP hydrogel was over 50% on the seventh day. PRP improved the thickness of the endometrium and uterus receptivity, suggesting that the CL-PF127@PRP hydrogel offers great promise for the clinical treatment of IUA.

(1) Background: The intra-oral behavior of clear thermoplastic dental materials can be influenced by various intrinsic and extrinsic factors. Aim: The purpose of this in vitro study was to evaluate the optical properties, color changes and whiteness variations of four thermoplastic polymers used for dental appliances, in a simulated oral environment. (2) Methods: Customized thermoformed specimens of four PETG thermoplastics were selected and investigated in this study: Leone [L], Duran [D], Erkodur [E] and Crystal [C]. The thermoplastic samples were divided into three groups related to pH values (neutral, acidic and basic). A period of 14 days was simulated. Five stages resulted: I. dessicated specimens; II. hydrated in artificial saliva; III. subsequent desiccated; IV. artificial aged; V. further dessicated. Optical CIE L*a*b* coordinates were determined and optical properties, like TP (translucency), OP (opalescence) values, color differences ΔE-NBS, white indexes in dentistry WI_D and white index differences ΔWI_D were calculated for all stages of the study, for each group of the materials. Statistical analyses were performed. (3) Results: Optical properties of PETG clear thermoplastic materials, like TP and OP, increase in a simulated oral environment and the changes become significant after artificial aging. Related to pH values, the optical behavior between the materials is significantly different. During artificial aging, the tested materials behave significantly differently in terms of optical properties. (4) Conclusions: After the simulated period of 14 days, TP and OP values increase, with a migration of the color towards red and yellow. Color changes in some cases even reach the level of extremely marked. Whiteness increases, and the differences are mostly perceptible, but partially exceed the limit of acceptability.

Epoxy resin filled with aluminum particles constitutes a polymer composite material commonly utilized in research and development departments to fabricate rapid tooling for prototyping new designs. This study developed aluminum-filled epoxy resin molds by incorporating surface-cooled cooling channels (SCCCs) to enhance cooling performance, validated through Moldex3D simulation and experimental analysis. The simulation revealed that a 1 mm mesh size was utilized to balance accuracy and efficiency, with simulations revealing the complete filling of the injection-molded product within 5 s. This study examines rapid tooling with surface-cooled cooling channels in low-density polyethylene injection molding. The reliable parameters include a melt temperature of 160 °C, a mold temperature of 30 °C, an injection pressure of 10 MPa, and a heat dissipation time of 20 s. These parameters effectively minimize the risk of mold cracking while ensuring efficient molding. The SCCC demonstrates superior cooling performance, enhancing cooling efficiency by 58.7% compared to the conventional conformal cooling channel. It reduces cooling time, enhances production capacity, and shortens delivery times. Additionally, it lowers energy consumption, carbon emissions, and the rate of product defects in large-scale manufacturing. A cooling mechanism of SCCC after LDPE injection molding was also proposed.

The search for new natural, sustainable, economical and biodegradable reinforcements for composite materials has increased in recent years, highlighting the importance of fibers from the natural environment. This work evaluates the use of tururi fibrous fabric as a reinforcement in a polymer matrix, using Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry and scanning electron microscopy. The mechanical and fractographic performance of composites reinforced with 2.5, 5.0 and 7.5% mass fraction of tururi in a polyester matrix is also investigated. The FTIR and XRD results identified groups characteristic of natural fibers and the presence of elemental constituents such as cellulose, hemicellulose and lignin. Thermogravimetry indicated good thermal stability near 246 °C. The morphology of the fibrous fabric is irregular and formed by tangles of threads. The mechanical behavior of the composites in bending revealed a variation in stress with the increase in the percentage of fabric in the matrix, explained by defects and failures due to low interfacial adhesion between the phases. Impact tests indicated that increasing the percentage of fabric in the matrix improves impact energy absorption, reflecting better adhesion and load distribution. Thus, the development of this natural composite is promising for applications in green and sustainable products.

In this study, a novel macromolecular flame retardant (MFR) with a phosphine oxide structure is successfully synthesized to improve the flame retardancy of polyamide 6 (PA6). Following this, the flame-retardant polyamide 6 (FR-PA6) is prepared via melt blending the MFR with PA6. Results indicate that the introduction of MFR has little effect on the melting and crystallization temperature of FR-PA6. While it slightly reduces the thermal stability of PA6, MFR significantly enhances its flame retardancy. The limiting oxygen index of FR-PA6 increases from 21.8% to 28.2%, and it successfully passes the UL-94 V-0 rating when it contains 0.5 wt% of phosphorus. Compared with pure PA6, the av-EHC of FR-PA6 is reduced by 32.2% and the SEA is increased by 66.7%. The MFR showed a flame-retardant mechanism in both the gas phase and the condensed phase. In the gas phase, the decomposition of MFR releases phosphorus-containing free radicals to interrupt the combustion chain reaction and reduces the concentration of the combustible caprolactam. In the condensed phase, the MFR promotes faster formation of melt droplets during combustion, taking heat away from the burning PA6 timely.

The aim of this study was to optimize a method for qualitative and quantitative determination of gaseous degradation products formed in the process of thermal decomposition in the sample. The toxicometric index was determined with the use of the coupled TG-FTIR technique (gas analyzer). The polyurethane (PUR) and polyvinyl chloride (PVC) were used for analytical studies. Based on the obtained results, it was concluded that the sample mass used for analysis, as well as the spectral range of the IR spectrum, has a crucial role in the qualitative and quantitative assessment of gaseous toxic degradation products generated during the thermal decomposition of polymeric materials. Using a gas analyzer, proprietary toxicity indices were developed, i.e., the partial toxicity index (IT_PC) and total toxicity index (IT_GC). It should be noted that the determined toxicity indices refer to a test sample not exceeding 10 mg. The small mass of the sample subjected to analysis allows for high resolution and repeatability of the results reading. The results of this study provide a significant methodological contribution to both the identification of gaseous degradation products formed during the thermal decomposition of materials and their quantitative detection.

This study addresses the high cost of traditional dental impression materials by introducing a novel composite material reinforced with wheat bran powder, aiming to reduce expenses while maintaining suitable mechanical performance. Tensile and compression test specimens were prepared according to the ASTM D412 and ASTM D575 standards, respectively, to evaluate the mechanical properties of the pure elastomer and the wheat-bran-reinforced composite. Comparative t-tests were conducted to analyze the tensile and compression strengths of both materials, focusing on their cost-effectiveness and suitability for dental applications. The results demonstrate that the wheat-bran-reinforced composite exhibits compression strength (105 MPa) comparable to that of the pure elastomer while offering controlled deformation and enhanced stiffness under compression. Although the composite shows reduced tensile strength (7 MPa vs. 11 MPa), its performance remains adequate for applications requiring moderate tensile properties. Notably, the new material reduces costs by approximately 50%, making it an economical and sustainable alternative for dental impression materials. This innovation aligns with sustainable practices by incorporating natural fibers and offers dentists a cost-effective solution without compromising on performance.

An active film-forming solution of chitosan and lemongrass essential oil was applied as a coating on paperboard, forming an alternative and sustainable packaging material for food applications. The active paper-film systems were characterized by color parameters, thermogravimetric analyses, contact angles, Fourier transform infrared spectroscopy, X-ray diffraction, mechanical properties, and cytotoxicity. The active coated paperboard was homogeneous and yellowish in appearance. The tensile strength (transverse and longitudinal directions) was directly influenced by increasing the number of layers of the chitosan-lemongrass active coating. The oil concentration significantly affected the Taber stiffness (transverse direction). The active coatings with higher concentrations of lemongrass essential oil altered the thermal stability of the coated paperboard. The contact angle values were characteristic of hydrophobic materials. The coated systems presented three characteristic peaks in the X-ray diffraction analysis-2θ = 16.5°, 22.9°, and 29.8°-and an amorphous halo at 18.9°. The cytotoxicity analysis of the active material (1:40:5) indicated potential reductions in the lemongrass essential oil content to maintain cell viability while ensuring insecticidal efficacy, supporting its safe use as food-contact active packaging. In this way, the active packaging system based on a chitosan coating containing lemongrass essential oil on paperboard could be a type of efficient active material packaging which is safe in contact with food and sustainable for the environment.

Nowadays, large amounts of wastewater arise from various industrial applications. The discharge of wastewater into the environment represents a threat to the aquatic ecosystem and human health. Thus, in the present study, innovative double-network (DN) hydrogels with pH-sensitive features and applicability as adsorbents in the treatment of leather dye wastewater were prepared. The polyelectrolyte, poly(N,N-dimethylaminoethyl methacrylate (PDMAEMA), was obtained via the radical polymerization process, while the supramolecular structure was co-assembled through physical interactions. As a novelty, the double network was obtained through the interpenetration of the supramolecular network in the cross-linked polymeric one. The new hydrogels were physico-chemically and morphologically characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and in terms of thermogravimetric analysis (TGA), swelling degree measurements, and dye adsorption studies. The DN hydrogels present interconnected macropores and high thermal stability. The swelling capacity of the dual network gels highlights a superadsorbent behavior at pH 3. Furthermore, the dye adsorption study highlights the effects of several variables (pH, concentration dose of adsorbent) on the ability of the gels to adsorb an anionic dye. The adsorption kinetics of the anionic dyes fitted the pseudo-first-order model (PFO). The estimated maximum adsorption capacities for the anionic dyes was 451 mg g^-1 for PDMAEMA and 545 mg g^-1 for DN gel.

This study involved the exposure of epoxy-coated basalt-plastic rebars, with diameters of 6 and 8 mm, to the open climate conditions of Yakutsk and Tiksi, located in the Arctic region of Russia. The exposure duration was 54 months. Basalt-plastic rebars were tested both untreated and after contamination with a set of neutral microorganisms resilient to cold climates, including spore-forming bacteria from the genus Bacillus, and mold fungi from the genera Aspergillus. Results showed that after 12, 24, and 54 months of exposure, the tensile strength and modulus of elasticity of untreated rebars increased by 5-14% due to the post-curing of the epoxy matrix. However, in biologically contaminated rebars, these indicators decreased on average by 11%. Bacterial cells and fungal mycelium, which penetrated surface irregularities of the rebars under open climate conditions, contributed to microcrack development, reducing the mechanical properties of the basalt-plastic rebars and causing additional moisture diffusion in the radial direction of the bars.