Advances in Polymer Technology最新文献

This paper presents an in-depth analysis of the PLGA-PEG-PLGA polymer, focusing on its synthesis and applications in advanced drug delivery systems (DDSs). PLGA-PEG-PLGA, a triblock copolymer, gains attention due to its biodegradability, biocompatibility, and thermosensitive properties, making it suitable for encapsulating both hydrophilic and hydrophobic compounds. The polymer’s ability to undergo sol-to-gel at body temperature allows controlled and targeted drug release, significantly enhancing the solubility of poorly soluble drugs, such as paclitaxel and irinotecan. The paper discusses the polymer’s synthesis via ring-opening polymerization (ROP) and explores its optimization using various methods, including microwave-assisted techniques and supercritical CO₂. Additionally, it examines the polymer’s cytotoxicity in in vitro and in vivo studies, emphasizing its low toxicity and ability to deliver chemotherapeutic agents more effectively. The study highlights the polymer’s potential in cancer therapy, biopharmaceutical delivery, and the development of dual-sensitive drug carriers.

Vulcanized latex films from different Hevea brasiliensis natural rubber clones, including RRIM600, RRIT251, and PB235, were prepared using the creaming process of concentrated latex. The protein content, morphology, molecular weight distribution (MWD), mechanical properties, dynamic mechanical analysis, and thermo-mechanical properties were studied. The morphological characteristics of the Hevea brasiliensis natural rubber clones were analyzed using transmission electron microscopy (TEM). The results indicated that the particle sizes of the three clones ranged from 1.0 to 2.5 µm. Moreover, the MWD exhibited a bimodal pattern in the RRIM600 and RRIT251 clones, leading to a high polydispersity index (PDI) that correlates with protein content. Additionally, the PB235 clone showed higher molecular weight (Mw) than the other clones, which affected the properties of the vulcanized latex films. The mechanical properties, dynamic mechanical properties, thermal properties from temperature scanning stress relaxation (TSSR) analysis, and swelling resistance were also studied. The results indicated that the crosslinked density of the vulcanized latex films is related to the bimodal MWD. This leads to increased physical interactions between the end chains of short and long rubber molecules. Moreover, the crosslinked density is associated with protein content. This study confirms that the MWD and non-rubber components in different natural rubber clones affect the properties of vulcanized rubber.

Conductive polymers are a notable breakthrough in electronic technology, providing distinctive electrical characteristics that render them appropriate for various uses in contemporary products like OLEDs (organic light-emitting diodes), batteries, sensors, and medical equipment. Their use in additive manufacturing (AM) processes represents a significant advancement, allowing for the direct integration of electronic functionality into intricate 3D-printed structures. This results in a reduction in production time and costs associated with conventional assembly methods. This paper examines different conductive polymers, including PANI (polyaniline), PPy (polypyrrole), and PEDOT (poly(3,4-ethylene dioxythiophene)), with a focus on their involvement in AM methods including fused deposition modeling and inkjet printing. Current developments in ink formulations, including those integrating graphene, are improving conductivity while also tackling environmental issues. However, there are still obstacles that need to be overcome, such as finding the right balance between conductivity and processability, maintaining stability in different environmental conditions, dealing with biocompatibility concerns, and optimizing compatibility with other materials. Continuing research is improving these materials, and conductive polymers show potential for transforming electronics and medical applications due to their ability to be scaled up, their flexibility, and their adjustable electronic properties. This review article offers a thorough summary of the latest research trends, difficulties, and future paths in the realm of electronics and AM that utilize conductive polymers.

The use of centrifugal spinning as a method for producing nanofibers has advantages over other methods, such as high production rates, large-scale production, and no need for high voltage. In this work, two different biodegradable materials are used in different mixture ratios to produce biodegradable composite fibrous membranes. Characterization methods demonstrated that the amount of added carboxymethyl cellulose (CMC) significantly affects the fiber formation and end-product properties. When the concentration of CMC is increased, the membranes become mechanically stronger, whereas the fiber formation ability becomes weaker. The CMC crystal clusters and their heterogeneous distribution determine the optical properties of the membranes. These fibrillar composite membranes are suitable for use in biodegradable and eco-friendly filtration systems.

The recycling of thermoplastic polymers from end-of-life vehicles is crucial to achieve a circular economy within the sector and prevent the accumulation of plastic waste by reusing it. However, several challenges in these processes present difficulties, making it challenging or impossible to recycle these materials for the same applications, impeding the closure of the life cycle and valorization of waste. The primary problem faced by plastic converters is the presence of superficial paint. In this study, we evaluate the implementation of chemical methods with varying conditions to remove paint from used bumpers thermoformed with polypropylene, with the aim of valorizing the plastic waste from these bumpers. We examine the various process variables, such as reagent concentration, temperature, time, and pH. Additionally, we analyze procedures to quantify the paint content in the different recycled samples and use this as a tool to compare the effectiveness of different paint removal processes.

In this study, an artificial neural network (ANN)–based method is presented to predict the experimental effective demolding forces (EDFs) produced during the injection molding of a polycarbonate polymer material. To evaluate the prediction accuracy and capability of the proposed method, three different algorithms, namely Levenberg–Marquardt (lm), BGFS quasi-Newton (bfg), and scale conjugate gradient (scg), were included in the proposed model. The generated models were validated by comparing the experimental and ANN results, which showed good quantitative agreement. The performance of the algorithms was evaluated using the R² and root mean square error (RMSE) values, which indicated that scg exhibited the best performance with an R² of 0.9655 and an RMSE of 0.0223. The relative contribution plot of the ANN models showed that packing pressure had a stronger influence than mold temperature, filling time, and melt temperature. These results will form the basis for predicting the EDF of a comparable molded part using ANN and will help to significantly improve the demolding properties of polymer materials.

The use of glass fiber-reinforced polymer (GFRP) bars is an innovative approach to replace traditional reinforcement of steel into concrete structures. GFRP bars provide notable benefits like corrosion resistance, electromagnetic neutrality, higher tensile stress by weight ratio, sustainability, and cost-effective construction reducing maintenance cost. However, challenges like brittleness, reduced ductility, and lower elastic modulus limit their practical applications. This research examines the flexural behavior of GFRP-reinforced concrete beams using experimental and numerical methods. Nonlinear finite element analysis (FEM) was performed in ABAQUS, employing a three-dimensional deformable model, concrete damage plasticity (CDP) theory, and detailed material properties for concrete, steel and GFRP. Four-point flexural load conditions were simulated, and mesh sensitive analysis was conducted to ensure model accuracy. Experimental results demonstrated that GFRP-reinforced beams had higher load-bearing capability, but wider cracks and larger deflections compared to steel-reinforced beams. Failure of flexural members primarily due to concrete crushing was observed. Numerical simulations closely exhibited experimental load deflection performance, stress distributions, and failure patterns with accuracy variation of ~10%–16%. This study highlights the potential of FEM for correctly simulating the performance of GFRP-reinforced concrete beams and comparing the numerical outcomes with experimental studies. It was observed that GFRP-reinforced beams had 20% more load-carrying capacity compared to steel-reinforced beams based on grade of concrete and size of reinforcement. Deflection values for GFRP-reinforced beams were higher compared to steel-reinforced beam leading to requirements for serviceability considerations. The outcome of the study exhibited the potential of GFRP as a superior reinforcing material for specific applications.

In this work, the impact of using grafted hair as reinforcing agent for making composites has been studied and compared with composites using virgin hair. For this purpose, the composites have been prepared via compression molding using a thermoplastic resin, poly(methyl methacrylate) (PMMA), as matrix, and virgin or grafted human hair (HH), HH_act-g-PMMA_1.75, and HH_act-g-PMMA_2, with 56% and 78% of grafting percentages, respectively, were taken as reinforcement material, and their properties have been compared. The hair weight fractions in composites were varied from 15% to 60%. The SEM micrographs of the fractured surface of the tensile specimen of virgin HH-reinforced PMMA composites show hair pullouts. In contrast, in graft copolymer-reinforced PMMA composites, failure mainly occurs at the hair and not at the hair–matrix interface, showing better adhesion. This was supported by AFM images in which a decrease in surface roughness for grafted hair-reinforced composites was observed. The PMMA composites with grafted hairs showed improved mechanical properties than PMMA in contrast to composites with virgin hairs in which there was loss of tensile strength. On addition of 15% of HH_act-g-PMMA_1.75, the tensile strength raised by 21.86%, while in the case of HHact-g-PMMA_2 graft copolymer, the tensile strength was increased by 87.44% w.r.t virgin HH. The hair content up to 45% showed improvement in mechanical properties; however, further increase in hair content leads to a decrease in the mechanical strength. Dynamic analysis also showed an increase in storage (E′) and loss modulus (E′′), enhanced with the increase in hair concentration and reached the maximum for the 55:45::PMMA:hair ratio. The increase in E′ and E′′ was more when grafted hairs were used as the reinforcing agents. As compared to composites with virgin HH, an increase of 57–98% for E′ and 46–80% for E′′ was observed for composites with HH_act-g-PMMA_1.75. Similarly, for HH_act-g-PMMA_2 hairs, an increase of 49–102% in E′ and 45–98% for E′′ was observed. The present work thus shows that the use of grafted hairs results in the enhancement of adhesion of hair and matrix resulting in the improved properties.

Polycarbonate (PC)/acrylonitrile–butadiene–styrene (ABS) blends with no compatibilizers have been manufactured commercially and widely used for many applications for many years. Although most studies have shown that compatibilizers can improve the product performance of PC/ABS alloys, there are still different scholars who have demonstrated that compatibilizers do not have the expected effect. This study investigated the effects of various types of compatibilizers on properties such as the impact strength of PC/ABS alloys. To make rubber particles better mixed and achieve fine dispersion, a closed torque rheometer was used to make PC/ABS alloys. To avoid the influence of flow orientation on rubber particle dispersion during injection molding, test specimens were prepared using the mold pressing method. PC-rich alloys with no compatibilizer show the best performance in all trial samples. Maleic anhydride grafted ABS (ABS-g-MAH), synthesized by emulsion polymerization, could not enhance properties significantly as a compatibilizer. Methyl methacrylate–butadiene–styrene (MBS), which has the same rubber content as ABS powder, could not improve performance either. Sufficient rubbers well-dispersed in styrene/acrylonitrile (SAN) and PC content are key factors in influencing the performance in PC-rich blends.

Crosslinking agarose with bisoxiranes and epihalohydrins has been explored for years and is widely applied in the manufacturing of chromatography beads as industrial standard. Nevertheless, the effect on the molecular structure of agarose and the resulting consequences when used as chromatographic adsorber are poorly investigated. Agarose beads modified with 1,4-butanediol diglycidyl ether (BDDE) and epichlorohydrin (ECH), respectively, were characterized regarding their pore size and diffusion coefficients. Modification with BDDE led to reduced pore sizes, whereas no influence could be observed when using ECH. After functionalization as cation exchanger, BDDE- and ECH-modified beads were analyzed among others regarding their binding capacity of lysozyme and γ-globulin. Therefore, the hypothesis of crosslinking-induced diffusion limitation, especially with BDDE, could be further strengthened. Finally, the data were described by calculating the static binding capacity and diffusion coefficient using a cubic grid model and Ogston model, respectively. Overall, those simplified models describe the data quite accurate, whereas the deviation of the model from the static binding capacity is 4% ± 17%, from the diffusion coefficient of the BDDE- or ECH-modified beads 1% ± 16% and from the effective diffusion coefficient of the further sulfonated and column packed beads 11% ± 27%.