Advances in Polymer Technology最新文献

This paper investigates the effect of poly(butylene adipate-co-terephthalate) (PBAT) on the mechanical and morphological properties of poly(lactic acid) (PLA) when the PLA is blended with 10%, 20%, and 30% PBAT and subjected to different draw ratios (DRs), followed by annealing at a fixed length. Results indicate that PBAT functions more as a strengthening agent than a toughening agent when the blend is drawn. Furthermore, both undrawn and most drawn samples exhibit higher crystallinity and lower cold crystallization temperatures (T_cc) (in proportion to PBAT ratio) compared to the unblended material, with crystallinity equilibrating at the highest measured draw ratio (DR) of 4, as determined by differential scanning calorimetry (DSC). The crystallinity of the annealed samples equilibrates at 45%–47%, demonstrating the effectiveness of heat treatment at the cold crystallization temperatures of the samples, as measured by DSC, which decreases with increasing DR. However, X-ray diffraction (XRD) results show that heat treatment at the original T_cc, specific to the undrawn PLA, results in higher crystal orientation.

Solvent-free polyurethane dispersions (PUDs), which disperse without the use of organic solvents, present a sustainable alternative for textile coating applications. The release of organic solvents into the environment has raised concerns because of their association with extreme weather events and their deleterious effects on human health. This study used an ecofriendly solvent-free process, along with polyester polyols derived from corn and other natural materials, to synthesize a series of PUDs with varying biomass contents (60, 50, 40, 30, and 0 wt.%). The successful synthesis of PUDs was verified using fourier transform infrared spectroscopy, and experiments were performed to determine their mechanical and thermal properties, nanoparticle characteristics, zeta potential, physical stability, and textile coating applications. The results of this study demonstrate the potential of the synthesized PUDs for enhancing the performance of textiles.

This study investigates the machining behavior of a sisal/bamboo fiber reinforced polyester matrix hybrid composite (10%/20%/70% weight ratio, unidirectional 0° orientation) through drilling and milling operations. Taguchi methods and Gray Relational Analysis (GRA) were employed to optimize machining parameters (spindle speed, feed rate, tool diameter, and depth of cut) while considering delamination, surface roughness (R_a), and material removal rate (MRR). ANOVA (analysis of variance) was utilized to analyze the influence of the parameters. Drilling results showed that spindle speed influenced entry delamination, while tool diameter significantly impacted exit delamination. Optimal drilling parameters (A₁B₃C₃: 380 rpm, 0.25 mm/rev, 10 mm) minimized delamination (DFentry = 1.10, DFexit = 1.50) while maximizing MRR (19.63 mm³/min). In milling, feed rate was the dominant factor influencing both delamination and R_a. Higher feed rates led to increased delamination and R_a. Higher spindle speeds reduced R_a. The optimal milling parameters (S₃F₃d₂: 1180 rpm, 0.06 mm/rev, 3 mm) minimized delamination (1.41) and R_a (0.17) while maximizing MRR (2548.8 mm³/min). Although feed rate showed the largest influence on MRR, none of the factors were found to be statistically significant in influencing MRR based on ANOVA. This study provided valuable insights for optimizing machining parameters to enhance performance and reduce defects in processing the biocomposite.

Brewer’s spent grains (BSGs) are lignocellulosic sources that can be considered promising economic alternatives to wood as biofillers to produce wood–plastic composites (WPCs). Given the high protein content (25 wt.%) of BSGs, alkaline hydrolytic solid–liquid (S/L) extractions were carried out at different pHs, with the goal of extracting as much protein as possible without altering or compromising the quality of the lignocellulosic matrix. Biocomposites with 10–50 wt.% biofiller were produced by blending polybutylene succinate (PBS) and poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBH) with native BSG (BSG), BSG treated at pH 10.5 (BSG-S2_T2) and BSG treated at pH 12 (BSG-S2_T3). The injection-molded compounds were characterized in terms of structural, rheological, mechanical, morphological, and thermal properties to investigate the potential impact of different biofillers on the overall compatibility of the two different biopolymer matrices as an alternative to conventional wood flour-based WPCs. Fourier transform infrared (FT-IR) spectra, thermal (differential scanning calorimetry [DSC]), and morphological (scanning electron microscope [SEM]) analyses revealed only minor interactions. The melt flow rate (MFR) analyses showed the increased viscosity in PBS-based biocomposites when the filler concentration increased. In contrast, for PHBH-based composites, an increase in MFR values was obtained under the same test conditions, with a maximum peak of 97% for S2_T3 30 wt.% filler. From a mechanical point of view, the addition of reinforcing fibers led to a more significant increase in Young’s modulus (E) in PBS-based composites as the biofiller content increased, up to 98%, compared to pure PBS. On the contrary, in PHBH-based composites, the addition of fillers led to a significantly lower increase, with values between 14% and 20% compared to pure PHBH. The tensile strength (σ_B) and elongation at break (ε_B) decreased proportionally in the two biopolymer matrices as the percentage of natural filler increased, with properties similar to traditional WPCs. These results are consistent with the literature and support the application of PBS and PHBH biocomposites filled with BSG as an environmentally friendly alternative to conventional plastics.

Recent advancements in biomedical engineering have shed light on the remarkable capabilities of self-healing hydrogels, particularly those derived from chitosan (CHS) or its derivatives. These hydrogels exhibit noteworthy properties such as self-healing (SH), biocompatibility, and responsiveness to various stimuli like pressure, temperature, and pH. Recently, different therapeutic approaches, especially gene therapy and chemotherapy, have been explored through the incorporation of CHS-based hydrogels with therapeutic agents. Despite their promise, the clinical application of CHS hydrogels has been limited owing to an inadequate combination of physical and chemical properties, resulting in uncontrolled swelling and suboptimal SH behavior, particularly in terms of mechanical properties. This comprehensive review will explore the mechanistic understanding of various functionalized CHS, shedding light on their ability to offer desired SH properties while enhancing swelling behavior. These advancements are crucial for applications in tissue engineering and wound management. This comprehensive review aims to serve as a guide to CHS-based self-healing hydrogels, emphasizing their potential in addressing diverse challenges in the field of biomedical engineering.

Nanocellulose (NC) extraction from agricultural waste and lignocellulosic biomass residues has drawn considerable interest due to its low cost and wide availability. The environmental issues linked to nonrenewable materials have underscored the need for renewable alternatives that are biocompatible, biodegradable, and eco-friendly. This study aimed to investigate the potential of Ethiopian highland bamboo Arundinaria alpina for NC extraction by using acid hydrolysis. An experimental design incorporating response surface methodology (RSM) was applied to identify the optimal hydrolysis process parameters for NC extraction. The optimum conditions for NC extraction were a reaction time of 60 min, temperature of 40°C, and acid concentration of 61.40 wt%, with a yield of 43.15%. Bamboo and extracted NC were characterized for their chemical composition, particle size distribution, and crystallinity, using Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and X-ray diffraction (XRD), respectively. The resulting NC had a particle size of 79.64 nm. XRD analysis revealed the crystallinity indices of the bamboo and its corresponding NC was 44.60% and 74.07%, respectively. These results indicate that highland bamboo A. alpina is a promising lignocellulosic source for sustainable NC extraction, optimization, and industrial applications.

To reveal the relationship between the dielectric constant and mechanical strength indices of polymer grouting materials, 40 groups of specimens with different densities were designed and prepared in the laboratory. The complex dielectric constants of the specimens within the frequency range of 500–6000 MHz were measured using a vector network analyzer (VNA) equipped with the open-ended coaxial probe. Based on the experimental data, relationship equations for the dielectric constant and conductivity as functions of density were constructed. Compared to conductivity, the dielectric constant was found to be less affected by frequency. By incorporating the results of engineering mechanics tests while using density as an intermediate medium, a mechanical performance index model based on dielectric properties and conductivity was developed. The study found that there are linearly increasing relationships with different increments between the bending strength, unconfined compressive strength, tensile strength, shear strength, shear modulus, and the dielectric constant and conductivity. Based on the research findings of this paper, the mechanical properties of polymers can be predicted through nondestructive testing technology using electromagnetic waves.

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.