Polyester Research Articles

Unsaturated polyester resin based composites: A case study of lignin valorisation

Materials from green resources boast a low carbon footprint, forming the foundation of the circular economy approach in materials science. Thus, in this study, waste poly(ethylene terephthalate) (PET) was subjected to depolymerization using propylene glycol (PG), and subsequent polycondensation with bio-based maleic anhydride (MA) produced unsaturated polyester resin (b-UPR). Bio-derived acryloyl-modified Kraft lignin (KfL-A) served as a vinyl reactive filler in the b-UPR matrix to create b-UPR/KfL-A composites. The structural characterization of KfL-A and b-UPR involved the use of FTIR and NMR techniques. The mechanical properties of the newly fabricated composites were assessed through tensile strength, Vickers microhardness, and dynamic mechanical tests. The addition of KfL-A to the rigid b-UPR matrix enhanced material flexibility, resulting in less stiff and hard materials while preserving composite toughness. For instance, incorporating 10 wt% of KfL-A in b-UPR led to a 17% reduction in hardness, a 48% decrease in tensile strength, and a 20% reduction in toughness. Positive environmental impact was achieved by incorporation of 64 wt% of renewable and recycled raw material. Analogously prepared b-UPR/KfL composites showed structural inhomogeneity and somewhat better mechanical properties. Transmission (TEM) and scanning (SEM) electron microscopies revealed a suitable relationship between mechanical and structural properties of composites in relation to the extent of KfL-A addition. The UL94V flammability rating confirmed that flame resistance increased proportionally with the KfL-A addition. Once deposited in a landfill, these composites are expected to disintegrate more easily than PET, causing less harm to the environment and contributing to sustainability in the plastics cycle.

Oligomeric oxidovanadium(IV) phosphates as a promising alternative to cobalt-based driers and accelerators

This study reports promising catalytic activity of oxidovanadium(IV) dialkyl phosphates those can serve as primary driers for air-drying paints and as accelerators for room-temperature curing of unsaturated polyester resins. It describes an improved synthetic protocol giving title compounds at high yields and clarifies their molecular structure. The behavior in solution and in formulation of alkyd resin was investigated by electron paramagnetic resonance. Strong catalytic activity is documented by standard tests on several commercial alkyd binders and one multipurpose unsaturated polyester resin.

Enhance the loss of sound transmission of glass using a thin polyester/silica aerogel composite as a new sound insulation

One of the problems of the glass is the noise pollution that is easily directed into the building. Using a very thin and cheap layer on the glass can effectively prevent the transmission of sound, reduce costs, and increase the peace of its residents. In this work, two types of silica aerogel (SA) were synthesized by using sodium silicate as a precursor in the sol-gel method in the presence (SA-U) and absence of ultrasound (SA-C). The synthesized SA samples were converted into discs under 100 bar pressure and investigated their sound transmission loss (STL). The average STL of SA-U sample was 32 dB, while it was 21 dB for SA-C. The synthesized SA samples in the presence and absence of ultrasound were added to polyester (PES) resin and prepared SA-U/PES and SA-C/PES composites. The prepared composites were deposited with a thickness of 1 mm on a glass with a thickness of 3 mm. The SA-C/PES composite was able to improve the STL of glass to 28.5 dB, while the SA-U/PES composite was able to improve it to 27.3 dB. The average STL of the glass was only 11.2 dB.

Impact of molybdenum disulfide diffused coir fiber on the physical, mechanical, thermal, and vibrational characteristics of polyester composites

AbstractThis research focuses on comparing the properties of molybdenum disulfide (MoS2) diffused coir fiber polyester composites (MCF‐PCs) with neat coir fiber polyester composites (NCF‐PCs) and exploring its applications in various industrial sectors such as automotive, construction and manufacturing, where mechanical strength and fire resistance are critical factors. The study aims to investigate the physical, mechanical, thermal degradation, fire performance, and vibration properties of these composites. Compression molding was used to develop composites with different coir fiber loadings (10%, 20%, and 30% by weight). MoS2 nanoparticles diffused on the fiber surface significantly improved mechanical characteristics, thermal stability, and fiber‐matrix compatibility. The findings indicate better crystallinity and physical properties in MCF‐PCs compared to NCF‐PCs. Morphological observations confirmed improved fiber‐matrix compatibility in MoS2‐diffused fiber composites with polyester. The MCF‐PC with 20% loading exhibited the highest tensile (28 ± 1.24 MPa), flexural (50 ± 0.50 MPa), and impact (15 ± 1.01 kJ/m2) strength. The flame retardancy of the composites was evaluated using a horizontal combustion test apparatus. In addition, MCF‐PCs exhibited better flame retardancy as evidenced by lower flame propagation velocity (9 ± 0.20 mm/min) and increased ignition time (13 ± 0.29 Sec). The MCF‐PC with 20% loading shows maximum natural frequencies of 77 ± 4.1 Hz.Highlights This study investigated MoS2‐diffused coir fiber‐reinforced polyester composites. Fiber‐matrix adhesion can be improved with modified fiber‐reinforced composites. The MoS2 diffusion on fibers improved the physical and mechanical properties of polyester composites. The MoS2 diffusion on fibers enhanced the thermal and vibrational characteristics of polyester composites. MoS2‐diffused natural fiber composites offer considerable research potential.

Proton exchange membranes based on sulfonated polybutylene fumarate: Preparation and characterization

AbstractBased on a novel unsaturated polyester, polybutylene fumarate (PBF), a series of sulfonated proton exchange membranes were prepared and characterized for direct methanol fuel cell application. In this work, PBF underwent sulfonation at different degrees, and the optimum degree of sulfonation (DS) was identified by assessing the hydrolytic stability. In the second step, an effective strategy to enhance the membranes' proton conductivity was adopted by the addition of the 2‐(1H‐Imidazol‐2‐yl) acetic acid (Im‐COOH) compound as a proton‐conducting agent to the sulfonated PBF (SPBF) matrix with the optimum DS. The results unveiled significant alterations in the physicochemical properties of PBF due to sulfonation, including an elevation in water uptake and the glass transition temperature (Tg), accompanied by the disappearance of the crystallinity within SPBF. In terms of electrochemical characteristics, the SPBF‐17.5 PEM demonstrated a proton conductivity of 3.36 × 10−3 S cm−1 and a methanol permeability of 1.068 × 10−7 cm2 s−1, yielding a selectivity of approximately 31,460 S s cm−3. Furthermore, the attractive interactions between SO3H and NH groups further elevated proton conductivity to 4.12 × 10−3 S cm−1, accompanied by a decrease in methanol permeability to 0.942 × 10−7 cm2 s−1, enhancing the selectivity parameter to 43,736 S s cm−3.

Machine learning assisted mechanical properties prediction of fine denier polyester fiber

In recent years, more and more attention has been attracted by fine denier polyester fibers in electronic information industry due to their unique structural and excellent mechanical properties. As known, the mechanical properties of fine denier polyester fibers have a close relationship with their melt-spinning process parameters, thus, it is worth further exploring the influence of process parameters on fiber mechanical properties (namely breaking strength, elongation at break and CV of breaking strength). This study aims to develop a novel prediction model based on the artificial neural network (ANN) to predict the key mechanical properties of fine denier polyester fibers. For this purpose, firstly, different specifications of fine denier polyester fibers with different mechanical properties are produced by adjusting the key melt-spinning parameters, namely spinning temperature, take-roll speed and metering pump speed. Then the experimental data is collected, analyzed and augmented with effect to be used for modeling. Next, a novel prediction model based on ANN is developed by importing the two-streams structure and two attention matrices to improve the feature abstraction for mechanical properties prediction. Lastly, different predictive performance indicators, namely root mean square error (RMSE), mean absolute percent error (MAPE) and the coefficient of determination (R2) are imported to evaluate the proposed model. For the total of three mechanical properties, the predicted results of the proposed model in terms of RMSE, MAPE and R2 are respectively 0.3499, 0.0906 and 2.9516.

A novel non-woven fabric from bamboo fiber in medical lifestyle products

The present study aims to investigate the appropriate size of bamboo fibers derived from waste bamboo and determine the optimal duration for soaking in bio-fermented water to facilitate fabric molding. Additionally, we seek to explore the properties of non-woven fabric products manufactured from bamboo fibers. The study factors encompass three grades of bamboo fibers, designated A, B, and C, as well as five levels of fermentation time: 2, 4, 6, 8, and 10 days. A Completely Randomized Design (CRD) experiment is planned to assess both physical and microbial properties. Furthermore, we will analyze the inhibition of Staphylococcus aureus (S. aureus) and Escherichia coli (E.coli) bacteria in accordance with AATCC test standards and determine the optimal ratio for non-woven fabric molding. Regarding the ratio of bamboo fiber to polyester fiber, we will investigate three levels: 50:50, 70:30, and 100:0, with the objective of designing medical lifestyle products.Preliminary findings indicate that grade B bamboo fibers exhibit a light brown color and a relatively thin structure, with lengths ranging from 1 to 3 cm, rendering them suitable for most fabric production processes. Notably, unfermented bamboo fibers demonstrate higher inhibition of S. aureus and E.coli bacterial growth compared to their fermented counterparts. Additionally, our results suggest that the ingredient ratio significantly impacts the molding process, with a 99.94% effect. Remarkably, a blend of bamboo fiber and polyester fiber in a 70:30 ratio can be mechanically processed to create needle-pressed fabric, utilizing a method that involves pressing and tight weaving. This innovative approach facilitates the production of antibacterial non-woven fabric products suitable for elderly individuals, ready for practical use in community settings as a best practice solution.

Low-temperature crack resistance of stone matrix asphalt mixtures under chloride salt dry-wet cycles

Given the current insufficient understanding of the low-temperature crack resistance performance and crack evolution patterns of asphalt mixtures under chlorinated salt wet-dry coupling environments, this study aims to fill this knowledge gap. We employed SMA-13 asphalt mixtures modified with different dosages of polyester fibers (0 %, 0.3 %, 0.35 %, 0.4 %, 0.45 %, 0.5 %) and tested their low-temperature crack resistance by conducting 0 to 8 wet-dry cycles in pure water and a 13.25 % chlorinated salt solution, to explore the improvement effect of polyester fibers on the performance of asphalt mixtures in such environments. The results indicate that an increase in the number of wet-dry cycles leads to a degradation of crack resistance performance across all fiber dosages, especially under the influence of chlorinated salt wet-dry coupling, where the adverse effects are more pronounced. Fracture energy analysis further confirms that 4 and 6 cycles of wet-dry cycling are effective indicators for evaluating the attenuation of low-temperature crack resistance under the long-term impact of wet-dry cycling. Through Digital Image Correlation (DIC) and Scanning Electron Microscopy (SEM) analyses, this study reveals the significant impact of wet-dry cycling on crack evolution and identifies 0.4 % as the optimal dosage of polyester fibers, significantly enhancing the low-temperature crack resistance performance of asphalt mixtures.

Depolymerization of PET Fibers from Textile Blends and Recovery of Terephthalic Acid

AbstractThe hydrolytic depolymerization of poly(ethylene terephthalate) (PET) fibers with solid sodium hydroxide was investigated. The study presents an innovative recycling approach for the recovery of virgin‐quality terephthalic acid (TA) from textile blends consisting of PET and elastane fibers. PET fibers were depolymerized for 5 min at 140 °C. An internal mixer served as an investigation platform for the experiments. The quality of TA is quantified based on its color value. Both the hydrolytic depolymerization of polyester fibers and the quality of the recovered TA are not impaired by the presence of up to 15 % elastane fibers in textile blends.

Engineering properties of hybrid polymer composites produced with different unsaturated polyesters and hybrid epoxy

In this study, the mechanical properties of hybrid polymer composites produced with different unsaturated polyesters and hybrid epoxy resins are investigated. The composites were produced by blending unsaturated polyester resins (i.e., orthophthalic, isophthalic, and terephthalic) and bisphenol-A-based epoxy-vinyl ester resin to produce single, binary and ternary blends. In doing this, a total of 14 different combinations were produced. The results show that the binary and ternary polymer blends tend to improve almost all the tested properties of the polymer composites. Further, the fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) results confirmed that the reason for enahcned properties is due to better crosslinking and longer chains of polymers produced in binary and ternary mixtures. The absence of peaks determining the styrene polymerization character for all mixtures also demonstrates that the polymerization reaction takes place in all mixtures. It is also believed that the binary and ternary resin mixtures have developed higher energy absorption compared to single resin composites. All of the mentioned has been achieved while the gelation temperatures of the hybrid resin mixtures were not changed significantly and they began gelation at the expected temperature values. In addition to the gelation, peak exotherm temperatures, and barcol hardness values demonstrated that all mixtures achieved sufficient curing. The result of this study is significant and point to the great potential of producing high performance polymer composites through the use of binary or ternary resin mixtures.

Strength and thermal insulation properties of foam-formed ceramic fiber paper with different reinforcement methods

Abstract Foam-forming technique imparts ceramic fiber paper with excellent uniformity, low density, and high porosity, but its strength loss must be compensated. Herein, a flexible and rigid foam-formed ceramic fiber network was manufactured by using different strength improvement methods and simultaneously investigated their strength and thermal insulation properties. Sufficient strength (1136 kPa) was achieved by combining Polyvinyl alcohol (PVA) 2 % and Polyester (PET) 3 %. However, the tensile strength of fiber networks would decrease under the contribution of inter-fiber bonding area reduced when the fiber length was longer than 24 mm. Benefiting from the developed flocculation system (aluminum sol-anionic polyacrylamide-carboxymethylcellulose), the strength of the foam-formed ceramic fiber network was 20 kPa, the retention rate increased from 75 % to 88 %, and the average aggregation factor of fillers in the Z direction was 0.67. By adjusting the ratio and Z-directional distribution of functional fillers, the sintered foam-formed paper with a tensile strength of 1300 kPa and compressive strength of 1000 kPa could be obtained. The thermal insulation performance (thermal conductivity 0.03252 W/(m·K)) was similar to the quartz fiber paper reinforced silica airgel, and the flame resistance was better than the commercialized aluminum silicate wool board.

Plastics in biogenic matrices intended for reuse in agriculture and the potential contribution to soil accumulation

The spread of biogenic matrices for agricultural purposes can lead to plastic input into soils, raising a question on possible consequences for the environment. Nonetheless, the current knowledge concerning the presence of plastics in biogenic matrices is very poor. Therefore, the objective of the present study was a quali-quantitative characterization of plastics in different matrices reused in agriculture as manures, digestate, compost and sewage sludges. Plastics were quantified and characterized using a Fourier Transform Infrared Spectroscopy coupled with an optical microscope (μFT-IR) in Attenuated Total Reflectance mode. Our study showed the presence of plastics in all the investigated samples, albeit with differences in the content among the matrices. We measured a lower presence in animal matrices (0.06–0.08 plastics/g wet weight w.w.), while 3.14–5.07 plastics/g w.w. were measured in sewage sludges. Fibres were the prevalent shape and plastic debris were mostly in the micrometric size. The most abundant polymers were polyester (PEST), polypropylene (PP) and polyethylene (PE). The worst case was observed in the compost sample, where 986 plastics/g w.w. were detected. The majority of these plastics were compostable and biodegradable, with only 8% consisting of fragments of PEST and PE. Our results highlighted the need to thoroughly evaluate the contribution of reused matrices in agriculture to the plastic accumulation in the soil system.

Development of sustainable dual core-spun yarns using several filaments and recycled cotton sourced from pre-consumer fabric waste

Textile industries are now focusing on sustainable issues in manufacturing operations to save the environment. The study focuses on the use of cotton fibers (recycled) sourced from fabric (knitted) waste (pre-consumer) to manufacture elastic yarn (dual-core) for denim fabric. The study involves the production of yarns (dual-core) using a redesigned ring spinning method with different elastomeric components, including T400® (Polyethylene terephthalate)/Polytrimethylene terephthalate), Polybutylene terephthalate (PBT), Polyester (PES), Lycra® (elastane), virgin cotton and cotton (recycled) fiber. The study investigates various yarn (Ne 18/1) characteristics such as strength, IPI (imperfection index), elongation %, unevenness %, and hairiness. It is noticed that the elongation and strength of recycled yarn (double core) are lower and IPI (Imperfection index), unevenness %, and hairiness values are higher than 100 % cotton (virgin) yarn (double core). One-way ANOVA (statistical analysis) is employed to assess the significance of differences among yarns manufactured from various core materials and found significant variation for all characteristics. Additionally, the article introduces the MOORA (multi-objective optimization based on ratio analysis) technique as a decision-making tool to determine the best yarn among three alternatives (PES yarn, PBT yarn, and T400 yarn) based on their properties, considering attributes and finding T400 filament containing yarn as the best option. The study introduces a sustainable approach using recycled cotton in yarn (double core) production and employs decision-making tools to assess and rank the performance of different yarn alternatives.

Influence of Alkali Treatment on Bamboo/Coconut Husk Hybrid Fibre Polyester Composite

This research addresses the importance of hybrid composites in material science, specifically, demonstrating the effective reinforcement of unsaturated polyester with bamboo and coconut husk fibre through alkali treatment. The primary problem this work aims to solve is the improvement of the mechanical properties of unsaturated polyester by combining it with bamboo and coconut husk fibres which contain both lignocellulosic and cellulose fibres. Alkali treatment, particularly, sodium hydroxide (NaOH) solution, was used in this study due to its cost-effective nature and its ability to enhance the strength of both individual fibres and resulting composite. The effect of NaOH treatment with concentrations ranging from 2 – 10 wt.% on dried hybrid fibres was investigated. Chemically treated fibre composites were discovered to have improved mechanical characteristics as both tensile tests and thermogravimetric analysis (TGA) showed higher strength and thermal stability after being treated. Notably, findings identified an optimal content of 8 wt.% NaOH solution for surface modification, showcasing the potential for using NaOH-treated waste fibres to reinforce polyester resin. The implications of this study extend to a promising avenue for enhancing the performance and application of natural fibre-reinforced composites. The insights provided here offer a foundation for advancing the utilization of hybrid composites.

Centrifugally spun superhydrophobic fibrous membranes with core-sheath structure assisted by hyper branched polymer and via click chemistry for high efficiency oil–water separation

Superhydrophobic fibrous membranes have been widely investigated to treat oily wastewater originated from oil spills and industrial organic pollutants. However, the applications of these membranes are usually limited by complex preparation process, high modification cost, and poor durability. In this research, we developed a cost-saving approach to construct the fiber with core-sheath structure by using centrifugal spinning, which was based on the viscosity difference of Polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), hyperbranched unsaturated polyester (HBPU). Subsequently, the hydrophobic long chain was attended on fiber surface through the mercaptan click reaction induced by ultraviolet light, which were assisted by the plenty of double bonds supplied by HBPU. Due to the coarse structure and low surface energy of the treated fibers, the fibrous membranes exhibited super hydrophobic properties for the water contact angle high as 156°. The separation capacity for water-in-oil emulsions were up to 7562.24 L·m−2·h−1 for the flux and separation efficiency were up to 99.27 %. Additionally, the flux and separation efficiency exhibited no significant changes over 50 cycles. Therefore, we provided a unique and straightforward technique for producing superhydrophobic separation fibrous membranes.

Amphiphilic molecules affording efficient aqueous degradation of unsaturated polyester resin

Enormous challenges have been encountered in the degradation and recycling of unsaturated polyester resin (UPR) in water, primarily due to its water resistance. Herein, a novel, efficient and green catalytic system of methanesulfonic acid (MSA)/sodium laurylsulfonate (SLS) was proposed to aqueously degrade UPR under mild conditions (200°C). This method is considerably milder compared to other reported works based on aqueous hydrolysis (230°C-380°C). What's more, amphiphilic SLS as a phase transfer reagent enhanced the concentration of catalyst at the H2O-UPR interface, which facilitated the mass transfer between organic motifs with inorganic reagents and thus accelerated the reaction. The NMR and FT-IR characterizations indicated the ester bonds were cleaved via hydrolysis with H2O catalyzed by MSA, and high value-added products, i.e., copolymer of styrene and maleic anhydride (SMA) and phthalic acid (PA), were reclaimed by a simple separation process, with the yield of 86.77% and 84.37%, respectively. Furthermore, a viable mechanism for degradation was proposed through the degradation performance of the model compounds. This study provides a practical approach for the chemical degradation and conversion of other resins containing ester bonds.

Chemically Recyclable and Biodegradable Vulcanized Rubber.

The cross-linked nature of vulcanized rubbers as used in tire and many other applications prohibits an effective closed-loop mechanical or chemical recycling. Moreover, vulcanization significantly retards the material's biodegradation. Here, we report a recyclable and biodegradable rubber that is generated by the vulcanization of amorphous, unsaturated polyesters. The elastic material can be broken down via solvolysis into the underlying monomers. After removal of the vulcanized repeat units, the saturated monomers, constituting the major share of the material, can be recovered in overall recycling rates exceeding 90%. Respirometric biodegradation experiments by 13CO2 tracking under environmental conditions via the polyesters' diol monomer indicated depolymerization and partial mineralization of the vulcanized polyester rubbers.

Knot Architecture for Biocompatible and Semiconducting 2D Electronic Fiber Transistors.

Wearable devices have generally been rigid due to their reliance on silicon-based technologies, while future wearables will utilize flexible components for example transistors within microprocessors to manage data. Two-dimensional (2D) semiconducting flakes have yet to be investigated in fiber transistors but can offer a route toward high-mobility, biocompatible, and flexible fiber-based devices. Here, the electrochemical exfoliation of semiconducting 2D flakes of tungsten diselenide (WSe2) and molybdenum disulfide (MoS2) is shown to achieve homogeneous coatings onto the surface of polyester fibers. The high aspect ratio (>100) of the flake yields aligned and conformal flake-to-flake junctions on polyester fibers enabling transistors with mobilities μ ≈1 cm2 V-1 s-1 and a current on/off ratio, Ion/Ioff ≈102-104. Furthermore, the cytotoxic effects of the MoS2 and WSe2 flakes with human keratinocyte cells are investigated and found to be biocompatible. As an additional step, a unique transistor 'knot' architecture is created by leveraging the fiber diameter to establish the length of the transistor channel, facilitating a route to scale down transistor channel dimensions (≈100 µm) and utilize it to make a MoS2 fiber transistor with a human hair that achieves mobilities as high as μ ≈15 cm2 V-1 s-1.

Bio-based epoxy and unsaturated polyester resins: Research and market overview

The presented study provides an overview of the current research achievements and the emerging market of bio-based thermosetting polymers. Environmental attributes related to bio-based polymers trigger a steadily growing interest in this novel and promising field. Due to their importance among thermosets in terms of composite applications and quantity, this review focusses on epoxy and unsaturated polyester resins. Current studies are mainly concerned with alternative renewable raw materials to substitute fossil content and their synthesis to improve their end-properties. A common target is the increase of bio-based content within the cured resin. In spite of today’s efforts in research, the recent market review reveals only few commercially available bio-based thermosetting resin systems. However, they are commonly suited for a broad variety of processing methods and applications with bio-contents up to 75%.

A facile strategy to simultaneously enhance the flame retardancy, toughness and ultraviolet shielding performance of unsaturated polyester resin: Adjusting the unsaturated degree of flame retardant

The impact of three phosphonate oligomers with different unsaturation degrees on the flame retardancy, mechanical properties and optical performance of unsaturated polyester resins (UPRs) were investigated. The three phosphonate oligomers were poly(2-butyne-1,4-diol phenylphosphonate) (PY) containing C C, poly(cis-2-butene-1,4-diol phenylphosphonate) (PE) containing CC and poly(1,4-butanediol phenylphosphonate) (PO) without unsaturated bonds. The flame retardancy and UV-shielding effect of UPRs were positively correlated with the unsaturation degree of oligomers. Specifically, only adding 20 wt% PY made UPR pass UL-94 V-0 rating and 22 wt% PE was needed, while 22%PO/UPR was still in UL-94 NR rating. Further, PE containing CC exhibited the highest efficiency in improving the toughness of UPR. The impact strength and elongation at break of 22%PE/UPR were significantly improved by 460 % and 200 % respectively, compared with pure UPR. Meanwhile, the high transparency of UPRs benefits from the good compatibility between oligomers and matrix. This work provides the basis for development and utilization of novel high-performance and multifunctional UPRs with potential versatile applications.