Thermoplastic Polyester Research Articles

Supercritical carbon dioxide foamed thermoplastic polyester elastomer with poly(lactic acid) blending: shrinkage reduction and expansion ratio improvement

Supercritical carbon dioxide foamed thermoplastic polyester elastomer with poly(lactic acid) blending: shrinkage reduction and expansion ratio improvement

Cellulose nanofibers enabled strong and flexible plant-derived thermoplastic polyester elastomer foams for high-performance thermally insulating applications

Flexible thermal insulation materials have garnered significant attention owing to the proliferation of flexible electronic devices and their diverse application environments. Plant-derived thermoplastic polyester elastomer (TPEE) foams emerge as promising candidates in the field of flexible thermal insulation. However, inevitable shrinkage behavior of TPEE foams would result in reduced porosity and inferior thermal insulation performance. Hence, a pioneering approach is proposed wherein cellulose nanofibers (CNF) are integrated into TPEE matrixes, complemented by microcellular foaming, aimed at mitigating shrinkage process and enhancing thermal insulation properties. In this work, the relaxation behavior of nanocomposite, corresponding to shrinkage process, has been elucidated through dynamic mechanical analysis. It's found that entanglement of CNF could heighten the internal friction with TPEE molecular chains, coupled with establishment of hydrogen bonds, thereby curbing relaxation phenomena and facilitating the attainment of foams with enhanced and stable porosity. The shrinkage ratio of TPEE/CNF composite foam could be reduced by 20 % without compromising the final porosity. The thermal conductivity would decrease to 37.9 mW/m·K for the TPEE/CNF composite foam with the higher porosity of 0.947. Moreover, the utilization of CNF presents a novel avenue for fabricating TPEE/CNF nanocomposite foams endowed with flexibility, lightweightness, increased porosity, and reduced thermal conductivity.

Ultra-high volume expansion ratio branched PBT/TPEE three-dimensional reticulated foams of supercritical CO2 melt foaming for efficient oil/water separation

The development of polymer reticulated foams with high expansion ratios (VER) for selective oil-adsorption applications has been hindered by technical challenges. In this article, high VER reticulated foam with outstanding selective oil-adsorption performance was realized through the synergistic effect of molecular topological structure and blending heterostructure. Branched polybutylene terephthalate(B-PBT)/thermoplastic polyester elastomer(TPEE) was prepared by blending reaction. Then, B-PBT/TPEE blends were foamed by supercritical CO2 melting foaming, a solvent-free process. The nano-scale TPEE, acting as the weak point, induced the cell wall to rupture and form reticulated foam after the B-PBT had expanded to a high VER. The branching topological structure endowed PBT high storage modulus(G’) and complex viscosity(η*), which support the expansion of foam and keep foam from collapsing before the melt solidification. As a result, ultra-high VER three-dimensional reticulated foams possessing VER of 46.9 and open-cell content of 97.8 % were prepared, which is higher about 200 % than the previous research. The water contact angle of reticulated foams is 132° and cyclohexane droplets diffuse into reticulated foam showing the contact angle of 0°, indicating the reticulated foam have oleophilicity and hydrophobicity. The adsorption capacity of the reticulated foam for various oils is from 24 to 67 g/g. Moreover, the adsorption rate constant of reticulated foam is 8 times more than that of conventional open-cell foam. These benefits from the unique cell structure and high VER of reticulated foam. The work provides a facile and novel method for the green preparation of high-performance oil/water separation materials.

Melt processing of biodegradable poly(butylene succinate) (PBS)—a critical review

AbstractThis review paper presents a comprehensive analysis of the melt processing of polybutylene succinate (PBS) blends and composites. PBS, a biodegradable and eco-friendly thermoplastic polyester, has garnered significant interest in sustainable material research. The paper collates and examines a wide range of studies focusing on the processability, optimization of processing parameters, and resultant mechanical properties of PBS when processed through several extrusion techniques and by injection molding. Key parameters such as melt temperature, screw speed, and mold temperature are considered for their impact on the quality and performance of the final product. The review highlights advancements in processing technologies and material modifications that enhance PBS properties, making it a viable alternative to traditional petroleum-based plastics. Furthermore, challenges and limitations in the current processing techniques are discussed, offering insights into potential areas for future research. The synthesis of findings from various studies provides a holistic understanding of the state-of-the-art in PBS processing, aiming to guide further developments in the field of biodegradable polymers. Overall, this review underscores the importance of optimized melt processing techniques in maximizing the potential of PBS as a sustainable material in diverse applications. Graphical abstract

Morphology and properties of carbon black‐filled thermoplastic vulcanizate (TPV) composites based on hydrogenated acrylonitrile butadiene rubber and thermoplastic polyester elastomer

AbstractThe unique morphology of thermoplastic vulcanizates (TPVs) reveals a significant correlation between the microstructure and performance, and the development of high‐performance TPV composites for specialized applications has become a current research priority. This study is devoted to developing heat‐ and oil‐resistant TPV composites filled with carbon black (CB) based on hydrogenated acrylonitrile butadiene rubber (HNBR) and thermoplastic polyester elastomer (TPEE) following the masterbatch procedure of dynamic vulcanization. Herein, it focuses on the effects of CB content on the morphology, filler network structure, and properties of the TPV/CB composites. As observed by morphological studies, CB nanoparticles are interconnected and aggregated to form a dual network structure of rubber and CB particles in the composite. With the increasing CB content, it's demonstrated that dual networks have enhanced and shifted to rigid. Consequently, the hardness, thermal stability, and oil resistance of TPV/CB composites are improved, with a 104% elevation in the stress at 300% strain. The flowability in the molten state, toughness (the elongation at break decreased from 690% to 310%), and elasticity deteriorated by oversized (0.5 ~ 1.2 μm) CB agglomerates and rigid rubber particles. This study gives new insight into the microstructure‐properties relationship of TPVs, offering theoretical guidance for fabricating HNBR‐based TPV composites.

Value-Added Products Derived from Poly(ethylene terephthalate) Glycolysis.

Among polymer wastes, poly(ethylene terephthalate) (PET) is the most important commercial thermoplastic polyester. Less than 30% of total PET production is recycled into new products. Therefore, large amounts of waste PET need to be recycled. We describe a feasible approach for the direct application of the glycolysis products of PET (GP-PET), without further purification, for the synthesis of value-added products. It was established that GP-PET is valorized via phosphorylation with phenylphosphonic dichloride (PPD), as well as with trimethyl phosphate (TMP). When PPD is used, a condensation reaction takes place with the evolution of hydrogen chloride. During the interaction between GP-PET and TMP, the following reactions take place simultaneously: a transesterification with the participation of the hydroxyl group of GP-PET and the methoxy group of TMP and an exchange reaction between the ester group of GP-PET and the methyl ester group of TMP. The occurrence of the exchange reaction was confirmed by 1H, 31P, 13C NMR, and GPC analysis. Thermogravimetric analysis (TGA) revealed that the percentage of a carbon residual (CR) implies the possibility of using the end products as flame retardant (FR) additives, especially for polyurethanes as well as thermal stabilizers of polymer materials or Li-ion cells.

Study of the effect of hexagonal boron nitride addition to thermoplastic polyester elastomer composites reinforced with carbon, glass and basalt fibers

Study of the effect of hexagonal boron nitride addition to thermoplastic polyester elastomer composites reinforced with carbon, glass and basalt fibers

Resource utilization of emulsion evaporation modified aluminum industrial refractory waste in the preparation of composite modified asphalt

AbstractAluminum industrial refractory waste pose a huge risk to the environment, and hence a safe resource utilization is mandatory to build a green industrial construction industry. Herein, a thermoplastic polyester elastomers‐spent refractory material (TPEE‐SRM) modifier having a two‐layer structure of “protective layer‐functional layer” was developed. Scanning electron microscopy and surface area analysis revealed that Eps used in the protective layer formed a dense film layer (50% decrease in specific surface) with a 97.7% sequestration of fluoride. As the reaction occurred in an organic solution, fluoride posed no risk to the environment. TPEE functional layer itself melted and dissolved with asphalt under high‐temperature conditions, and hence it established a strong interfacial interaction with asphalt. This led to an increase of 99.73% in the complex modulus (G*) and 41.75% in the rutting‐resistance performance (Jnr) of the TPEE‐SRM composite modified asphalt than that of the pristine styrene‐butadiene‐styrene (SBS) modified asphalt. The performance of the TPEE‐SRM/SBS composite modified asphalt after 10 years of use was also evaluated by conducting high pressure aging simulation tests. The linear amplitude scanning test results showed a 27.1‐fold increase in Nf 5.0%. Owing to the efficient and green modification method, the newly designed TPEE‐SRM modifier poses great application prospects and feasibility for designing advanced functional modified asphalt for construction and highway industries alongside a suitable disposal aspect for SRM.

Crystallization of Poly(ethylene terephthalate): A Review.

Poly(ethylene terephthalate) (PET) is a thermoplastic polyester with excellent thermal and mechanical properties, widely used in a variety of industrial fields. It is a semicrystalline polymer, and most of the industrial success of PET derives from its easily tunable crystallization kinetics, which allow users to produce the polymer with a high crystal fraction for applications that demand high thermomechanical resistance and barrier properties, or a fully amorphous polymer when high transparency of the product is needed. The main properties of the polymer are presented and discussed in this contribution, together with the literature data on the crystal structure and morphology of PET. This is followed by an in-depth analysis of its crystallization kinetics, including both primary crystal nucleation and crystal growth, as well as secondary crystallization. The effect of molar mass, catalyst residues, chain composition, and thermo-mechanical treatments on the crystallization kinetics, structure, and morphology of PET are also reviewed in this contribution.

Investigation of electrospinning parameters and fiber collection methods on morphology of thermoplastic polyester elastomer fibers

Electrospinning is an easy and simple process for the preparation of ultrafine fibers with tunable morphology. Thermoplastic Elastomers (TPEs) are engineering polymers with an elastomeric nature that can be processed as thermoplastics. They can be classified based on their chemical structure and polyester-based TPEs are counted as high-performance materials due to their mechanical properties and can be used for various applications from automotive, construction, furniture, and consumer goods. In this study, electrospun polyester-based thermoplastic elastomer fibers were prepared and characterized. Thermoplastic polyester elastomer, Hytrel 4056 was used as the polymer, and chloroform was used as a solvent. The effects of polymer: solvent weight ratio, feed rate, applied voltage, and collector type were investigated in terms of fiber formation and morphology. For this aim, the polymer: solvent weight ratio was varied as 1:7, 1:11, and 1:15; the feed rate was set to 1 and 3 ml h-1. To collect the fibers metal plate and water bath collectors were used at a constant needle-to-collector distance under 10, 15, and 20 kV. The viscosity of the polymer solutions was measured as a function of the polymer: solvent ratio to observe the effects of viscosity on fiber morphology.

Enhancing Mechanical Performance of High-Density Polyethylene at Different Environmental Conditions with Outstanding Foamability through In-Situ Rubber Nanofibrillation: Exploring the Impact of Interface Modification.

In this study, we utilized in situ nanofibrillation of thermoplastic polyester ether elastomer (TPEE) within a high-density polyethylene (HDPE) matrix to enhance the rheological properties, foamability, and mechanical characteristics of the HDPE nanocomposite at both room and subzero temperatures. Due to the inherent polarity differences between these two components, TPEE is thermodynamically incompatible with the nonpolar HDPE. To address this compatibility issue, we employed a compatibilizer, styrene/ethylene-butylene/styrene copolymer-grafted maleic anhydride (SEBS-g-MA), to reduce the interfacial tension between the two blend components. In the initial step, we prepared a 10% masterbatch of HDPE/TPEE with and without the compatibilizer using a twin-screw extruder. Subsequently, we processed the 10% masterbatch further through spun bonding to create fiber-in-fiber composites. Scanning electron microscopy (SEM) analysis revealed a significant reduction in the spherical size of HDPE/TPEE particles following the inclusion of SEBS-g-MA, as well as a much smaller TPEE nanofiber size (approximately 60-70 nm for 5% TPEE). Moreover, extensional rheological testing revealed a notable enhancement in extensional rheological properties, with strain-hardening behavior being more pronounced in the compatibilized nanofibrillar composites compared to the noncompatibilized ones. SEM images of the foam structures depicted substantial improvement in the foamability of HDPE in terms of the cell size and density following the nanofibrillation process and the use of the compatibilizer. Ultimately, the in situ rubber fibrillation and enhancement of HDPE and TPEE interface using a compatibilizer led to increasing the HDPE ductility at room and subzero temperatures while maintaining its stiffness.

Contribution of cellulose nanofibrils on the strengthening and toughening of neat and blended polylactide specimens; and the differences after 3D-printing

The main purpose of this study was to use “green materials” approach by investigating effects of only 1 wt% Cellulose Nanofibrils (CNF) on the strengthening and toughening of neat and blended polylactide (PLA) biopolymer matrix. For this purpose, first of all effects of CNF were investigated in PLA/CNF biocomposite specimens. After blending of PLA with 10 phr bio-based thermoplastic polyester (b-TPE) elastomer, effects of CNF were investigated also for this PLA/b-TPE/CNF ternary biocomposite specimens. Mechanical tests revealed that due to the efficient strengthening and toughening mechanisms, CNF increased flexural strength of PLA by 33%, while b-TPE increased fracture toughness of PLA by 104%. When CNF and b-TPE were incorporated together, synergism in the strength and toughness values were occurred. All bioblend and biocomposite specimens were produced by using the same “melt mixing” technique in a laboratory size twin-screw extruder, and their test specimens were shaped by conventional “compression molding”. Since shaping by “3D-printing” is frequently used in the biomedical sectors, another distinctive aim of this study was to reveal whether there were any differences in the strength and toughness values of specimens after their 3D-printing. It was observed that due to the “textured” structure of 3D-printed specimens, their flexural strength values were approximately 20% lower, while fracture toughness values were approximately 20% higher.

Utilizing poly(4‐hydroxybutyrate) as a reinforcing additive to produce high‐performance and biodegradable PBAT blends tailored for foaming applications

AbstractPoly(butylene‐adipate‐co‐terephthalate) (PBAT) is recognized for its advantages as a biodegradable thermoplastic polyester. However, its application is often limited due to low strength and poor processability. In contrast, poly(4‐hydroxybutyrate) (P4HB) emerges as a fully biodegradable polyester characterized by high strength, excellent toughness, and facile processing. In this study, P4HB was employed to reinforce PBAT, and glycidyl methacrylate grafted onto poly(4‐hydroxybutyrate) (P4HB‐g‐GMA) was introduced as an effective compatibilizer to address their inherent incompatibility. The study explored the influence of P4HB‐g‐GMA content on the mechanical, thermal, morphological, and rheological properties of the blends. The findings revealed that P4HB‐g‐GMA significantly enhanced the compatibility, mechanical properties, and melt strength of PBAT/P4HB blends. Furthermore, various PBAT/P4HB foams were prepared through a batch foaming process, employing supercritical CO2 as a physical foaming agent. The volume expansion ratio and cell size of PBAT/P4HB foams increased with higher levels of the compatibilizer.

High-Expansion Injection-Molded Thermoplastic Polyester Elastomer Foam with Oriented Cellular Structure and Anisotropic Compressive Properties

High-Expansion Injection-Molded Thermoplastic Polyester Elastomer Foam with Oriented Cellular Structure and Anisotropic Compressive Properties

Influence of SiC and ZnO Doping on the Electrical Performance of Polylactic Acid-Based Triboelectric Nanogenerators.

Polylactic acid (PLA) is one of the most widely used materials for fused deposition modeling (FDM) 3D printing. It is a biodegradable thermoplastic polyester, derived from natural resources such as corn starch or sugarcane, with low environmental impact and good mechanical properties. One important feature of PLA is that its properties can be modulated by the inclusion of nanofillers. In this work, we investigate the influence of SiC and ZnO doping of PLA on the triboelectric performance of PLA-based tribogenerators. Our results show that the triboelectric signal in ZnO-doped PLA composites increases as the concentration of ZnO in PLA increases, with an enhancement in the output power of 741% when the ZnO concentration in PLA is 3 wt%. SiC-doped PLA behaves in a different manner. Initially the triboelectric signal increases, reaching a peak value with enhanced output power by 284% compared to undoped PLA, when the concentration of SiC in PLA is 1.5 wt%. As the concentration increases to 3 wt%, the triboelectric signal reduces significantly and is comparable to or less than that of the undoped PLA. Our results are consistent with recent data for PVDF doped with silicon carbide nanoparticles and are attributed to the reduction in the contact area between the triboelectric surfaces.

Composite phase change materials with room-temperature-flexibility

Phase change materials (PCMs) have attracted considerable attention for effectively addressing the problem of thermal energy supply–demand mismatch. However, the practical application of PCMs is still hindered by inherent challenges such as crystalline rigidity, leakage susceptibility, and poor thermal conductivity. In this research, on the basic of thermal control provided by phase change storage and the elastic behavior supported by thermoplastic polyester elastomer at room temperature, we fabricated a new type of composite PCM (CPCM) that exhibits flexibility even at room temperature. This CPCM demonstrates good shape and thermal stability. Furthermore, the carbon nanotubes-COOH modified with lauric acid (LA) can be uniformly dispersed within the CPCM matrix, thereby enhancing the thermal conductivity of the CPCM. Additionally, the composite material exhibits a promising thermal management performance for high-temperature lithium-ion (Li-ion) batteries. These findings open up new possibilities for the development of room- temperature flexible CPCMs.

Seamless, Self-Transformation of Thermoplastic Polyesters into Vitrimers Through Bond Exchange-Triggered Cross-Linking.

In this study, a seamless, self-transformation system of linear thermoplastic polyesters into the sustainable cross-linked polymers, vitrimers, is demonstrated. The key is the use of polyesters bearing abundant hydroxyl side groups, which are synthesized via the reaction using dithiol molecules bearing ester units and diepoxy molecules. The polymerization reaction progresses efficiently at relatively low temperature due to the click nature of the thiol-epoxy reaction, which provides the hydroxyl side groups along the polyester chain. The tin catalyst (stannous octoate) is added in the initial polymerization, and the catalyst also works to cross-link the polyesters via intermolecular transesterification bond exchange simply by heating at high temperatures. By adjusting the degrees of cross-linking, the mechanical properties as well as the thermal properties are well tuned. The bond exchange can still be activated in the final cross-linked sample; and thus, the material behaves as vitrimers, exhibiting mechanical recyclability. The application of a new type of hot melt adhesive, where the post-coating tuning/enhancement of adhesion strength is realized, is also demonstrated. On the whole, the present system is very simple but proposes a new application window of bond exchange concept into self-transformation polymers.

Highly tough and flame retardant polystyrene composites by elastomeric nanofibers and hexagonal boron nitride

Thermoplastics flammability remains a considerable threat during fire incidents. Conventionally, halogen-free fire retardant (FR) additives are incorporated into thermoplastics to reduce fire hazards. However, the incorporation of FR additives compromises the mechanical properties (most notably, toughness) of thermoplastics, which has impeded the development of thermoplastic products that possess both high mechanical and fire retarding performances. This study reports an in situ nano-fibrillation strategy to fabricate thermoplastics that exhibit fire retarding properties and a combination of high stiffness and toughness. The proposed composites were composed of in situ thermoplastic polyester elastomer (SBC) nanofibers within a polystyrene (PS) matrix containing hexagonal boron nitride (hBN) as the FR additive. The presence of elastomeric nanofibers successfully mitigated the losses in mechanical performances caused by the incorporation of 2 wt% hBN. Specifically, the inclusion of 15 wt% SBC nanofibers significantly enhanced the toughness of the PS-hBN composite by 350% with negligible effects on the stiffness as compared to neat PS. Furthermore, the presence of nanofibers resulted in synergies with hBN to fabricate composites with enhanced fire retarding performance since the total heat release (THR) of PS-hBN composite decreased from 212 to 189 MJ m−2 with 10 wt% nanofibers. Thus, nanofibers behave as a multifunctional component that compensated for the losses in mechanical performances caused by hBN incorporation, while enhancing the fire retarding performance. This strategy can be effectively implemented to fabricate the next generation of polymer composites with high fire retarding and mechanical properties for various applications including energy storage packs for batteries and electronics.

Reversible Sensing Technologies Using Upcycled TPEE: Crafting pH and Light Responsive Materials towards Sustainable Monitoring.

Multiresponsive materials with reversible and durable characteristics are indispensable because of their promising applications in environmental change detections. To fabricate multiresponsive materials in mass production, however, complex reactions and impractical situations are often involved. Herein, a dual responsive (light and pH) spiropyran-based smart sensor fabricated by a simple layer-by-layer (LbL) assembly process from upcycled thermoplastic polyester elastomer (TPEE) materials derived from recycled polyethylene terephthalate (r-PET) is proposed. Positively charged chitosan solutions and negatively charged merocyanine-COOH (MC-COOH) solutions are employed in the LbL assembly technique, forming the chitosan-spiropyran deposited TPEE (TPEE-CH-SP) film. Upon UV irradiation, the spiropyran-COOH (SP-COOH)molecules on the TPEE-CH-SP film undergo the ring-opening isomerization, along with an apparent color change from colorless to purple, to transform into the MC-COOH molecules. By further exposing the TPEE-CH-MC film to hydrogen chloride (HCl) and nitric acid (HNO3) vapors, the MC-COOH molecules can be transformed into protonated merocyanine-COOH (MCH-COOH) with the simultaneous color change from purple to yellow.

A natural butter glyceride as a plasticizer for improving thermal, mechanical, and biodegradable properties of poly(lactide acid)

Polylactic acid (PLA) is a biobased and biodegradable thermoplastic polyester with great potential to replace petroleum-based plastics. However, its poor toughness and slow biodegradation rate affect broad applications of PLA in many areas. In this study, a glycerol triester existing in natural butter, glycerol tributyrate, was creatively explored and compared with previously investigated triacetin and tributyl citrate, as potential plasticizers of PLA for achieving improved mechanical and biodegradation performances. The compatibilities of these agents with PLA were assessed quantitively via the Hansen solubility parameter (HSP) and measured by using different testing methods. The incorporation of these compounds with varied contents ranging from 1 to 30 % in PLA altered thermal, mechanical, and biodegradation properties consistently, and the relationship and impacts of chemical structures and properties of these agents were systematically investigated. The results demonstrated that glycerol tributyrate is a novel excellent plasticizer for PLA and the addition of this triester not only effectively reduced the glass transition, cold crystallization, and melting temperatures and Young's modulus, but also led to a significant improvement in the enzymatic degradation rate of the plasticized PLA. This study paves a way for the development of sustainable and eco-friendly food grade plasticized PLA products.