Thermoplastic Polyurethane Research Articles

Construction of Fire Safe Thermoplastic Polyurethane/Reduced Graphene Oxide Hierarchical Composites with Electromagnetic Interference Shielding.

Incorporating outstanding flame retardancy and electromagnetic interference shielding effectiveness (EMI SE) into polymers is a pressing requirement for practical utilization. In this study, we first employed the principles of microencapsulation and electrostatic interaction-driven self-assembly to encapsulate polyethyleneimine (PEI) molecules and Ti3C2Tx nanosheets on the surface of ammonium polyphosphate (APP), forming a double-layer-encapsulated structure of ammonium polyphosphate (APP@PEI@Ti3C2Tx). Subsequently, flame-retardant thermoplastic polyurethane (TPU) composites were fabricated by melting the flame-retardant agent with TPU. Afterwards, by using air-assisted thermocompression technology, we combined a reduced graphene oxide (rGO) film with flame-retardant TPU composites to fabricate hierarchical TPU/APP@PEI@Ti3C2Tx/rGO composites. We systematically studied the combustion behavior, flame retardancy, and smoke-suppression performance of these composite materials, as well as the flame-retardant mechanism of the expansion system. The results indicated a significant improvement in the interface interaction between APP@PEI@Ti3C2Tx and the TPU matrix. Compared to pure TPU, the TPU/10APP@PEI@1TC composite exhibited reductions of 84.1%, 43.2%, 62.4%, and 85.2% in peak heat release rate, total heat release, total smoke release, and total carbon dioxide yield, respectively. The averaged EMI SE of hierarchical TPU/5APP@PEI@1TC/rGO also reached 15.53 dB in the X-band.

3D printed electro-responsive system with programmable drug release

Precision medicine is the next frontier in pharmaceutical research, aiming to improve the safety and efficacy of therapeutics for patients. The ideal drug delivery system (DDS) should be programmable to provide real-time controlled delivery that is personalised to the patient's needs. However, little progress has been made in this domain. Herein, we combined two cutting-edge technologies, conductive polymers (CPs) and three-dimensional (3D) printing, to demonstrate their potential for achieving programmable controlled release. A DDS was formulated where the CP provided temporal control over drug release. 3D printing was used to ensure dimensional control over the design of the DDS. The CP used in this study is known to be fragile, and thus was blended with thermoplastic polyurethane (TPU) to achieve a conductive elastomer with sound mechanical properties. Rheological and mechanical analyses were performed, where it was revealed that formulation inks with a storage modulus in the order of 103–104 Pa were both extrudable and maintained their structural integrity. Physico-chemical analysis confirmed the presence of the CP functional groups in the 3D printed DDS. Cyclic voltammetry demonstrated that the DDS remained conductive for 100 stimulations. in vitro drug release was performed for 180 min at varying voltages, where a significant difference (p < 0.05) in cumulative release was observed between either ±1.0 V and passive release. Furthermore, the responsiveness of the DDS to pulsatile stimuli was tested, where it was found to rapidly respond to the voltage stimuli, consequently altering the release mechanism. The study is the first to 3D print electroactive medicines using CPs and paves the way for digitalising DDS that can be integrated into the Internet of Things (IoT) framework.

Developing a multifunctional gradient pore structure Janus membrane loaded with MB@ZIF-8 nanoparticles and hydroxyapatite for guided periodontal bone regeneration

The guided tissue regeneration (GTR) procedure has become an important process for the treatment of periodontal tissue regeneration, using the membrane as a mechanical barrier to generate a distance across the defect that subsequently allowing bone regeneration. Due to the complexity of periodontal microenvironment caused by bacterial infections, inflammation, and fibrous tissue penetration, the guided tissue regeneration membrane is required to have antibacterial and barrier functions. We developed a loaded methylene blue @ ZIF-8 and hydroxyapatite gradient thermoplastic polyurethane Janus membrane for antibacterial osteogenic and barrier. This Janus membrane with a porous gradient structure was prepared to use phase-conversion method. The rough layer facilitated cell growth and promoted periodontal bone regeneration, whereas the smooth layer isolated the growing fiber tissue.The rapid release of reactive oxygen species in the early stage and continuous release of zinc ions by methylene blue @ZIF-8 can achieve long-term synergistic antibacterial effect, with antibacterial rates of 84 % and 72 % against Escherichia coli and Staphylococcus aureus, respectively, which can effectively reduce the local inflammation caused by bacteria. In summary, we applied the Janus membrane to a rat periodontal bone defect model, and the membrane showed good surgical performance, barrier properties, osteogenic properties, and antibacterial effects, which could have broad application prospects in the treatment of periodontal bone defects.

On the reusable compressive behavior of multi-directional auxetic origami metamaterials

Origami metamaterials exhibit abnormal mechanical properties through artful structural design. To further explore the mechanical behavior of reentrant metamaterials, a multi-directional auxetic origami metamaterial (AOMM) was designed, and its negative Poisson’s ratio effect was analyzed through the diagram of load bearing and deformation. Theoretical models related to geometric parameters, relative density, folding rate, equivalent elasticity and load plateau were established to reveal the deformation transformation mechanism, and the influence of size parameters on the equivalent elastic constants was drawn. Using thermoplastic polyurethane (TPU) as the substrate, two types of multi-directional AOMMs were fabricated by 3D printing, and quasi-static compression experiments were performed. The results show that the TPU AOMMs has a reusable compressive capacity, whose compressive mechanical behaviors are mainly contributed by the buckling instability and large deformation of sidewall. There is a coupling effect between the cross connection boundaries, which results in the difference in mechanical properties of AOMM with different geometric sizes. The prediction results of relative density, load plateau and yield strain through equivalent theories approximate that of experimental results. Simultaneously, finite element analyses were conducted, which agrees well with the experiments. These foundings may provide reference for the design and application of novel auxetic or origami metamaterials.

Effect of nano-filler/matrix interfacial friction on temperature-dependent fatigue property of flexible pressure sensor

Flexible pressure sensors based on polymeric nanocomposites have attracted widespread attention owing to exceptional low-temperature fatigue tolerance, yet the damage evolution of the nano-filler/matrix interface is still unclear. Herein, we prepare Cu/MXene/multi-wall carbon nanotubes (MWCNTs)/thermoplastic polyurethane (TPU)/Cu and Cu/MXene/MWCNTs/carbon black (CB)/TPU/Cu pressure sensors using solution blending-casting method, and systematically investigate the influence of the nano-fillers/matrix interfacial friction damage on low-temperature bending fatigue of the sensor under cyclic bending. It is found that the sensing performance of the device with binary [MXene/MWCNTs] synergistic network decreases by 65 % with decreasing temperature from 20 down to − 40 °C under 20,000 bending cycles, while that of the sensor with ternary [MXene/MWCNTs/CB] synergistic network drops by only 14.9 %. For the ternary composites, owing to the introduction of CB particles, the synergistic lubrication effect among the nano-fillers and the nano-mechanical interlocking interface between the nano-fillers and the polymer can cooperatively enhance the anchorage of the nano-fillers to the TPU chains, and hence alleviating friction energy accumulation at the nano-fillers/polymer interface. Our work shows that the synergistic reinforcing strategy may be valuable for the development of ultra-flexible sensors with low-temperature fatigue resistant.

Wearable Colorful Nanofiber of Thermoplastic Polyurethane (TPU) Mechanical and Colorfastness Properties by Dope Dyeing

Wearable Colorful Nanofiber of Thermoplastic Polyurethane (TPU) Mechanical and Colorfastness Properties by Dope Dyeing

A new approach to photochromic nanofiber‐based ultraviolet sensors with grayscale adaptation

AbstractThe purpose of UV sensors is to detect ultraviolet radiation, which is crucial for various applications, such as skin protection, environmental monitoring, and industrial processes where UV exposure poses risks. These sensors provide real‐time data to ensure safety and optimize performance in relevant fields. In this context, the aim of this study was to develop easy‐to‐use UV sensors using photochromic nanofibrous materials. Photochromic nanofibers were obtained by electrospinning thermoplastic polyurethane and a spirooxazine dye. Two solvent systems (only dimethylformamide and a dimethylformamide:dichloromethane mixture) and three dye concentrations (0.5%, 2%, and 5%) were used to produce the nanofibers. Uniform and bead‐free nanofibers were obtained using a dimethylformamide:dichloromethane solvent system. The fatigue resistance of the photochromic nanofibers was tested, revealing a maximum color loss of 14% after 20 on‐off UV cycles. Nanofibers produced with a dimethylformamide:dichloromethane solvent system and a 0.5% dye concentration were chosen for UV sensor design due to their high total color difference. These photochromic nanofibers served as UV indicators, and a grayscale‐ adapted scale was used for evaluation. A UV sensor prototype capable of accurately determining UV exposure levels was successfully developed using photochromic nanofibers. This spectrally selective UV sensor can offer remarkable potential in managing the impact of UVR in our day‐to‐ day life.Highlights Bead‐free, uniform nanofibers were obtained using a DMF:DCM solvent system. The nanofibers returned to their original colorless state in 5 min. The photochromic nanofibers showed high fatigue resistance. The nanofiber color indicated the UV intensity by comparing via adapted grayscale.

Biomimetic Structurally Colored Film for High‐Performance Radiative Cooling

AbstractIn recent years, passive radiative cooling has garnered considerable attention as a sustainable thermal regulation without relying on external energy sources, thus mitigating pollutants generation. However, an intrinsic limitation of these cooling systems lies in the reflective glare, often characterized by an ivory or silvery appearance. This drawback limits their practical application, especially where both functional efficiency and aesthetic appeal are pivotal. Herein, a biomimetic approach inspired by Saharan silver ants' thermoregulatory capabilities is adopted. These ants, equipped with distinctive triangular‐shaped hair, maintain body temperature lower than the ambient air. Leveraging insights from this natural model, a reusable silicon template is employed to fabricate a metasurface structural colored film with a triangular prism array structure using thermoplastic polyurethane (TPU) and the phase separation technique. The film demonstrates an average emissivity of 96% within the atmospheric window and an average solar reflectivity of 93%, leading to a maximum temperature reduction of 8.6 °C during daytime and 5.9 °C at night. Furthermore, the film displays stretchability and mechanical resilience, bolstered by the microscale prismatic structure enhancing superhydrophobicity. This work introduces a biomimetic strategy aimed at augmenting thermal emission while reconciling the challenge of achieving visual appealand high radiative cooling performance.

EMI-shielding response of GO/Fe3O4/polypyrrole(PPy)/thermoplastic polyurethane (TPU) composites

In the present study, thermoplastic polyurethane was reinforced with GO/Fe3O4/PPy nanocomposites with varying GO:Fe3O4 ratio to develop high-performance electromagnetic interference (EMI) shields. GO/Fe3O4/PPy fillers were prepared by adding polypyrrole (PPy) nanotubes, synthesized by the soft-template method from oxidative polymerization of pyrrole, to graphene oxide decorated with Fe3O4 nanoparticles prepared by a sonochemical method. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy were performed to reveal the structural and morphological properties of GO/Fe3O4/PPy nanofillers, and the structure and thermal properties of the GO/Fe3O4/PPy/TPU nanocomposites was studied by cryofracture SEM and thermogravimetry (TGA). The effect of GO:Fe3O4 ratio on the electrical conductivity, magnetic permeability, permittivity, and electromagnetic-wave-shielding performance of GO/Fe3O4/PPy/TPU nanocomposites was investigated in the X-band frequency range. The maximum EMI efficiency was 4.81 dB with increasing GO:Fe3O4 ratio in GO/Fe3O4/PPy/TPU composites, with blocking of 66.72 % of the incident electromagnetic wave.

A Fabric-Based Strain Sensor with a Microbridge Structure and the Supercapacitor-Powered Integrated Sensing System.

Developing fabric-based strain sensors with high sensitivity and stability is in high demand for wearable electronics. Herein, carbon nanotubes (CNTs) and polypyrrole (PPy) are coated on a thermoplastic polyurethane (TPU) fabric as strain sensors. A microbridge structure, in which CNT bridges the stretching-induced cracks, has been designed for the TPU-CNT-PPy strain sensor. The microbridge structure can significantly enhance the electrical resilience, ensuring the improved sensitivity and stability of strain sensors. As a result, our TPU-CNT-PPy strain sensors deliver high sensitivity (GF = 231.5) with a broad working range (150%) and fast response and recovery time (166/195 ms). In addition, our TPU-CNT-PPy could also be used as flexible electrodes of the microsupercapacitors (MSCs) as a power supplier for the integrated sensing system. The TPU-CNT-PPy-based MSCs exhibit a high specific capacitance (460.3 mF cm-2 at 0.5 mA cm-2) and excellent cycling stability (96.69% capacitance retention for 10,000 charge/discharge cycles). Finally, we demonstrated an integrated sensing system using TPU-CNT-PPy as both MSCs and strain sensors, where the current signals of the sensors could be well detected via Bluetooth. This study offers a microbridge strategy to fabricate strain sensors with high sensitivity and stability and develops an integrated sensing system for the actual applications of wearable electronics.

Transparent and High-Refractive-Index Titanium Dioxide/Thermoplastic Polyurethane Nanocomposites.

Transparent nanocomposite films made of surface-modified titanium dioxide nanoparticles and thermoplastic polyurethane are prepared via film casting approach showing enhanced refractive indexes and mechanical properties. Two different sets of composites were prepared up to 37.5 wt % of inorganic nanoparticles with a diameter <15 nm, one set using particles capped only with oleic acid and a second one with a bimodal system layer made of oleic acid and mPEO-5000 as coating agents. All of the composites show significantly enhanced refractive index and mechanical properties than the neat polymeric matrix. The transparency of nanocomposite films shows the excellent dispersion of the inorganic nanoparticles in the polymeric matrix avoiding aggregation and precipitation phenomena. Our study provides a facile and feasible route to produce transparent nanocomposite films with tunable mechanical properties and high refractive indices for various applications.

Advancements in MXene Composite Materials for Wearable Sensors: A Review.

In recent years, advancements in the Internet of Things (IoT), manufacturing processes, and material synthesis technologies have positioned flexible sensors as critical components in wearable devices. These developments are propelling wearable technologies based on flexible sensors towards higher intelligence, convenience, superior performance, and biocompatibility. Recently, two-dimensional nanomaterials known as MXenes have garnered extensive attention due to their excellent mechanical properties, outstanding electrical conductivity, large specific surface area, and abundant surface functional groups. These notable attributes confer significant potential on MXenes for applications in strain sensing, pressure measurement, gas detection, etc. Furthermore, polymer substrates such as polydimethylsiloxane (PDMS), polyurethane (PU), and thermoplastic polyurethane (TPU) are extensively utilized as support materials for MXene and its composites due to their light weight, flexibility, and ease of processing, thereby enhancing the overall performance and wearability of the sensors. This paper reviews the latest advancements in MXene and its composites within the domains of strain sensors, pressure sensors, and gas sensors. We present numerous recent case studies of MXene composite material-based wearable sensors and discuss the optimization of materials and structures for MXene composite material-based wearable sensors, offering strategies and methods to enhance the development of MXene composite material-based wearable sensors. Finally, we summarize the current progress of MXene wearable sensors and project future trends and analyses.

Joint Exfoliation of MXene by Dimensional Mismatched SiC/ZIF-67 Toward Multifunctional Flame Retardant Thermoplastic Polyurethane.

The single-layer MXene fully demonstrates the advantages of 2D materials, especially catalytic, conductive, and mechanical properties. However, the high energy consumption and low efficiency faced by MXene in the divestiture process are still challenges that need to be solved urgently. In this article, dimension mismatch and collaborative stripping strategies are skillfully combined to easily realize the transformation from multi-layer MXene to single layer. In addition, the functionalized MXene@SiC@polyaniline (MXene@SiC@PANI) nano-hybrid materials are used as fillers to improve the thermal conductivity, flame retardant, and antibacterial properties of thermoplastic polyurethane (TPU). The surface temperature of TPU/MXene@SiC@PANI composites increased from 33.4°C to 59.8°C within 10 s. In addition, the antibacterial efficiency of TPU composites against Escherichia coli and Staphylococcus aureus is 69.6% and 88.9%, respectively. Compared with pure TPU, the peak heat release rate and total heat release are reduced by 71.4% and 34.6%, respectively. The flame-retardant mechanism of MXene hybrid materials is systematically discussed. It is worth noting that the introduction of PANI enhances the compatibility between the filler and the polymer, effectively maintaining the mechanical properties of the TPU itself. This work provides a convenient method for the multi-functional practical application of TPU.

Preparation of CNT/CNF/PDMS/TPU Nanofiber-Based Conductive Films Based on Centrifugal Spinning Method for Strain Sensors.

Flexible conductive films are a key component of strain sensors, and their performance directly affects the overall quality of the sensor. However, existing flexible conductive films struggle to maintain high conductivity while simultaneously ensuring excellent flexibility, hydrophobicity, and corrosion resistance, thereby limiting their use in harsh environments. In this paper, a novel method is proposed to fabricate flexible conductive films via centrifugal spinning to generate thermoplastic polyurethane (TPU) nanofiber substrates by employing carbon nanotubes (CNTs) and carbon nanofibers (CNFs) as conductive fillers. These fillers are anchored to the nanofibers through ultrasonic dispersion and impregnation techniques and subsequently modified with polydimethylsiloxane (PDMS). This study focuses on the effect of different ratios of CNTs to CNFs on the film properties. Research demonstrated that at a 1:1 ratio of CNTs to CNFs, with TPU at a 20% concentration and PDMS solution at 2 wt%, the conductive films crafted from these blended fillers exhibited outstanding performance, characterized by electrical conductivity (31.4 S/m), elongation at break (217.5%), and tensile cycling stability (800 cycles at 20% strain). Furthermore, the nanofiber-based conductive films were tested by attaching them to various human body parts. The tests demonstrated that these films effectively respond to motion changes at the wrist, elbow joints, and chest cavity, underscoring their potential as core components in strain sensors.

Efficacy of auxetic lattice structured shoe sole in advancing footwear comfort-From the perspective of plantar pressure and contact area.

Designing footwear for comfort is vital for preventing foot injuries and promoting foot health. This study explores the impact of auxetic structured shoe soles on plantar biomechanics and comfort, motivated by the integration of 3D printing in footwear production and the superior mechanical properties of auxetic designs. The shoe sole designs proposed in this study are based on a three-dimensional re-entrant auxetic lattice structure, orthogonally composed of re-entrant hexagonal honeycombs with internal angles less than 90 degrees. Materials fabricated using this lattice structure exhibit the characteristic of a negative Poisson's ratio, displaying lateral expansion under tension and densification under compression. The study conducted a comparative experiment among three different lattice structured (auxetic 60°, auxetic 75° and non-auxetic 90°) thermoplastic polyurethane (TPU) shoe soles and conventional polyurethane (PU) shoe sole through pedobarographic measurements and comfort rating under walking and running conditions. The study obtained peak plantar pressures (PPPs) and contact area across seven plantar regions of each shoe sole and analyzed the correlation between these biomechanical parameters and subjective comfort. Compared to non-auxetic shoe soles, auxetic structured shoe soles reduced PPPs across various foot regions and increased contact area. The Auxetic 60°, which had the highest comfort ratings, significantly lowered peak pressures and increased contact area compared to PU shoe sole. Correlation analysis showed that peak pressures in specific foot regions (hallux, second metatarsal head, and hindfoot when walking; second metatarsal head, third to fifth metatarsal head, midfoot, and hindfoot when running) were related to comfort. Furthermore, the contact area in all foot regions was significantly associated with comfort, regardless of the motion states. The pressure-relief performance and conformability of the auxetic lattice structure in the shoe sole contribute to enhancing footwear comfort. The insights provided guide designers in developing footwear focused on foot health and comfort using auxetic structures.

Functionalized Zr‐MOFs for Enhancing Flame Retardancy and Smoke Suppression Performance on TPU

AbstractMetal‐Organic Framework (MOF) materials can be used as flame‐retardants and smoke suppressants for polymers. As a MOF material, UIO‐66(Zr) possesses higher thermal stability and controllable pore size. In this paper, UIO‐66(Zr), NH2‐UIO‐66(Zr), and SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr) was fabricated to improve the flame retardant and smoke suppression performance of thermoplastic polyurethanes (TPU). The experimental results show that compared with neat TPU (LOI value 19.1 %), 2 % usage of UIO‐66(Zr) and NH2‐UIO‐66(Zr) can endow TPU with 26 % LOI value and vertical combustion rating of V‐1. Moreover, SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr) provide TPU with above 27.8 % LOI value and vertical combustion rating of V‐0. Meanwhile, the CCT results showed that the peak heat release rate and total heat release of TPU‐U5 (added 2 % GO‐modified NH2‐UIO‐66(Zr)) are 299.52 Kw ⋅ m−2 and 68.21 MJ m−2, much lower than that of neat TPU, which are 1180.05 Kw ⋅ m−2and 104.87 MJ m−2, respectively. The TGA, char residue EDS and XRD analysis show that SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr) could generate zirconium metal oxide during the combustion process, which acts as a physical barrier to prevent the TPU matrix by promoting the generation of carbonization layer. The zirconium metal oxide and carbonization layer also can confine flammable gases, which can delay the ignition time and hinder the overflow of gas. In addition, NH2‐UIO‐66(Zr) could generate non‐flammable N2 diluting the concentration of flammable gases. The mechanical properties of TPU composites can maintain more than 87 % of the neat TPU after the addition of 2 % SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr). These results indicate that functionalized Zr‐MOFs composites could act as excellent flame‐retardants in TPU.

Energy harvesting with thermoplastic polyurethane nanofiber mat integrated with functionalized multiwalled carbon nanotubes

Energy harvesting with thermoplastic polyurethane nanofiber mat integrated with functionalized multiwalled carbon nanotubes

In vitro and in vivo evaluation of biohybrid tissue-engineered vascular grafts with transformative 1H/19F MRI traceable scaffolds

Biohybrid tissue-engineered vascular grafts (TEVGs) promise long-term durability due to their ability to adapt to hosts' needs. However, the latter calls for sensitive non-invasive imaging approaches to longitudinally monitor their functionality, integrity, and positioning. Here, we present an imaging approach comprising the labeling of non-degradable and degradable TEVGs' components for their in vitro and in vivo monitoring by hybrid 1H/19F MRI. TEVGs (inner diameter 1.5 mm) consisted of biodegradable poly(lactic-co-glycolic acid) (PLGA) fibers passively incorporating superparamagnetic iron oxide nanoparticles (SPIONs), non-degradable polyvinylidene fluoride scaffolds labeled with highly fluorinated thermoplastic polyurethane (19F-TPU) fibers, a smooth muscle cells containing fibrin blend, and endothelial cells. 1H/19F MRI of TEVGs in bioreactors, and after subcutaneous and infrarenal implantation in rats, revealed that PLGA degradation could be faithfully monitored by the decreasing SPIONs signal. The 19F signal of 19F-TPU remained constant over weeks. PLGA degradation was compensated by cells’ collagen and α-smooth-muscle-actin deposition. Interestingly, only TEVGs implanted on the abdominal aorta contained elastin. XTT and histology proved that our imaging markers did not influence extracellular matrix deposition and host immune reaction. This concept of non-invasive longitudinal assessment of cardiovascular implants using 1H/19F MRI might be applicable to various biohybrid tissue-engineered implants, facilitating their clinical translation.

Preparation of high-performance laminated glass interlayer by modifying epoxy resin composite polyurethane

Laminated glass has been widely used in glass curtain walls, windshields, and other structures due to its high safety, light weight, and aesthetics. The safety of polymer laminated glass depends on the performance of the polymer between the glasses. Polyurethane elastomer (PU) has become a universal polymer material due to its excellent mechanical strength and toughness. The aliphatic thermoplastic polyurethane has attracted people's interest about its application in the field of laminated safety glass due to its transparency and adhesion. In this work, a polyurethane-modified epoxy (EK-PU) composite film with superior bonding strength, mechanical properties, and transparency was successfully achieved. The tensile strength of the PU composite film was confirmed to be 45 MPa, while the bonding strength was 4.73 MPa. The improvement is attributed to the change of microphase separation structure and the introduction of silicone. The excellent impact resistance of the laminated glass based on polyurethane composite film have been confirmed by the falling ball impact test, which is 6.5 times of the common PU film. The laminated glass based on the EK-PU film will be applied in aerospace, defense, and automotive fields.

Facile fabrication of lightweight and high expanded TPU/PBS bead blend foam with segregated microcellular network for reduced shrinkage and enhanced interface bonding

The emergence of expanded thermoplastic polyurethane foam beads (ETPU) has expanded the application range of polymer foam materials. However, most of the prepared bead foam products suffer from high shrinkage rate, high density, and poor interfacial bonding, severely affecting the mechanical stability and lightweighting of the products. Herein, this study constructed thermoplastic polyurethane/polybutylene succinate (TPU/PBS) bead blend foams with a segregated microcellular network structure (SMNS) for the first time, where the TPU/PBS continuous phase formed the SMNS and the bead phase was consisted of TPU foam beads. The results showed good interfacial bonding between the continuous and bead phases. By adding PBS to the continuous phase, the shrinkage percentage of TPU/PBS bead blend foam decreased from 79.19 % to 67.31 %, reduced by 15.0 %. In addition, the foam expansion ratio gradually decreased with increasing PBS content, dropping from 12.07 to 9.03. Moreover, TPU/PBS bead blend foams exhibited good energy absorption and mechanical stability without sacrificing thermal insulation performance. This work effectively reduced the shrinkage of TPU based foam materials, offering a simple and economical solution for the preparation of dimensionally stable, well-interfaced, and lightweight polymer foams.