Porous Polyurethane Research Articles

Engineering transplantable human lymphatic and blood capillary networks in a porous scaffold

Due to a relative paucity of studies on human lymphatic assembly in vitro and subsequent in vivo transplantation, capillary formation and survival of primary human lymphatic (hLEC) and blood endothelial cells (hBEC) ± primary human vascular smooth muscle cells (hvSMC) were evaluated and compared in vitro and in vivo. hLEC ± hvSMC or hBEC ± hvSMC were seeded in a 3D porous scaffold in vitro, and capillary percent vascular volume (PVV) and vascular density (VD)/mm2 assessed. Scaffolds were also transplanted into a sub-cutaneous rat wound with morphology/morphometry assessment. Initially hBEC formed a larger vessel network in vitro than hLEC, with interconnected capillaries evident at 2 days. Interconnected lymphatic capillaries were slower (3 days) to assemble. hLEC capillaries demonstrated a significant overall increase in PVV (p = 0.0083) and VD (p = 0.0039) in vitro when co-cultured with hvSMC. A similar increase did not occur for hBEC + hvSMC in vitro, but hBEC + hvSMC in vivo significantly increased PVV (p = 0.0035) and VD (p = 0.0087). Morphology/morphometry established that hLEC vessels maintained distinct cell markers, and demonstrated significantly increased individual vessel and network size, and longer survival than hBEC capillaries in vivo, and established inosculation with rat lymphatics, with evidence of lymphatic function. The porous polyurethane scaffold provided advantages to capillary network formation due to its large (300–600 μm diameter) interconnected pores, and sufficient stability to ensure successful surgical transplantation in vivo. Given their successful survival and function in vivo within the porous scaffold, in vitro assembled hLEC networks using this method are potentially applicable to clinical scenarios requiring replacement of dysfunctional or absent lymphatic networks.

3D porous polyurethane (PU)/ triethanolamine modified hydroxyapatite (TEA-HA) nano composite for enhanced bioactivity for biomedical applications

3D porous polyurethane (PU)/ triethanolamine modified hydroxyapatite (TEA-HA) nano composite for enhanced bioactivity for biomedical applications

Porous 3D polyurethane composite scaffolds with incorporation of highly mineralized calcium citrate for bone tissue engineering

High mineralization activity is a crucial requirement in bone tissue engineering. In this study, a novel calcium citrate compounded amorphous calcium phosphate (CAP)/polyurethanes (PUs) composite porous 3D scaffold was developed by in situ polymerization via gas foaming method. The physical and chemical properties were characterized and discussed. The results showed that the HDI can react mildly with hydroxyl (–OH) groups of PEG, while gas foaming action was caused by the release of CO2 occurred in the reactive process, resulting in a uniform porous structure of PUs scaffold. The porosities of the synthetic PEGCAP porous scaffolds are all above 70% with high interconnectivity, while the porosity decreased 27% with increasing CAP to 40%. Furthermore, the mechanical properties of porous scaffolds enhanced about 16 times after addition of CAP. After immersing in simulated body fluid (SBF), the surface structure of the porous scaffold kept stable, and surface deposits formed, indicating that the porous scaffold has good mineralization activity. In addition, the in vitro cells proliferation assay confirms the excellent bioactivity of PEGCAP porous scaffolds.

Tailored highly porous, templated polyurethane for sand consolidation

AbstractA novel polymeric resin formulation is developed to mitigate sand production from subterranean formations composed of unconsolidated or weakly consolidated sands via a chemical sand consolidation approach. The developed formulation aims to minimize the formation permeability loss commonly observed in a chemical sand consolidation treatment. The new formulation is a water‐in‐oil high internal phase emulsion with poly(ε‐caprolactone) polyol and isophorone diisocyanate monomer incorporated in the external oil phase. Highly porous, emulsion templated polyurethane forms through the reaction between polyol and isocyanate under elevated temperature. Additionally, CO2 generated through the reaction between excess isocyanate monomer and water leads to the formation of more pores in the cross‐linked polymeric network. When the developed formulation is applied for sand consolidation treatment, the interconnected pores formed after resin curing act as “channels” in the consolidated products and allow the produced fluid such as oil, water, or gas to easily flow through, thereby limiting permeability reduction. The effectiveness of using porous polyurethane material for sand consolidation is evaluated through a compressive strength and permeability study of the consolidated sandpacks prepared with this chemistry.

Green fabrication of double-sided self-supporting triboelectric nanogenerator with high durability for energy harvesting and self-powered sensing

The first double-sided self-supporting triboelectric nanogenerator (DS-TENG) with high durability and output performance is developed. A sustainable and scalable supercritical carbon dioxide (scCO2) foaming technique is used to fabric porous composite thermoplastic polyurethane (TPU) foams with regular bumps and valleys by embedding a stainless steel mesh (SSM) inside. When packaged using two silicone rubber films, the DS-TENG realizes simultaneous utilization of both sides of the composite foam and effectively prevents the SSM electrode from erosion, which significantly enhances the output performance and durability while maintaining high flexibility. The working mechanism of the DS-TENG is elaborated by manipulating the structure of the composite foam via changing the mesh grid and the foaming conditions. Attributing to the wear resistance of the comprising materials and compact device configuration, the DS-TENG exhibits exceptional durability and long-term stability. Moreover, the DS-TENG demonstrates tremendous potential in self-powered sensing of pressing and bending, monitoring human walking and sitting behaviors, and assisting pugilist training. This work provides a new design of compact self-supporting TENGs with reliable long-term performance and paves a cost-effective approach for green and scale fabrication of TENGs.

Multifunctional, Light‐Weight Wearable Sensor Based on 3D Porous Polyurethane Sponge Coated with MXene and Carbon Nanotubes Composites

AbstractWith the rapid development of wearable electronics, a resistive sensor with high performance and multifunctional monitoring abilities turns out to be a great challenge for industrial application fields. Herein, a wearable 3D porous polyurethane (PU) sponge sensor coated with MXene and carbon nanotubes (CNTs) composites is self‐assembled through a simple ultrasonic dip‐coating process. The alternate assembly and the synergistic effect of MXene and CNTs contribute to a tough and complete 1D/2D conductive network, which significantly extends the measurement ability of the proposed MXene/CNTs@PU sensor from a wide‐compressive strain range (−80%) to a wide‐stretching strain range (60%). Moreover, benefit from this unique tough multidimensional MXene/CNTs structure, the presented sensor is endowed with excellent electrical response and stability during the long‐term reproducibility test over 5000 cycles. This study also demonstrates the versatile applications (stretching and compression) of the MXene/CNTs@PU sensor, such as detecting subtle expressions, vocal vibrations, body actions of human motions, and lighting light emitting diode lamps. Thus, this advanced sensor indicates great potential for emerging applications in human–machine interaction, healthcare, and wearable devices.

Precision 3D printed meniscus scaffolds to facilitate hMSCs proliferation and chondrogenic differentiation for tissue regeneration

BackgroundThe poor regenerative capability and structural complexity make the reconstruction of meniscus particularly challenging in clinic. 3D printing of polymer scaffolds holds the promise of precisely constructing complex tissue architecture, however the resultant scaffolds usually lack of sufficient bioactivity to effectively generate new tissue.ResultsHerein, 3D printing-based strategy via the cryo-printing technology was employed to fabricate customized polyurethane (PU) porous scaffolds that mimic native meniscus. In order to enhance scaffold bioactivity for human mesenchymal stem cells (hMSCs) culture, scaffold surface modification through the physical absorption of collagen I and fibronectin (FN) were investigated by cell live/dead staining and cell viability assays. The results indicated that coating with fibronectin outperformed coating with collagen I in promoting multiple-aspect stem cell functions, and fibronectin favors long-term culture required for chondrogenesis on scaffolds. In situ chondrogenic differentiation of hMSCs resulted in a time-dependent upregulation of SOX9 and extracellular matrix (ECM) assessed by qRT-PCR analysis, and enhanced deposition of collagen II and aggrecan confirmed by immunostaining and western blot analysis. Gene expression data also revealed 3D porous scaffolds coupled with surface functionalization greatly facilitated chondrogenesis of hMSCs. In addition, the subcutaneous implantation of 3D porous PU scaffolds on SD rats did not induce local inflammation and integrated well with surrounding tissues, suggesting good in vivo biocompatibility.ConclusionsOverall, this study presents an approach to fabricate biocompatible meniscus constructs that not only recapitulate the architecture and mechanical property of native meniscus, but also have desired bioactivity for hMSCs culture and cartilage regeneration. The generated 3D meniscus-mimicking scaffolds incorporated with hMSCs offer great promise in tissue engineering strategies for meniscus regeneration.Graphical

Effect of binder-aggregate ratio on the mechanical and functional properties of porous polyurethane cement mixture

ABSTRACT Polyurethane mixtures are regarded as novel polymer pavement materials that can overcome the shortcomings of poor mechanical properties and loose particles of open-graded friction course (OGFC). Owing to its high strength after curing, polyurethane binder improves the mechanical connection at the aggregate-aggregate contact point, which effectively enhances the service performance of permeable pavement. However, the relationship between the binder content and the mechanical and functional properties of polyurethane mixture has not clearly understood yet. The objective of this study is to investigate the influence of the binder-aggregate ratio on the mechanical and functional properties using laboratory tests. Firstly, the effect of binder content on the mechanical properties of the mixture is examined by Marshall stability test, uniaxial compression test, and bending beam test. Secondly, the functional properties of the mixtures are characterised by Cantabro test, permeability test, computed tomography, and particle clogging test. Finally, the durability of the mixtures is characterised by hydrolysis resistance test and ultraviolet radiation degradation test. The results reveal that the content of binder has a significant impact on the mechanical and functional properties of the mixture. It is necessary to maintain a balance between the mechanical and functional properties.

Hierarchical network structural composites for extraordinary energy dissipation inspired by the cat paw

The proverbial “nine lives” of cats are attributed to the capacity of the felines to withstand jumps and falls from a high-rise without being fatally wounded, and this is due in large part to their impact-resistant paw pads. The pads possess a complex architecture of multiscale collagen fiber networks and adipose mass chambers. We propose in this paper the concept of a hierarchical composite made of porous polyurethane (PU) main network skeletons coated with graphene oxide (GO)/multiwalled carbon nanotubes (MWCNTs), freeze-dry constructed secondary membrane network configurations with GO/MWCNTs, and embedded in a polyborondimethylsiloxane (PBDMS) matrix. The design of the composite is inspired by the architectures of collagens present in the cat paw and the composites provide significant creep resistance, load bearing, shape recovery and also stiffness tailoring. More importantly, the hierarchical composites possess remarkable high energy dissipations during quasi-static cyclic compression and dynamic mechanical loadings as vibration (damping capacity: 160% increase compared to the pure matrix) and impact (impacting energy absorption: ∼100%). The multiscale deformation mechanisms are analyzed and discussed with the support of finite element simulations. The main fibrous and secondary membranous networks generated during the manufacturing of the composite act as multiscale confinements to the lipid-like matrix, so that the matrix with reversible B-O bonds can significantly contribute to the unusual energy dissipation characteristics. Similar to the cat paws, the hierarchical composites are also soft, flexible and show significant potential for safety wearing devices in sport and broad engineering applications.

Self‐Healing and Flexible Porous Nickel/Polyurethane Composite Based on Multihealing Systems and Applications

AbstractWith the development of science and technology, the need for high performance sensors is more and more urgent to deal with different needs and environments. In this study, a flexible strain sensor with performance of self‐healing is developed based on porous nickel as conductive filler and polyurethane (PU) with hydrogen bonding, disulfide bond, and metal coordination bond as polymer matrix. Porous nickel is prepared by a new biotemplates method, and the effects of reaction temperature and concentration of NiCl2·6H2O on the morphology of porous nickel are studied. Polyurethanes containing hydrogen bonding, disulfide bonds, and metal coordination bonds are prepared, and the mechanical properties and self‐healing properties of polyurethanes with different contents of hard and soft segments are studied. A strain sensor is prepared by mixing porous nickel and polyurethane. The effect of filler content on mechanical properties, self‐healing properties, and electrical self‐healing properties is studied. The sensor is attached to the joints of human limbs, and the peak diagram of time‐relative resistance changes is obtained through the cyclic and repeated movements of the limbs. The sensor has excellent sensitivity.

Investigation on mechanical properties and water stability of porous polyurethane concrete

Abstract Porous polyurethane concrete (PPUC) is a novel material for permeable pavements and is considered as an alternative to porous asphalt or porous cement concrete. However, studies of the mechanical properties of PPUC are still insufficient. In this study, the comprehensive mechanical properties and water stability of PPUC with different gradations and polyurethane dosages were investigated, and its water damage mechanism was preliminarily explored. The results show that the flexural strength and Marshall stability of PPUC can more easily reach the index in the standards of porous cement concrete or porous asphalt, while the compressive strength and abrasion resistance are the weak points of its mechanical properties and need to be further optimized. The mechanical properties and water stability of PPUC were effectively improved by increasing the polyurethane dosage and using continuously graded aggregates. PPUC is more susceptible to water damage because water reacts with the residual isocyanate groups within the polyurethane film to generate carbon dioxide gas, which reduces the cohesion and adhesion performance of polyurethane film. This study provides a comprehensive understanding of the mechanical properties of PPUC and an initial insight into the mechanism of water damage.

Polyurethane-Nanolignin Composite Foam Coated with Propolis as a Platform for Wound Dressing: Synthesis and Characterization.

This piece of research explores porous nanocomposite polyurethane (PU) foam synthesis, containing nanolignin (NL), coated with natural antimicrobial propolis for wound dressing. PU foam was synthesized using polyethylene glycol, glycerol, NL, and 1, 6-diisocyanato-hexane (NCO/OH ratio: 1.2) and water as blowing agent. The resultant foam was immersed in ethanolic extract of propolis (EEP). PU, NL-PU, and PU-NL/EEP foams were characterized from mechanical, morphological, and chemical perspectives. NL Incorporation into PU increased mechanical strength, while EEP coating showed lower strength than PU-NL/EEP. Morphological investigations confirmed an open-celled structure with a pore diameter of 150–200 μm, a density of nearly 0.2 g/cm3,, and porosity greater than 85%, which led to significantly high water absorption (267% for PU-NL/EEP). The hydrophilic nature of foams, measured by the contact angle, proved to be increased by NL addition and EEP coating. PU and PU-NL did not show important antibacterial features, while EEP coating resulted in a significant antibacterial efficiency. All foams revealed high biocompatibility toward L929 fibroblasts, with the highest cell viability and cell attachment for PU-NL/EEP. In vivo wound healing using Wistar rats’ full-thickness skin wound model confirmed that PU-NL/EEP exhibited an essentially higher wound healing efficacy compared with other foams. Hence, PU-NL/EEP foam could be a promising wound dressing candidate.

Molecular Ferroelectric-Based Flexible Sensors Exhibiting Supersensitivity and Multimodal Capability for Detection.

Although excellent dielectric, piezoelectric, and pyroelectric properties matched with or even surpassing those of ferroelectric ceramics have been recently discovered in molecular ferroelectrics, their successful applications in devices are scarce. The fracture proneness of molecular ferroelectrics under mechanical loading precludes their applications as flexible sensors in bulk crystalline form. Here, self-powered flexible mechanical sensors prepared from the facile deposition of molecular ferroelectric [C(NH2 )3 ]ClO4 onto a porous polyurethane (PU) matrix are reported. [C(NH2 )3 ]ClO4 -PU is capable of detecting pressure of 3Pa and strain of 1% that are hardly accessible by the state-of-the-art piezoelectric, triboelectric, and piezoresistive sensors, and presents the ability of sensing multimodal mechanical forces including compression, stretching, bending, shearing, and twisting with high cyclic stability. This scaling analysis corroborated with computational modeling provides detailed insights into the electro-mechanical coupling and establishes rules of engineering design and optimization for the hybrid sponges. Demonstrative applications of the [C(NH2 )3 ]ClO4 -PU array suggest potential uses in interactive electronics and robotic systems.

Three-Dimensional Printing of a Flexible Capacitive Pressure Sensor Array in the Assembly Network of Carbon Fiber Electrodes and Interlayer of a Porous Polyurethane Dielectric

Three-Dimensional Printing of a Flexible Capacitive Pressure Sensor Array in the Assembly Network of Carbon Fiber Electrodes and Interlayer of a Porous Polyurethane Dielectric

The Influence of Microstructure on Sound Absorption of Polyurethane Foams through Numerical Simulation

Front Cover: The structure of isocyanate contains unsaturated bonds and has high activity. It easily reacts with some organic or inorganic substances with active groups. In the preparation of polyurethane foam, a porous polyurethane foam can be generated by reacting isocyanate radicals with the hydroxyl compound in the plant-based polyol. This is reported by Shuming Chen and co-workers, in article number 2000075.

Study on Cyclic Compressive and Dynamic Mechanical Properties of Porous Polyurethane Composites Prepared with Hollow Silica Microspheres.

Porous polycaprolactone-based polyurethane composites containing hollow silica microspheres were synthesized by one-step bulk polymerization. The effects of incorporated hollow silica microspheres on the cyclic compressive and dynamic mechanical properties of the composites were examined. Cyclic compression testing was carried out to record the accumulated stress versus strain profiles during 100 continuous loading and unloading cycles and to study the compressive behavior and time-dependent recovery of the composites. The effects of frequency on the dynamic mechanical properties of the composites was also investigated using a dynamic mechanical analyzer. Cole-Cole and Wicket plots were drawn to check the validity of the time-temperature supposition of the composites in the temperature and frequency ranges considered. Master curves of the composites were constructed based on the time-temperature superposition principle to obtain the long-term dynamic mechanical behavior of the composites.

Effect of Hollow Silica Microspheres on Compressive and Dynamic Mechanical Properties of Hydroxyl-Terminated Polybutadiene-Based Polyurethane Composites.

Porous polyurethane composites containing hollow silica microspheres were prepared by one-step bulk polymerization to study cyclic compressive and dynamic mechanical properties of the composites. Cyclic compression testing was conducted to record the stress versus strain curves during the loading and unloading cycles and in order to study the compressive behavior and time-dependent recovery of the composites. Effect of frequency on the dynamic mechanical properties of the composites was also evaluated using dynamic mechanical analysis. Master curves were constructed based on time-temperature superposition principle in order to show long-term dynamic mechanical behavior of the composites.

Evaluation of the acoustic performance of polyurethane foams embedded with rock wool fibers at low-frequency range; design and construction

The present study aimed to focus on improving acoustic and mechanical characteristics by embedding the polyurethane foam (PUF) with the rock wool fibers (RWF) of diverse values (0–3 wt%) that were synthesized using the polymerization process. In addition, the association between non-acoustical parameters and sound absorption characteristics of the porous polyurethane foams was investigated. Moreover, indicators of effective non-acoustic parameters, including air-flow resistance (AFR), porosity, volumetric density, and microstructure were determined. The results showed sound absorption properties were highly enhanced when polyurethane composite foam (PUF/RWF) (i.e. 1, 2, and 3 wt%) were used, as compared to the pristine PUF. Furthermore, the sound absorption coefficient (SAC) of PUF composite was highly enhanced in the frequency range of 400 to 1600 Hz when the foam was combined with an RWF amount of 2 wt%. Besides, the density and AFR increased with the addition of different contents of RWF. Open porosity composite foams strongly depended on AFR and volumetric density (i.e. a negative association with RWF content). The use of the excessive amount of the RWF (RWF > 2 wt%) caused intramolecular agglomeration, which resulted in reduced sound absorption efficiency. Finally, multiple regression analysis was used to investigate the association between SAC and non-acoustic parameters, including AFR, porosity, volumetric density, and RWF amount, which revealed a well proportion between experimental data and statistical analysis.

Preparation of superhydrophobic and superoleophilic polyurethane foam for oil spill cleanup

Preparation, characterization and applications of a novel polyurethane based superhydrophobic and superoleophilic absorbent were studied for the purpose of oil-spill cleanup or water-oil/organic solvent separation. Porous superhydrophobic polyurethane foam was synthesized, followed by a one-step reaction to incorporate copper oxide nanoparticles (nano CuO) and n-hexadecylamine (HDA) onto the surface framework of the polyurethane foam with the aids of oxidative self-polymerization of dopamine. The morphology, thermal stability, and surface wettability of the modified polyurethane foam were characterized by scanning electron microscope, infrared spectroscopy, thermogravimetry, and water contact angle instrumentation. The water contact angle and water sliding angle of the foam up to 153° and 6° respectively, indicating that the modified polyurethane foam had good superhydrophobicity. It was demonstrated that the absorption capacity of the foam for oils/organic solvents was up to 45 times its own weight. The oils/organic solvents absorbed in the foam could be easily recovered by simply pressing, and an oil absorption capacity of higher than 90% was retained after 50 cycles of usage. This study provided a feasible strategy for the preparation of superhydrophobic and superoleophilic foams for water-oil/organic solvent separation.

Zwitterionic hydrogel coated superhydrophilic hierarchical antifouling floater enables unimpeded interfacial steam generation and multi-contamination resistance in complex conditions

• A zwitterionic hydrogel coated evaporator is developed for solar steam generation. • The superhydrophilic surfaces and channels guarantee unimpeded water supply. • The evaporator possesses multi-contamination resistance to salt, oil, and biofouling. Continuous water pumping and steam generation are key factors in long-term solar-driven evaporation for fresh water production. However, current solar desalination devices easily get contaminated by salt accumulation, oil spill or marine fouling in real-world applications, causing blockage, corrosion or even invalidation. Developing antifouling coatings that can protect the devices from multi-contamination is a superior option to guarantee the longevity of the devices and stable fresh water generation. Herein, a superhydrophilic hierarchical antifouling floater (SHAF) consisted of zwitterionic hydrogel coated polyurethane (PU), polystyrene (PS) foam and cotton swabs, is developed. The porous PU fabric is competent to fragment water into ultra-fine droplets, increasing the vapor pressure and promoting the evaporation process. The zwitterionic coating can bind water molecules to form a hydration layer, thus leading to stable water transport and fascinating fouling resistance. Integrated with these merits, this SHAF accelerates water evaporation rate up to ~2.2 kg m −2 h −1 with a photothermal conversion efficiency of 93.5%. It also exhibits prominent microbial resistance with 96.2% against E. coli and ~100% against diatom. Additionally, due to the hydration shield induced by the zwitterionic coating, the SHAF surface is endowed with self-cleaning property even against crude oil pollution. Therefore, the SHAF with highly efficient water evaporation and multi-contamination resistance is a potential candidate for solar-driven fresh water production from seawater or even wastewater.