Polyurethane Materials Research Articles

Characterization and Comparison of Anammox Immobilization in Polyvinyl Alcohol, Polyethylene Glycol and Water-Borne Polyurethane

Anammox bacteria were embedded with different mass fractions of polyvinyl alcohol (PVA), polyethylene glycol (PEG) and water-based polyurethane (WPU) materials. The embedded immobilized pellets with different particle sizes of about 2.8–3.2 mm were prepared. The effects of the mass fraction of the embedding material (PVA 6–12%, PEG 6–9%, WPU 10%) and the concentration of activated carbon added in the embedding process (0–4%) on the pellet was investigated. The performance of pellet formation, sedimentation rate, mechanical strength, expansion coefficient, and elasticity were compared and analyzed under different immobilization conditions, and the parameters of each embedding step were optimized. Anammox immobilized pellets prepared with 10% polyvinyl alcohol (PVA), 2% sodium alginate (SA), and 2% powdered activated carbon were proposed. The effects of salinity on anammox were investigated through a batch test, and the optimal reaction conditions were selected to carry out the operation test. The functional groups of embedded and unembedded anammox sludge were detected using the infrared spectrum. A continuous flow sequencing batch reactor (SBR) demonstrated stable operation with immobilized anammox. Scanning electron microscopy revealed that the immobilized anammox pellets appeared as irregular particles, with each micro-unit predominantly being spherical. Additionally, a minor presence of rod-shaped bacteria was also noted. After 30 days of stable operation of the reactor, the ammonia nitrogen removal rate reached 84.7%.

Synthesis of High Mechanical Strength and Thermally Recyclable and Reversible Polyurethane Adhesive by Diels–Alder Reaction

AbstractRecyclability of polyurethane materials is significant to relieve environmental problems caused by damaged polymers. Inspired by plenty of self‐healing properties based on dynamic covalent bonds. A high mechanical strength and thermally reversible polyurethane adhesive are acquired through co‐polymerization of poly‐1,4‐butylene adipate glycol (PBA), soybean oil‐based polyol (MESO), and toluene diisocyanate (TDI) whose linear polymer chains are constructed by Diels–Alder reaction between furfuryl alcohol (FA) and bismaleimide (BMI), named DAPU. Further, the obtained polyurethane adhesives show great recyclability, mechanical performance (Whose tensile strength can reach 91.7 MPa), and appropriate self‐healing ability through the thermally reversible Diels–Alder covalent bonds and hydrogen bonds between urethane groups, which may pave a way for further development of recyclable materials.

Assessment of the Biodegradability and Compostability of Finished Leathers: Analysis Using Spectroscopy and Thermal Methods.

In this study, the biodegradation properties of leather treated with various finishing chemicals were evaluated in order to enhance the sustainability of leather processing. We applied advanced analytical techniques, including FT-IR, thermogravimetric analysis (TGA), and solid-state NMR spectroscopy. Leather samples treated with different polymers, resins, bio-based materials, and traditional finishing agents were subjected to a composting process under controlled conditions to measure their biodegradability. The findings revealed that bio-based polyurethane finishes and acrylic wax exhibited biodegradability, while traditional chemical finishes like isocyanate and nitrocellulose lacquer showed moderate biodegradation levels. The results indicated significant differences in the biodegradation rates and the impact on plant germination and growth. Some materials, such as black pigment, nitrocellulose lacquer and wax, were beneficial for plant growth, while others, such as polyurethane materials, had adverse effects. These results support the use of eco-friendly finishes to reduce the environmental footprint of leather production. Overall, this study underscores the importance of selecting sustainable finishing chemicals to promote eco-friendly leather-manufacturing practices.

Eco-friendly Indigo Dyeing of 3D-Printed Thermoplastic Polyurethane Material Using Glucose and Calcium Hydroxide

Eco-friendly Indigo Dyeing of 3D-Printed Thermoplastic Polyurethane Material Using Glucose and Calcium Hydroxide

Biodegradable Polyurethane Derived from Hydroxylated Polylactide with Superior Mechanical Properties.

Developing biodegradable polyurethane (PU) materials as an alternative to non-degradable petroleum-based PU is a crucial and challenging task. This study utilized lactide as the starting material to synthesize polylactide polyols (PLA-OH). PLA-based polyurethanes (PLA-PUs) were successfully synthesized by introducing PLA-OH into the PU molecular chain. A higher content of PLA-OH in the soft segments resulted in a substantial improvement in the mechanical attributes of the PLA-PUs. This study found that the addition of PLA-OH content significantly improved the tensile stress of the PU from 5.35 MPa to 37.15 MPa and increased the maximum elongation to 820.8%. Additionally, the modulus and toughness of the resulting PLA-PU were also significantly improved with increasing PLA-OH content. Specifically, the PLA-PU with 40% PLA-OH exhibited a high modulus of 33.45 MPa and a toughness of 147.18 MJ m-3. PLA-PU films can be degraded to carbon dioxide and water after 6 months in the soil. This highlights the potential of synthesizing PLA-PU using biomass-renewable polylactide, which is important in green and sustainable chemistry.

Sensitivity Differences in Testing of Polyurethane Condoms’ Lubricant Compatibility

Abstract Over-the-counter (OTC) personal lubricants (PLs) generally have less potent effects on condoms’ mechanical properties than do appropriate positive controls. Therefore, to assess the compatibility of OTC PLs with condoms, a test method must be more sensitive than those employed to capture the effect of a strong positive control. Using various percent compositions of selected common ingredients in commercial PLs, we attempted to differentiate between the sensitivities of different methods for testing lubricant effects on polyurethane (PU) condoms. After discrete applications of each composition, we studied induced stresses and stress-to-strain ratios at various strain rates, and stress reduction at a constant stretch, in PU condom coupons at 37°C. Swelling was studied at room temperature (RmT). Changes in the induced stress and stress-to-strain ratio because of low percent composition of a potent surrogate component were detectable only at low strain rates. A few low percent compositions of potent ingredients – though they induced insignificant changes in the material as detected by tensile testing and did not swell the PU material – noticeably reduced the percent stress at a constant stretch. Slower strain rates in tensile testing were necessary to detect the effects of low potency combinations, whereas stress reduction was the most efficient detector of change at a constant physiologically relevant strain. Absence of swelling and insignificant changes in tensile properties at high strain rates did not guarantee an absence of interactions. Manufacturers now have a more sensitive method for capturing the interactions of PU condoms with OTC PLs, which are generally less potent than appropriate positive controls.

Experimental and theoretical investigation of a miniature simple pressure pulsation attenuator lined with porous polyurethane material

A miniature simple pressure pulsation attenuator (PPA) lined with porous polyurethane material is designed and a theorical model is established for analyzing the pressure pulsation attenuation performance of PPA. The effect of internal structural parameters of PPA and external operating conditions on attenuation performance is investigated theoretically and experimentally. Spectral intensity is used as a new method to evaluate the pressure pulsation attenuation, and other common index such as pressure pulsation rate and frequency spectrum are also compared in detail. The results show that spectral intensity can more accurately reflect the overall effect of pressure pulsation and the attenuation effect at a specific frequency. The present PPA is more suitable for low static pressure and can effectively eliminate low-frequency and high-frequency pressure pulsation. In addition, the diameter and number of pores can affect the pressure pulsation attenuation. Insertion loss of PPA exhibits multiple peaks, which are mainly influenced by liner length and liner material. Furthermore, the flow rate increases as the pulsation frequency increases for the piston pump based on frequency control, which can cause the pulsation attenuation performance to basically remain unchanged. The research offers valuable insights for the design, optimization, and analysis of PPA in seawater hydraulic system.

Synthesis and characterization of polyurethane-based self-luminous pavement coatings: a performance evaluation study

Improving the nighttime vision of drivers is essential, given the growing advancements in urban transportation. In this study, polyurethane-based self-luminous pavement coatings (PSCs) were prepared by doping luminous powders (LPs) into the polyurethane materials. The superior optical properties and chemical stabilities of these coatings were ensured by synthesizing the polyurethane-based material. Then, the PSCs were evaluated for their comprehensive performances, such as luminescence, aging resistance, and abrasion resistance, using various characterization methods, including fluorescence spectral analysis, Fourier-transform infrared spectroscopy, fluorescence microscopy, and mechanical property testing. The results show that the 50-mesh LP has the optimal overall performance, with an initial luminescence that exceeds those of the 100 and 400 meshes. The initial brightness of the PSC is mainly influenced by the LP and increases with dosage. The lattice structure and luminescent properties of the luminescent material did not change after coating preparation. The peak excitation wavelength of 420 nm implies that the coating has the best excitation effect under UV light. The primer-marking coating effectively improves the abrasion resistance of the PSC, and the mass loss of the PSC with a coating thickness of 0.4 kg/m2 is 52.9% of that without the primer-marking coating, with the optimal coating thickness being 0.6 kg/m2. This research provides an innovative solution to improve nighttime roadway lighting, which provides useful support for the sustainable development of urban transportation infrastructures and construction of intelligent transportation systems.

Study on the coupling effect and failure mechanism of mesh fabric reinforced polyurea coating

Mesh fabric reinforced polyurethane coating is a typical type of fiber reinforced polymer composite structure. Some designers proposed to replace the substrate material of the fabric reinforced polyurethane coating with the polyurea material. However, there is a lack of research on the analysis and design of this kind of structure. This study investigated the coupling effect between the mesh fabric and polyurea substrate and explored the mechanical behavior and failure pattern of the mesh fabric reinforced polyurea coating. The deformation behavior and load-carrying capacity of the composite coating were also analyzed compared with the traditional fiber reinforced polyurethane composite coating. The main conclusions are as follows: Fabric fiber fracture leads to instantaneous stress pulse in the polyurea substrate, fiber fracture surface, and stress-pulse-induced microcracks lead to the overall cross-section pull-off failure. The polyurea material exhibits a higher strength (10 MPa∼30 MPa). Mesh fabric induced defects lead to a strength decrease of 12.2 % and an elongation decrease of more than 90 %. The mesh fabric could undermine the strength and deformation capacity of the polyurea substrate, playing a negative role in the material's performance. The polyurethane material generally exhibits a lower strength of no more than 10 MPa. The mesh fabric could increase the tensile strength by 14 times. The mesh fabric could increase the strength of the polyurethane coating substrate, bringing a certain strengthening effect. The mesh fabric can be adopted to strengthen the substrate when the substrate material's tensile strength is lower than that of the mesh fabric. When the substrate tensile strength exceeds the strength of the mesh fabric, it is not recommended to use the mesh fabric.

Effect of the silanization process on the fire resistance and thermal properties of closed-cell foams with sunflower husk ash

The topics covered in this paper are relevant to the further development of polyurethane materials and propose a new method for producing sustainable and innovative foams. In this study, the effect of filler silanization on the flammability and thermal stability of rigid polyurethane foam (RPUF) was investigated. The RPUF composites study was preceded by an analysis of sunflower husk ash (SHA). Thermal decomposition behaviour and particle size distribution were carried out for the SHA samples. More, the elemental composition and structure of the fillers were investigated. The use of silanization of the filler results in homogenization of its structure. Sunflower husk ash has higher characteristic melting points than most biomass ashes and good thermal stability. The foam flammability results were preceded by an analysis of density and cell morphology. The use of silanized filler in RPUFs results in a homogenized structure and a 14 % reduction in apparent density. A wide range of tests were carried out as part of the flammability tests, which included: limiting oxygen index (LOI), gross calorific value, cone calorimeter, and optical density test. Additionally, thermal analysis methods were used to investigate the thermal stability of the foams. Flammability tests carried out confirm the positive effect of filler salinization on flammability. Heat release during combustion is reduced by 10 % and the release of toxic gases is also reduced. On the other hand, the thermal stability results are similar for foam with unmodified filler and those with silanized ash. Based on the comprehensive flammability and smoke results, a trend towards improved flame-retardant properties of RPUFs was observed.

Characterization of Blow-Spun Polyurethane Scaffolds-Influence of Fiber Alignment and Fiber Diameter on Pericyte Growth.

In this study, fibrous polyurethane (PU) materials with average fiber diameter of 200, 500, and 1000 nm were produced using a solution blow spinning (SBS) process. The effects of the rotation speed of the collector (in the range of 200-25 000 rpm) on the fiber alignment and diameter were investigated. The results showed that fiber alignment was influenced by the rotation speed of the collector, and such alignment was possible when the fiber diameter was within a specific range. Homogeneously oriented fibers were obtained only for a fiber diameter ≥500 nm. Moreover, the changes in fiber orientation and fiber diameter (resulting from changes in the rotation speed of the collector) were more noticeable for materials with an average fiber diameter of 1000 nm in comparison to 500 nm, which suggests that the larger the fiber diameter, the better the controlled architectures that can be obtained. The porosity of the produced scaffolds was about 65-70%, except for materials with a fiber diameter of 1000 nm and aligned fibers, which had a higher porosity (76%). Thus, the scaffold pore size increased with increasing fiber diameter but decreased with increasing fiber alignment. The mechanical properties of fibrous materials strongly depend on the direction of stretching, whereby the fiber orientation influences the mechanical strength only for materials with a fiber diameter of 1000 nm. Furthermore, the fiber diameter and alignment affected the pericyte growth. Significant differences in cell growth were observed after 7 days of cell culture between materials with a fiber diameter of 1000 nm (cell coverage 96-99%) and those with a fiber diameter of 500 nm (cell coverage 70-90%). By appropriately setting the SBS process parameters, scaffolds can be easily adapted to the cell requirements, which is of great importance in producing complex 3D structures for guided tissue regeneration.

Odor-Active Compounds in Flexible Polyurethane Materials

Flexible polyurethane (PU) materials find extensive use in upholstery, mattresses, and automobiles, yet the molecular background of their odor is still inadequately understood. To address this gap, we aimed at identifying major odorants in fifteen samples representing eight common types of flexible PU materials. The volatiles isolated from the samples were subjected to activity-guided screening via gas chromatography-olfactometry. Structures were assigned by comparing odor, retention data, and mass spectra to those of authentic reference compounds. This approach led to the identification of 50 odorants, 39 of which had not previously been described in PU. The odorants belonged to a wide range of compound classes, including tertiary amines, fatty acid oxidation products, short-chain aldehydes, trioxocanes, pyrazines, aromatic hydrocarbons and heterocycles, chlorinated compounds, phenol derivatives, fragrance compounds, and nitriles. For some odorants, further insights were gained into their origins and release behavior. For example, the odorous 1,4-dimethylpiperazine had been used as a catalyst, and propanal was shown to be not only a PU odorant but also the precursor of an odor-active trioxocane. Additionally, the quantitation of acetaldehyde and propanal suggested their continuous regeneration from the samples. While the sources of other compounds still have to be clarified, the data obtained in this study could pave the way for odor reduction strategies in the production of PU materials, ultimately resulting in an improved odor and consumer experience.

Tri-phase flame retardant system towards advanced energy-saving building materials with highly efficient fire and smoke toxicity reductions

The extensive usage of rigid polyurethane foam (RPUF) as an energy-saving building materials in construction has raised concerns about fire risks and toxic hazards. To address these challenges, a melamine-derived polyol (MADP) was synthesized using the Mannich reaction, resulting in inherently flame-retardant RPUF materials with the introduction of flame-retardant functional groups. Furthermore, a novel MoS2-Cu2O nanohybrid was prepared and employed to enhance flame retardancy and suppress smoke toxicity in RPUF through a cooperative effect with expandable graphite (EG). The resulting M-RPUF/EG/MoS2-Cu2O nanocomposite exhibited remarkable fire safety, as evidenced by significant reductions in peak heat release rate (PHRR), total heat release (THR), total smoke production (TSP), and peak carbon monoxide (CO) release, amounting to 76.9 %, 64 %, 82 %, and 99 % respectively, compared to pristine RPUF. Furthermore, the nanocomposite effectively addressed interfacial defects and significantly enhanced the mechanical property and thermal stability. The significant improvement in fire safety is mainly ascribed to the catalytic charring effect of MADP and EG, as well as the catalytic oxidation of MoS2-Cu2O nanohybrids, resulting in the formation of a thermally stable protective layer in the condensed phase. Based on these results, the integration of the tri-phase flame retardant system holds great potential for advancing the development of fire-safe polyurethane materials.

RETRACTED: Screening of hindered phenol antioxidants by quantum chemical method for improving the aging properties of polyurethane railpad in railway

Polyurethane material has excellent performance and is widely used as railpad in railway, but it is prone to aging and fatigue during long-term service, resulting in a decrease in its performance. In order to improve the aging and fatigue resistance of polyurethane railpad, as well as the efficiency of screening antioxidant, this paper first used quantum chemical method to calculate three types of grafted hindered phenolic antioxidants. Then, polyurethane elastomer railpads with grafted preferred hindered phenolic antioxidants were prepared, and thermal oxidative aging experiments and thermo-oxygen-fatigue coupling aging experiments were conducted. The research results indicate that 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid molecules have better antioxidant properties. When the degradation rate is less than 20%, the activation energy of polyurethane railpads with grafted hindered phenolic antioxidants is about 20% higher than that of ungrafted materials. After 200 days of thermal oxidative aging, polyurethane railpads with grafted hindered phenolic antioxidants maintain high tensile strength and elongation at break, while maintaining stable static stiffness. Their carbonyl index and loss tangent increase only by 10% and 14.8%, respectively, while unmodified samples increase by 29.4% and 26.4%. Scanning electron microscopy also shows a significant reduction in surface cracks on polyurethane railpads grafted with hindered phenolic antioxidants.

A Comprehensive Review of Reactive Flame Retardants for Polyurethane Materials: Current Development and Future Opportunities in an Environmentally Friendly Direction.

Polyurethanes are among the most significant types of polymers in development; these materials are used to produce construction products intended for work in various conditions. Nowadays, it is important to develop methods for fire load reduction by using new kinds of additives or monomers containing elements responsible for materials' fire resistance. Currently, additive antipyrines or reactive flame retardants can be used during polyurethane material processing. The use of additives usually leads to the migration or volatilization of the additive to the surface of the material, which causes the loss of the resistance and aesthetic values of the product. Reactive flame retardants form compounds containing special functional groups that can be chemically bonded with monomers during polymerization, which can prevent volatilization or migration to the surface of the material. In this study, reactive flame retardants are compared. Their impacts on polyurethane flame retardancy, combustion mechanism, and environment are described.

Electric Susceptibility at Partial Coverage of a Circular One-Side Access Capacitive Sensor with Rigid Polyurethane Foams.

The capability of dielectric measurements was significantly increased with the development of capacitive one-side access physical sensors. Complete samples give no opportunity to study electric susceptibility at a partial coverage of the one-side access sensor's active area; therefore, partial samples are proposed. The electric susceptibility at the partial coverage of a circular one-side access sensor with cylinders and shells is investigated for polyurethane materials. The implementation of the relative partial susceptibility permitted us to transform the calculated susceptibility data to a common scale of 0.0-1.0 and to outline the main trends for PU materials. The partial susceptibility, relative partial susceptibility, and change rate of relative partial susceptibility exhibited dependence on the coverage coefficient of the sensor's active area. The overall character of the curves for the change rate of the relative partial susceptibility, characterised by slopes of lines and the ratio of the change rate in the centre and near the gap, corresponds with the character of the surface charge density distribution curves, calculated from mathematical models. The elaborated methods may be useful in the design and optimization of capacitive OSA sensors of other configurations of electrodes, independent of the particular technical solution.

Perspective on the Development of Monomer Recovery Technologies from Plastics Designed to Last.

In order to prevent the current unsustainable waste handling of the enormous volumes of end-of-use organic polymer material sent to landfilling or incineration, extensive research efforts have been devoted toward the development of appropriate solutions for the recycling of commercial thermoset polymers. The inability of such cross-linked polymers to be remelted once cured implies that mechanical recycling processes used for thermoplastic materials do not translate to the recycling of thermoset polymers. Moreover, the structural diversity within the materials from the use of different monomers as well as the use of such polymers for the fabrication of fiber-reinforced polymer composites make recycling of these materials highly challenging. In this Perspective, depolymerization strategies for thermoset polymers are discussed with an emphasis on recent advancements within our group on recovering polymer building blocks from polyurethane (PU) and epoxy-based materials. While these two represent the largest thermoset polymer groups with respect to the production volumes, the recycling landscapes for these classes of materials are vastly different. For PU, increased collaboration between academia and industry has resulted in major advancements within solvolysis, acidolysis, aminolysis, and split-phase glycolysis for polyol recovery, where several processes are being evaluated for further scaling studies. For epoxy-based materials, the molecular skeleton has no obvious target for chemical scission. Nevertheless, we have recently demonstrated the possibility of the disassembly of the epoxy polymer in fiber-reinforced composites for bisphenol A (BPA) recovery through catalytic C-O bond cleavage. Furthermore, a base promoted cleavage developed by us and others shows tremendous potential for the recovery of BPA from epoxy polymers. Further efforts are still required for evaluating the suitability of such monomer recovery strategies for epoxy materials at an industrial scale. Nonetheless, recent advancements as illustrated with the presented chemistry suggest that the future of thermoset polymer recycling could include processes that emphasize monomer recovery in an energy efficient manner for closed-loop recycling.

Recent Advances in Preparation and Structure of Polyurethane Porous Materials for Sound Absorbing Application.

Various acoustic materials are developed to resolve noise pollution problem in many industries. Especially, materials with porous structure are broadly used to absorb sound energy in civil construction and transportation area. Polyurethane (PU) porous materials possess excellent damping properties, good toughness, and well-developed pore structures, which have a broad application prospect in sound absorption field. This work aims to summarize the recent progress of fabrication and structure for PU porous materials in sound absorption application. The sound absorption mechanisms of porous materials are introduced. Different kinds of structure for typical PU porous materials in sound absorption application are covered and highlighted, which include PU foam, modified PU porous materials, aerogel, templated PU, and special PU porous materials. Finally, the development direction and existing problems of PU material in sound absorption application are briefly prospected. It can be expected that porous PU with high sound absorption coefficient can be obtained by using some facile methods. The design and accurate regulation of porous structures or construction of multilayer sound absorption structure is favorably recommended to fulfill the high demand of industrial and commercial applications in the future work.

Dendronized polyurethanes showing improved mechanical properties and unprecedent thermoresponsiveness

Introduction of topological structures to polyurethanes (PUs) may impart them with different microphase separation, which would be beneficial to afford them novel properties and expand their applications. Herein, a series of dendronized polyurethanes (DPUs) were synthesized with polyols carrying three-fold dendritic OEGs as the soft segment and either aliphatic or aromatic isocyanates as the hard segments. Different from conventional PUs with linear polyols as the soft segments, DPUs contain soft segments with spherical pendants, which may contribute different phase separation. In addition, dendritic OEGs afford DPUs with excellent thermoresponsiveness. Films from aliphatic DPUs and those from the mixture of aromatic DPU and linear PU were prepared. These thermoresponsive DPU films show tunable regulation capacity for encapsulated guests during thermally-induced aggregation of the dendritic OEGs. Remarkably, the phase separations of DPUs were found to be closely related to the amount of dendritic OEGs, and the PU films exhibited excellent mechanical properties with suitable amount of dendritic OEGs as the soft segment. Therefore, dendronization of PUs not only can modulate their microphase separation, but also provides a unique approach to develop PUs materials with novel properties.

Light- and heat-induced shape deformation polyurethane actuators that combine self-healing capabilities

Materials commonly experience physical damage during regular usage, and the implementation of self-healing materials can effectively repair this damage, thereby prolonging the lifespan of the materials. We have successfully synthesized a polyurethane material, S-PU, by introducing azobenzene and reversible disulfide bonds through co-polymerization. The S-PU film not only exhibits light-induced bending, heat-induced recovery ability, but also good self-healing properties. The disulfide bonds in S-PU accelerate the dynamic exchange as the polymer chains flow under heated conditions, enabling self-repairing without affecting the mechanical properties of the material. S-PU is a self-repairing material that can repair damage in a variety of ways. By combining dual-stimulus response characteristics with self-healing properties, this work provides a new idea for self-healing materials and opens more directions for the practical application of the material.