Soft Segments Of Polyurethane Research Articles

Understanding the Interactions between Soft Segments in Polyurethanes: Structural Synergies in Blends of Polyester and Polycarbonate Diol Polyols.

There are no previous studies on the interactions between polyols of different nature as a model for understanding the interactions between soft segments in PUs. In this study, different blends of two polyols of different natures (polyester-PE, and polycarbonate diol-CD) and similar molecular weights were prepared and their structural, thermal, surface, viscoelastic, and self-adhesion properties were assessed. Different experimental techniques were used: infrared spectroscopy (ATR-IR), differential scanning calorimetry (DSC), X-ray diffraction, thermal gravimetric analysis (TGA), and plate-plate rheology. PE showed a larger number of structural repeating units and a higher number of polar groups than CD, but the carbonate-carbonate interactions in CD were stronger than the ester-ester interactions in PE. The blending of CD and PE imparted synergic structural properties, particularly in the blends containing less than 50 wt.% PE, they were associated with the disrupt of the carbonate-carbonate interactions in CD and the formation of new ester-carbonate and hydroxyl-carbonate interactions. CD + PE blends with less than 50 wt.% PE exhibited higher glass transition temperatures, a new diffraction peak at 2θ = 24°, one additional thermal degradation at 426-436 °C, and a less-steep decline of the storage moduli. Furthermore, the different interactions between the polyol chains in the blends were also evidenced on their surface properties, and all CD + PE blends showed self-adhesion properties which seemed related to the existence of ester-carbonate and carbonate-carbonate interactions.

The Performance and Distribution of Polyurethane-Modified Asphalt That Exhibits Different Molecular Weights

To analyze the effect of polyol on polyurethane (PU)-modified asphalt, three different soft segments of polyurethane were synthesized, and we utilized the reaction of MDI (diphenylmethane diisocyanate) with PU650, PU1000, and PU1400. With respect to molecular weight, the effect of polyol on the performance of modified asphalt was analyzed, and the asphalt was modified by using three different polyurethanes. To analyze the PU samples, the Fourier transform infrared spectroscopy (FTIR) tests and gel permeation chromatography (GPC) tests were selected; by contrast, to analyze the rheological properties and modification mechanism of asphalt, the dynamic rheology test (DSR), low-temperature bending creep test (BBR), multi-stress repetitive creep test (MSCR), FTIR, and differential scanning calorimetry (DSC) were selected. The results indicate that the molecular weight of polyol affects the molecular structure of polyurethane, the distribution of soft and hard segments, the content of soft segments, and the distribution of asphaltene in asphalt; thus, the asphalt modification effect occurs differently. The storage stability and high-temperature stability of the polyurethane-modified asphalts that were synthesized using three different polyols (i.e., polyols that exhibit different molecular weights) did not differ considerably, and the PU1400-modified asphalt exhibited the best low-temperature performance.

In Situ High‐performance Gel Polymer Electrolyte with Dual‐reactive Cross‐linking for Lithium Metal Batteries

Lithium metal batteries have been considered as one of the most promising next‐generation power‐support devices due to their high specific energy and output voltage. However, the uncontrollable side‐reaction and lithium dendrite growth lead to the limited serving life and hinder the practical application of lithium metal batteries. Here, a tri‐monomer copolymerized gel polymer electrolyte (TGPE) with a cross‐linked reticulation structure was prepared by introducing a cross‐linker (polyurethane group) into the acrylate‐based in situ polymerization system. The soft segment of polyurethane in TGPE enables the far migration of lithium ions, and the ‐NH forms hydrogen bonds in the hard segment to build a stable cross‐linked framework. This system hinders anion migration and leads to a high Li+ migration number ( = 0.65), which achieves uniform lithium deposition and effectively inhibits lithium dendrite growth. As a result, the assembled symmetric cell shows robust reversibility over 5500 h at a current density of 1 mA cm−2. The LFP¦¦TGPE¦¦Li cell has a capacity retention of 89.8% after cycling 800 times at a rate of 1C. In summary, in situ polymerization of TGPE electrolytes is expected to be a candidate material for high‐energy‐density lithium metal batteries.

Dual-hard phase structures make mechanically tough and autonomous self-healable polyurethane elastomers

It is a key challenge to combine high mechanical strength and excellent autonomous self-healing properties in one elastomer to match the requirements of commercial applications. Chemical cross-linking or ordered crystalline domains can afford high mechanical strength but are often based on the cost of losing autonomous self-healing performance. To address this dilemma, a strategy involving dual hard-phase structures was developed to reinforce self-healing polyurethane elastomers, by introducing plant oil-derived aliphatic chains into the hard segments. The dangling fatty acids not only allow segmental motion of the hard domains but also suppress the crystallization within polyurethane soft segments. The tailored dual-hard phase structure and dynamic chain motion are responsible for outstanding mechanical properties (tensile strength to 21.8 MPa and toughness of 131.6 MJ m−3) and autonomous self-healing ability (∼100 % healing efficiency). Furthermore, a versatile mechanical robust flexible conductor is conveniently constructed with an auto-repair capability at ambient conditions. This work represents a molecular design paradigm of simultaneously integrating balanced mechanical strength, durability, and self-healing ability for high-performance elastomers that can find applications such as skin-inspired wearable devices.

Preparation of multicolor microcapsules and their application in smart color-switching textiles

Spiropyran and spiroxazine photochromics have attracted increasing attention in optical data storage, optical switches, and anti-counterfeiting for decades. To expand the applications of spiropyran and spiroxazine, the durability and multi-color changes of spiropyran and spiroxazine still need to be explored. In this article, based on the subtractive principle of dyes, multi-color spiropyran and spiroxazine microcapsules with uniform particle sizes were prepared by the interfacial polymerization method via using compounds (spiropyran and spiroxazine) of different colors as the core material, and polyurethane as the shell material. Among them, toluene diisocyanate and polyethylene glycol constitute the hard and soft segments of polyurethane, respectively. The color of spiropyran and spiroxazine microcapsules can effectively switch between color and colorless, showing excellent photo fatigue resistance. The average particle size of microcapsules is 2.951 µm, and the particle distribution index value is 0.314, which shows the particle size is small and uniform. The maximum thermal decomposition temperature is 426°C, demonstrating good thermal stability. The hydrophobic photochromic fabric was prepared by coating multi-color spiropyran and spiroxazine microcapsules on cotton knitted fabric and hydrophobic treatment. The hydrophobic photochromic fabric is hydrophobic and stain resistant, and exhibits multi-color dynamic switching and long-lasting use. After 50 cycles of washing, the water contact angle of the fabric remains about 109°, showing its good washing resistance and water repellency. In addition, spiropyran and spiroxazine microcapsules are also applied in template and screen printing to impart rich and dynamic color-changing effects to fabrics, fabricating photochromic fabrics. Photochromic fabrics have potential applications in civilian and military fields.

Polyurethane foam materials and their industrial applications

AbstractIn this review article, polyurethane (PU) foam materials are presented in various industrial applications. PU foams have started to replace metals and plastics in various engineering applications by combining the hardness and durability of metal with the flexibility of rubber. PU foams can be synthesized with various isocyanates, polyols, chain extenders and crosslinkers to serve many specific applications, such as bio‐based composite foam, flexible hard/soft PU foam, polymer foam etc. There are different factors to change of hard and soft segments of PUs. These changes form different products, such as urethane, biurets, allophanates and isocyamurates, etc. This review article mostly concentrates on the basic chemistry of the building blocks of PUs and recent developments in industrial applications of PU foams, such as insulator material, sound insulators, refrigerator and freezing insulators, furniture, shoes, automotive materials, coatings and adhesives and other applications. © 2022 Society of Industrial Chemistry.

Preparation and Properties of PED-TDI Polyurethane-Modified Silicone Coatings.

To explore the influence mechanisms of polyurethane soft segments on modified silicone coatings, a series of modified coatings was prepared by introducing different contents of hydroxypropyl-terminated polydimethylsiloxane (PDMS2200) into the soft segment of polyurethane. ATR-FTIR, NMR, CLSM, AFM, contact angle measurement, the tensile test, bacterial adhesion, and the benthic diatom adhesion test were used to investigate the structure, morphology, roughness, degree of microphase separation, surface energy, tensile properties, and antifouling properties of the modified coatings. The results show that PDMS2200 could aggravate the microphase separation of the modified coatings, increase the surface-free energy, and reduce its elastic modulus; when the microphase separation exceeded a certain degree, increasing PDMS2200 would decrease the tensile properties. The PED-TDI polyurethane-modified silicone coating prepared with the formula of PU-Si17 had the best tensile properties and antifouling properties among all modified coatings.

Environmentally friendly plant‐based waterborne polyurethane for hydrophobic and heat‐resistant films

AbstractWaterborne polyurethane (WPU) is an environmentally friendly material using water as dispersion medium. However, it is significantly restricted that most of the soft segments in WPUs come from oil. In this work, environmentally friendly and low‐cost castor oil is used as the soft segment of polyurethane, and KH550 modification could improve the thermal stability and flexibility of CWPU. The results show that the particle size of the modified CWPU nano‐emulsion gradually increased to 60.48 nm. Through FTIR and XPS analysis, KH550 is successfully introduced into the castor oil‐based waterborne polyurethane system. After the CWPU‐3% film is treated with NaCl, NaOH, HCl solution and high temperature, the groups in the system remain unchanged which shows CWPU‐3% film having good chemical resistance and high temperature resistance. When the addition amount of KH550 is 3%, the maximum contact angle of the CWPU film was 92.39° which reveals good hydrophobic property. The tensile strength of the films increased from 10.2 MPa to 12.8 MPa, and the elongation at break decreased from 841.3% to 658.9%. The thermal stability of the CWPU films modified by KH550 were also improved. The modified CWPU film has excellent hydrophobicity, chemical resistance and temperature resistance.

Polyurethane‐based polymer electrolyte for lithium ion batteries: a review

AbstractFor the past decade, lithium ion batteries have dominated the high‐performance and mobile markets. Despite their domination in many sectors, the development of contemporary commercial lithium ion batteries is hampered by safety concerns such as leakage, burning and even explosions caused by organic liquid electrolytes with low boiling points. Polymer electrolytes are a promising option to solve or mitigate these issues. Polymer electrolytes have the advantages of low flammability, good flexibility, excellent thermal stability and high safety. Among others, polyurethane (PU) has attracted attention as a promising polymer electrolyte candidate for the future. The soft and hard segments of the polymeric chain given by polyols and isocyanates, respectively, give PU its characteristic multiphase structure. The PU's soft segment can operate as a polymeric solvent to solvate the cations, while the hard segment can be functionalized to retain a wider range of electrochemical stability, allowing the construction of polymer electrolytes in electrochemical devices. Numerous researchers have concentrated on developing high‐performance PU‐based polymer lithium ion batteries. Nonetheless, low lithium ion conductivity characteristics remain the most significant obstacles to its commercialization. In order to tackle the issues and improve the overall performance, both physical and chemical modifications are widely investigated to form a PU‐based polymer electrolyte. In the light of this work, this review discusses PU as a polymer host and the approaches to increase its ionic conductivity, including polymer blending, copolymerization, crosslinking, filler addition, plasticization, salt dopant addition as well as the integration of PUs into polymeric ionic liquids. In this review, previous work regarding PU‐based polymer electrolytes from 1988 to 2021 is discussed and summarized. © 2022 Society of Industrial Chemistry.

Experimental and molecular dynamics simulation investigation on filler reinforcement for property enhancement of PU composites

The effect of filler modification on polyurethane (PU) properties was investigated by experimental and molecular dynamics simulation. Ultra-thin wearing course (PUTWC) was prepared using PU composite as a binder. The results indicated that, compared with composite with mineral powder, the tensile strength and elongation at break of PU composite (PUNC) containing CaCO3 increased by 32.7% and 15.8%, also exposed an appropriate viscosity. Stronger interaction energy and smaller free volume distribution existed in PUNC interface, which was obviously related to the PU soft segment. Additionally, prepared PUTWC using the single-layer paving method and PUNC of 1 kg. (m2)−1 showed high-skid resistance.

The Influence of Fly Ash on the Foaming Behavior and Flame Retardancy of Polyurethane Grouting Materials.

Polyurethane (PU) grouting material has been widely utilized to control water inrush in mining fields. However, the application has been limited by its high cost and poor flame retardancy. Here, we use the fly ash (FA), a waste from coal of the iron-making industry and power plants, as a partial replacement of conventional filler in PU grouting materials to reduce the production cost and the environmental pollution of FA. The surface-modified FA-filled PU (PU/FA) composites were prepared by room-temperature curing. The effects of FA contents (φ) on the structure, foaming behavior, thermal stability, mechanical properties, hydrophobic properties, and flammability of PU grouting materials were examined. Results showed that the higher the φ, the more porous the PU/FA composites are, resulting in a lower density and lower mechanical properties. The relationship between the compression modulus E and the density ρ of the PU/FA composites was E ∝ ρ1.3. In addition, the surface-modified FA improved the compatibility between the hard and soft segment of PU in the PU/FA composite, giving the composites enhanced thermal stability, high hydrophobicity, and flammability resistance.

Designing Polyurethane Solid Polymer Electrolytes for High-Temperature Lithium Metal Batteries

Potentially high-performance lithium metal cells in extreme high-temperature electrochemical environments is a challenging but attractive battery concept that requires stable and robust electrolytes to avoid severely limiting lifetimes of the cells. Here, the properties of tailored polyester and polycarbonate diols as the soft segments in polyurethanes are investigated and electrochemically evaluated for use as solid polymer electrolytes in lithium metal batteries. The polyurethanes demonstrate high mechanical stability against deformation at low flow rates and moreover at temperatures up above 100 °C, enabled by the hard urethane segments. The results further indicate transferrable ion transport properties of the pure polymers when incorporated as the soft segments in the polyurethanes, offering designing opportunities of the polyurethane by tuning the soft segment ratio and composition. Long-term electrochemical cycling of polyurethane-containing cells in lithium metal batteries at 80 °C proves the stability at elevated temperatures as well as the compatibility with lithium metal with stable cycling maintained after 2000 cycles.

Flexible crosslinking of polyurethane using grafted poly(dimethylsiloxane) with Epichlorohydrin and Bisphenol A end groups and its impact on the mechanical properties and low-temperature flexibility

Poly(dimethylsiloxane) (PDMS) was grafted onto polyurethane (PU), and Epichlorohydrin and Bisphenol A were attached to the free ends of PDMS groups and used to link the grafted PDMS to thereby introduce flexible crosslinks between the PU chains. The flexible crosslinks enhanced the crosslink density and solution viscosity of PU but did not change the melting and crystallization behaviors of the soft segments of PU. In particular, the flexible PDMS crosslinks increased the maximum tensile stress by up to 300% and the maximum tensile strain up to 180%. The shape recovery capability at 10°C and the shape retention capability at −25°C were maintained above 90% with the flexible crosslinking. Grafted PDMS moderately improved the low-temperature flexibility of PU due to its flexibility at low temperature. The flexible crosslinks of grafted PDMS successfully improved the tensile strength, shape recovery, and low-temperature flexibility of the PU.

Study on the preparation and performance comparison of side-chain hydroxyl-terminated polybutadiene derivatives with narrowly molecular weight distribution used for polyurethane

Hydroxy-terminated oligomers with narrow molecular weight distribution using as soft segment of polyurethane can significantly increase the modulus, tensile strength, and elongation at break of the polyurethane. Thus, design and synthesis of new hydroxy-terminated oligomers having narrow molecular weight distribution can improve the properties of polyurethane and further expand the use range of polyurethane. A set of side-chain hydroxyl-terminated polybutadiene (HTPB) derivatives were successfully synthesized by anionic polymerization and blue light photocatalytic thiol-ene reaction. Firstly, HTPB with narrow molecular weight distribution was synthesized via anionic polymerization using mono-lithium based initiator and followed by de-protection. Then, HTPB derivatives with different side-chains such as butyl, ethyl acetate, or myristyl, namely HTPBbut, HTPB eac and HTPBtet, were obtained by blue light photocatalytic thiol-ene reaction using Ru(bpy)3Cl2 as photoredox catalyst and HTPB as matrix polymer. Similar with HTPB, those HTPB derivatives also have narrow molecular weight distribution. Polyurethane elastomers (PUs) were synthesized with HTPB or HTPB derivatives as soft segment, toluene diisocynate (TDI) as hard segment, and 1, 4-butanediol as chain extender. Compared study the performances of polymers, the results showed that glass transition temperature (Tg) and viscosity of HTPB derivatives were increased when short-chain side groups were introduced. But instead, Tg and viscosity of HTPB derivatives was reduced following long-chain side groups being grafted. Through comparing research of properties for PUs, tensile strength is reduced and elongation at break is augmented, when side groups were introduced in HTPB backbone. Research on the contact angle tests of PUs indicated that the contact angle of PUs using HTPB, HTPBbut or HTPBeac as soft segment, is similar, and PUs using HTPBtet as soft segment has a larger contact angle about 137.2 °C.

Synthesis and characterization of the non-isocyanate poly(carbonate-urethane)s obtained via polycondensation route

This paper presents a non-solvent and non-isocyanate synthetic route towards the linear aliphatic and aliphatic–aromatic poly(carbonate-urethane)s. As the polyurethane hard segment precursors, urethane diols were applied. These monomers were obtained in two steps. Firstly, the bis(methyl carbamate)s of appropriate diamine were prepared using dimethyl carbonate. Next, the urethane diols were obtained via transurethanization of alkylene or arylene bis(methyl carbamate)s with an excess of 1,5-pentanediol. As a polyurethane soft segment precursor, an amorphous oligo(hexamethylene-co-pentamethylene carbonate) diol was used. The influence of the polyurethane structure on mechanical and thermal properties of the obtained non-isocyanate poly(carbonate-urethane)s was studied. It was found that the presence of pentamethylene carbonate units facilitates removal of the low-molar-mass polycondensation products from the system and decreases the time of reaction needed to gain high-molar-mass polymers. The poly(carbonate-urethane)s were characterized by 1H NMR, 13C NMR, and FT-IR spectroscopies, MALDI-ToF spectrometry, DSC, TGA, GPC, and mechanical testing. The aliphatic poly(carbonate-urethane)s exhibited tensile strengths >40 MPa, while the aliphatic–aromatic ones showed tensile strengths up to 50 MPa. Poly(carbonate-urethane) possessing the 80 wt% of hard segments based on 1,4-diaminobutane displayed comparable mechanical properties to commercially available isocyanate-based poly(carbonate-urethane)s e.g. Bionate® PCU 80A and Carbothane® PC3575A.

Nonconstant enthalpy of thermosetting solid-solid phase change materials controlled by light

Phase change materials (PCMs) based on the principle of latent heat thermal energy storage have been highly concerned by researchers and widely developed in various fields. However, for traditional PCMs, especially thermosetting solid-solid change materials (SSPCMs) which usually consist of crosslinking structure, the phase change enthalpy was fixed once the materials were constructed. To turn the constant enthalpy into adjustable one, we incorporated the light-sensitive methyl red (MR) groups into polyurethane-based SSPCMs. The MR-containing SSPCMs exhibit amplified enthalpy and increased melting temperature (Tm) after activated by UV light compared with the inactivated ones. UV treatment can promote the crystallization of the soft segment in polyurethane due to the light-induced isomerization of MR groups and visible light causes reverse effect of the activated samples that the enthalpy, Tm and crystallization get back to the original degree, which indicates the nonconstant enthalpy. A separation theory was proposed to explain the increased enthalpy and Tm caused by the cis configuration of MR groups.

Superhydrophobic and breathable SiO2/polyurethane porous membrane for durable water repellent application and oil-water separation

Electrospun polyurethane membrane with porous structure could be used for waterproof and breathable applications, however, due to polar groups in the soft segment of polyurethane, water would easily permeate the membrane. The water repellency of polyurethane membrane could be improved by grafting hydrophobic silica particles onto the membrane to construct rough surface and low energy epidermis. Polyurethane membrane was chemically modified with 4,4′-methylenebis(phenyl isocyanate) to obtain a reactive group, which was then coupled with (3-aminoproyl) triethoxysilane. Thereafter, the treated membrane was added to the preparation solution of hydrophobic silica particles. Herein, the particles constructed the rough surface of the membrane, and hexadecyltrimethoxysilane endowed the membrane with hydrophobic epidermis. The resultant membrane exhibited significant hydrophobicity with high water contact angles (WCA) and low sliding angles (SA) to different aqueous solutions. Under cyclic stretching, the modified membrane displayed durable water repellency (WCA varied between 152.7 and 154.9°, SA fluctuated between 5.0 and 6.5°) and high breathability (8.4 kg·m−2·d−1). Furthermore, the hydrophobic membrane was superoleophilic and had high permeation fluxes for various oils. It could effectively separate (98.5%) the dichloromethane-water mixture over 30 separation cycles.

Effects of biomass diatom frustule on structure and properties of polyurethane elastomer

ABSTRACTInorganic particles can dramatically promote the mechanical and thermal properties of polymer materials. However, the study on the effects of inorganic particles on the structure and properties of polymers, as well as the structure–property relationship, is still challengeable. Biomass diatom frustule can be applied to modify polyurethane (PU) elastomer due to its unique network structure, outstanding thermal stability, and wide availability. The PU/modified diatom (MD) frustule composites were prepared by bulk polymerization using PU as substrate and MD frustule as reinforcing phase. The effects of MD frustule on the structure and properties of PU elastomers and the structure–property relationship of composites were investigated. The results reveal that the composites have a certain degree of improvement in the mechanical properties and thermal stability as compared with pristine PU elastomer. It is ascribed to a relatively strong interaction between the MD frustule and PU, so the addition of MD frustule can change the interaction between hard segments and soft segments of PU as well as microphase separation structure. This research provides an experimental basis for the potential application of biomass diatom frustule. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48452.

Flexible and coatable insulating silica aerogel/polyurethane composites via soft segment control

We herein propose a facile approach to fabricate foldable and coatable silica aerogel polyurethane composites (APCs). For the flexibility control, the soft segment of polyurethane (PU) is manipulated. The change in soft segment length induces a difference in overall glass transition temperature of PU. When the silica aerogel content is increased, the PU with a shorter soft segment length shows brittle fracture behavior, while the PU with a longer soft segment length shows no breakage after bending. The thermal insulation properties of APCs were enhanced by 72% reduction in thermal conductivity upon 30 wt% aerogel loading and theoretically verified by a micromechanics-based thermal conductivity model considering the effects of interface and agglomeration. In addition, for the combustion behavior measurements, heat release rate and heat release capacity are substantially reduced for the APCs compared to neat PUs. Those enhanced thermal insulation properties may have a commercial impact on thermal insulation applications.

Change in surface properties of polydimethylsiloxane/polyurethane/carbon nanotubes elastomeric coatings

Addition of polydimethylsiloxane (PDMS) to polyurethane (PU) improves mechanical, surface and bulk properties. PDMS plays the role of a soft segment in PU because of its low surface tension and glass transition temperature. This polymer blend shows highly segregated morphology allowing production of thermoplastic elastomers with properties in between a crosslinked elastomer and thermoplastic depending on composition. In this study, PDMS/PU blends were synthesized in situ and the effects of PDMS composition, the type and content of catalyst, solvent and isocyanates molecular weight as well as carbon nanotubes (CNTs) incorporation on the surface properties of the resulting elastomeric coatings were discussed. Different measurements including contact angle, SEM, AFM, FTIR and elemental composition analyses were used for interpretations. The competition between OH terminating groups of PDMS and polycaprolactone was the key controlling over the hydrophilicity of the resulting PDMS/PU coatings. Such effect was studied by monitoring the changes in surface properties of the cured coatings. The results revealed that by adjusting the above-mentioned parameters, surface chemistry of the cured films were changed. PDMS introducing to PU resulted in a rise in water contact angle from 93° to 113°, which indicated a considerable surface hydrophobicity. Moreover, solvent selection exhibited a crucial role on surface roughness. CNTs incorporation resulted in surface hydrophobicity enhancement, as featured by a rise in water contact angle from 100 to 135°, suggesting the possibility of surface tailoring by optimizing PDMS and CNTs concentrations.