Crosslinked Waterborne Polyurethane Research Articles

Improving Water Resistance and Mechanical Properties of Crosslinked Waterborne Polyurethane Using Glycidyl Carbamate

Waterborne polyurethane (WPU) often suffers from poor water resistance and mechanical properties due to hydrophilic emulsifiers. To address these issues, this study introduces glycidyl carbamate (GC) as a crosslinker to improve WPU performance. Three types of GC were synthesized using aliphatic, cycloaliphatic, and aromatic isocyanates, respectively. The crosslinked network was established through a reaction between the epoxide group of GC and the carboxylic acid and amine groups of WPU. Among these, the WPU film utilizing aromatic isocyanate-based GC exhibited the highest crosslink density, modulus, hardness, and water resistance, due to the rigidity of the aromatic molecular structure. However, the film displayed excessive brittleness, resulting in reduced tensile strength, along with yellowing typically associated with aromatic compounds. The WPU crosslinked with cycloaliphatic GC demonstrated the next best mechanical properties and water resistance, with a 2.7-fold increase in tensile strength, a 1.5-fold increase in hardness, and a 66% reduction in the water swelling ratio compared to neat WPU. This study presents a novel and effective strategy to enhance the water resistance and mechanical properties of WPU films, making them suitable for advanced coating applications.

Liquid metal-enhanced self-healing dual-hard-phase cross-linked waterborne polyurethane for flexible sensors

Flexible strain sensors are increasingly recognized in areas such as health monitoring, mechanical operations, and infrastructure due to their ability to detect minute mechanical signals and conform to irregular surfaces. As sophisticated smart materials, these sensors demand exceptional sensitivity, durability, and robust self-healing capabilities. In this paper, methyl 2,6-dihydroxybenzoate and 2,2′-diaminodiphenyl disulfide were introduced into waterborne polyurethane to form a dual-hard-phase crosslinked matrix, which is characterized by dynamic covalent disulfide bonds and reversible hydrogen bonds. The resultant WPU-D5B2 material exhibits outstanding tensile strength (34.80 MPa) and toughness (190.5 MJ m−3), with a 97.4 % degree of self-healing at 50 ℃ for 2 h. Remarkably, this material maintains 83 % of its original mechanical performance even following recycling processe. This method significantly enhances the performance of flexible strain sensors in complex environments. Consequently, a composite conductor was prepared by blending self-healing waterborne polyurethane (WPU), graphene oxide (GO), and liquid metal (LM). Graphene oxide formed an efficient electronic conductive network, while liquid metal served as a conductive medium, filling microgaps to maintain the integrity of the electron pathway. This innovative dual-conductive mechanism ensures reliable performance in applications such as advanced flexible sensors.

Synthesis and Application of Non-ionic Inner Cross-Linked Water-Borne Polyurethane

Synthesis and Application of Non-ionic Inner Cross-Linked Water-Borne Polyurethane

Dynamically Cross-Linked Waterborne Polyurethanes: Transalkylation Exchange of C–N Bonds Toward High Performance and Reprocessable Thermosets

Thermosetting waterborne polyurethanes (WPUs) have received wide attention because of their excellent chemical resistance, mechanical properties, and low water absorption. However, their permanent network structure hinders their reprocessing applications, making it vital to prepare reprocessable thermosetting WPUs to minimize plastic pollution. Herein, for the first time, the cross-linked WPUs with excellent reprocessability were designed and synthesized by introducing covalent adaptable networks (CANs) in the form of quaternary ammonium alkyl chains. Our methodology combined CO2-triggered WPUs (CO2-triggered WPUs) with 1,6-diiodohexane. After the CO2 evaporated during film formation, the CO2-triggered WPUs left tertiary amine groups as reaction precursors, which could cross-link into a WPU CAN with 1,6-diiodohexane. All cross-linked WPUs possessed classic vitrimer performance including stress relaxation and malleability, as confirmed by stress-relaxation and hot-press tests. The results showed that cross-linked WPUs had excellent reprocessability and high mechanical properties, and the recovery ratios of the mechanical properties for the recycled samples were over 80% and the tensile strength was more than 17 MPa. More importantly, the cross-linked WPUs’ antibacterial rates of Staphylococcus aureus and Escherichia coli were 94.3 and 89.5%, respectively. This research offers a new method to synthesize high-performance WPUs via facile quaternary ammonium reversible cross-linking and demonstrates that WPU CANs have great potential as sustainable materials.

Synthesis and Characterization of Cross-Linked Waterborne Polyurethane Dispersion

Due to high-performance property, many industries interested recently for production of waterborne polyurethane dispersions (WPUDs). In the present study first WPUDs were prepared by polyaddition reaction of hydroxy terminated unsaturated polyesters (HTUPEs) and isophorone diisocyanate (IDPI) in presence of dibutyl dilaurate (DBTL) as a catalyst. Cross-linking bridge were created between WPUD chains to enhance the thermal and mechanical properties by addition of ethylene diacrylate, hydroxy ethyl acrylate as end capped and methyl ethyl ketone peroxide cobalt naphthenate as a catalyst. All the resultant cross-linked WPUDs (designated as CWPUDs) were studied by thermal and mechanical properties.

An unparalleled H-bonding and ion-bonding crosslinked waterborne polyurethane with super toughness and unprecedented fracture energy.

Self-healing polyurethane elastomers have been extensively studied; however, developing an eco-friendly self-healable waterborne polyurethane (WPU) with exceptional mechanical properties remains a great challenge. Herein, we report healable, and highly tough WPU elastomers with unprecedented crack tolerance by introducing the concerted interactions of strong multiple H-bonds and ionic bonds in the network. The WPU elastomer demonstrated that the microphase separation structure contributes to an ultrahigh tensile strength (≈58 MPa), super toughness (≈456 MJ m-3), and unprecedented record fracture energy (≈320 kJ m-2). Due to the dynamic reconstruction of reversible H-bonds and ionic bonds, the WPU elastomer demonstrates a robust self-healability at 50 °C, allowing complete recovery of mechanical properties. Importantly, the thermoplasticity and reprocessability of WPUs enable direct 3D printing of different objects and electrospinning of tubes, showing great potential for expanding their application scope in soft robots and artificial stents.

Elastic, Conductive Coating Layer for Self‐Standing Sulfur Cathode Achieving Long Lifespan Li–S Batteries

AbstractThe shuttle of polysulfide and severe volume change of sulfur cathodes, are the bottlenecks in the practical application of lithium–sulfur batteries, and need to be solved through further exploration of simple and scalable strategies. Herein, an elastic and conductive coating layer is designed and synthesized, by combining water soluble conducting polymer modified carbon nanotubes (PASANTs) with crosslinked waterborne polyurethane (cWPU). It shows high electronic conductivity and excellent resilience. As a result, a lithium–sulfur battery with cWPU/PASANTs coated cathode is able to achieve an outstanding cycle stability with a capacity of 70.8% after 500 cycles at 0.5C and an excellent rate performance (specific capacity of 1130 mAh g−1 at 0.1C and maintain 68.2% at 2C). This work embodies a systematic design concept, which shows the application prospects of large‐scale production, and is expected to be further applied to other easily pulverized high‐specific‐capacity materials such as silicon and tin.

Fabrication of Crosslinked Waterborne Polyurethane with Low-Gloss and Micro Roughness for Matting Application

A groups of cross-linked waterborne polyurethane (CPU) coatings were successfully synthesized and characterized. The CPU emulsions could achieve low gloss effect without addition of any matting agents by the formation of self-roughed surface. Rheological research shows that the emulsions comply with the Herschel-bulkley pseudoplastic fluid model with a yield stress, and exhibited the same behaviors as the gel. SEM and AFM illustrated the rough surface morphology of the films, and a series of roughness parameters were calculated. In general, the resulted CPU emulsions can provide moderate roughness levels, good hardness and adhesive strengths after film-forming, which were very appropriate for use as matt coating.

The reinforcing effect of crosslinkable waterborne polyurethane/polysiloxane composite emulsion by aqueous sol–gel method

A highly branched polysiloxane (S2) was prepared by an aqueous sol–gel process and used as an underlying crosslinker to modify silanized waterborne polyurethane (WPUS), and a novel crosslinked waterborne polyurethane (WPU)/polysiloxane composite with low VOC features was obtained. The good dispersibility of polysiloxane (S2) was proved by both TEM and DLS analyses, implying that the polysiloxane had an excellent intermiscibility with the WPU. The larger silsesquioxane network in the composite was proved by XPS, which was generated from the condensation of the Si–OH groups of polysiloxane and WPUS. On the basis of tensile results, the content of polysiloxane had a significant impact on the mechanical properties. The reinforcing and toughening synergy effect was found in the composite with a low concentration of S2. According to micrographs of the fracture surface, the dominating toughening mechanism was dependent on microcracks, while the high concentration of polysiloxane turned into silica particles in the WPU matrix, resulting in force concentration and degradation of the mechanical properties. However, the Young’s modulus increased with the increasing content of S2. Additionally, the incorporation of the crosslinked silsesquioxane structure also improved the hydrophobic properties and thermal stability of the composite.

Preparation and properties of cross-linked waterborne polyurethane based on solvent-free route

Intrinsic cross-linked waterborne polyurethane (CWPU) was successfully synthesized for the first time through solvent-free condensation polymerization, in which green castor oil (CO) was used as the cross-linking agent. The totally solvent-free process was realized by using hydrophilic polypropylene glycol as hydrophilic segment, which was synthesized by the esterification of polypropylene glycol with pyromellitic dianhydride. The effect of CO content in the soft segment of the prepared CWPU on emulsion properties was investigated by laser particle size distribution test, and the prepared CWPU emulsion showed uniform size distribution (0.117–0.275 µm) and milky white appearance after storing at ambient temperature for 6 month. Additionally, the effect of CO content in CWPU films on static mechanical properties, dynamic mechanical properties, hydrophilicity and thermal stability was also studied by tensile test, dynamic mechanical analysis, water absorption and contact angle measurement as well as thermogravimetric analysis. The prepared cross-linked CWPU films have good stability and outstanding mechanical strength (11.94–34.51 MPa), making them adequate supplement for the conventional waterborne polyurethanes.

Structure and surface properties of a novel bulk-matte waterborne polyurethane coating composite

This paper reports on a novel self-matte or bulk-matte waterborne polyurethane coating composite with inherently extremely low gloss. The coating composite was comprised of a siloxane-containing waterborne polyurethane (SPU) resin and a crosslinked waterborne polyurethane (CPU) resin. The CPU resin was mainly responsible for fabricating the micro-rough surface of the film, which was achieved by a crosslinking reaction between the waterborne polyurethane and bisphenol A-type epoxy E-44 resin. The SPU resin was used to improve the comprehensive properties of the film, which was ascribed to the addition of silane coupling agent KH792. Compared with traditional matte coatings, this coating composite made it possible to avoid high loadings of matting agent and to arrive at highly flexible low-gloss finishes. Gloss levels of as low as a few tenths of a percent, even at high incidence angles, have been achieved with zero loading of extraneous dulling agent. The chemical structures of the SPU and CPU resins were characterized by FTIR-ATR and NMR spectra. The micro-rough topographies and surface rough degrees of the SPU, CPU and their 50%/50% composite films were measured by SEM and MSP, respectively. The particle sizes and particle morphologies of the SPU and CPU resins were imaged by TEM. Finally, the comprehensive properties of the SPU, CPU and their 50%/50% composite resins were evaluated, including the water contact angle, film transparency, tensile strength and storage stability.

Antibacterial and Biocompatible Cross-Linked Waterborne Polyurethanes Containing Gemini Quaternary Ammonium Salts.

A cross-linked waterborne polyurethane (CPTMGPU) with long-term stability was developed from poly(ethylene glycol) (PEG), polyoxytetramethylene glycol (PTMG), isophorone diisocyanate (IPDI), l-lysine, and its derivative diamine consisting of gemini quaternary ammonium salt (GQAS), using ethylene glycol diglycidyl ether (EGDE) as a cross-linker. Weight loss test, X-ray photoelectron spectroscopy (XPS) measurements, and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) were performed to prove the surface structure and stability of these CPTMGPU films. Furthermore, the GQAS-bearing CPTMGPUs show repeatable contact-active antibacterial efficacy against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) bacteria and do not show any inhibition effect against fibroblasts in vitro. After subcutaneous implantation in rats, the CPTMGPU films manifest good biocompatibility in vivo, despite the presence of a typical foreign body reaction toward surrounding tissues and mild systematic inflammation reaction that could be eliminated after a short implantation period, as demonstrated by histology and immunohistochemistry combined with interleukin (IL)-1β, IL-4, IL-6, IL-10, and TNF-α analysis though enzyme-linked immunosorbent assay (ELISA) and real-time quantitative polymerase chain reaction (qRT-PCR). Therefore, these cross-linked waterborne polyurethanes hold great promise for antibacterial applications in vivo.

Crosslinked waterborne polyurethane with high waterproof performance

Fluorinated acrylate and siloxane waterborne polyurethanes with crosslinked structure exhibit low water absorption, high water contact angles, and high mechanical/thermal properties.

Cellulose crosslinked pH-responsive polyurethanes for drug delivery: α-hydroxy acids as drug release modifiers

Cellulose crosslinked waterborne polyurethanes (PUs) based on poly ɛ-caprolactone with lactic acid/glycolic acid/dimethylol-propionic acid as a drug release modifiers cum chain extenders were prepared. PUs were loaded with felodipine and drug release was monitored at different pH values. The structure of the polymers was characterized by FTIR, DSC & TGA and SEM. The encapsulation of dug inside PU matrix and the morphology of polymer after drug release were studied by using SEM. All the PUs were observed to degrade under highly basic conditions. The PUs act as pH sensitive drug carriers with an added advantage of modulated release rate as a function of acid chain extenders. The rate of release of the drug was significantly faster at pH 7.4 as compared to gastric pH 1.2, with same incubation time. The PUs reported in the present study may be suitable for medical applications like vaginal drug delivery and colon specific drug delivery.

Preparation and Application of Blocked & Crosslinked Waterborne Polyurethane Microemulsion as Paper Strengthening Agent

By means of self-emulsifying, blocked & crosslinked cationic polyurethane (CBPU) microemulsion was prepared with isophorone diisocyanate (IPDI), polycaprolactone glycol, bisphenol A, methyldiethanolamine (MDEA) as cationic hydrophilic chain-extending agent, ̴̵̹̹̱̼̽͊̿˰̱̓˰̷̲̼̳̻̹̿̾˰̷̵̱̾̈́˰̴̱̾˰̞˽̫˸́˼́˽̴̵̸̹͉̼̽̈́˽̂˽̵̱̳͉̼̈́˹̵̸͉̼̭̈́˽ڂ˽̴̸̴̵̸̹͉͈͉͉̼̱̹͂̿̈́̽̾̿˰̴̵̱̱̹̀͂̿̀̾̽˸̠̔̔˹˰̱̓˰̷̳̼̹̻̹͂̿̓̓̾̾˰̷̵̱̾̈́˾˰̶̶̵̳̈́̓̕˰̶̿˰̸̵̈́˰̠̥̓̒˰̵̴̲̼̳̻̿˰̱̹͂̈́̿˰̿̾˰̸̵̈́˰̸͉̹̳̱̼̀̓˰̵̵̹̀͂̿̀͂̈́̓˰̶̿˰̸̵̈́˰̵̵̴̱̈́͂̈́˰̵̱̀̀͂˰̵̵͇͂˰̴̵̴̹̓̈́ͅ˾˰̸̵̤˰̵̵̵͈̹̱̼̀͂̽̾̈́˰̵̼͂̓̈́̓ͅ˰̸͇̓̿˰̓̈́͂uctures of tertiary amine group, imidazole ring and urethane group are found in CBPU molecular structure. The morphology of the particle is uniform spheric structure and its size is related to the content of tertiary amine groups of CBPU. The paper strength, especially the wet strength can be obviously increased with the increasing of the blocked ratio of CBPU. The optimum blocked ratio of CBPU is 10%.

이소포론 디이소시아네이트와 폴리(테트라메틸렌 글리콜)/폴리디메틸실록산 디올 혼합 폴리올을 사용한 수분산성 폴리우레탄의 합성과 특성 분석

디올 성분으로 폴리(테트라메틸렌 글리콜)(PTMG)과 함께 말단에 히드록시에틸기를 갖는 폴리디메틸실록산(PDMS-OH)을 혼합하여 사용하면서, 이소시아네이트 화합물로 이소포론 디이소시아네이트를, 수분산성을 부여하기 위해 디메틸올 프로피온산을, 가교제로 트리메틸올프로판을, 사슬연장제로 부탄디올을 사용하여 실록산 성분을 포함하는 선형 및 가교형 수분산성 폴리우레탄(WPU-Si)을 합성하였다. PTMG와 PDMS-OH 혼합 비율을 달리하여 합성한 선형 및 가교형 WPU-Si 에멀젼의 안정성을 분석하였고, 이들을 필름으로 제조하여 표면 특성과 <TEX>$T_g$</TEX>, 인장 강신도 변화를 분석하였다. PDMS 함량이 많아질수록 시료의 소수성이 증가하고 <TEX>$T_g$</TEX>가 높아졌으며, 파단 인장강도는 증가하고 파단 신장률은 감소하였다. Linear and cross-linked waterborne polyurethanes (WPUs) based on isophorone diisocyanate and mixed diols of poly(tetramethylene glycol)/hydroxyethyl-terminated polydimethylsiloxane (PDMS-OH) were synthesized with dimethylol propionic acid as an anionic component, trimethylolpropane as a cross-linking agent, and butanediol as a chain extender and characterized. The hydrophobicity, <TEX>$T_g$</TEX>, stress-strain behaviors of the linear or cross-linked siloxane-containing WPU (WPU-Si) films with different PDMS content were analyzed by using water contact shape analyzer, energy dispersive spectrometer, dynamic mechanical analyzer, and universal testing machine. The results reveal that as the PDMS content increased, the hydrophobicity of WPU-Si films increased, <TEX>$T_g$</TEX> moved to higher temperature, the breaking stress increased, and the breaking strain decreased.

Investigations on oxidised starch based waterborne polyurethane nanocomposites

An attempt was made to prepare a series of new oxidised starch cross-linked waterborne polyurethanes (PUs) by reaction between PU prepolymer and oxidised corn starch. All of the samples were characterised by conventional methods, and their physical, mechanical and hydrophobic properties were studied. The results showed that the presence of oxidised starch gave rise to significant differences in the composition and morphology of PUs and affected the mechanical properties of the final products with regard to the pure polymer. Tensile strength of the modified PU film containing 10 wt-% oxidised starch was up to 14·9 MPa, and its water absorption was as low as 4·9%, resulting from the dual effects of the changed morphology and intermolecular cohesion in this system.

Effects of different biomaterials: Comparing the bladder smooth muscle cells on waterborne polyurethane or poly-lactic-co-glycolic acid membranes

Tissue engineering materials have often been used to repair bladder damage caused by conditions, such as infection, resection, inflammation, and trauma. However, the concept of generating a functional urinary bladder using autologous cells obtained from a biopsy specimen combined with a biomaterial scaffold remains a challenge. Previously, we presented a new method for synthesizing a biocompatible, mechanically sound, nontoxic, and cross-linked waterborne polyurethane (WBPU) as a potential material for bladder regeneration. Here, we further evaluated the response of bladder smooth muscle cells (BSMCs) seeded on WBPU membranes in comparison with the gold standard biomaterial, poly-lactic-co-glycolic acid. Specifically, we observed the BSMC attachment, proliferation, and α-actin distribution at 1 day, 3 days, and 5 days after membrane seeding. We found that significantly more cells attached and proliferated on the WBPU membranes after 3 days and 5 days of culture, and the cells exhibited greater organization and a wider distribution of α-actin compared with BSMCs cultured on poly-lactic-co-glycolic acid membranes. These preliminary data offer promise for the use of WBPU biomaterials in bladder tissue engineering.

Preparation and Characterization of Waterborne Polyurethane Crosslinked by Urea Bridges

Waterborne polyurethanes are an interesting alternative to current solvent based polyurethanes used in many industries because of their high performance. In this study, waterborne polyurethane dispersion were prepared by polyaddition reaction using Polyethylene glycol (PEG Mw 2000) and isophorone diisocyanate (IPDI) in presence of dibutyltin dilaurate (DBTL) as catalyst. The urea bridges were created between waterborne polyurethane chains to improve rheological, thermal and mechanical properties by the incorporation of hexamethylene diisocyanate (HDI) as crosslinking agent. Several properties of crosslinked waterborne polyurethane were measured by particle size distribution, viscosity measurement, IR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and strength testing. This method improves the properties of waterborne polyurethane (WPD) in increasing the crosslinking density by forming strong network and hydrogen bonds between polyurethane chains.

Synthesis and properties of crosslinked waterborne polyurethane

Waterborne polyurethane prepolymer was prepared by the reaction of isophorone isocyanate(IPDI), polyether polyol(PTMG), dimethylol propionic acid(DMPA) and trimethylol propane(TMP), which was modified by silicane coupling agent(APTES) to form highly crosslinked polyurethane emulsion. The films of the waterborne polyurethane were prepared. The structure of the polyurethane was characterized by Fourier transform infared spectrometer (FTIR), X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The mechanical properties and water absorption of the films were measured. FT-IR indicates that APTES reacted with -NCO of polyurethane. XRD and DSC shows that crystallinity of polyurethane decreased with the increase of w(APTES). Tensile strength increases as the NCO/OH ratio increases. Tensile strength of films increases with increase of w(DMPA) and elongation at break decreases. The water absorption decreases with the increase of w(TMP) when w(TMP) is lower than 1.8%. As the mass fraction of APTES increases from 0% to 10%, the tensile strength of PU films increased from 18 MPa to 28 MPa, water absorption and ethanol absorption decreased.