Superfoldable Bamboo by Microwrinkling Engineering for 3D Origami Structures.

In this study, a waterborne polyurethane (WPU) is synthesized by using polytetramethylene ether glycol (PTMEG) to form the soft segment, 1,4-butanediol (BDO) as the chain extender, n-methyldiethanolamine (MDEA) as a hydrophilic chain extender, and isophorone diisocyanate (IPDI) to form the hard segment. Furthermore, the modified cationic WPU emulsion and its films are created through a reaction between the WPU and a linear polyether-blocked amino silicone (LEPS), which is an organosilicon compound that imparts flexibility. The properties of the structure and formed WPU films are then characterized by using Fourier transform infrared spectrometry, a thermogravimetric analysis, atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, as well as by measuring the water contact angle, testing the water absorption, etc. It is found that, with an increase in the LEPS content in the WPU, the particle size of the modified WPU emulsion is increased, the WPU films are more flexible, and the resistance of the modified WPU films to heat and water are increased, while the crystallinity is reduced. The polysiloxane chain segment, which is added to the LEPS-modified WPU emulsion, is significantly enriched on the surface of the modified WPU films, while there are no adverse effects of the LEPS-modified WPU emulsion on the adhesive force between the WPU and substrate. When the LEPS content of the WPU is 14.0 wt%, the modified WPU emulsion and film provide the best performance.

Waterborne polyurethane (WPU) prepolymer was synthesised by the reaction of poly(butylene itaconate) ester (PBI, Mn = 1109 g/mol), 1,6-hexanediol, dimethylol propionic acid (DMPA), 2,4-toluene diisocynate (TDI), hydroxyethyl acrylate (HEA), and absolute ethanol as blocking agent, triethylamine as neutralizer. Cross-linked WPU was synthesized by trimethylolpropane (TMP) as crosslinker. The influences of PBI, DMPA, and TMP content on WPU emulsions and films were investigated. The structure of WPU was determined by Fourier transform infrared (FTIR) spectra, thermal properties and glass transition temperature of WPU films were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively, and morphology of the emulsion particles was observed by transmission electron microscopy (TEM). Through TGA, the heat resistance of the cross-linked WPU film was better than WPU film. By DSC analysis, glass transition temperature of cross-linked WPU film (21 °C) was higher than WPU film (10 °C).

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.

The self-cleaning and antibacterial properties of waterborne polyurethane (WPU) films are realized by constructing a micronano structure on its surface via the controlled aggregation of graphitic carbon nitride (g-C3N4) nanosheets. Based on the hydrogen bonding between the C═O groups in WPU and NH- groups in g-C3N4, the g-C3N4 nanosheets can be well dispersed in the WPU films. Further increasing the concentration of the g-C3N4 nanosheets in the WPU dispersion during the coating causes the enrichment of the g-C3N4 nanosheets, triggering a minor aggregation and forming a concave-like structure with nm to μm scale on the surface. Due to the photocatalytic capability of the g-C3N4 nanosheets, free radicals are formed when exposed to visible light illumination, which, together with the large specific surface area of the micronano structure, decompose common stains on the WPU surface. More than 95% of daily lives stains, such as soy sauce, can be removed from the hybrid WPU films with micronano structure on the surface after exposure to visible light for only 1 h. Besides hydrophilic stains, the hybrid WPU films with micronano structure on the surface are also highly resistant against lipophilic stains and exhibit antibacterial properties. 99.8% of S. aureus bacteria and 100% of E. coli bacteria can be efficiently killed on the hybrid WPU film surface after exposure to visible light for 2 h. Based on these unique properties, the hybrid WPU films with micronano structure on the surface are highly suitable for the interiors of cars, indoor furniture, or faux-leather garnets.

Development of clean performance-tunable waterborne polyurethane using acetyl tributyl citrate for transferable holographic films

While increasing the number of these extenders improves the stability of the waterborne polyurethane (WPU) emulsion, it also decreases the thermal stability of the WPU film, creating a challenge that needs to be addressed. In this study, a class of scalable anionic chain extenders featuring amide functional groups is thoughtfully designed for industrial applications. Diethanolamine reacts with various anhydrides, serving as an internal emulsifier in WPU production. The prepared WPU features a narrow particle size distribution, averaging between 100 and 250 nm, resulting in excellent stability even after centrifugation at 3000 rpm. Introducing an amide‐functional emulsifier into the WPU structure improved thermal stability, with T5 wt% ranging from 276.5 to 293.1°C. Mechanical test results indicate that the WPU1 film demonstrates impressive mechanical performance, featuring a tensile strength of 13.55 MPa and an elongation at a break of 980%. The resulting WPU films show strong adhesion to different surfaces, with lap shear strength for carbon steel varying from 4.67 to 5.14 MPa. This presents an innovative approach to balancing the emulsifying capability with the water resistance feature of WPU. This study offers a promising alternative to DMPA, emphasizing its potential for future use in WPU industrial production and applications.Highlights Synthesis of amide‐functional anionic chain extenders. Enhanced thermal stability and emulsion performance. WPU with optimized colloidal characteristics. WPU films with enhanced thermal stability. A viable alternative to 2,2‐dimethylpropionic acid‐based systems.

Antiglare waterborne polyurethane/modified silica nanocomposite with balanced comprehensive properties

A self-colored waterborne polyurethane film with natural curcumin as a chain extender and excellent UV-Absorbing properties

The recycling and reuse of construction waste have not only effectively protected natural resources but also promoted the sustainable development of the environment. Therefore, in this article, waterborne polyurethane (WPU) as a promising new polymer reinforcement material was proposed to reinforce the road demolition waste (RDW), and the mechanical performance of WPU-reinforced RDW (named PURD) was investigated using triaxial unconsolidated and undrained shear (UU) and Scanning Electron Microscope (SEM) tests. The results showed that under the same curing time and confining pressure, the shear strength of PURD increased with the increase in WPU content. When the WPU content was 6%, the WPU presented the best reinforcement effect on RA. The failure strain of PURD increased with the increase in confining pressure, but increased first and then reduced with the increase in WPU content. The specimens with 5% WPU content showed the best ductility. At the curing time of 7 and 28 days, the internal friction angle and cohesion of PURD increased with the increase in WPU content, and they reached a maximum when the WPU content was 6%. The internal friction angle barely budged, but the cohesion increased obviously. The enhancement effect of WPU was attributed to the spatial reticular membrane structure produced by wrapping and bonding particles with the WPU film. Microscopic analysis showed that with the increase in WPU content, the internal pore and crack size of PURD gradually decreased. As the WPU content increased, the WPU film became increasingly thicker, which increased the adhesion between WPU and RA particles and made the structure of PURD become increasingly denser.

Waterborne polyurethanes with novel chain extenders bearing multiple sulfonate groups

Effects of sulfonated polyol on the properties of the resultant aqueous polyurethane dispersions

Although tremendous efforts have been dedicated to developing environmentally friendly bio‐based waterborne polyurethane (WPU) dispersions from vegetable oil, the fabrication of WPU dispersions solely derived from vegetable oil‐based polyol with excellent comprehensive properties is still challenging. In the present work, novel bio‐based WPU dispersions derived from castor oil and soy polyol is successfully modified by phosphorus‐nitrogen chain extender [bis(2‐hydroxyethyl)amino]‐methyl‐phosphonic acid dimethyl ester (BH). The structure and properties of the dispersions and films are characterized systematically by Fourier transform infrared spectroscopy, thermogravimetric analysis , mechanical test, and limiting oxygen index (LOI), etc. The results indicate that bio‐based WPU films display moderate mechanical performance by adjusting BH content, and the WPU film containing 100% BH with 47.8% biobased content has a tensile strength of 8 MPa and the highest Young's modulus of 62.3 MPa. The incorporation of BH can increase the production of char residue. The flame retardancy of WPU films increase gradually with the BH molar content, and the LOI value of the WPU100 with 1.53 wt% phosphorus content can reach as high as 28.1%. This work may provide a new approach to develop high biobased content, eco‐friendly, flame retardant WPU for application in the surface coating industry.

Synthesis and properties of self-crosslinking waterborne polyurethane with side chain for water-based varnish

A series of ambient-temperature self-crosslinked waterborne polyurethanes denoted as WBPUs were successfully synthesized by incorporating a novel diol chain extender bearing two ketone groups, 2,2-bis(4-(2-hydroxypropoxy levulinate)phenyl)-propane (BHLPP), which was prepared using 2,2-bis(4-(2,3-epoxypropoxy)phenyl)-propane and levulinic acid, with 4,4-methylenedicyclohexyl diisocyanate, poly-neopentylene adipate glycol, and dimethylolpropionic acid. After post-adding adipic dihydrazide (ADH), self-crosslinking was achieved by the reaction between the ketone (–CO–) of BHLPP and the hydrazine (–NHNH2) of ADH during film formation. For comparison, noncrosslinked waterborne polyurethane (WPU) without BHLPP and ADH was prepared. The structure of BHLPP was characterized by IR and NMR. The properties of the WPU and WBPU dispersions were investigated by measuring the stability, particle size, and morphology. The effects of the ratio of n(–NHNH2)/n(–CO–) and the content of BHLPP were studied in terms of hardness, water resistance, solvent resistance, and thermal properties of WPU and WBPU films. The WBPU dispersions exhibited excellent stability, bimodal distribution, and regular spheroid morphology. The optimal ratio of n(–NHNH2)/n(–CO–) for ketone–hydrazine self-crosslinking was 0.75:1. Importantly, the WBPU films showed superior hardness, water resistance, solvent resistance, and thermal properties to WPU film.

The stability of polyurethane (PU) is of critical importance for applications such as in coating industry or as biomaterials. To eliminate the environmental concerns on the synthesis of PU which involves the use of organic solvents, the aqueous-based or waterborne PU (WBPU) has been developed. WBPU, however, may be unstable in an electrolyte-rich environment. In this study, the authors reported the stability of biodegradable WBPU in the buffered saline solutions evaluated by atomic force microscopy (AFM). Various biodegradable WBPU films were prepared by spin coating on coverslip glass, with a thickness of ∼300 nm. The surface AFM images of poly(ε-caprolactone) (PCL) diol-based WBPU revealed nanoglobular structure. The same feature was observed when 20% molar of the PCL diol soft segment was replaced by polyethylene butylenes adipate diol. After hydration in buffered saline solutions for 24 h, the surface domains generally increased in sizes and became irregular in shape. On the other hand, when the soft segment was replaced by 20% poly(l-lactide) diol, a meshlike surface structure was demonstrated by AFM. When the latter WBPU was hydrated, the surface domains appeared to be disconnected. Results from the attenuated total reflectance infrared spectroscopy and x-ray photoelectron spectroscopy indicated that the surface chemistry of WBPU films was altered after hydration. These changes were probably associated with the neutralization of carboxylate by ions in the saline solutions, resulting in the rearrangements of soft and hard segments and causing instability of the WBPU.