Polyurethane Prepolymer Research Articles

Pretreated cellulose fiber for enhancing fire resistance of flexible polyurethane foam composites with reinforced properties

To promote environmentally sustainable behavior, it is meaningful to develop a simple preparation method of polyurethane foam (PUF) with excellent performance and degradability. Herein, PUF composites were economically and conveniently synthesized by mixed foaming of polyurethane prepolymer and cellulose nanocrystals (CNCs). After the hydrolysis of dissolving pulp fibers with formic acid (FA), hydrophobic ester groups were introduced in CNCs, thereby increasing the surface hydrophobicity of PUF composites. CNCs acted as a reinforcement agent capable can replace 10% up to 60% prepolymer for foaming, the modified PUF exhibiting gradient morphology structure and enhanced specific mechanical and thermal properties. When the CNCs replacement ratio was 50%, the maximum compressive stress was 1103.19 kPa, which is 21-fold that of the original foam. Remarkably, the addition of CNCs enhanced thermal insulation performance of the prepared foam, which of thermal conductivity decreased from 0.0780 W/mK to 0.0549 W/mK. The upgraded polyurethane foam composites promise to open exciting new windows on producing fire resistance PUF with enhanced performance.

Performance study and tunnel waterproofing application of polyurethane prepolymer prepared by prepolymer and acetone combination

Performance study and tunnel waterproofing application of polyurethane prepolymer prepared by prepolymer and acetone combination

Study on direct shear strength properties of sand mixed with polyurethane prepolymer and sisal fiber

Study on direct shear strength properties of sand mixed with polyurethane prepolymer and sisal fiber

A novel green polyurethane adhesive based on castor oil and tannic acid with excellent water, salt, acid, alkali and antibacterial properties

In recent decades, solvent-free polyurethane adhesives from renewable sources are increasingly needed for engineering and biomedical applications. However, the significant drawbacks persist in bio-based polyurethane adhesives, including low moisture resistance, high sensitivity to variations in pH and salt, a sophisticated synthesis route, and costly adhesive building blocks. Inspired by the catecholic properties of mussel foot proteins, we used tannic acid as a crosslinker to strengthen the capabilities of castor-oil-based adhesives through a facile yet robust strategy. After directly mixing at room temperature, tannic acid was bonded with polyurethane prepolymer to construct a dual-network of noncovalent interaction and covalent crosslinks, hence improving the crosslinking density and cohesive connections. In addition, the adhesive and substrate interface interactions were strengthened. Owing to the diverse bonding abilities, the dry shear strength rose from 1.1 to 9.5 MPa. After immersing in water for 200 h, the largest wet shear strength was 5.2 MPa. Furthermore, this adhesive strength also increases at pH 2,12 and ionic strength of 0.2 M NaCl, demonstrating excellent adhesiveness (∼11.8 MPa). The easy-to-make adhesive also has outstanding bacterial resistance. The utilization of tannic acid and the formation of a dual network are a new strategy for developing green high-performance adhesives with biomass feedstock.

Feasibility Analysis of Polyurethane-Prepolymer-Modified Bitumen Used for Fully Reclaimed Asphalt Pavement (FRAP).

Asphalt pavement recycling technology with high reclaimed asphalt pavement (RAP) content has always been limited by unsatisfactory pavement performance and the rising cost of pavement materials. To address these challenges, polyurethane-prepolymer-modified bitumen (PPB) was proposed to be utilized as the asphalt binder of fully reclaimed asphalt pavement (FRAP) in this study. The proper formula of the PPB binder was determined based on a range of tests. The rheological behavior and tensile properties of the PPB binder were then investigated, and the economic cost of materials was discussed as well. Results revealed that the PPB system can be obtained through chemical synthesis using readily available raw materials. The reaction of polyurethane prepolymer and chain extender provides PPB with significant improvement in temperature susceptibility, rutting resistance, and tensile properties. It is also demonstrated in this study that the PPB mixture containing 100% RAP, on the whole, takes advantage of cost-saving especially compared to the epoxy asphalt mixture. Therefore, the PPB binder exhibits a favorable application prospect in FRAP.

Green synthesis of end-capped polyurethane prepolymer with high storage stability and its effects on bitumen properties

To increase the storage stability of polyurethane prepolymer (PUP), environmentally friendly end-capped PUP modifier was prepared to modify asphalt, which can improve the performance of bitumen while protecting the environment. Physical, chemical and mechanical characterizations of the end-capped PUP and the modified bitumen were conducted to fundamentally understand its modification mechanism. The outcomes demonstrated that the storage stability of PUP can be significantly increased by end-capping technology. End-capped PUP can be successfully uncapped in bitumen and used to modify bitumen. As a result of the interaction between PUP and the active spots within asphaltene and bituminous resin, urethane, urea, and amide linkages were created, creating a cross-linked structure. The modification procedure encourages the transformation of resin into asphaltene and the reconstruction of asphaltene. With the reorganization of asphaltene molecules and the strengthening of cross-linking, PUP modified bitumen have greatly improved their high temperature resistance. However, as curing time increases, bitumen's chemical composition changes, resulting in decreased low-temperature performance, but it is still better than the base bitumen. This research prepared high storage stability PUP and explored the mechanism of PUP to modify bitumen, which has guiding significance for the usuage of PUP modified bitumen.

Metal-free organocatalysts for high hydrolytic stability single component polyurethane adhesives and their application in decorative insulation facades manufacturing

We focused on developing polyurethane (PU) adhesives with superior ambient thermal and hydrolytic stability, a crucial factor for industrial productivity. Our approach involved creating PU prepolymers that can withstand varying temperatures in ambient conditions. These prepolymers consist of conventional isocyanate-terminated polyurethane and metal-free acid:base organic catalysts, with the stability of the adhesive relying on the organocatalyst employed. We tested a series of 11 latent organocatalysts derived from the reaction between 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and various acids. Among these, the catalyst based on 1-naphthoic acid exhibited exceptional stability, lasting at least 3 h at 60 °C and an average relative humidity of 65% under vigorous stirring. We assessed this stability using a fan-based stirrer and analyzed the curing conditions kinetically through DSC. Furthermore, our adhesive formulation is environmentally friendly as it is free of metals, specifically tin (typically present in catalysts such as dibutyltin dilaurate). This quality enhances its sustainability. To validate the practical applicability of the adhesives, we conducted tests using decorative facade models composed of siliciclastic sandstone extracted from a quarry in Vilviestre del Pinar (Burgos, Spain. Latitude: 41.951024° N, longitude: 3.078283° W) and extruded polystyrene (XPS). The results demonstrated the excellent hydrolytic and thermal stability of the adhesives, highlighting their significant potential for panel manufacturing in this context.

On the 3D printability of one-part moisture-curable polyurethanes via direct ink writing (DIW)

On the 3D printability of one-part moisture-curable polyurethanes via direct ink writing (DIW)

Investigation of the Physicochemical Interactions and Modification Effects of Polyurethane on Asphalt Binder

Polyurethane (PU) is a synthetic polymeric material with excellent mechanical properties and chemical designability. An in-depth understanding of the synergetic effect between polyurethane and asphalt binder is needed to produce durable PU-modified asphalt paving materials. This study focuses on the physicochemical changes, the states of in situ synthesized PU, and the modification effects of PU after PU prepolymers and chain extenders are added into asphalt binder. Investigation methods involve the Fourier transform infrared (FTIR) spectroscopy, partial Corbett separation, confocal fluorescence microscopy, particle size distribution test, rheological test, and theoretical calculation. It was found that the incorporation of PU has no obvious chemical influence on the asphalt binder and the main working principle of PU modification is its physical dispersion in asphalt binder. In situ synthesized PU is uniformly dispersed in asphalt binder and the size distribution of PU particles follows a log-normal distribution. As PU content exceeds 15%, the formed PU particles in asphalt binder are noticeably enlarged. Moreover, PU modification leads to significant improvements in asphalt binder properties, including high-temperature rutting resistance, elastic recovery, and deformation resistance. Rheological experiments and theoretical calculations under the framework of suspension rheology indicate that PU-modified asphalt binder can be reasonably modeled as a bimodal solid particle suspension, and the dynamic viscosity of PU-modified asphalt binder is predominantly determined by the dynamic viscosity of the maltenes and the volume fractions of PU and asphaltenes.

Physicochemical characterization of titanium dioxide inks for digital textile printing based on newly developed polyurethane prepolymers

PurposeThis paper aims to study the physical and chemical characteristics of inkjet titanium dioxide inks for cotton fabric digital printing.Design/methodology/approachDifferent dispersing agents through the reaction of glycerol monooleate and toluene diisocyanate were prepared and then performed by using three different polyols (succinic anhydride-modified polyethylene glycol PEG 600, EO/PO Polyether Monoamine and p-chloro aniline Polyether Monoamine), to obtain three different dispersing agents for water-based titanium dioxide inkjet inks. The prepared dispersants were characterized using FTIR to monitor the reaction progress. Then the prepared dispersants were formulated in titanium dioxide inkjet inks formulation and characterized by particle size, dynamic surface tension, transmission electron microscopy, viscosity and zeta potential against commercial dispersants. Also, the study was extended to evaluate the printed polyester by using the prepared inks according to washing and crock fastness.FindingsThe obtained results showed that p-chloro aniline Polyether Monoamine (J) and succinic anhydride modified polyethylene glycol PEG 600 (H) dispersants provided optimum performance as compared to commercial standards especially, particle size distribution data while EO/PO Polyether Monoamine based on dispersant was against and then failed with the wettability and dispersion stability tests.Practical implicationsThese ink formulations could be used for printing on cotton fabric by DTG technique of printing and can be used for other types of fabrics.Originality/valueThe newly prepared ink formulation for digital textile printing based on synthesized polyurethane prepolymers has the potential to be promising in this type of printing inks, to prevent clogging of nozzles on the printhead and to improve the print quality on the textile fiber.

Fabrication and performance of phase change microcapsules with fatty acid monoglyceride based waterborne polyurethane as the shell

AbstractPolyurethane phase change microcapsules (PU‐PCMs) with high encapsulation efficiency are fabricated with ethyl palmitate as the phase change material and fatty acid monoglyceride based waterborne polyurethane as the shell. The compositions and morphologies of microcapsules are characterized by Fourier transform infrared spectrometer (FT‐IR), field scanning electron microscope (FSEM) and laser particle size analyzer. The encapsulation efficiency and phase change performances of microcapsules are investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results show that PU‐PCMs have smooth surface and spherical shape and the size of about 300 nm. TGA and DSC results show that the encapsulation efficiency of ethyl palmitate in PU‐PCMs prepared with fatty acid monoglyceride is up to 92.3%, which is much higher than that of PU‐PCMs prepared with other diols. The fatty acid monoglyceride based polyurethane prepolymer has better affinity with ethyl palmite than polyurethane prepolymer prepared with other diols, which causes the high encapsulation efficiency of phase change materials. The result of DSC show that the melting enthalpy of fatty acid monoglyceride based PU‐PCMs is 81.6 J g−1and the phase change temperature is 26.75°C. After 200 heating/cooling cycle test, the phase change temperatures and shapes of microcapsules remain unchanged, which show that the microcapsules have good phase change stability. The temperature‐regulating performance and application of the PU‐PCMs in fabricating semi‐transparent temperature‐regulating glass are conducted and investigated. Results of these investigations indicate that PU‐PCMs fabricated from fatty acid monoglyceride show promising applications in heat‐energy storage and temperature‐regulation fields.

Effects of the molecular weight of soft segment of polycaprolactone polyurethane prepolymer on the properties of polyurethane composites with high wood content

Developing green composite with high biomass content is one crucial way to realize the strategy of ‘carbon reduction’. The type of polyurethane prepolymer and its soft segment’s structure have an important influence on the structure and properties of composite materials. This work focused on preparing different kinds of wood powder-polyurethane prepolymer (WCLPU) composite with high biomass content to study the effects of the molecular weight of the soft segment of the polyurethane prepolymer (PCLPU) on the structure and properties of the composites. The results showed that the composite materials with 70 wt% wood content exhibited high strength and good bending performance. Specifically, with decreasing molecular weight of the PCLPU soft segment, the bending strength and bending modulus of the modified WCLPU composite also increased. This work has laid a foundation for studying the effects of the molecular weight of the PCLPU soft segment on the structure and properties of composite materials.

Effects of poly(butanediol adipate ester) based polyurethane prepolymer content on structure and properties of PLA–diatomaceous earth composites

AbstractDeveloping green composites has received intense attention among the scientific community because of their ability to help alleviate the global environmental pollution challenges. This current work focused on preparing a bio‐based composite material with desirable performance using renewable materials like diatomaceous earth, and polylactic acid (PLA) with poly(butanediol adipate ester) prepolymer (PBAPU) as a compatibilizer. The composites were prepared by reactive mixing using an intensive mixer. Subsequently, the effects of the PBAPU content on the structure and properties of the composites were studied. From the test results, it was revealed that increasing the PBAPU content resulted in an increasing trend in the properties of the composites. For instance, the thermal stability of the composites was improved as the PBAPU content was increased, and the best thermal stability was obtained when 20 wt% PBAPU was added. In addition, the mechanical properties test results showed that the elongation at break and impact strength of the composites increased with increasing PBAPU content. On the contrary, the tensile strength of the composites decreased with increasing PBAPU content. The scanning electron microscope images showed that the compatibility between the PLA matrix and PBAPU in the composites was improved significantly. Based on the analysis of the test results for the material's structure, morphology, thermal stability, fluidity, and other properties, it can be concluded that a bio‐based composite material with desirable performance was successfully prepared.

Triethoxysilane End-Functional Branched Waterborne Polyurethane Adhesives for Leather Substrates

In order to improve the adhesion and water resistance of waterborne polyurethane (WPU) adhesive, a kind of amino-terminated hyperbranched organosilicon (HPSi-NH2) was first synthesized by using trimethylchlorosilane, diethoxydimethylsilane, and γ-aminopropyltriethoxysilane (KH550) as raw materials. Then, HPSi-NH2, as the cross-linking agent, was used to modify the polyurethane prepolymer to obtain HPSi-NH2-modified WPU (HSiPU). The single-factor experiment results showed that when the amount of HPSi-NH2 was 2.0 wt %, the adhesion properties of HSiPU-2 were the best. Compared with the HSiPU-0 film, the water absorption rate of the HSiPU-2 film decreased by 10.9%, the water contact angle increased by 26.3°, the tensile strength increased by 10.1 MPa, and the elongation at break increased from 630.7 to 813.0%. HSiPU adhesive was used in the bonding of the goat leather substrate, and the results showed that the peel strength of leather bonded by HSiPU-2 was increased from 1.38 to 3.15 N/mm, and the maximum peel force was increased from 1.67 to 5.51 N/mm, which indicated that the bond strength of HSiPU adhesive with different contents of HPSi-NH2 can be used for bonding substrates with different cohesion strengths.

Manual applied polyurethane-urea: High performance coating based on CO2-based polyol and polyaspartic ester

Brushable polyurea based on slow reactive process was prepared by simple, mild and solvent-free method. Firstly, polyurethane prepolymer was synthesized from poly (propylene carbonate) diol (PPCD, copolymer of propylene oxide/CO2) and 4,4′-dicylocyhexylmethane diisocyanate (HMDI). Polyurethane-urea (PPCD–PUU) was then obtained by the chain extension of prepolymer with polyaspartic ester (PAE). The mechanical properties of PPCD–PUU were optimized by adjusting the content of –NCO in the prepolymer and the ratio of prepolymer to PAE. The mechanical strength, thermal resistance, solvent resistance and hydrolysis resistance of PPCD–PUU were compared with those of PUUs derived from polypropylene glycol and poly-caprolactone diol. The results showed that the comprehensive mechanical properties of PPCD–PUU were balanced when the R value was 1.15 and the content of –NCO was 8 %. The tensile strength was 20.5 MPa, the elongation at break was 352 %, and the Young's modulus was 168.2 MPa. Especially, after soaking in 10 % H2SO4 aqueous solution, 10 % NaOH aqueous solution and 10 % NaCl aqueous solution for 24 h, the tensile properties were basically unchanged. Manual applied polyurethane-urea based on commercial PPCD has broad application prospects because it avoids the use of expensive spraying equipment.

Starch Modified Tough Biocompatible Polyurethane/acrylamide bio Composites: Physicochemical Properties and Biodegradation Studies

Biodegradable bio composites with potential applications in medical implants were prepared with starch content by in situ polymerization technique using polyurethane prepolymers. (PU) and acrylamide (AAM) monomers. The structure and properties of bio composites were evaluated. FT-IR spectroscopy showed bonding between N=C=O functional group terminated polyurethanes confirmed improved compatibility of prepolymers, AAM, starch and bio composites. The DSC data are the glass transition (Tg) of the bio composite and ordinary polyacrylamide (PAAM) network. By incorporating starch and polyurethane in the form of an interpenetrating network into a polyacrylamide network, mechanical and thermal properties of bio composites due to higher crosslink density given by hard segment content. We studied the swelling behavior of both bio composites and individual PAAM networks under different pH conditions to validate their biocompatibility and potential use in biomedicine setting. The hydrolytic stability of biocomposites and PAAM networks was investigated using phosphate buffer. Hydrolytic stability of biocomposites was found to be higher comparison with PAAM network. Morphological analysis of the samples showed uniform distribution and good interfacial adhesion. Improves sample biodegradability it was revealed by the soil runoff test.

PREPARATION AND STUDY OF A PU-MODIFIED EPOXY RESIN COLD PATCHING MIXTURE

Focusing on the problems of low strength and insufficient water stability of the cold patch mixture for asphalt pavement, a polyether polyurethane prepolymer with high activity was prepared in this experiment, and then the epoxy resin was modified with the prepolymer to prepare a kind of epoxy-resin-mixture pothole-repair material with high strength and high toughness. The content of polyurethane prepolymer was optimized using a low-temperature tensile test and a normal-environment-condition mechanical test, and the mechanical properties and road performance of the PU-modified epoxy-resin mixture were studied with a rutting test, bending test, Cantabro scattering and a splitting test. The results show that PU prepolymer-modified epoxy resin can effectively increase the toughness and strength of the binder, and that the toughness and mechanical properties of 20 phr PU prepolymer are the best. The road performance of the PU-modified epoxy-resin cold patch mixture is excellent. There is little difference between the immersion scattering loss rate and the standard loss rate, and both are less than 4 %, indicating that the mixture has excellent anti-scattering and water-loss performance. It is very suitable as a cold patch material for pavement pits. Due to its comprehensive road performance and reasonable price, the use of the PU-modified epoxy resin binder content of 4 % is recommended.

Combined use of novel chitosan-grafted N-hydroxyethyl acrylamide polyurethane and human dermal fibroblasts as a construct for in vitro-engineered skin

A rich plethora of information about grafted chitosan (CS) for medical use has been reported. The capability of CS-grafted poly(N-hydroxyethyl acrylamide) (CS-g-PHEAA) to support human dermal fibroblasts (HDFs) in vitro has been proven. However, CS-grafted copolymers lack good stiffness and the characteristic microstructure of a cellular matrix. In addition, whether CS-g-PHEAA can be used to prepare a scaffold with a suitable morphology and mechanical properties for skin tissue engineering (STE) is unclear. This study aimed to show for the first time that step-growth polymerizations can be used to obtain polyurethane (PU) platforms of CS-g-PHEAA, which can also have enhanced microhardness and be suitable for in vitro cell culture. The PU prepolymers were prepared from grafted CS, polyethylene glycol, and 1,6-hexamethylene diisocyanate. The results proved that a poly(saccharide-urethane) [(CS-g-PHEAA)-PU] could be successfully synthesized with a more suitable microarchitecture, thermal properties, and topology than CS-PU for the dynamic culturing of fibroblasts. Cytotoxicity, proliferation, histological and immunophenotype assessments revealed significantly higher biocompatibility and cell proliferation of the derivative concerning the controls. Cells cultured on (CS-g-PHEAA)-PU displayed a quiescent state compared to those cultured on CS-PU, which showed an activated phenotype. These findings may be critical factors in future studies establishing wound dressing models.

Synthesis and nonlinear optical properties of polyurethane composites containing a pyrene derivative.

The pyrene derivative (PD) was synthesized with pyrene-1-carboxaldehyde and p-aminoazobenzene by a Schiff base reaction. Then the obtained PD was dispersed in polyurethane (PU) prepolymer to prepare polyurethane/pyrene derivative PU/PD materials with good transmittance. The nonlinear optical (NLO) performances of the PD and PU/PD materials were studied by the Z-scan technique under picosecond and femtosecond laser pulses. The PD has reverse saturable absorption (RSA) properties under the excitation of 532nm 15ps pulses, 650 and 800nm 180fs pulses, and a low optical limiting (OL) threshold (0.01J/c m 2). The PU/PD has a larger RSA coefficient than that of the PD under 532nm 15ps pulses. With the enhanced RSA, the PU/PD materials exhibit excellent OL (OL) performance. Good NLO properties, high transparency, and easy processing performances make the PU/PD an excellent choice for use in OL and laser protection fields.

Dual-crosslinked starch−poly(ester urethane)−oligochitosan films with high starch content: Application as biodegradable food packaging

This work offered a dual-crosslinking strategy to prepare starch−poly(ester urethane)−oligochitosan (SPEO) composites with high starch content (> 46 wt%). The crosslinking agent polycaprolactone-based polyurethane prepolymer (PPUP) with terminal −NCO groups and pendant −CHO groups was first synthesized. Then, the starch was modified by PPUP to form a crosslinked structure linked by urethane bonds. Oligochitosan (OCS) was subsequently introduced to produce another crosslinked structure linked by imine bonds, and the films were fabricated by compression molding. The chemical structures and physical performance of SPEO were characterized. Crystallinity, micromorphology and thermal analysis demonstrated that the dual-crosslinking structures enhanced the composite compatibility, which improved their mechanical properties. The surface hydrophilicity, water absorption, and in vitro degradation rate increased slowly with increasing OCS content, while a high crosslinking density provide a good barrier to water vapor permeation and therefore decreased the water vapor permeability (< 128 g/(m2∙24 h)). Due to the residual −NH2 groups of OCS, the composite film of SPEO-6 exhibited certain bacteriostatic activity against E. coli and S. aureus. Furthermore, the cytotoxicity of the composite films was assayed by the MTT method, and relative growth rates were much higher than 75% after incubation for 72 h, indicating high cytocompatibility and non-toxicity to food. The dual-crosslinked high-starch-content composites possessing high security, superior mechanical properties, good biodegradability, low water vapor permeability, and certain bacteriostatic capacity hold great potential to substitute petroleum-derived plastics for fresh-keeping food packaging applications.