Polyurea Matrix Research Articles

Mechanical Robust and Conductive Polyurea Nanocomposites Using Graphene Platelets

Graphene, renowned for its exceptional surface area, electrical and thermal conductivity, and gas permeation resistance, serves as an excellent filler for enhancing the properties of polyurea (PUA). In this study, graphene platelets (GNPs) were mass-produced via thermal expansion of graphite intercalation compound followed by ultrasonic exfoliation. These GNPs were then incorporated into PUA using a straightforward mixing method to create PUA/GNPs composites. Characterization using SEM and a high resistivity meter revealed strong interfacial bonding between GNPs and the PUA matrix, facilitated by isophorone diisocyanate (IPDI) and Jeffamine D2000 (D2000). This robust interaction significantly improved the composites' performance. Notable enhancements in mechanical properties were observed: tensile strength increased by approximately 79% at 0.5 vol%, impact strength by 15.7% at 0.2 vol%, and tear strength by 30.6% at 0.5 vol%,. These improvements underscore the effectiveness of GNPs as reinforcing fillers, significantly boosting the durability and robustness of the PUA composites. Additionally, the study examined the effect of varying graphene content on the electrical properties of the composites, revealing substantial improvements in electrical conductivity. This research presents a practical strategy for developing high-performance PUA/GNPs composites, leveraging GNP's unique properties to enhance both mechanical and electrical characteristics. The study contributes valuable insights into the synthesis and property enhancement of GNPs nanocomposites, paving the way for further advancements in the field of multifunctional materials.

Porous liquids assisted in-situ generated Co-LDH@MOF heterostructure with abundant defects for flame retardant and mechanical enhancement in polyurea composites

Preventing aggregation and inducing homogeneous dispersion of flame retardant nanofillers is critical to enhance the fire safety and mechanical properties of nanocomposites. Although chemical modifications are commonly used to improve the filler’s compatibility with the polymer chain, such methods are often cumbersome and limited. Herein, porous liquids (PLs) with flame retardant function were constructed in which porous defect-Co-LDH@ZIF-67 (d-LDH@ZIF) heterostructure particles were converted into liquid materials by electrostatic interaction with a large-volume solvent. This is also the first report of PLs in the field of flame retardant. Specifically, the d-LDH@ZIF heterostructure was designed by defect engineering and in situ growth strategy to compensate for the low catalytic activity and specific surface area of Co-LDH, and to serve as a rigid porous framework for PLs. Numerous cobalt/oxygen vacancies and lattice defects in the d-LDH@ZIF heterostructure have also been proven to confer higher flame retardancy relative to Co-LDH. d-LDH@ZIF porous liquids (PLs-d-L@Z) presents favorable liquid characteristics and achieves a monodisperse state in the polyurea matrix. The limiting oxygen index of polyurea composites blended with 20 wt% PLs-d-L@Z (3 wt% d-LDH@ZIF content) can be increased to 24.2 % and pass the V-0 rating in the UL-94 test. Moreover, the peak of heat release rate, total heat release, and total smoke production are reduced by around 40.4, 27.0, and 39.9 %, respectively, compared to neat polyurea. Emphatically, the PLs-modified polyurea composites exhibit significantly improved mechanical and impact resistance properties, as well as favorable chemical resistance. This strategy of liquefying solid flame retardant fillers will open an avenue to the design of functional nanomaterials for fire safety and other potential applications.

A study on tung oil-infused polyurea microcapsules: Prioritizing self-healing with bioassay-based toxicity and antibiofilm evaluations

This study presents a novel approach to enhancing the longevity and efficacy of dental materials through the incorporation of Tung oil into polyurea microcapsule coatings. Tung oil is renowned for its superior moisture barrier and antimicrobial properties, and when merged with the durable nature of polyurea, it creates a coating poised to substantially improve self-healing capabilities in dental applications. Focusing on the dual objectives of mechanical fortitude and biocompatibility, this research meticulously evaluates the coatings' proficiency in withstanding the rigors of the oral environment and their compatibility with oral tissues. Employing a suite of bioassays, we meticulously assess the toxicity and antibiofilm characteristics of these coatings, in addition to their self-healing efficiency. These evaluations measure the coatings’ ability to autonomously repair physical damage and counteract microbial colonization. The results reveal that tung oil significantly enhances the polyurea matrix's intrinsic self-repair features, which proves crucial in resisting the abrasive and microbial challenges prevalent in the oral cavity. The modified coatings demonstrate marked improvements in wear resistance and microbial interaction, heralding a significant advancement in dental material technology. This in-depth analysis corroborates the amplified capabilities of Tung oil-infused polyurea coatings and paves the way for future investigations into the integration of natural oils within medical-grade material design, opening a new chapter in the synthesis of biomaterials tailored for oral healthcare advancements.

Poorly-/well-dispersed Fe3O4: Abnormal influence on electromagnetic wave absorption behavior of high-mechanical performance polyurea

In this work, novel core–shell Fe3O4 nanoparticles were prepared by self- assembly technology using phytate-melamine aggregates (PM) or phytate-melamine-Fe3+ aggregates (PM-Fe) as building block. A polyurea (PUA) matrix was filled with magnetic nanoparticle. The influence of Fe3O4, Fe3O4@PM or Fe3O4@PM-Fe content and dispersion on the mechanical and electromagnetic wave (EMW) absorption properties of PUA composite were investigated. Good dispersion of modified Fe3O4 in PUA matrix was obtained. Loading well-dispersed Fe3O4 significantly enhanced the mechanical properties of their PUA nanocomposite under quasi-static tensile, nanoindentation, and dynamic compression tests. Excellent EMW absorption performance of PUA/Fe3O4@PM nanocomposite was desired. Although well-dispersed Fe3O4@PM could effectively enhance the mechanical properties, nonetheless it surprisingly plays a negative role in the EMW absorption performance. The Fe3O4@PM with high dispersion and interfacial compatibility in the PUA matrix was detrimental to EMW absorption performance, which contradicts the well accepted EMW absorption mechanisms. A novel mechanism and model were suggested, along with a fresh understanding of the role of Fe3O4 in the EMW absorption of PUA composite. Furthermore, the Fe3O4@PM-Fe, obtained by constructing a conductive network on the surface of Fe3O4@PM, was used to investigate this assumption. The radar cross section simulation also demonstrated the superior EMW attenuation capability of PUA nanocomposites in the service condition. This work is beneficial to the development of EMW absorber, not limited to Fe3O4 magnetic nanoparticles.

Enhancing the protective performance of anti-impact, corrosion resistant and flame retardant polyurea coatings using bio-based supramolecular decorated montmorillonite

Developing bio-based nano-additives for enhancing mechanical strength, corrosion resistance, and flame retardancy in polyurea (PUA) coatings at low loading levels is crucial for human well-being and environmental preservation. In this study, montmorillonite (MMT) was first exfoliated by ball milling with the aid of chitosan, and then further co-assembled with phytic acid and urea to form a nanohybrid (CPN@MMT). The resulting CPN@MMT nanohybrid exhibited good compatibility and dispersibility within matrix and endowed PUA composites with improved anti-impact, corrosion resistant and flame retardant properties. Remarkably, the addition of CPN@MMT improved the mechanical and impact protection properties of PUA coatings. Electrochemical and salt spray tests confirmed that the excellent anti-corrosion performance of PUA composite coating stemmed from the dispersed nano-sheets forming a protective nano-barrier. CPN@MMT in the PUA matrix formed a compact char layer, reducing heat release and smoke by inhibiting heat diffusion and volatile gas evaporation, as evidenced by cone calorimeter and TG-FTIR tests. The enhanced fire safety was primarily attributed to the physical barrier, catalytic charring and dilution effect of CPN@MMT. Hence, a green and feasible method was developed to create bio-based nano-additive in PUA coatings with anti-impact, corrosion resistant and flame retardant performance.

Dual Microcapsules Encapsulating Liquid Diamine and Isocyanate for Application in Self-Healing Coatings

Dual microcapsule systems, especially those based on the polyurea matrix, have emerged as pivotal components driving innovation in self-healing materials, thanks to the intrinsic properties of polyurea, primarily diamine and diisocyanate, rendering it an optimal choice for enhancing self-healing coatings. However, the encapsulation of polyurea components is fraught with substantial technical hurdles. Addressing these challenges, a novel methodology has been devised, leveraging n-heptane as a solvent in the liquid diamine emulsion process to facilitate the synthesis of diamine microcapsules. These microcapsules exhibit a uniform spherical morphology and a robust shell structure, with an encapsulated core material ratio reaching 39.69%. Analogously, the encapsulation process for diisocyanate has been refined, achieving a core material percentage of 10.05 wt. %. The integration of this bifunctional microcapsule system into diverse polymeric matrices, including epoxy resins and polyurethanes, has been demonstrated to significantly enhance the self-healing efficacy of the resultant coatings. Empirical validation through a series of tests, encompassing scratch, abrasion, and saltwater immersion assays, has revealed self-healing efficiencies of 21.8% and 33.3%, respectively. These results indicate significant improvements in the durability and self-repair capability of coatings, marking a notable advancement in self-healing materials with promising potential for tailored applications in automotive, aerospace, and construction industries.

Dimensional change of red phosphorus into nanosheets by metal–organic frameworks with enhanced dispersion in flame retardant polyurea composites

Red phosphorus (RP) is a promising polymeric flame retardant due to its abundance of flame-retardant elements. Unfortunately, the irregular size of RP leads to poor dispersion in polymer matrices, which greatly limits its wide application in flame-retardant polymer materials. Here, RP is transformed into a two-dimensional (2D) lamellar structure by a simple green method, while ZIF-67 nanoparticles are grown in situ and uniformly embedded in them. The 2D porous RP@ZIF (2D RP@ZIF) composites exhibit excellent flame-retardant properties and mechanical properties in polyurea (PUA) matrix. The peak heat release rate, total heat release, the peak of smoke production rate and total smoke production of PUA composites added with 5 wt% 2D RP@ZIF decreased by 48.0 %, 54.2 %, 20.4 % and 22.2 %, respectively. Due to its well compatibility, the elongation at break and tensile strength of PUA composites were 308.02 % and 9.21 N in the mechanical test, respectively. Compared with previous work, this is the first time that a 2D RP hybrid flame retardant has been prepared by metal organic framework and applied to flame retardant PUA.

Polyurea-Graphene Nanocomposites-The Influence of Hard-Segment Content and Nanoparticle Loading on Mechanical Properties.

Polyurethane and polyurea-based adhesives are widely used in various applications, from automotive to electronics and medical applications. The adhesive performance depends strongly on its composition, and developing the formulation-structure-property relationship is crucial to making better products. Here, we investigate the dependence of the linear viscoelastic properties of polyurea nanocomposites, with an IPDI-based polyurea (PUa) matrix and exfoliated graphene nanoplatelet (xGnP) fillers, on the hard-segment weight fraction (HSWF) and the xGnP loading. We characterize the material using scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA). It is found that changing the HSWF leads to a significant variation in the stiffness of the material, from about 10 MPa for 20% HSWF to about 100 MPa for 30% HSWF and about 250 MPa for the 40% HSWF polymer (as measured by the tensile storage modulus at room temperature). The effect of the xGNP loading was significantly more limited and was generally within experimental error, except for the 20% HSWF material, where the xGNP addition led to about an 80% increase in stiffness. To correctly interpret the DMA results, we developed a new physics-based rheological model for the description of the storage and loss moduli. The model is based on the fractional calculus approach and successfully describes the material rheology in a broad range of temperatures (-70 °C-+70 °C) and frequencies (0.1-100 s-1), using only six physically meaningful fitting parameters for each material. The results provide guidance for the development of nanocomposite PUa-based materials.

Hollow Superstructure In Situ Assembled by Single-Layer Janus Nanospheres toward Electromagnetic Shielding Flame-Retardant Polyurea Composites.

A dodecahedral superstructure consisting of a single layer of Janus spheres containing ZIF-67 nanodots is prepared by in situ polymerization, with ZIF-67 and bio-based phytic acid (PA) as templates and dopants. It is used to improve the flame retardant, electromagnetic (EMI) shielding, and thermal conductivity properties of polyurea (PUA). By adding 5wt% polyaniline@cobalt phytate-2.0 (PANI@Co-PA-2.0), the peak of heat release rate and the peak of smoke production rate are reduced by 54.9 and 59.9%, respectively. The peak of CO and CO2 production also decreased by 46.2 and 53.1%, respectively. A decrease in the absorption intensity of aliphatic and aromatic volatiles is also observed. The fire safety of PUA is greatly improved. In addition, PUA/PANI@Co-PA-2.0 exhibits an EMI shielding capability of 22.4dB with the help of reduced graphene oxide, which confirms the possibility of PUA material application in the field of electromagnetic shielding. The 5wt% filler increases the tensile strength of the PUA matrix to 6.3MPa, and the composite material obtains good thermal conductivity. This work provides a viable method for the preparation of a flame-retardant, conductive, and electromagnetic refractory PUA substrate.

Synthesis and Application of Modified Lignin Polyurea Binder for Manufacturing a Controlled-Release Potassium Fertilizer

Conventional potassium chloride granules have inefficient applications in agricultural production due to particle irregularity and low fluidity. The application of controlled-release potassium chloride could increase the potassium-use efficiency and alleviate the shortage of potassium ore resources. In this study, a well-rounded potassium chloride fertilizer core was prepared, using the graft modification of polyurea to enhance the coating rate and release performance. The adhesive and tensile characteristics of the modified polyurea binder, as well as the granule properties of modified polyurea binder potassium chloride, were studied to determine the ideal lignin-grafted ratio. The effect of the modified polyurea binder with potassium chloride on the properties of coated fertilizer was investigated. The findings, shown by radar maps of the binder’s properties, demonstrated that the ideal mass ratio of the modified lignin polyurea binder to urea is 1:2. The Fourier-transform infrared spectroscopy results demonstrated that the amino functional groups of lignin were enhanced, improving the product’s interfacial compatibility with the polyurea matrix. Compared to humic acid (HA; 12%) and bentonite (Ben; 30%) treatments, the granule intensity of the 9.9%—1:2 treatment considerably increased by 139.10% and 38.86%, respectively, while the static angle of the granules reduced by 16.67% and 3.81%. The 28-day cumulative release rate of the modified polyurea (9.9%—2:1) with a 5% coating thickness was the lowest (28%), 42% lower than that of the lowest conventional treatment. In summary, the creation of a bio-lignin polyurea binder under the optimum conditions reduced the need for petrochemical-based materials, allowed the preparation of fertilizer with granules of increased fluidity, and enabled the successful coating of a high-salt potassium fertilizer, offering a novel technique for the high-value application of potash fertilizer coating.

Synergistic effect of combined blast loads on UHMWPE fiber mesh reinforced polyurea composites

UHMWPE fiber mesh reinforced polyurea (UFRP) composites are a proposed improvement method that involves incorporating UHMWPE fiber mesh into polyurea coating. Experiments and theoretical analysis were conducted to examine the failure and blast resistance performance of the UFRP under combined air-blast and fragments. The mechanism of UFRP composite failure, the self-healing effect, and counterintuitive behaviors were identified and investigated. Fiber mesh improved structural strength and stopped fracture development, while polyurea increased ductility and protected against blast fragment dispersion. The addition of UHMWPE fiber mesh improved the polyurea matrix's load transmission, integrity, and fracture resistance, and it can even altered the material's failure mode from shear punching to tensile. The loose and elastic filler was generated as polyurea melted in the impact hole as a result of the thermal effect of the impact process and the dynamic action of the penetration of the fragments. The joint load was classified into three categories based on the space-time connection of the loads, the loading duration, and the structure's reaction mechanism. The synergistic effect of the combined loading on the composite plates was evaluated, and an analytical model was developed to examine the occurrence. Synergy is contingent upon not just the reaching moment and duration of the loads, but also the reaction of the structures.

Polyaspartic polyurea/graphene nanocomposites for multifunctionality: Self-healing, mechanical resilience, electrical and thermal conductivities, and resistance to corrosion and impact

Polyurea elastomers have attracted increasingly more attention due to excellent mechanical performance, and their wide industrial applications are in need of multifunctionality such as thermal conductivity. We herein prepared polyaspartic polyurea elastomers with optimal tensile strength and fracture strain by adjusting the isocyanate index and free isocyanate content. As a class of nanofiller, isocyanate-modified graphene nanoplatelets (IP-GNPs) were developed and they formed a stable, robust interface with the polyurea matrix, resulting in mechanical reinforcement and multifunctionality. The nanocomposite at 0.05 vol% of IP-GNPs revealed a tensile strength of 15.72 ± 0.67 MPa, representing an increment of 108.21% over pure polyurea, with excellent resistance to acidic and alkali corrosion. After 9 h of post-maintenance at 60 °C, the nanocomposite reached a healing efficiency up to 80.10% as driven by hydrogen bonds. An electrical percolation threshold was observed at 3.61 vol% of IP-GNP for the nanocomposites. The thermal conductivity reached 38.49 W/m K at 7.00 vol% due to the formation of the IP-GNP network in polyurea, where the electron thermal conductivity plays a dominant role. In comparison with those high thermal conductivity values obtained by back-filling polymers into a network established beforehand, this facile approach would be highly favored in industry for the development of elastomer nanocomposites with multifunctionality for many applications, e.g. smart sensors, protective coatings, energy harvesting, etc.

The improved thermal and mechanical properties of polyurea nanocomposites with SiC

Polyurea as one kind of polymer is widely used in the field of protective under blast and impact loading. Polyurea matrix with nanofillers has superior mechanical properties than the pure polyurea. In this work, in order to develop polyurea with thermal stability and high mechanical properties, using Silicon carbide (SiC) as the nanofillers, polyurea nanocomposites with different content of SiC nanoparticles were prepared via in-situ polymerization method. The morphology and structure of SiC/polyurea nanocomposites were characterized by using SEM, XRD and FTIR. From the structure studies, the nanofillers of SiC had not altered the basic structure of polyurea. Thermal stability and mechanical properties were also studied by TGA and tensile testing machine, respectively. The results indicated that the incorporation of SiC nanoparticles (1.5 wt%) into polyurea could obviously improve thermal properties and mechanical properties in comparation with the pure polyurea. The enhancement of performance is relative to SiC nanoparticles reinforced polyurea matrix and high temperature properties of SiC. At higher content of SiC, the mechanical properties of SiC/polyurea nanocomposites tend to decrease. It can be inferred from the results that SiC/polyurea nanocomposites have the potential for using in protective structures.

Flame retardancy and anti-impact performance of polyurea composite coating reinforced by modified ammonium polyphosphate and two-dimensional nano-fillers

The protection performance of polyurea (PUA) coating is limited due to its intrinsic flammability. In order to develop a PUA composite coating with outstanding flame retardant and anti-impact performance simultaneously, in this paper the modified ammonium polyphosphate (MAPP) and two-dimensional (2D) nanofillers of graphene oxide (GO) and Mg-Al layered double hydroxides (LDH) were introduced into PUA matrix. Thermal stability and combustion behavior of PUA composites were studied by thermogravimetric analyzer and cone calorimeter. Results show that PUA composite sample with 17 wt% MAPP, 1.5 wt% GO and 1.5 wt% LDH exhibited remarkable flame-retardant and fire protective performance. The flame retardancy index increases to 1.7 from 1.0 with the time required to burn out and total heat release THR being dramatically decreased by 31.0 % and 33.4 %, respectively. The dynamic mechanical properties of PUA composites at the strain rate as high as 4500 s−1 were investigated. The dynamic mechanical behavior of the PUA composite shows strong strain rate effect. The introduction of the flame retardant does not substantially damage the energy dissipating capacity and anti-impact performance of the PUA matrix. Interfacial properties of PUA composites were studied by standard avulse and shear methods. The PUA composites with LDH and GO could form stronger bonding with the steel compared to neat PUA.

Tribological Behaviors of Natural Fiber Reinforced Nanofilled Polyurea Matrix Composites at High Temperatures

ABSTRACT The properties of natural fibers such as poor ultraviolet (UV) resistance and hydrophilicity that reduce the durability of composites limit their usage as reinforcements in polymer matrix composites. To compensate this, new types of composites are proposed in the present study. The tribological behaviors of multiphase composites with polyaspartic polyurea matrix produced by vacuum assisted resin transfer molding (VARTM) technique with jute reinforced, filled by graphene nanoplatelets (GNPs) and titanium dioxide (TiO2) nano-fillers at high temperatures are investigated. The wear tests were performed under 10, 20, and 30 N loads, at 60% humidity and temperatures of 100°C, 125°C, and 150°C using a heat moduled pin-on-disc tribotester with an AISI 4140 counter-surface disc having an average surface roughness value of 1.033 µm. The tests were carried out under dry friction conditions along 6000 m sliding distance at a sliding speed of 2 m/s. The results show that the wear damage types changed according to the nano-filler type. Wear loss and specific wear rate increased with increasing temperature and load in almost all types of composites. Using nano-filler caused irregularities in the change of the friction coefficient.

Experimental study of UV induced tensile properties deterioration and chemical aging of polyurea–POSS composites

Ultraviolet (UV) radiation present in natural sunlight degrades the chemical and mechanical properties of polymeric matrices in composites. Polyurea possess a unique set of chemical and mechanical properties due to its complex microstructure comprising of hard and soft segments (phases). The primary objective of the work presented here is to characterize the chemical and mechanical degradation of pure polyurea and polyurea - polyhedral oligomeric silsesquioxane (POSS) nanocomposites subjected to UV radiation exposure for 45 days. Control specimen in as-received condition (reference specimen) and UV-aged tensile test specimen are tested in the study. Analysis of Fourier transformed infrared (FTIR) spectra for UV-aged polyurea and polyurea-POSS composites reveals that the addition of POSS nanoparticles accelerate the deterioration of polyurea matrix by breaking the hard phase network and altering the mechanism of degradation for the soft phase present in polyurea microstructure. The deterioration of hard and soft segments cause a significant reduction in tensile properties of polyurea-POSS composites.

Effects of Fiber Volume Fraction and Length on the Mechanical Properties of Milled Glass Fiber/Polyurea Composites.

Composites of polyurea (PU) reinforced with milled glass fiber (MGf) were fabricated. The volume fraction and length of the milled glass fiber were varied to study their effects on the morphological and mechanical properties of the MGf/PU composites. The morphological attributes were characterized with scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The SEM investigations revealed a uniform distribution and arbitrary orientation of milled glass fiber in the polyurea matrix. Moreover, it seems that the composites with longer fiber exhibit better interfacial bonding. It was found from the FTIR studies that the incorporation of milled glass fiber into polyurea leads to more phase mixing and decreases the hydrogen bonding of the polyurea matrix, while having a negligible effect on the H-bond strength. The compression tests at different strain rates (0.001, 0.01, 0.1, 1, 2000 and 3000 s−1) and dynamic mechanical properties over the temperature range from −30 to 100 °C at 1 Hz were performed. Experimental results show that the compressive behavior of MGf/PU composites is nonlinear and strain-rate-dependent. Both elastic modulus and flow stress at any given strain increased with strain rate. The composites with higher fiber volume fraction and longer fiber length are more sensitive to strain rate. Furthermore, the elastic modulus, stress at 65% strain and energy absorption capability were studied, taking into account both the effect of fiber volume fraction and mean fiber length. It is noted that an increase in fiber volume fraction and fiber length leads to an increase in elastic modulus, stress at 65% strain and absorbed energy up to ~103%, 83.0% and 137.5%, respectively. The storage and loss moduli of the composites also increase with fiber volume fraction and fiber length. It can be concluded that the addition of milled glass fiber into polyurea not only improves the stiffness of the composites but also increases their energy dissipative capability.

A novel self-cleaning functional composite coating with extraordinary anti-corrosion performance in high pressure CO2 conditions

This study demonstrates an alternative method for fabricating a novel integrated anticorrosion self-cleaning functional coating using the GO nanosheets with the TiO2–ZnO heterostructure to effectively induce charge separation and to accomplish photoinduced hydrophilic conversion. Through ultraviolet light (UV) irradiation, the PFDTMS-modified filler transformed from hydrophobic to hydrophilic, while the fluorine groups on the surface of the filler still existed. Research of EIS shows that the impedance at 0.01 Hz of 20% F/T-Z-G Polyurea coating was about 1 × 103 times higher than polyurea coatings, after 24 h of immersion in 2.8 MPa, 110 °C pure CO2 and NaCl solution. The results demonstrate that F/T-Z improves the dispersion of GO and make the polyurea matrix denser, inhibiting the diffusion of corrosive medium. Additionally, the GO and fluorine groups strengthen the shielding performance of the coating. Moreover, the TiO2–ZnO heterojunction traps H2O molecules to form hydroxyl radicals (OH•). Simultaneously, Fe2+ and Fe3+ combine with OH• to form Fe3O4, and the passivation film was formed on the surface of steel. It is believed that this hydrophilic-hydrophobic integrated functional coating will be an excellent candidate for technological applications, such as anticorrosion, self-cleaning materials and composite coatings.

Remotely fast response healing crosslinked polyurea nanocomposites with recyclability via two-step method

The development of dynamic bonds-based nanocomposites with excellent mechanical properties and multi-stimulated self-healing capabilities is critical for the design of high-performance self-healing materials. In this study, dynamic nanocomposites based on carboxyl-functionalized multiwalled carbon nanotube (CNT-COOH) fillers and a crosslinked polyurea (CPU) matrix were prepared through a facile two-step method involving in situ photo-induced polymerization and hot compression. Herein, the effect of CNT-COOH concentration on the properties of the resulting CPU@CNT nanocomposites was studied. The proposed novel method promoted the formation of a strong interfacial bond between the CNT-COOH and CPU. The dynamic nanocomposites exhibited excellent and rapid photo-induced self-healing abilities and regained their mechanical properties after damage. This can be attributed to the synergistic effect of the dynamic exchange reactions in the CPU matrix and the efficient photo-thermal effect of the fillers. The nanocomposite prepared using 1% CNT-COOH exhibited excellent toughness (up to 36.57 ± 1.28 MJ m−3), high stretchability (ca. 607 ± 50%), high tensile strength (7.36 ± 0.51 MPa), efficient photo-thermal shape memory effect, and good recyclability. Therefore, the facile method demonstrated in this study paves a way for the design of high-performance nanocomposites with rapid self-healing properties for sensing and flexible electronic applications.

Layered Clay-Graphene Oxide Nanohybrids for the Reinforcement and Fire-Retardant Properties of Polyurea Matrix.

Nanostructures are more and more evolved through extensive research on their functionalities; thus, the aim of this study was to obtain layered clay–graphene oxide nanohybrids with application as reinforcing agents in polyurea nanocomposites with enhanced thermal–mechanical and fire-retardant properties. Montmorillonite (MMT) was combined with graphene oxide (GO) and amine functionalized graphene oxide (GOD) through a new cation exchange method; the complex nanostructures were analyzed through FTIR and XPS to assess ionic interactions between clay layers and GO sheets by C1s deconvolution and specific C sp3, respective/ly, C-O secondary peaks appearance. The thermal decomposition of nanohybrids showed a great influence of MMT layers in TGA, while the XRD patterns highlighted mutual MMT and GO sheets crystalline-structure disruption by the d (002) shift 2θ = 6.29° to lower values. Furthermore, the nanohybrids were embedded in the polyurea matrix, and the thermo-mechanical analysis gave information about the stiffness of MMT–GO nanocomposites, while GOD insertion within the MMT layers resulted in a 30 °C improvement in the Tg of hard domains, as shown in the DSC study. The micro CT analysis show good dispersion of inorganic structures within the polyurea, while the SEM fracture images revealed smooth surfaces. Cone calorimetry was used to evaluate fire-retardant properties through limiting the oxygen index, and MMT–GOD based nanocomposites showed a 35.4% value.