Polyurethane-modified Epoxy Research Articles

Effect of Diatomite on the Mechanical and Electrical Properties of Polyurethane/Epoxy Resin Composites

ABSTRACT Epoxy resin is widely utilized for the encapsulation of power semiconductor devices, necessitating excellent insulation properties, mechanical performance, and moisture resistance. In this study, hexadecyltrimethoxysilane was employed to modify diatomite, which was then combined with polyurethane-modified epoxy resin to fabricate a series of filled composites with varying diatomite content. The influence of diatomite content on the mechanical properties, thermal properties, and insulation performance of the polyurethane/epoxy resin composites was investigated. Experimental results showed that, under the synergistic effect of polyurethane and diatomite, the composite containing 4 wt.% diatomite exhibited improvements of 13.95% and 61.11% in tensile strength and flexural strength, respectively, compared to the epoxy resin. The elongation at break and flexural displacement also increased by 22.46% and 68.23%, respectively. Furthermore, the incorporation of diatomite effectively compensated for the thermal losses caused by polyurethane, enhancing thermal stability. Electrical property tests indicated that the addition of diatomite reduced the dielectric constant and conductivity of the epoxy resin while simultaneously improving its breakdown strength.

Preparation of high-performance laminated glass interlayer by modifying epoxy resin composite polyurethane

Laminated glass has been widely used in glass curtain walls, windshields, and other structures due to its high safety, light weight, and aesthetics. The safety of polymer laminated glass depends on the performance of the polymer between the glasses. Polyurethane elastomer (PU) has become a universal polymer material due to its excellent mechanical strength and toughness. The aliphatic thermoplastic polyurethane has attracted people's interest about its application in the field of laminated safety glass due to its transparency and adhesion. In this work, a polyurethane-modified epoxy (EK-PU) composite film with superior bonding strength, mechanical properties, and transparency was successfully achieved. The tensile strength of the PU composite film was confirmed to be 45 MPa, while the bonding strength was 4.73 MPa. The improvement is attributed to the change of microphase separation structure and the introduction of silicone. The excellent impact resistance of the laminated glass based on polyurethane composite film have been confirmed by the falling ball impact test, which is 6.5 times of the common PU film. The laminated glass based on the EK-PU film will be applied in aerospace, defense, and automotive fields.

Mechanical and adhesive properties of RTV silicone rubber blended with silicone polyurethane modified epoxy resin

To enhance mechanical, adhesive, and thermal properties of Room Temperature Vulcanized (RTV) silicone rubber, a silicon-containing polyurethane/epoxy resin modifier (ESiPU) was developed. A three-phase system of polyurethane/epoxy resin/silicone rubber was prepared through blending, modification, and co-curing. FT-IR and 1H-NMR were employed to characterize the chemical structure of ESiPU. Microscopic analysis revealed improved compatibility between modified epoxy resin and silicone rubber. Mechanical testing showed significant enhancements in tensile strength, elongation at break, and adhesive strength, with RTV-20phr exhibiting increases of 236, 266, and 259%, respectively. Thermogravimetric analysis indicated higher initial decomposition temperature compared to pure RTV. At the same time, the char residue at 800 °C increased to 8.67%. TG-IR analysis demonstrated ESiPU’s ability to delay thermal degradation. Contact angle test confirmed improved hydrophobicity. Overall, the developed silicone rubber system exhibits promising mechanical and thermal properties, suggesting potential for aerospace heat protection applications.

Study on preparation and properties of polyurethane modified epoxy resin lotion cementing slurry

To solve the problems of poor cementing quality and weak consolidation performance of deep-water shallow cementing cement, a low-temperature curable polyurethane-modified epoxy resin lotion (WER) was prepared with epoxy resin and polyurethane as raw materials, and its hydrophilic groups (carboxyl and ether bonds) were self emulsified. The results show that the modified WER lotion cement slurry has good fluidity and stability. Its thickening transition time is less than 16 min, which can effectively prevent gas channeling. In addition, its low-temperature mechanical properties have been significantly improved, and its compressive strength has increased by 42.4% and 44.5% compared to net slurry cement within 3 and 7 days, while its elastic modulus has decreased by 34.1% and 42.4%, respectively.

Preparation of Polyurethane-Modified Epoxy Coating Materials Based on Vegetable Oil Derivated Ester

This study utilize vegetable oil derivatives as a polyol in polyurethane. A modification of epoxy using polyurethane was done using ester derivative of vegetable oils as polyols, which was polyethylene glycol monooleate (PEGMO). The PEGMO was synthesized via an esterification reaction. The synthesis of polyurethane-modified epoxy using polyethylene glycol monooleate ester (PME-PEGMO) was conducted by reacting epoxy, tolonate and PEGMO. Analysis results of FTIR and H-NMR showed a new absorption peak derived from the urethane bond. The mechanical and thermal properties were characterized by a universal testing machine (UTM) and thermogravimetry analysis (TGA), respectively. According to the analysis results, it is shown that the addition of polyethylene glycol monooleate ester-based polyurethane on epoxy improved the mechanical properties of the epoxy, from 69.61 kgf/cm2 to139.80 kgf/cm2. However, it decreased the thermal stability of the epoxy. At 500°C, the mass of epoxy was remaining 28%, while the PME-PEGMO was only 13%.
 
 

An epoxy-modified polyurethane composite coating with repetitive self-healing function for anti-cavitation, anticorrosion, and antifouling applications

Erosion and fouling are important factors that affect the performance of power components of large cargo ships. Inspired by animal cartilage tissue, an epoxy modified polyurethane composite coating (FD-EPU) with reproducible self-healing properties was successfully prepared. FD-EPU was endowed with excellent resistance to cavitation, corrosion, and fouling due to the presence of functional reduced graphene oxide (FrGO) and 2-octyl-4,5-dichloroisothiazolinone (DCOIT). The introduction of FrGO with multiple hydrogen bonds into coatings increased the tensile strength of FD-EPU by 3.56 MPa and exhibited excellent cavitation resistance (with a mass loss of 4.7 mg under continuous cavitation for 60 h). In addition, the barrier effect of FrGO enabled FD-EPU to possess outstanding anticorrosion ability. After being immersed in 3.5 wt% NaCl for a duration of 15 days, the |Z|0.01Hz value of FD-EPU was found to remain at 9.18 × 109 Ω·cm2. The modification of epoxy resulted in FD-EPU coatings with improved adhesion by 53.5 % compared to non-modified coatings, with a bond strength of 23.8 MPa on stainless steel. The incorporation of DCOIT and FrGO endowed FD-EPU with good antifouling properties (removal of more than 97.5 % of bacteria and removal rate of microalgae up to 96.2 %). Furthermore, FD-EPU exhibited outstanding opto-thermal self-healing capability, with a self-healing efficiency of 61 % after 30 s of near-infrared light irradiation. This work provides a new inspiration for the protection of large cargo ship power components.

Improving activity and barrier properties of epoxy modified polyurethane coating with in-situ polymerized polypyrrole functionalized graphene oxide

The limited dispersibility and lack of active anti-corrosion properties of graphene oxide (GO) have hindered its application in corrosion resistance. In this study, we graft the corrosion inhibitor benzotriazole (BTA) on the surface of GO to achieve pH response release, providing active corrosion protection for epoxy modified polyurethane (EP-PU) coating. An environmentally friendly composite material with a sandwich-like structure was synthesized by in-situ polymerization of pyrrole to improve GO dispersion and prevent rapid release of BTA. The electrochemical impedance spectroscopy (EIS) shows that adding 0.15% GBP enhances the coating's anti-corrosion performance. The dual functions of passive and active corrosion enable the GBP/EP-PU coating to provide long-term corrosion protection for metal substrates.

Eco-Friendly Epoxy-Terminated Polyurethane-Modified Epoxy Resin with Efficient Enhancement in Toughness

Polyurethane is widely used to toughen epoxy resins due to its excellent comprehensive properties and compatibility. However, some demerits of polyurethanes limit their applications, such as the harsh storage condition of isocyanate-terminated polyurethane (ITPU), the limited amount of ITPU in epoxy resin, and using solvents during the preparation of polyurethane-modified epoxy resins. To address these issues, in this study, we reported a facile and green approach for preparing epoxy-terminated polyurethane (EPU)-modified epoxy resins with different EPU contents. It was found that the toughness of the epoxy resin was significantly improved after the addition of EPU. When the EPU content was 30 wt%, the elongation at break and toughness were improved by 358.36% and 73.56%, respectively. In comparison, the toughening effect of EPU outperformed that of ITPU. Moreover, the high content of EPU did not significantly decrease the glass transition temperature and had little effect on the thermal stability of the epoxy resin.

Synthesis of epoxy resin-based aqueous polyurethane and application to polyester-cotton fabric finishing

In this work, epoxy resin (EP)-based aqueous polyurethane (PU) anionic PU dispersion was synthesized by the prepolymer and self-emulsification method. The PU prepolymer was first synthesized to serve as seeds. Then, trimethylolpropane and A-type EP (E-51) were introduced into it, followed by neutralization and emulsification reactions, and, finally, it formed a crosslinking network structural waterborne PU emulsion. The effect of epoxy contents on the particle size, rheological properties, storage stability, thermal stability, mechanical properties, and hydrophilicity of the resulting PU films was systematically investigated. The results showed that the PU dispersions displayed excellent storage stability and crosslinking density, and the glass transition temperature of the composite films was increased. The properties of self-made epoxy-modified polyurethane emulsion and polyester-cotton fabric before and after finishing were tested. The wrinkle resistance, hydrophobicity, and strength of the finished polyester/cotton fabric are improved, and it exhibits better color fastness to washing and rubbing.

Performance Research and Formulation Optimization of High-Performance Local Insulation Spray Coating Materials.

Bird pest control has become a major task for the operation and maintenance of distribution network lines. Epoxy resin that cures quickly at room temperature can be used to coat locations where birds frequently build their nests. However, epoxy resin has enormous internal stress and is brittle, so it is essential to toughen it. In this paper, for a room temperature curing system composed of polyurethane-modified epoxy resin and a polythiol curing agent, three kinds of particles, i.e., Al2O3, SiO2, and Mg(OH)2, were used to modify a polyurethane modified epoxy resin. Orthogonal experiments were designed to study the effects of different fillers on the comprehensive properties of polyurethane-modified epoxy resins. The experimental results showed that there were not only independent effects of different kinds if particles on the resin, but also synergistic effects of multiple particles. Nanoparticles can reduce the defects introduced by microparticles to a certain extent and improve the mechanical and electrical properties of the resin. The overall performance of the resin was optimized when the amounts of SiO2, Al2O3, and Mg(OH)2 were 1.7%, 2.5%, and 7%, respectively. The tensile strength of the resin was increased by 70%, the elongation at a break by 67.53%, and the breakdown strength by 20.31% compared with before the addition of filler. The microscopic morphology and thermal properties of the resin before and after the addition of filler were also studied. Adding fillers caused more cracks to absorb part of the energy when the resin matrix was stressed and increased the rigidity of the resin matrix and the resin’s glass transition temperature (Tg) by 13.48 °C. Still, the temperature corresponding to the maximum rate of weight loss (Tmax) remained unchanged.

Low Viscosity Polyurethane Modified Epoxy Resin Grouting for Steel Ring Reinforcement of Subway Tunnel

Steel ring reinforcement technology is an effective method to eliminate the damage of tunnel structure caused by ground load, surrounding foundation pit and underground water source. The grouting material used to fill the gap between the tunnel segment and the steel ring should have the characteristics of low viscosity, high strength, rapid curing at room temperature and anti-subway vibration. In this work, a special polyurethane modified epoxy resin grouting was fabricated to overcome the inherent brittleness of epoxy resin, and was combined with the reactive diluent and the amine curing agent to suit the above applications. The results showed that both tensile and impact strength of epoxy resin grouting modified by polyurethane were improved obviously compared with those without modification, presenting an obvious toughening effect. Although the viscosity increased slightly, it can still meet the perfusion requirements of steel ring reinforcement of subway tunnels.

Effect of reaction time on the molecular weight distribution of polyurethane modified epoxy and its properties

This paper studied the synthesis of polyurethane modified epoxy via simultaneous reaction by varying the reaction time to 30, 60, and 90 min. The polypropylene glycol and tolonate as polyurethane components were reacted simultaneously with epoxy in the presence of catalyst dibutyltin dilaurate without prepolymer polyurethane first. The effect of various reaction times on polyurethane modified epoxy (PME) properties was studied by analyzing molecular weight distribution, viscosity, epoxy equivalent weight, pot life, dry-to-touch time, elongation at break, tensile strength, and compared to the unmodified epoxy. The various reaction time processes of polyurethane-modified epoxy tend to increase the molecular weight and influence the molecular weight distribution of PME. It indicated that the reactivity polymerization of epoxy resin with polyurethane component increased with reaction time. Furthermore, these properties affect other properties, i.e., viscosity, epoxy equivalent weight, pot life, and tensile strength increase.

Durability evaluation of mechanical and bonding properties of polyurethane-modified waterborne epoxy resin for road

ABSTRACT To further improve the application quality of the waterborne epoxy resin (WER) in road engineering, a variety of WER and polyurethane-modified WER were prepared. The WER was treated by acid solution immersion, alkali solution immersion, salt solution immersion, oil immersion or artificial-accelerated aging. The mechanical properties of the WER before and after the treatment by various methods were tested. Based on the ideal point method of entropy weight, the influence degree of each treatment method on the mechanical properties of the WER was analysed, and the mechanical properties decay and residual mechanical properties of the WER were evaluated. The bonding durability of the WER was analysed. The results show that after the xenon lamp aging treatment, the mechanical properties of the WER decreased most significantly. The mechanical durability of the WER modified by polyurethane is improved to a certain extent, and the retention rates of their mechanical properties are >85%. After treatment by various corrosion or aging methods, the retention rates of mechanical properties of the PUE-E44 WER are >89.29%, showing an improved corrosion and aging resistance. The residual mechanical and bonding properties of the PUD-E51 WER are at a high level, and still show improved mechanical and bonding properties.

Study on Epoxy Resin-Modified Asphalt Binders with Improved Low-Temperature Performance

Epoxy resin-modified asphalt binder (ERMAB) has been wildly used in the pavement of steel bridges, while the improvement on its low temperature is still a big challenge to researchers. This paper tries to improve the low-temperature performance of ERMAB by optimizing the modifier, epoxy resin. Firstly, three epoxy resins and three amine curing agents were prepared and used for the modification of asphalt binders. Secondly, the formula and prepared methods of ERMABs were optimized and determined through compatibility, viscosity growth rate, and tensile tests. Thirdly, an overall comparison on the phase structure, thermal stability, low-temperature performance, temperature and frequency dependence, and fatigue performance of prepared ERMABs and control sample were made. Results show that polyurethane-modified epoxy resin or dimer acid-modified epoxy resin, with a suitable curing agent, can significantly improve the low-temperature performance of ERMAB, and the curing time meets the construction requirements. Compared with the control sample, the two ERMABs have basically the same rheological properties at medium temperature, but slightly worse high-temperature performance and fatigue resistance. The significance of this paper lies in proposing a feasible way to improve the low-temperature performance of ERMAB.

Poly(amidoamine) dendrimer-grafted carbon nanotubes as a hybrid multifunctional curing agent for epoxy-modified polyurethane

Carbon nanotube (CNT) grafted with hyperbranched poly(amidoamine) (PAMAM) dendrimer (CNTD) were used as a multifunctional curing and composite agent of polyurethane (PU) terminated with epoxy units. Amino-functionalized CNT was used as the core for grafting the first generation of PAMAM dendrimer by sequential addition of methyl acrylate and ethylenediamine. Two different epoxy-terminated PUs (PUB and PU-PMDA) were prepared from the reaction of poly(ethylene glycol), excess amounts of hexamethylene diisocyanate, and different chain extenders (1,4-butanediol for PUB and pyromellitic dianhydride (PMDA) for PU-PMDA), and subsequent end group transformation of the isocyanate groups to epoxy functionalities using glycidol. Fourier transform infrared spectra and thermogravimetric analysis (TGA) results showed that CNTD was successfully prepared. TGA thermograms revealed that thermal decomposition of composites were carried out in two main steps related to the soft and hard segments. In addition, char content and thermal stability of the composites were increased with increasing the CNTD content. Most importantly, the PMDA chain extender resulted in high thermal stability of the epoxy-terminated PU composites. X-ray diffraction and scanning and transmission electron microscopies presented morphological and structural properties of nanotubes and hybrid composites.

Internal stress analysis of epoxy adhesively‐boned joints based on their thermomechanical properties at cryogenic temperature

AbstractInternal stress analysis is essential to structural design of materials applied in cryogenic engineering. In this contribution, thermomechanical properties including dynamic thermomechanical properties and thermal expansion behavior of four epoxy resins, namely the polyurethane modified epoxy resin (PUE), diglycidyl ether of bisphenol A (DGEBA), tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) and triglycidyl‐p‐aminophenol (TGPAP) were studied by dynamic thermomechanical analysis. Internal stress of the epoxy layer in the bonded joint was calculated based on the thermomechanical properties. Meanwhile, the structure‐cryogenic property relationship of epoxy resins were investigated. Results demonstrate that internal stress in the four epoxies bonded joints is 6 ~ 21 MPa at −150°C, and is positively correlated with the average thermal expansion coefficient (CTE) of epoxy resins. TGDDM and TGPAP showed higher retention of lap shear strength both at −196°C and after temperature cycling due to their lower CTE. Morphology of the fractured surface of bonded joints demonstrated that internal stress is responsible for the severe interface failure at −196°C. It reveals that selection of epoxy resins with low CTE is beneficial for designing high‐performance epoxy adhesive systems served at cryogenic temperature.

Flexible thin microwave absorbing patch: flake carbonyl iron and chopped carbon fibers oriented in resin matrix

Microwave absorbing patches are used in a wide range of applications including mobile devices, digital devices and electronic products. Here, we used flake carbonyl iron (FCI) and chopped carbon fibers (CF) as double absorbers to fabricate thin microwave absorbing patches by tape-casting method. FCI and CF were oriented in polyurethane-modified epoxy resin (PMER) matrix, resulting in strong anisotropy of the microstructure. The effects of CF content (from 0 to 0.3 wt%) on thermal stability, electromagnetic properties and microwave absorbing properties were investigated. The prepared patches exhibit good flexibility, and the addition of CF is beneficial to enhance the thermal stability of composites. A suitable amount of CF can reduce the thickness of absorber and broaden the absorption bandwidth. The oriented FCI/CF/PMER composite containing 60 wt% FCI and 0.3 wt% CF shows a wide absorbing bandwidth of 11 GHz (RL < − 5 dB) with a thickness as thin as 0.7 mm. Excellent microwave absorbing properties with a thin thickness are ascribed to the synergistic effect of dual absorbents, multiple interface polarization, balanced impedance match and structural anisotropy in the composites. These provide an effective idea to tune the peak frequency of RL and absorbing bandwidth.

Hydraulic Abrasion-Resistant Elastic Epoxy Resin Materials

The abrasion of hydraulic concrete structures caused by the washing action of flowing water is a common problem and cannot be solved by simply increasing the strength of the concrete. To ensure safe operation, increase in service life and reduction of maintenance costs of hydraulic concrete structures and the development of abrasion-resistant materials are required. In this work, polyurethane-modified epoxy resin was synthesized using the interpenetrating network technology (IPN). After many mixing experiments, the ratio of polyether amine to alicyclic amine in Component B was determined to be 29 : 14 and the ratio of Component A to Component B was 7 : 3. With these ratios, elastic epoxy achieved a tensile strength of more than 15 MPa and an elongation rate of more than 20%, thus balancing strength and toughness. The effects of the curing conditions, the ratio of Component A to Component B, and diluents and fillers on tensile strength and elongation of the elastic epoxy resin were analyzed. The results of the analysis indicated that the curing duration should be over 7 days, the optimal proportion of Component A to Component B should be 7 : 3, and the diluent of the elastic epoxy material should be the bifunctional butanedioldiglycidyl ether (622). The reliability of this material was determined by pull-out testing, adhesion, and tensile strength testing. The underwater steel ball test and ring test were adopted as the abrasion-resistance tests for the elastic epoxy resin material. The results showed that the abrasion-resistance performance of elastic epoxy coating improved hundreds of times over that of common concrete. Although the wearing strength was reduced with pressure, the elastic epoxy coating still retained excellent abrasion-resistance performance. At last, future application prospects of elastic epoxy improvement products are introduced and need further reach.

Effect of the stoichiometric ratio on the crosslinked network structure and cryogenic properties of epoxy resins cured at low temperature

Recently, epoxy resins with outstanding cryogenic performance have attracted much attention for low-cost space exploration. Since the structure-property relationship is the foundation of materials design, the present study investigates the effect of the stoichiometric ratio of active-hydrogen to epoxy-group ([H]/[E]) on the crosslinked network structure and cryogenic properties of a polyurethane modified epoxy resin (PUE). The average molecular weight (Mc) and integrity of the crosslinked network structure in PUE thermosets are studied by dynamic mechanical analysis and FTIR. Cryogenic properties including the coefficient of thermal expansion (CTE) and tensile properties of all PUE thermosets are determined. The results show that increasing the [H]/[E] stoichiometric ratio from 0.7 to 1.3 can decrease the Mc of PUE thermosets cured at low temperature. The crosslinked network structure of PUE thermosets with lower Mc possesses smaller CTE. The tensile strength of the thermosets at 77 K is increased to about 105 MPa when the [H]/[E] stoichiometric ratio reaches 1.3. And appropriately excessive content of curing agent is necessary to get optimum mechanical properties at RT and 77 K for these low-temperature cured PUE thermosets. Finally, the influence of the [H]/[E] stoichiometric ratio on the fracture mechanism of PUE thermosets is discussed in terms of the morphological characteristic of the propagation zones on the fracture surface of the tensile samples as well.

Synthesis of Polyurethane/Silica Modified Epoxy Polymer Based on 1,3-Propanediol for Coating Application

Studies on the synthesis of polyurethane/silica modified epoxy polymer using 1,3-propanediol has been conducted. Synthesis of polymers made by reaction of tolonate and 1,3-propanediol (ratio NCO/OH=2.5) as the building blocks of polyurethane with diglycidyl ether bisphenol A (DGEBA) epoxy and catalyst dibutyltin dilaurate (DBTL).The total weight of the polyurethane used was 20% (w/w) of the total epoxy. Based on Fourier Transform Infrared (FTIR) and 1H-Nuclear Magnetic Resonance (1H-NMR) spectra indicated the existence of a new bond that is formed from the reaction of isocyanate group and hydroxyl group, where the hydroxyl groups derived from epoxy and 1,3-propanediol. The addition of silica (5, 10, and 15% w/w to epoxy) into the epoxy-modified polyurethane has been carried out through sol-gel reaction of tetraethyl orthosilicate (TEOS). The isocyanate conversion rate for the addition of silica 5, 10, and 15% are 95.69; 100, and 100%, respectively. The morphology and element identification by Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis (SEM/EDX), showed that Si element has been successfully added in the polymer. From the tensile strength and elongation analysis, also thermal stability analysis using Thermal Gravimetric Analyzer (TGA), the increase of silica amount into the polyurethane modified epoxy did not significantly affect to thermal properties, but decrease the tensile strength of the polymer.