Epoxy-terminated Polyurethane Research Articles

Co-enhancement of toughness and strength of room-temperature curing epoxy adhesive derived from hydroxyl-terminated polybutadiene based polyurethane resin

Incorporation of flexible chains into epoxy adhesives facilitates toughening but usually poses an opposite effect on strengthening. Herein, by combining hydroxyl-terminated polybutadiene (HTPB) with polyether diol as soft chains, epoxy-terminated polyurethane (EHTPU) is synthesized, a strategy balancing strengthening and toughening is developed. The use of polyolefin soft chains substantially contributes to sea-island phase separation for maintaining low glass transition temperature (Tg) and high strength and toughness simultaneously. Specifically, the modified epoxy adhesive has seen a significant increase in shear strength to 19.75 MPa, tensile strength to 48.25 MPa and fracture toughness to 3.63 MPa·m1/2, with increment of 914 %, 268 %, and 149 %, respectively, compared to neat epoxy. Moreover, even under low temperatures of -45 °C, the modified epoxy resin can still maintain a high shear strength, demonstrating excellent low-temperature adhesion performance. At the same time, the incorporation of EHTPU does not significantly affect the overall thermal stability of the epoxy resin, meeting the requirements for stability in practical applications. It is worth mentioning that the adhesive exhibit excellent bonding performance under different environments and substrates, indicating that this composite material has broad application prospects in various industrial fields. These findings provide valuable insights into optimizing the performance of epoxy resins by controlling the introduction of specific modifiers and offer new ideas and methods for the development of room temperature curing epoxy resin adhesives.

Development and characterization of anti-cracking epoxy asphalt for steel deck pavement

Despite being commonly utilized in long-span steel deck pavement, epoxy asphalt continues to encounter certain obstacles, including excessive strength and insufficient resistance to cracking. This study proposed a novel approach to incorporating epoxy-terminated polyurethane prepolymers (ETPU) as a toughener to prepare an anti-cracking epoxy asphalt binder. The reaction process, viscosity-time behavior, tensile properties, and dynamic mechanical features of the ETPU-modified epoxy asphalt binder were comprehensively evaluated through a series of tests. Additionally, the fundamental pavement performance, fracture resistance, and fatigue resistance of ETPU-modified epoxy asphalt mixtures were thoroughly assessed. The addition of ETPU can significantly enhance the damping properties of epoxy asphalt, while maintaining its strength and construction retention time without any significant compromise. The formation of a chemical bond between epoxy-amine molecules and asphalt molecules significantly enhanced the compatibility between the epoxy resin phase and asphalt, thereby improving its damping properties. Both the fracture resistane and the fatigue resistance of ETPU-modified epoxy asphalt mixtures were found to be superior to that of commonly used epoxy asphalt mixtures in engineering. The modification mechanism was ultimately derived through the integration of infrared spectral analysis, thereby presenting an economically viable and highly efficient toughening pathway for epoxy asphalt. Therefore, this study indicated a wide-ranging potential for application in the realm of steel bridge deck pavement.

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.

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.

Modification of carbon nanotube with poly(amidoamine) dendritic structures to prepare a multifunctional hybrid curing component for epoxidized polyurethane and novolac resins

Dendritic poly(amidoamine) (PAMAM)-grafted carbon nanotube (CNTD), as a multifunctional hybrid curing component of epoxy-based resins, was prepared using a divergent method. Amino-functionalized CNT was utilized as a core for grafting the first generation of PAMAM dendritic structure by sequential addition of methyl acrylate and ethylenediamine. Epoxy-terminated polyurethane (EPU) and epoxidized novolac resin (ENR) were prepared and used as the epoxy-based polymers of the hybrid composite products. Proton nuclear magnetic resonance spectroscopy was used to study the structure of EPU. Fourier transform infrared spectra were used to prove each of the modification steps during preparation of CNTD. The characteristic peaks of CNTD at 1532 cm−1 originating from combination of stretching and bending vibrations of C–N and N–H bands, respectively, and the peaks at 2930 and 2859 cm−1 assigned to the stretching vibrations of C-H band of methylene groups confirms this claim. In addition, different char residues of CNT and CNTD in thermogravimetric analysis (TGA) curves confirmed addition of the organic parts and successful preparation of CNTD. Structural properties of the hybrid composites were investigated by X-ray diffraction analysis. The hard and soft segment contents of 34.46 and 65.54 wt% were obtained from X-ray diffraction curves. Char contents of 89.6 and 85.6% at 700 °C for the CNT and CNTD shows that the PAMAM modifier content is about 4 wt%. TGA thermograms of the hybrid composites revealed that thermal characteristics of the hybrid composite composed of ENR matrix and high content of CNTD are higher than the other hybrid composites. The ENR-based hybrid composite with 4 wt% of CNTD showed the highest char residue of 55.2% and degradation peak point of 413.6 °C. Morphology of the neat and PAMAM-modified nanotubes were also studied by scanning electron microscopy and transmission electron microscopy.

Synthesis and application of a novel 5-hydroxymethyl resorcinol diglycidyl ether-terminated polyurethane

Epoxy resin containing active hydroxymethyl group, 5-hydroxymethyl resorcinol diglycidyl ether, was synthesized to produce 5-hydroxymethyl resorcinol diglycidyl ether-terminated polyurethane (ETPU1000). The synthesized epoxy resin is a small monomer molecule, and no polymer is produced during the synthesis process. A monomer contains one hydroxyl group, and more flexible polyurethane segments can be introduced into the main chain when synthesizing the epoxy-terminated polyurethane. The synthesis process of ETPU1000 was investigated by FT-IR spectroscopy. The disappearance of NCO peak in the FT-IR spectrum showed that diisocyanate has completely reacted to form ETPU1000. Then, a series of epoxy cured systems were prepared by changing the mass ratio of ETPU1000 and the diglycidyl ether of bisphenol A (DGEBA), and cured with 4,4'-diaminodiphenyl methane (DDM). The effect of the content of ETPU1000 on the thermal properties, mechanical properties and fracture morphology of epoxy cured systems were investigated. The results showed that when the DGEBA/ETPU1000 blends with 75 wt% ETPU1000, impact strength of the cured systems reached 29.6 kJ·m−2, which significantly increased by 176.6% compared to that of neat epoxy. Scanning electron microscopy (SEM) was used to observe the fracture surfaces of cured DGEBA/ETPU1000 blends, which showed obvious ductile fracture characteristics.

Sustainable production of polyurethane from castor oil, functionalized with epoxy- and hydroxyl-terminated poly(dimethyl siloxane) for biomedical applications

A sustainable method has been employed for the production of a biomedical material in an economical way. Among biomedical polymers, two mostly used polymers are silicones (PDMS) and polyurethanes (PU). PDMS can outperform other polymers due to its biocompatibility and flexibility, but its high cost became a major roadblock for many applications. PU can be produced from a variety of sustainable resources in a cost effective manner. In this work, vegetable oil-based PU is blended with PDMS to produce a biomedical material which can contribute to the economy and environment. In this method, siliconized epoxy-terminated polyurethanes (EPDMS) were prepared from castor oil, 4,4’ methylene-bis-(cyclohexyl isocyanate), glycidol, and hydroxy-terminated poly-(dimethyl siloxane) (HTPDMS). The properties of the resulting products were compared with virgin PU with a NCO/OH ratio of 1.2:1 and epoxy-terminated PU (EPU) with a polyol/diisocyanate/glycidol ratio of 1:3:3. The structural elucidation of PU, EPU, and EPDMS were carried out by FTIR and 1HNMR spectroscopic techniques. The effect of incorporation of siloxane and glycidol on the thermal properties of PU was analyzed by thermogravimetric analysis and differential scanning calorimetry analysis. The improved hydrophobicity of the EPDMS was observed from water contact angle measurements. The surface morphology was examined using atomic force microscopy analysis. In vitro cytotoxicity analysis revealed the cytocompatibility of the EPDMS which makes them suitable for biomedical applications.

Influence of diisocyanate, glycidol and polyol molar ratios on the mechanical and thermal properties of glycidyl-terminated biobased polyurethanes

A series of epoxy terminated polyurethanes (EPUs) were synthesized from castor oil, 4, 4’methylene bis (cyclohexyl isocyanate) (H12MDI) and 2,3 epoxy-1-propanol (glycidol) by changing the molar ratio of H12MDI: glycidol to polyol. FTIR, 1HNMR and solid state 13C CP/MAS NMR spectroscopy analysis revealed the presence of epoxy linkages within the polyurethane (PU) backbone. Thermogravimetric analysis (TGA) shows that, EPU4 with a polyol: diisocyanate: glycidol molar ratio of 1:6:6 exhibited an initial decomposition temperature of 128 °C, which was 26 °C higher than that of EPU1 (1:3:3 molar ratio). Differential scanning calorimetry (DSC) shows an upward shift in the glass transition temperature (Tg) with increasing molar ratio. Mechanical analysis demonstrated that the tensile modulus of EPU4 was found to be 7.8 times greater than that of the EPU1. The crosslinking densities of EPUs were determined by swelling studies which revealed a gradual increment in the crosslinking density with increasing epoxy content within the PU. The surface morphology of cryo-fractured surfaces of EPUs were determined through scanning electron microscopy (SEM) to analyze the phase dispersion of epoxy and PU.

Guanidine hydrochloride embedded polyurethanes as antimicrobial and absorptive wound dressing membranes with promising cytocompatibility

Preparation and assessments of novel absorptive wound dressing materials with efficient antimicrobial activity as well as very good cytocompatibility were described in this work. An amine terminated poly(hexamethylene guanidine hydrochloride) was prepared and used as curing agent of different epoxy-terminated polyurethane prepolymers. The structures of prepared materials were elucidated by evaluation of their 1H NMR and FTIR spectra. The recorded tensile strength of membranes confirmed the excellent dimensional stability of the film type dressings even at fully hydrated conditions. Therefore, these dressings could protect the wound bed from external forces during the healing period. The structurally optimized dressing membranes could preserve the desired moist environment over the wounded area, as a result of their balanced equilibrium, water absorption and water vapor transmission rate. Therefore, a very good condition for stimulation of self-healing of wound bed was attained. Also, owing to the presence of guanidine hydrochloride moieties embedded into the structure of dressings, efficient antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans were detected. In vitro cytotoxicity assay of the prepared dressings revealed cytocompatibility of these materials against fibroblast cells. Therefore, they could support cell growth and proliferation at the wounded area.

Synthesis and properties of high-solids hybrid materials obtained from epoxy functional urethanes and siloxanes

Abstract In this work series of novel high-solids crosslinked hybrid networks based on the epoxy-terminated polyurethane prepolymer and the comb-like structure co-poly(dimethyl)(methyl, 3-glycidoxypropyl)siloxane cured with diethylenetriamine, were obtained. The viscosity lowering of epoxy-terminated polyurethane prepolymer with temperature allowed for the preparation of the hybrid systems without using of any solvent. The structure of the obtained poly(urethane–siloxane) thermosets was confirmed by FT-IR spectroscopy. The DSC studies reveal, that the addition of siloxane resulted in the decrease of the glass transition temperature of the hybrid materials. The synthesized poly(urethane–siloxane) networks are hydrophobic, with the free surface energy of 17–31 mJ/m 2 . An increased amount of siloxane resulted in an increase of water contact angle and decrease of degree of water absorption as well as of FSE, which confirms a hydrophobic nature of the employed siloxane. Some properties of obtained hybrid materials based coatings were also studied.

Preparation and characterization of novel antibacterial castor oil-based polyurethane membranes for wound dressing application

Preparation of novel antibacterial and cytocompatible polyurethane membranes as occlusive dressing, which can provide moist and sterile environment over mild exudative wounds is considered in this work. In this regard, an epoxy-terminated polyurethane (EPU) prepolymer based on castor oil and glycidyltriethylammonium chloride (GTEAC) as a reactive bactericidal agent were synthesized. Polyurethane membranes were prepared through cocuring of EPU and different content of GTEAC with 1,4-butane diamine. The physical and mechanical properties, as well as cytocompatibility and antibacterial performance of prepared membranes were studied. Depending on their chemical formulations, the equilibrium water absorption and water vapor transmission rate values of the membranes were in ranges of 3-85% and 53-154g m(-2) day(-1), respectively. Therefore, these transparent membranes can maintain for a long period the moist environment over the wounds with low exudates. Detailed cytotoxicity analysis of samples against mouse L929 fibroblast and MCA-3D keratinocyte cells showed good level of cytocompatibility of membranes after purification via extraction of residual unreacted GTEAC moieties. The antibacterial activity of the membranes against Escherichia coli and Staphylococcus aureus bacteria was also studied. The membrane containing 50% GTEAC exhibited an effective antibacterial activity, while showed acceptable cytocompatibility and therefore, can be applied as an antibacterial occlusive wound dressing.

Synthesis and evaluation of novel absorptive and antibacterial polyurethane membranes as wound dressing

Preparation and evaluation of new polyurethane membranes for wound dressing application was considered in this work. The membranes were prepared through amine curing reaction of epoxy-terminated polyurethane prepolymers and an antibacterial epoxy-functional quaternary ammonium compound (glycidyltriehtylammonium chloride, GTEACl. To render the prepared membranes to be highly absorptive of wound exudates, poly (ethylene glycol) polyols were introduced into the polyurethane networks. Evaluation of biocompatibity via both MTT assay and direct contact with two different cell lines (fibroblast and epidermal keratinocytes) reveled that membranes with appropriate loading of GTEACl showed proper biocompatibility. Promising antibacterial activity of the prepared membranes against Staphylococcus aureus and Escherichia coli bacteria was confirmed by both agar diffusion and shaking flask methods. The membranes with balanced crosslink density and ionic groups' concentration possessed appropriate hydrophilicity and water vapor transmission rate; therefore, they could prevent the accumulation of exudates and decrease the surface inflammation in the wounded area.

Epoxy Modified Polyurethanes Coated High Modulus Carbon Fiber: Synthesis and Properties Studies

With toluene 2, 4-diisocyanate (TDI), polyethylene glycol (PEG) and 2,3-Epoxy-1-prop -anol (glycidol) used as the raw materials, two epoxy terminated polyurethanes (EPU) was synthesized by prepolymerization and closed end. Moreover, EPU with high toughhess is chosen as a coating agent for carbon fiber with three ethylene tetramine (TETA) as curing agen. The influence of the content of crosslinking agent in the coating layer on properties of composites and the mechanism of interface toughness are investigated. The chemical structure and thermal property of the EPU were studied with FTIR, 1HNMR and TGA, respectively. It proves that the thermal stability of EPU is more stable than epoxy coating. The interlaminar shear strength (ILSS) of the sized high modulus carbon fiber/epoxy composites is improved to 71MPa, which increased by 19.4% compared with the composites reinforced by unsized high modulus carbon fiber, and DMTA show that using EPU as a new kind of polymer coating for carbon fiber is a feasible method to improve the interfacial performance of high modulus carbon fiber/epoxy composites.

Synthesis, Characterization and Preliminary Investigation of Blood Compatibility of Novel Epoxy-modified Polyurethane Networks

To prepare elastomers with acceptable physical properties and good blood compatibility, polyurethane networks were synthesized via crosslinking reaction of epoxy-terminated polyurethane prepolymers (EUPs) and hexamethylene diamine. EUPs were prepared by reacting glycidol and NCO-terminated polyurethanes. All new materials were characterized by conventional spectroscopic methods and properties were evaluated and correlated to their structure. Cytotoxcicity evaluation for the films of samples based on mouse fibroblasts (L929) revealed that these elastomers posed no threat to these cells. In vitro platelet-rich plasma contact test showed reduced number of adhered platelets on the surface of the films, particularly for those with maximum crystallinity and microphase structures and high hydrophilicity. The results obtained implied the potential for the utilization of these elastomers in biomedical applications.

Preparation and properties of novel biodegradable polyurethane networks based on castor oil and poly(ethylene glycol)

Polyurethane networks based on castor oil (CO) as a renewable resource polyol and poly(ethylene glycol) (PEG) with tunable biodegradation rates as potential candidates for biomedical implants and tissue engineering were synthesized through the reaction of epoxy-terminated polyurethane prepolymers (EPUs) with 1,6-hexamethylene diamine curing agent. EPUs themselves were prepared from reaction of glycidol and isocyanate terminated polyurethane prepolymers made from CO or PEG and 1,6-hexamethylene diisocyanate. All of the polymers were characterized by conventional methods, and their physical, mechanical and viscoelastic properties were studied. The results showed that the degradation rate and mechanical properties of final products could be controlled by the ratio of PEG or CO based EPUs in the final products. Increasing the PEG based EPU content caused an increase in hydrolytic degradation rate and mechanical properties. Evaluation of the L-929 fibroblast cells' interaction with prepared polymeric films showed nontoxic behavior and good cytocompatibility.

Synthesis, characterization and properties of novel thermally stable poly(urethane-oxazolidone) elastomers

Oxazolidone-incorporated polyurethane elastomers based on hydroxyl terminated polycaprolactone, were synthesized and characterized. Reaction of epoxy-terminated polyurethane with isocyanate librated from a blocked polyisocyanate was the strategy followed. The reaction condition was optimized through preparation of model oxazolidones. Epoxy-terminated polyurethanes were prepared from reaction of glycidol with NCO-terminated polyurethane prepolymers and curing agent was synthesized from the reaction of trimethylol propane, toluene diisocyanate and N-methyl-aniline. Incorporation of heterocyclic oxazolidone groups into the polyurethane backbone caused improvements in thermal and mechanical properties. Investigation of structure-property relationship for prepared elastomers showed that the main determining factors for observed properties were crosslink density, crystallinity and content of oxazolidone rings.