Tribological performance and thermal behavior of epoxy resin nanocomposites containing polyurethane and organoclay

A series of epoxy resin nanocomposites modified by polyurethane and organically modified montmorillonite was prepared by effectively dispersing the organically modified montmorillonite in interpenetrating polymer networks (IPNs) of epoxy and polyurethane via the sequential polymeric technique and in situ polymerization. The tribological performance of the resultant EP/PU nanocomposites was investigated by a pin‐on‐disc tester, and the results showed that adding polyurethane and organically modified clay to the EP matrix had a synergistic effect on improving tribological performance of EP/PU nanocomposites. The morphologies of the worn surface were studied by scanning electron microscopy (SEM) observations, and the results indicated that the mechanism of improving tribological performance of EP/PU nanocomposites was different from that of pure EP or pure EP/PU IPNs. The thermal behavior of these nanocomposites was also investigated by thermogravimeric analysis (TGA), and the results indicated that adding organically modified clay to the matrix remedied the deterioration of the thermal degradation temperature of the interpenetrating networks. Copyright © 2008 John Wiley & Sons, Ltd.     

Study on thermal properties of polyurethane nanocomposites based on organo-sepiolite

The effects of sepiolite modified with γ-aminopropyltriethoxylsilane (KH550-Sp) on thermal properties of polyurethane (PU) nanocomposites were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TG), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and tensile test. The DSC results showed that the glass transition temperature of hard segments in PU/KH550-Sp nanocomposite increased with the increase of KH550-Sp, because sepiolite restricted the formation of hydrogen bonding within hard segments of polyurethane. TG results revealed that the thermal stability of PU was improved by KH550-Sp, and the onset decomposition temperature for PU nanocomposites with a KH550-Sp content of 3 wt% was about 20 °C higher than that for pure PU. The tensile properties of pure PU and nanocomposites before and after ageing 120 °C for 72 h were determined, and it was observed that the percentage loss in tensile strength decreased with the addition of KH550-Sp because of an oxidation barrier of KH550-Sp confirmed by ATR-FTIR.     

Fabrication and characterization of polyurethane patch loaded with palmarosa and cobalt nitrate for cardiac tissue engineering

Cardiac patches are attractive option in overcoming the morbidities associated with cardiac disorders. Nanofibrous scaffolds were fabricated using polyurethane (PU) added with palmarosa (PR) and cobalt nitrate (CoNO₃) using an electrospinning technique. Several characterizations were employed namely field emission scanning electron microscopy, wettability measurement, attenuated total reflectance infrared spectroscopy, thermal analysis, surface roughness measurements, and tensile testing. Further, biological response of the electrospun nanofibers were tested through coagulation study and MTS assay. As-spun composite mats showed smaller fibers than pure PU as depicted in morphology analysis. The interaction of PU with PR and CoNO₃ was confirmed in infrared spectrum and thermal analysis. The incorporation of the PR decreased the wettability and while CoNO₃ addition resulted in the hydrophilic nature as depicted in the contact angle measurements. Mechanical properties testing showed that elongation at break for the pristine PU was increased with the addition of PR and CoNO_3. The surface measurements depicted that the incorporation of PR resulted in the improvement of the surface roughness while the addition of CoNO₃ reduced the surface roughness of the pristine PU. The electrospun nanocomposites showed delayed blood clotting time compared to the pristine PU as shown in coagulation study. Both composites supported the better proliferation of fibroblast cells than pure PU. Therefore, novel composites with smaller fiber diameter, hydrophilicity, better mechanical properties, improved blood compatibility parameters, and good cell viability rates would be a promising candidate for cardiac tissue engineering.     

Interpenetrating polymer networks of polyurethane and maleimide-terminated polyurethane for biomedical applications

Interpenetrating polymer networks (IPNs) of polyurethane (PU) and maleimide-terminated polyurethane (UBMI) were prepared by using a simultaneous polymerization technique. The effects of the UBMI molecular weight and amounts of the UBMI in the IPNs on the mechanical properties, dynamic mechanical properties, degree of compatibility, water absorption, surface properties and dynamic thrombosis were investigated. Bulk structure and surface properties were analyzed in order to correlate their blood compatibility. The IPNs exhibited a higher ultimate tensile strength especially when the UBMI with short soft chains was introduced. The heterogeneous characteristics were found for the IPNs when longer soft segment chains were incorporated in the PU component polymer. The presence of hydrophilic/hydrophobic alternative microdomains on the IPN surface was proposed to be the reason for good blood compatibility. The degree of compatibility, compositions of each domain and content of each domain in the matrix were calculated and correlated with the blood compatibility.     

Fabrication and characterization of a novel wound scaffold based on polyurethane added with Channa striatus for wound dressing applications

Abstract

Wound healing is a complex process and it involves restoration of damaged skin tissues. Several wound dressings comprising naturally made substances are constantly investigated to assist wound healing. In this research, a new wound dressing based on polyurethane (PU) supplemented with essence of Channa striatus (CS) fish oil was made by electrospinning. Morphological study depicted the reduction in fiber diameter than PU with the addition of fish oil (0.552?±?0.109?μm for 8:1 v/v% and 0.519?±?0.196?μm 7:2 v/v%) than the pristine PU (0.971?±?0.205?µm). Fourier transform infrared spectroscopy (FTIR) analysis revealed the presence of fish oil in the composite as identified through increasing peak intensity. Fish oil resulted in the hydrophilic behavior (88?±?3 (8:1 v/v) and 70?±?6 (7:2 v/v)) as revealed in the contact angle analysis. Thermal gravimetric analysis (TGA) showed the superior thermal behavior of the wound dressing patch compared to the PU. Atomic force microscopy (AFM) analysis insinuated a decrease in the surface roughness of the pristine polyurethane with the added fish oil. Coagulation assays signified the delay in the blood clotting time portraying its anti-thrombogenic behavior. Hemolytic assay revealed the less toxic nature of the developed nanocomposites with the red blood cells (RBC’s) depicting its safety with blood. Hence, polyurethane nanofibers supplemented with fish oil made them as deserving candidates for wound dressing application.     

Thermal,mechanical and electroactive shape memory properties of polyurethane (PU)/poly (lactic acid) (PLA)/CNT nanocomposites

Polymer blend nanocomposites based on thermoplastic polyurethane (PU) elastomer, polylactide (PLA) and surface modified carbon nanotubes were prepared via simple melt mixing process and investigated for its mechanical, dynamic mechanical and electroactive shape memory properties. Chemical and structural characterization of the polymer blend nanocomposites were investigated by Fourier Transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD). Loading of the surface modified carbon nanotube in the PU/PLA polymer blends resulted in the significant improvement on the mechanical properties such as tensile strength, when compared to the pure and pristine CNT loaded polymer blends. Dynamic mechanical analysis showed that the glass transition temperature (T_g) of the PU/PLA blend slightly increases on loading of pristine CNT and this effect is more pronounced on loading surface modified CNTs. Thermal and electrical properties of the polymer blend composites increases significantly on loading pristine or surface modified CNTs. Finally, shape memory studies of the PU/PLA/modified CNT composites exhibit a remarkable recoverability of its shape at lower applied dc voltages, when compared to pure or pristine CNT loaded system.     

Green synthesis of nickel oxide particles and its integration into polyurethane scaffold matrix ornamented with groundnut oil for bone tissue engineering

Physiochemical properties of the fabricated scaffolds play a crucial role in influencing the cellular response for the new tissue growth. In this study, electrospun polyurethane (PU) scaffolds incorporated with green synthesized nickel oxide nanoparticles and groundnut oil (GO) were fabricated using electrospinning technique. First, synthesis of nickel oxide (NiO) was done using leaf extract of Plectranthus amboinicus (PA) via microwave-assisted technique. Synthesized nanoparticles were confirmed through Energy-dispersive X-ray spectroscopy (EDX) analysis and size of the particles were in the range of 800–950?nm. Fiber morphology of the fabricated scaffolds was analyzed using scanning electron microscope (SEM) which showed decrease in fiber diameter for the fabricated composites compared to the pristine PU. The wettability studies showed an increase in contact angle for developed composites than the pure PU. Thermal analysis depicted an increase in thermal behavior for the PU/GO/NiO compared to the pristine PU. Surface roughness values were obtained through atomic force microscopy (AFM) which showed a decrease in roughness while adding GO and NiO to the PU. Finally, the fabricated composites showed enhanced deposition of calcium content than the pristine PU. These results corroborated that the developed composites have a significant effect on the fiber morphology, wettability, thermal behavior, surface roughness, and mineral deposition depicting its versatility for bone regeneration.     

Application of Nano-Hydroxyapatite Derived from Oyster Shell in Fabricating Superhydrophobic Sponge for Efficient Oil/Water Separation

The exploration of nonhazardous nanoparticles to fabricate a template-driven superhydrophobic surface is of great ecological importance for oil/water separation in practice. In this work, nano-hydroxyapatite (nano-HAp) with good biocompatibility was easily developed from discarded oyster shells and well incorporated with polydimethylsiloxane (PDMS) to create a superhydrophobic surface on a polyurethane (PU) sponge using a facile solution–immersion method. The obtained nano-HAp coated PU (nano-HAp/PU) sponge exhibited both excellent oil/water selectivity with water contact angles of over 150° and higher absorption capacity for various organic solvents and oils than the original PU sponge, which can be assigned to the nano-HAp coating surface with rough microstructures. Moreover, the superhydrophobic nano-HAp/PU sponge was found to be mechanically stable with no obvious decrease of oil recovery capacity from water in 10 cycles. This work presented that the oyster shell could be a promising alternative to superhydrophobic coatings, which was not only beneficial to oil-containing wastewater treatment, but also favorable for sustainable aquaculture.     

Synthesis and characterization of a novel polyurethane/polypyrrole‐p‐toluenesulfonate (PU/PPy‐pTS) electroactive nanofibrous bending actuator

Electroactive actuators based on conductive polymers currently have attracted a great deal of attention. In this study, a nanofibrous structure of polypyrrole (PPy) was used to fabricate an electroactive bending actuator. For this purpose, polyurethane/PPy (PU/PPy) nanofibrous bending actuator was fabricated through the combined use of electrospinning and in‐situ chemical polymerization. The response surface methodology (RSM) was considered to find the optimal electrospinning conditions for producing PU nanofibers with the minimum diameter. The in‐situ chemical polymerization method was then used to prepare a conductive layer of PPy on the surface of optimum electrospun nanofibers with p‐toluenesulfonate (pTS) as the dopant. The coated nanofibers were used in the fabrication of PU/PPy‐pTS nanofibrous bending actuator. The morphology and electrical, thermal, electrochemical, and electrochemomechanical properties of the fabricated actuator were investigated. By using optimum conditions of electrospinning, PU nanofibers were obtained with a diameter of 221 nm. The results showed that the produced PU/PPy‐pTS nanofibers enjoy good thermal stability and have an electrical conductivity of about 276.34 S/cm. The obtained cyclic voltammetric and dynamo‐voltammetric responses showed that the dominant mechanism of actuation in the fabricated PU/PPy‐pTS nanofibrous actuator is the exchange of perchlorate anions with a partial exchange of lithium cations in 1M lithium perchlorate electrolyte solution. The fabricated actuator was capable of undergoing 141° reversible angular displacement during a potential cycle. The results demonstrated that, given high porosity, large specific surface area, flexibility, and desirable electrical properties, PU/PPy nanofibrous electroactive actuator provides a lot of potential for developing artificial muscle applications.     

Polymeric Nanocomposites of Polyurethane Block Copolymers and Functionalized Multi‐Walled Carbon Nanotubes as Crosslinkers

Summary: We report on a new route to synthesize polymeric carbon nanotube‐polyurethane (PU) nanocomposites. Multi‐walled carbon nanotubes (MWNTs) functionalized by chemical modification were incorporated as a crosslinker in prepolymer, which was prepared from a reaction of 4,4′‐methylene bis(phenylisocyanate) and poly(ε‐caprolactone)diol. The reinforcing effect of carbon nanotubes in crosslinked MWNT‐PU nanocomposites was more pronounced as compared to that in conventional MWNT‐PU nanocomposites. The optimum content of chemically modified MWNTs for crosslinking with polyurethane was determined to be approximately 4 wt.‐% in our samples, based on observation of a NCO peak in FT‐IR spectroscopy. MWNT‐crosslinked polyurethane containing 4 wt.‐% modified MWNTs showed the highest modulus and tensile strength among the composites and pure PU. The presence of functionalized MWNTs in the polymeric nanocomposite yielded enhancement in the thermal stability due to crosslinking of the MWNTs with PU.

Possible configuration for MWNT‐PU nanocomposite molecules and FT‐IR spectra of samples obtained during reaction of prepolymer with functionalized MWNTs (second step).     

Polyaniline-coated coconut fibers: Structure,properties and their use as conductive additives in matrix of polyurethane derived from castor oil

Electrically conducting fibers based on coconut fibers (CF) and polyaniline (PANI) were prepared through in situ oxidative polymerization of aniline (ANI) in the presence of CF using iron (III) chloride hexahydrate (FeCl_3.6H₂O) or ammonium persulfate (APS) as an oxidant. The PANI-coated coconut fibers (CF-PANI) displayed various morphologies, electrical conductivities and percentages of PANI on the CF surface. For both systems, a PANI conductive layer was present on the CF surface, which was responsible for an electrical conductivity of around 1.5 × 10⁻¹ and 1.9 × 10⁻² S cm⁻¹ for composites prepared with FeCl₃.6H₂O and APS, respectively; values that are similar to that of pure PANI. In order to modify the structure and properties of polyurethane derived from castor oil (PU) both CF-PANI and pure PANI were used as conductive additives. The PU/CF-PANI composites exhibited higher electrical conductivity than pure PU and PU/PANI blends. Additionally, the PU/CF-PANI composites showed a variation in electrical resistivity according to the compressive stress applied, indicating that these materials could be applied for pressure-sensitive applications.     

The potential of biomimetic nanofibrous electrospun scaffold comprising dual component for bone tissue engineering

Oils play a putative choice for alleviating various symptoms associated with bone-related disorders. In this present study, polyurethane (PU) scaffold encompassing with Mahua oil (MO) and propolis (PP) were developed using the electrospinning technique. Morphological analysis showed the reduction in the diameter of the electrospun scaffold with blending of MO and MO/PP into the PU matrix. The strong interactions between PU, MO, and PP were evident through the infrared spectrum and thermal analysis. The wettability results showed the hydrophobic nature in electrospun PU/MO scaffold and hydrophilic behavior in electrospun PU/MO/PP scaffold. Mechanical testing indicated the enhancement in the strength of the PU due to the addition of MO and PP. Moreover, the fabricated scaffolds exhibited nontoxicity, low hemoglobin release and improved blood clotting time as evident in the coagulation studies. The cell proliferation studies showed the enhanced fibroblast cell adhesion in the developed nanocomposites than the pristine PU. Hence, the fabricated PU scaffolds blended with MO and PP having desirable properties can serve as a valuable candidate for bone tissue repair.     

Natural and acid-treated attapulgite reinforced soybean oil-based polyurethane/epoxy resin interpenetrating polymer networks

Soybean oil-based polyurethane (PU)/epoxy (EP) interpenetrating polymer network (IPN) nanocomposites were prepared with natural attapulgite (N-ATT) and acid-treated attapulgite (A-ATT). The structure, glass transition, damping properties, thermal stability, mechanical properties and morphology of PU/EP IPN/ATT nanocomposites were characterized by X-ray diffraction (XRD), dynamic mechanical analysis (DMA), thermogravimetric analyzer, universal test machine and scanning electronic microscope (SEM). XRD showed that interaction with PU did not change the crystal structures of ATT. DMA results revealed the addition of ATT improved the glass transition temperature of the soybean oil-based PU/EP IPN, especially for A-ATT. However, the incorporation of ATT slightly decreased the damping properties of the soybean oil-based PU/EP IPN. Tensile tests confirmed that A-ATT had a significant reinforcement effect on the soybean oil-based PU/EP IPN. The tensile strength of the soybean oil-based PU/EP IPN increased by 56% with the addition of 4 mass% A-ATT. SEM demonstrated the relatively uniform dispersion of both N-ATT and A-ATT in the soybean oil-based PU/EP IPN matrix.

     

Production,blood compatibility and cytotoxicity evaluation of a single stage non-woven multicomponent electrospun scaffold mixed with sesame oil,honey and propolis for skin tissue engineering

Scaffolds used in skin tissue engineering must mimic the native function of the extracellular matrix (ECM) and facilitate the fibroblast cell response for new tissue growth. In this study, a novel dressing scaffold based on polyurethane (PU) with sesame oil, honey, and propolis was fabricated by electrospinning. Scanning electron microscopy (SEM) images showed that the diameter of the electrospun scaffolds decreased by blending sesame oil (784?±?125.46?nm) and sesame oil/honey/propolis (576?±?133.72?nm) into the PU matrix (890?±?116.911?nm). Fourier infrared (FT-IR) and thermogravimetric (TGA) analysis demonstrated the formation of hydrogen bonds and interaction between PU and sesame oil, honey, and propolis. Contact-angle measurement indicated reduced wettability of PU/sesame oil scaffold (114?±?1.732) and improved wettability (54.33?±?1.528) in the PU/sesame oil/honey/propolis scaffold. Further, tensile tests and atomic force microscopy (AFM) analysis indicated that the fabricated composite membrane exhibited enhanced mechanical strength and reduced surface roughness compared to the pristine PU. The developed composite displayed less toxicity to the red blood cells (RBC’s) compared to the pristine PU. Cytotoxicity assay showed enhanced cell viability of HDF in electrospun scaffolds than pristine PU after 72?h culture. These enhanced properties of the developed scaffolds suggest the potential of utilizing them in skin tissue engineering.     

Preparation and Flame Retardancy of Polyurethane/POSS Nanocomposites

Polyurethane/polyhedral oligomeric sisesquioxane (PU/POSS) nanocomposites were syn-thesized via polymerization utilizing the compatibility between POSS nanoparticles and 4,4'-diphenyl methylene diisocyanate. Scanning electron microscope images and Fouriertransform infrared spectra revealed that POSS nanoparticles were dispersed in PU matrix.Thermal gravimetric analysis was employed to investigate the thermal decomposition be-havior of PU/POSS nanocomposites at elevated temperatures. Then fire performance wasevaluated by limiting oxygen index, underwriters laboratories 94 testing and char residue morphology. These results showed that the addition of POSS promoted the formation of char residues which were covered on the surface of polymer composites, leading to the im-provement of thermal stability and flame retardancy.     

A novel approach to fluorinated polyurethane by macromonomer copolymerization

For the first time, through macromonomer radical copolymerization, a novel fluorinated polyurethane (FPU) was synthesized based on partly acrylate-endcapped polyurethane macromonomers with hexafluorobutyl acrylate (HFBA). Partly acrylate-endcapped polyurethane (PU) macromonomers were synthesized using isophronediisocyanate (IPDI), dimethylol propionic acid (DMPA), polyethylene adipate glycols (PEA) etc. The novel fluorinated polymer, which bore PU side chains and fluorinated side chains, was confirmed by F¹⁹ NMR spectroscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis, scanning electron spectroscopy (SEM) etc. Copolymerization of polyurethane macromonomers with hexafluorobutyl acrylate (HFBA) was briefly investigated. The surface tension of FPU solution was measured and showed sharply decrease compared to that of pure polyurethane. Results from SEM showed a uniform size distribution of phase micro-domains on the fracture surface of FPU.     

Surface modification of aluminum hypophosphite and its application for polyurethane foam composites

Aluminum hypophosphite (AHP) is surface modified by melamine derivative to fabricate reactive solid flame retardant (MCAHP) for polyurethane foam. MCAHP is successfully prepared and characterized by FTIR and SEM. The flame-retarded efficiency of MCAHP in PU is higher than that of AHP. It demonstrated that MCAHP has better compatibility in PU matrix compared with AHP based on the SEM observation. After surface modification, due to the reaction between MCAHP and PU matrix, crosslinking might be formed between MCAHP and PU matrix, which contributes to the excellent compatibility of MCAHP in PU matrix, and as a result, the glass transition temperature of PU/MCAHP is 4 °C higher than that of PU/AHP. The thermal behavior of PU composites is characterized by TG and TG-FTIR, and results suggest the sublimation of melamine at about 320 °C because of the decomposition of the melamine derivative. The sublimation of melamine can consume abundant heat and dilute the oxygen concentration, which is benefit for the improvement of flame retardancy.     

Dual Spinneret Electrospun Polyurethane/PVA-Gelatin Nanofibrous Scaffolds Containing Cinnamon Essential Oil and Nanoceria for Chronic Diabetic Wound Healing: Preparation,Physicochemical Characterization and In-Vitro Evaluation

In this study, a dual spinneret electrospinning technique was applied to fabricate a series of polyurethane (PU) and polyvinyl alcohol–gelatin (PVA/Gel) nanofibrous scaffolds. The study aims to enhance the properties of PU/PVA-Gel NFs loaded with a low dose of nanoceria through the incorporation of cinnamon essential oil (CEO). The as-prepared nCeO₂ were embedded into the PVA/Gel nanofibrous layer, where the cinnamon essential oil (CEO) was incorporated into the PU nanofibrous layer. The morphology, thermal stability, mechanical properties, and chemical composition of the produced NF mats were investigated by STEM, DSC, and FTIR. The obtained results showed improvement in the mechanical, and thermal stability of the dual-fiber scaffolds by adding CEO along with nanoceria. The cytotoxicity evaluation revealed that the incorporation of CEO to PU/PVA-Gel loaded with a low dose of nanoceria could enhance the cell population compared to using pure PU/PVA-Gel NFs. Moreover, the presence of CEO could inhibit the growth rate of S. aureus more than E. coli. To our knowledge, this is the first time such nanofibrous membranes composed of PU and PVA-Gel have been produced. The first time was to load the nanofibrous membranes with both CEO and nCeO₂. The obtained results indicate that the proposed PU/PVA-Gel NFs represent promising platforms with CEO and nCeO₂ for effectively managing diabetic wounds.     

Effects of organophilic montmorillonite on hydrogen bonding, free volume and glass transition temperature of epoxy resin/polyurethane interpenetrating polymer networks

Epoxy resin nanocomposites containing organophilic montmorillonite (oM) and polyurethane were prepared by adding oM to interpenetrating polymer networks (IPNs) of epoxy resin and polyurethane (EP/PU). The dispersion degree of oM in EP/PU matrix was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fourier transform infrared spectrometry (FT-IR) showed that strong interactions existed between oM and EP/PU matrix, and oM had some effect on hydrogen bonding of these EP/PU IPNs nanocomposites. Positron annihilation spectroscopy (PALS) and differential scanning calorimetry (DSC) measurements were used to investigate the effect of oM and PU contents on free volume and glass transition temperature (T_g) of these nanocomposites. The PALS and DSC results clearly showed that the presence of oM led to a decrease in the total fractional free volume, which was consistent with increasing T_g upon addition of oM, ascribed to increasing hydrogen bonding in interfacial regions of oM and EP/PU matrix and enhancing the miscibility between EP phase and PU phase. In addition, with increasing PU content, the total fractional free volume increased, corresponding to decreasing T_g.     

采用层层自组装与光化学修饰法在聚氨酯表面固定生物多糖衍生物

采用层层自组装技术与光化学修饰方法相结合在聚氨酯材料表面固定生物多糖衍生物,首先合成具有光反应活性的叠氮壳聚糖,再在聚氨酯基材表面进行叠氮壳聚糖与香菇多糖硫酸酯的层层自组装,然后通过光化学反应对自组装多层膜修饰层进行交联,制备得到生物多糖衍生物层层自组装与光化学表面修饰的聚氨酯材料.通过红外光谱、X射线光电子能谱、水接触角测量仪、抗菌活性测试、溶血试验和血小板黏附测试等方法对被修饰聚氨酯材料的表面性能和生物性能进行了分析,测试结果表明修饰后的聚氨酯材料表面的亲水性和血液相容性得到改善,并且被修饰材料对大肠杆菌具有良好的抑制效果.