Polyurethane Elastomer Films Research Articles

TiO2 nano-filler and ionic liquid-blended polyurethane elastomer films for enhanced antistatic applications

TiO2 nano-filler and ionic liquid-blended polyurethane elastomer films for enhanced antistatic applications

Back Cover: Excited State Charge‐Transfer Complexes Enable Fluorescence Color Changes in a Supramolecular Cyclophane Mechanophore (Angew. Chem. Int. Ed. 42/2022)

Mechanochromic mechanophores visualize stress applied to polymers. In their Communication (e202209225), Christoph Weder, Yoshimitsu Sagara et al. demonstrate the first cyclophane mechanophore utilizing charge–transfer complex emission. Polyurethane elastomer films in which the mechanophore is covalently embedded exhibit instantly reversible emission color change between orange and blue upon deformation. The spatial separation of the luminophore and quencher leads to vivid mechanochromic luminescence.

Surface wettability and strong adhesion of medical polyurethane elastomer porous films by microphase separation

Inspired by geckos and parthenocissus tricuspidata, bionic high-adhesive materials have attracted great attention in the fields of environmental protection, biomedicine and intelligent control. The key is how to select appropriate materials and preparation methods to design materials with strong adhesion similar to the geckos. In this paper, the polyurethane elastomer (PUE) porous films with medical grade were successfully prepared by microphase separation method, and the microstructure, surface wettability and adhesion were investigated. It was found that the growth parameters (such as relative humidity, concentration and curing time) had important effects on the microstructure and morphology of PUE films. After modification with 1-dodecanethiol, the contact angle on the surface of the PUE film increased from the pre-modification value of 80° to 165°, but the corresponding rolling angle remained constant. The honeycomb PUE porous films have specially strong adhesion similar to geckos and parthenocissus tricuspidata, which will be expected to apply to the medical domain such as used as the external plaster to ensure adequate contact with skin and also prevent the evaporation of drugs and water.

Super stretchable chromatic polyurethane driven by anthraquinone chromogen as a chain extender.

A novel polyurethane elastomer (PUE) that exhibited high tensile strength, large elongation at break, great color strength and supreme color fastness was successfully designed and synthesized. The PUEs were prepared with isophorone diisocyanate (IPDI) as hard segments, polycarbonate diol (PCDL)/polytetrahydrofuran glycol (PTHF) as mixed soft segments, and anthraquinone chromogen as the chain extender agent. The relationships between the mechanical properties/color performance and chromogen addition content were investigated. The chromogen actual access rate of the obtained BPUEs was evaluated by UV-Vis. The clear tortuous surface and entanglements were exhibited in PUEs micromorphology structure, indicating a significant reinforcement of mechanical properties. Elongation-at-break and tensile strength reached the maximum value 2394% at 1% (BPUE1) and 18.29 MPa at 5% (BPUE5), respectively, and then decreased as chromogen addition content increased. Mechanical testing results correlate well with XRD and SEM findings, which proved that anthraquinone chromogen induced an improvement in phase separation. Furthermore, BPUE films displayed high color strength and excellent color fastnesses. The rubbing fastness and washing fastness of BPUE1 and BPUE0.5 reached grade 5, respectively. These inspiring findings suggest that PUE films with superb performance have potential to be directly applied in the textile field.

Response to Applied Voltage to Polyurethane Soft Actuators with Loaded Weights

We are investigating a polymer soft actuator using a poly urethane elastomer film that bends by an applied voltage, which is based on the electrostriction. In this article, the bending magnitude was studied in a weight-loaded condition. It was found that the thinner film can bend the more without any load, but that the film of 200-μm thickness gave the largest bending when weights were loaded. The thickness of some degree is critical for large bending torque.

Electrode Effects on Polyurethane Soft Actuator

A polymer soft actuator is under investigation using a poly urethane elastomer film that bends by means of an applied voltage, which is based on the electrostriction. Bending experiments were performed under different metal electrodes deposited the both sides of the film. Even if the thickness of the both electrodes is the same, the metal of the both electrodes is desirable to be the same to bend more. It is suggested that the balance of the physical properties of the both metal is critical for larger bending.

Strain-induced molecular aggregation states around a crack tip in a segmented polyurethane film under uniaxial stretching

The development of molecular aggregation structures during stretching deformation and local structure mapping around a crack tip of a segmented polyurethane elastomer film were investigated by in situ simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) and by micro-beam WAXD, respectively. Both the hard segment (HS) domain orientation and the strain-induced crystallization of poly(ε-caprolactone) chains were tracked by the WAXD pattern due to the high crystallinity of the symmetric non-bulky aliphatic HS structure. Strain-induced crystallization occurred locally at the vicinity of the crack tip, and the crystallinity immediately decayed in the exterior, whereas the HS domain orientation was observed throughout the stretched film. The mechanisms underlying crack arrest and the mechanical strength of polyurethane elastomer films are associated with the local strain-induced crystallization at the crack tip, the mechanical stability of the HS domains, and the avoidance of local stress concentration through the HS domain orientation.

Thermal and mechanical properties of two kinds of hydroxyl-terminated polyether prepolymers and the corresponding polyurethane elastomers

In order to analyze the differences in performance between two kinds of hydroxyl-terminated polyether (HTPE) binders, the curing reaction kinetics of the prepolymers and polyfunctional isocyanate (N-100) molecules and the thermal properties of the prepolymers and the corresponding polyurethane (PU) elastomers were studied by non-isothermal differential scanning calorimetry. The mechanical properties of PU elastomers were also studied by uniaxial tensile tests. With these data, the binder type could be chosen more appropriately for its application in rocket propellant formulations. The results showed that the reactivity of hydroxyl-terminated block copolyether (TPEG) with an isocyanate group is higher than that of hydroxyl-terminated random copolyether (PET). The chain flexibility of TPEG was less than that of PET, but the stereoregularity and crystallization ability of the former were superior. Compared to the prepolymers, the chain flexibility of the corresponding PU elastomers was reduced, and the crystallization ability became weaker such that their onset of crystallization was delayed. After the prepolymers were reacted with N-100, the thermal properties of PU elastomers remained consistent with their respective prepolymers. In summary, it was concluded that the mechanical properties of TPEG/N-100 PU elastomer films were found to be superior to the PET/N-100 films.

Spontaneous wettability patterning via creasing instability

Surfaces with patterned wettability contrast are important in industrial applications such as heat transfer, water collection, and particle separation. Traditional methods of fabricating such surfaces rely on microfabrication technologies, which are only applicable to certain substrates and are difficult to scale up and implement on curved surfaces. By taking advantage of a mechanical instability on a polyurethane elastomer film, we show that wettability patterns on both flat and curved surfaces can be generated spontaneously via a simple dip coating process. Variations in dipping time, sample prestress, and chemical treatment enable independent control of domain size (from about 100 to 500 μm), morphology, and wettability contrast, respectively. We characterize the wettability contrast using local surface energy measurements via the sessile droplet technique and tensiometry.

Synthesis and characterization of photoactive polyurethane elastomers with 2,3-dihydroxypyridine in the main chain

Photoactive polyurethane elastomers with pyridine derivatives in the polymer backbone were synthesized by chain-extending isocyanate end-capped prepolymers with 2,3-dihydroxypyridine. The isocyanate-terminated prepolymers were obtained from poly(tetramethylene oxide) glycol of molecular weight 1400 (Terathane 1400) and 1,6-hexamethylene diisocyanate. The properties of the linear heterocyclic polyurethane were compared with properties of the crosslinked heterocyclic polyurethane obtained by chain extension with various crosslinkers. Heterocyclic polyurethane elastomers were characterized using Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), dynamic mechanical analysis (DMA), contact angle measurements, and mechanical analysis. Static mechanical measurements showed greater elongation and tensile strength for polyurethanes with a lower content of heterocyclic groups in the hard segment. The static contact angles of the cast films of these polymers indicated that the nature of the hard segment influences the surface polarity. The dynamic mechanical spectra revealed that linear polymers have two transition temperatures as results from a clear phase separation caused by high-intermolecular hydrogen bonds in the regions of pyridine units and urethane groups. Polyurethane elastomer films with pyridine moieties in the main chain form a photosensitive material. If stored in laboratory conditions (light, ambient air atmosphere), the color of the films changes from white to black. These photo-induced structural changes are studied by H NMR measurements.

Dependence of fungal biodegradation of PEG/castor oil-based polyurethane elastomers on the hard-segment structure

In the context of protecting of the environment, this work studies the biodegradation of PEG-based polyurethane elastomer films in the presence of the soft rot fungus Chaetomium globosum, determined via the Petri-dish test. Using PEG with high-molecular weight (MW = 1500) as a chain extender led to polyurethane elastomers with lower physical crosslink density and higher swelling rates. The structural modifications in the hard-segment area (C O and N–H peaks) are considerable and were analyzed by FTIR spectroscopy. Biodegradation lowers the final mechanical properties, but increases yield points, especially in the case of polyurethane elastomers crosslinked with castor oil. Polyurethane elastomer samples showed visible degradation proved by the mechanical weakening of the films. Thus, breaking strains decrease from 670–1180% to 500–680% and tensile strengths decreased from 11.5–27.5 MPa to 4–11.5 MPa after 130 days of fungal biodegradation. The changes in the morphology of the polyurethane films surface were analyzed by SEM and have been found to exhibit increasing porous structure and fungal hyphae. The effects of the hard-segment composition of the polyurethane elastomers on the fungal biodegradation behaviour were investigated.

Behavior of bending motion of polyurethane film with carbon nanofiber as electrode

The behavior of bending motion by an electric field for a polyurethane elastomer (PUE) film for which vapor grown carbon fiber (VGCF) was used as an electrode was examined. When the electric field was applied to the PUE film with the VGCF electrode, it bent towards the cathode side. In the case wherein the PUE film was doped with sodium acetate, it was observed that the bending displacement of the PUE film with the VGCF electrode was larger than for the undoped PUE film. The absolute value of the charge current was similar to that of the discharge current in doped PUE film with the VGCF electrode and this result corresponds to less leakage current. Highly efficient charge holding was also observed in the doped PUE film with the VGCF electrode, since the steady current by applying an electric field was less than 0.1μA.

Carbon-Nanotube-Enhanced Direct Electron-Transfer Reactivity of Hemoglobin Immobilized on Polyurethane Elastomer Film

In this study, we investigate the direct electron-transfer reactivity of immobilized hemoglobin (Hb) on a polyurethane elastomer (PUE) film for biosensor designs. The PUE film synthesized by an additional polymerization possesses good biocompatibility, uniformity, and conformability and is ready for protein immobilization. Electrochemical and spectroscopic measurements show that the presence of multiwalled carbon nanotubes (MWNTs) increased the protein-PUE interaction, varied polymer morphology, improved the permeability and the conductivity of the PUE film, and thus facilitated the direct electron transfer between the immobilized Hb and the conductivity surface through the conducting tunnels of MWNTs. The immobilized Hb maintains its bioactivities and displays an excellent electrochemical behavior with a formal potential of -(334 +/- 7) mV. The addition of NaNO2 leads to an increase of the electrocatalytic reduction current of nitrite at -0.7 V. This allows us to develop a nitrite sensor with a linear response range from 0.08 to 3.6 mM. The proposed method opens a way to develop biosensors by using nanostructured materials mixed with low electrical conductivity matrixes.

Wrinkled polypyrrole electrode for electroactive polymer actuators

As an electrode for a bending-electrostrictive polyurethane actuator, we prepared a wrinkled polypyrrole electrode, expecting the following two effects because the wrinkled electrode could easily elongate by smoothing the wrinkles: (1) conductivity of the electrode would not decrease with the field-induced surface elongation of the actuator, and (2) the electrode would not constrain the actuation. The wrinkled electrode was prepared through in situ deposition of polypyrrole onto the polyurethane elastomer film that was being uniaxially drawn. After the deposition, the film was released from the drawing to make the electrode wrinkle. The conductivity of the wrinkled electrode did not decrease at elongation rates less than 40%. The bending actuation of the polyurethane film with the wrinkled electrode was improved more than twice that as compared with an unwrinkled one. In addition, doping the polyurethane with sodium acetate also improved the actuation. By these improvements, the bending actuation reached 7 mm in radius of curvature within 0.2 s when the applied voltage was 1000 V.

Electro-striction effect of polyurethane elastomer (PUE) and its application to actuators

The polyurethane elastomers (PUEs) without solvent similar to a polymer gels have been found to show the electro-striction effect. We proposed the application to an actuator utilizing the electro-striction effect of PUEs. PUEs were synthesized by prepolymer technique and were polymerized in the form of films by casting method. The actuator is a monomorph type which is formed metal electrodes on the both surfaces of PUE films by thermal or ion-beam-assisted deposition method. While, it was tried to operate the actuators under low voltage by inducing C 60 derivative into PUEs. Both the normal PUE and the PUE doped fullerenol increased with increasing an applied voltage. All of samples were bent in the direction of the cathode, and they have polarity effect. The bends of the PUE films doped fullerenol were larger than that of the normal PUE films and it became possible to operate at low voltage. Also, the pincette type actuator could smoothly pick up a sponge like a finger.

Preparation and characterization of electrostrictive polyurethane films with conductive polymer electrodes

All-polymer electrostrictive soft films were developed for the first time by depositing conductive polymer (polypyrrole) directly on both sides of solution-cast electrostrictive polyurethane elastomer films. The final composite films are flexible with strong adhesion between the polyurethane film and the conductive polymer electrode. The conductivity (sheet resistivity ∼1000 Ω/□), of the polymer electrode is appropriate for its intended use. The compatible interface between the polypyrrole electrode polymer and the electrostrictive polyurethane significantly improves the acoustic and optical transparency of these composite films, compared with using a metal electrode film. The all-polymer films also exhibit comparable dielectric properties to gold-electroded polyurethane films in the temperature range from −40°C to +80°C. The temperature range covers the soft segment glass transition temperature of the polyurethane elastomers, which is about −20°C. The films also show large electric field induced strain responses which are dependent on film thickness and measurement frequency. The electrostrictive characteristics in the all-polymer films show similarities to those of the films with gold electrodes under identical measurement conditions. © 1998 John Wiley & Sons, Ltd.

Preparation and characterization of electrostrictive polyurethane films with conductive polymer electrodes

All-polymer electrostrictive soft films were developed for the first time by depositing conductive polymer (polypyrrole) directly on both sides of solution-cast electrostrictive polyurethane elastomer films. The final composite films are flexible with strong adhesion between the polyurethane film and the conductive polymer electrode. The conductivity (sheet resistivity ∼1000 Ω/□), of the polymer electrode is appropriate for its intended use. The compatible interface between the polypyrrole electrode polymer and the electrostrictive polyurethane significantly improves the acoustic and optical transparency of these composite films, compared with using a metal electrode film. The all-polymer films also exhibit comparable dielectric properties to gold-electroded polyurethane films in the temperature range from −40°C to +80°C. The temperature range covers the soft segment glass transition temperature of the polyurethane elastomers, which is about −20°C. The films also show large electric field induced strain responses which are dependent on film thickness and measurement frequency. The electrostrictive characteristics in the all-polymer films show similarities to those of the films with gold electrodes under identical measurement conditions. © 1998 John Wiley & Sons, Ltd.

Effects of molecular weight and molecular weight distribution of polyester based soft segments on the physical properties of linear polyurethane elastomers

AbstractLinear polyurethane elastomers were synthesized in dimethyl acetamide (DMAc) solution, starting from 4,4′‐methylene diisocyanate 1,4‐butanediol, and polyester diols of two different molecular weights (MW) and each with a series of molecular weight distributions (MWD). Diol samples of various MWD's were prepared by blending polyesters of different MW. Polyurethane elastomer films were cast from solution, and characterized with the effect of the molecular weight and molecular weight distribution of the polyester diols on the physico‐mechanical and morphological properties of the polyurethane elastomers investigated. Most properties studied depended strongly on the MW of polyester soft segments; the MWD influenced primarily the relaxation behaviour of the polyurethane samples. Our data indicates that these phenomena are related to variations of the amounts of high MW polyester diols. The dynamic‐mechanical measurements and the polymer morphology studies indicate that a diffuse, mixed amorphous phase exists in these polymers; the amount of the phase depends on MW and MWD of the polyester segment, but the intrinsic properties are essentially independent of the MWD of the polyester segment.