Thermoplastic Urethanes Research Articles

Triboelectric-material-pairs selection for direct-current triboelectric nanogenerators

Direct-current triboelectric nanogenerator (DC-TENG) arising from electrostatic breakdown exhibits unique merits over conventional alternating-current TENGs, such as the constant-current output and high output charge density. The selection of appropriate triboelectric material pair (TMP) is important for improving its performance. Here, we propose a universal strategy for the TMP selection of DC-TENG by simultaneously considering the friction, dielectric and triboelectric performance. Based on assessing five basic parameters in DC-TENG, including the friction coefficient, surface charge density, leakage current, breakdown charge density and breakdown efficiency, it is found that the thermoplastic urethanes (TPU)-ethylene-tetra-fluoro-ethylene (ETFE) pair presents considerable output performance. Finally, a micro-structured DC-TENG with a designed power-management circuit was fabricated to further demonstrate the enhanced performance of DC-TENG with TPU-ETFE as the TMP. This work provides an effective strategy to select appropriate TMPs to optimize the performance of DC-TENG, facilitating its practical applications.

Scalable fabrication of super-elastic TPU membrane with hierarchical pores for subambient daytime radiative cooling

Passive radiative cooling materials (PRCMs) has arose widespread concern with the advantage of cooling a surface by radiating heat to the cold outer space and reflecting sunlight. However, the cooling effect sharply deteriorated in the stretching state. Besides, widespread reflectivity within visible light (VIS) and near-infrared (NIR) range remained a huge challenge for the structure design. Herein, we proposed a porous thermoplastic urethanes (TPU) membrane with a high thermal emissivity of 95% and a sunlight reflectivity of 93%. Abundant hierarchical pores with submicro and micro sizes generate when the solvent of the TPU sol is exchanged by water, which tremendously strengthens the sunlight-reflecting behavior of the porous TPU membrane, especially in the NIR region. By covering the porous TPU membrane on the top, the temperature of the substrate, model house, and hood of the car cool up to 8.8, 16.3, and 18.0 °C, respectively, compared to the bare state. Moreover, the porous TPU membrane shows outstanding elastic cooling properties that the damage of IR emissivity and sunlight reflectivity was minimal even in a tensile strain of 450%.

Mechanical properties of 3D-printed hierarchical structures based on Sierpinski triangles

Incorporating structural hierarchy in the design of engineering composites can be used to tailor or enhance the physical and mechanical properties for specific functionalities. In this study, we propose a design of hierarchical triangular composite (HTC) composed of multi-scale Sierpinski triangles and fabricated using 3D printing with thermoplastic urethanes (TPU) material. A comprehensive framework incorporating theoretical and experimental methods is developed to study the effects of hierarchy order on the quasi-static, dynamic properties and energy absorption performance. Under in-plane quasi-static compression, it is found that higher-order HTC exhibits multi-stage deformation modes due to the non-uniform distribution of substructures, resulting in exceptional compression strength and energy absorption performance, which are increased by 30% and 200% than compared to lower order structures, respectively. Based on the deformation modes, an analytical model is derived to predict the compressive strength, which is validated by numerical and experimental results. In terms of specific energy absorption, the higher-order HTC also demonstrates enhanced performance compared to other honeycomb composite of TPU materials. Under high velocity dynamic impact, it is observed that although the multi-stage deformation mode cannot be activated for higher-order HTC, the fluctuations in dynamic response curve can still be reduced as a result of layer-by-layer collapse of substructures. Moreover, an analytical model using rigid-perfectly plastic-lock (R-PP-L) is employed to explain the dynamic behavior and predict the plateau stress under various impact velocities, which is verified by numerical simulations with good agreement. This study elucidates the effect of structural hierarchy on the mechanical properties and energy absorption performance, and the results are of potential engineering use in the design of lightweight impact-protective composites.

Improved dielectric properties of PVDF nanocomposites with core–shell structured BaTiO 3 @polyurethane nanoparticles

Polymer nanocomposites with improved dielectric permittivity and high breakdown strength are extremely desirable for the flexible electronic devices and power systems. The compatibility of fillers and polymer matrix is important in determining the dielectric and breakdown strength properties. The core–shell structure concept is useful to improve the compatibility of fillers with polymer matrix. Herein, an organic thermoplastic urethanes (TPU) polymer shell was successfully grafted on the surface of barium titanate (BaTiO3, BT) and such a TPU shell improved the permittivity and breakdown strength of TPU@BT/PVDF polymer nanocomposites greatly. The permittivity of TPU@BT/PVDF nanocomposites with 12 wt% fillers at 102 Hz was up to 13.5, which was 1.5 times higher than that of pure poly(vinylidene fluoride) (PVDF). The improvement of the dielectric properties could be attributed to the enhanced interfacial polarisation between BT nanoparticles and TPU shell. Besides, the compatibility of BT nanoparticles and PVDF matrix was improved after the introduction of TPU shell. Accordingly, a highest breakdown strength value about 373 MV/m was obtained for the TPU@BT/PVDF nanocomposites with 7 wt% fillers. The core–shell strategy could be extended to a variety of inorganic fillers to improve the dielectric and breakdown strength properties of polymer nanocomposites.

Effect of Chain Length for Dicarboxylic Monomeric Units of Polyester Polyols on the Morphology, Thermal and Mechanical Properties of Thermoplastic Urethanes

AbstractPolyester polyols of 2000 g mol−1 M mass were synthesized via polyesterification reaction of butane‐1,4‐diol (1,4‐BDO) with linear dicarboxylic acids (DCAs) of odd and even carbon numbers, ranging from C4 to C10. Melt transition temperatures and crystallization enthalpies of polyester polyols demonstrated differing trends between odd and even chain lengths of their DCA monomeric units, with the latter possessing higher melt transition temperatures and melting enthalpies. The underlying cause of this difference may be attributable to the formation of a crystalline phase between the polyols' alkyl groups, which leads to proper alignment of ester bonds to allow for formation of dipoles that effectively cancel the local polarization. Thermoplastic urethanes (TPUs) were prepared by reacting the polyester polyols with 4,4′‐methylene bis(phenyl isocyanate) (4,4′‐MDI) and 1,4‐BDO chain extender at mole ratio of 1:2:1, respectively. Morphology, thermal and mechanical properties of TPUs were measured. Mechanical properties of TPUs also differ according to even vs. odd chain length of DCA monomeric units: higher hardness, tensile strength, hysteresis and tensile set for the former. The difference in properties is likely related to differences in phase segregation between hard and soft segments as a result of formation of hydrogen bonds as well as dipole–dipole interactions. Therefore, these findings have practical significance in the selection of polyester polyols to design TPUs for their specific applications.

Thermal and mechanical properties of thermoplastic urethanes made from crystalline and amorphous azelate polyols

ABSTRACTPolyester polyols from renewable resources have gained significant interest in the field of polyurethane chemistry. Two sets of segmented TPUs were prepared from crystalline and amorphous azelate polyols, 4,4′‐methylenebis(phenyl isocyanate), and 1,4‐butanediol as a chain extender at a mole ratio of 1:2:1, respectively. Bio‐1,3‐propanediol (1,3‐PDO) and 1,5‐pentanediol (PTDO) were used to prepare crystalline azelate polyols, while 1,2‐propanediol (1,2‐PDO) and 2,2′‐dimethyl‐1,3‐propanediol (NPG) were used to prepare amorphous azelate polyols. All TPUs displayed clear glass transition temperatures (T gs) in between −36 and − 24 °C, associated with azelate polyols soft segments, which are decreasing with increasing diols chain lengths in azelate polyols. TPUs based on crystalline azelate polyols exhibited higher mechanical properties and better heat resistance in comparison to their counter parts. Besides, TPU based on 1,3‐PDO azelate showed lower percentage of hysteresis indicating lower heat build‐up. This is essentially good for TPUs that are to be used in dynamic applications such as rollers and wheels. Hence, the study on structure–property correlation of the crystalline and amorphous azelate polyols and their effect on TPUs properties suggest that crystalline azelate polyols are suitable for dynamic application of TPU, and amorphous azelate polyols are suitable for coatings and adhesives applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47890.

Preparation of Polylactide Composite with Excellent Flame Retardance and Improved Mechanical Properties

Despite the good biodegradable and mechanical properties, poly(lactic acid) still suffers from a highly inherent flammability, which restricts its applications in the electric and automobile fields. In order to improve the flame retardancy of PLA, in this work, melamine polyphosphate (MPP) and zinc bisdiethylphosphinate (ZnPi) were firstly incorporated into PLA, and the synergistic effect of them on flame retardance of PLA was investigated using limiting oxygen index (LOI), UL-94 vertical measurement, scanning electron microscopy (SEM) and cone calorimeter tests etc. The results showed that PLA composite with 15 wt% of MPP/ZnPi (3:2) had the best flame-retardant efficiency with LOI value of 30.1 and V0 rating in UL-94 tests, which was far better than using MPP or ZnPi alone. What is more, although a wide range of flame retardants have been developed to reduce the flammability, so far, they normally compromise the mechanical properties of PLA. On the premise of maintaining good flame-retardant performance, we improved the toughness of flame-retardant PLA composite, and the impact strength of flame-retardant PLA composite was more than tripled (8.08 kJ/m2) by adding thermoplastic urethanes (TPU). This work offers an innovative method for the design of the unique integration of extraordinary flame retardancy and toughening reinforcement for PLA materials.

Effect of Immobilized Antithrombin III on the Thromboresistance of Polycarbonate Urethane

The surface of foils and vascular grafts made from a thermoplastic polycarbonate urethanes (PCU) (Chronoflex AR) were chemically modified using gas plasma treatment, binding of hydrogels—(1) polyethylene glycol bisdiamine and carboxymethyl dextran (PEG-DEX) and (2) polyethyleneimine (PEI)—and immobilization of human antithrombin III (AT). Their biological impact was tested in vitro under static and dynamic conditions. Static test methods showed a significantly reduced adhesion of endothelial cells, platelets, and bacteria, compared to untreated PCU. Modified PCU grafts were circulated in a Chandler-Loop model for 90 min at 37 °C with human blood. Before and after circulation, parameters of the hemostatic system (coagulation, platelets, complement, and leukocyte activation) were analyzed. PEI-AT significantly inhibited the activation of both coagulation and platelets and prevented the activation of leukocytes and complement. In conclusion, both modifications significantly reduce coagulation activation, but only PEI-AT creates anti-bacterial and anti-thrombogenic functionality.

Interfacial rheology of coextruded elastomeric and amorphous glass thermoplastic polyurethanes

In this work, we report on the sensitivity of rheometrical techniques to the nature and size of the interface/interphase in coextruded thermoplastic urethanes (TPUs). In particular, the interphases developed during coextrusion of an amorphous glass (hard) TPU (Isoplast® ETPU 301) with one of two elastomeric (soft) TPUs (Estane® TPU 58277 and Estane® TPU X1175) were studied. Differences in the thickness and nature of the interphase of the two coextruded bilayer films were observed by atomic force microscopy. In one case, the interphase is thicker and rough, and in the other case, it is thinner and flat. Rheology was used in order to probe the type and characteristics of the interphases, with coextruded films having been tested in steady shear, small-amplitude oscillatory shear (SAOS), uniaxial extension, and stress relaxation after a step strain in shear. The results were compared with theoretical predictions assuming zero-thickness interfaces and no interfacial slip. For SAOS and stress relaxation experiments, expressions were deduced in order to enable such a prediction to be made. Of all four rheometrical tests, only stress relaxation after a step shear did not follow the theoretical predictions and, thus, was sensitive enough to detect the presence of the interphase.

The Discussion of Manufacturing Peanut Hull and TPU Composites by Hot Pressing

In order to recycle the waste peanut hull and TPU(thermoplastic urethanes), the composite made from peanut hull powder which was used as reinforcing material and TPU which was used as matrix material by the method of blending and hot pressing was discussed. The parameters of molding process were designed by orthogonal experiment. The tensile property, bending property and impact property of composite materials were tested in this study. The molding process parameters were optimized with the methods of range analysis and single factor analysis. The results showed that the optimum conditions were given as followings: concentration of peanut hull powder was 60%, hot pressing temperature was 170°C, hot pressing pressure was 12Mpa, and hot pressing time was 5min. Under above conditions, excellent mechanic properties were achieved, which were that tensile strength was 19.63MPa, bending strength was 25.74MPa, impact energy absorption was 1.33 KJ/m2.

Biodegradation of Thermoplastic Polyurethanes from Vegetable Oils

Thermoplastic urethanes based on polyricinoleic acid soft segments and MDI/BD hard segments with varied soft segment concentration were prepared. Soft segment concentration was varied from, 40 to 70 wt%. Biodegradation was studied by respirometry. Segmented polyurethanes with soft segments based on polyricinoleic acid degrade relatively slow losing about 11% carbon after 30 days, but faster than corresponding petrochemical polyesterurethanes. Since biodegradation proceeds mainly through the soft segments, higher soft segment content polymers displayed slightly higher biodegradation. Polyurethanes with dispersed hard domains in the soft phase displayed slightly faster biodegradation than those with co-continuous morphology. Polyester diol degrades slower than castor oil but significantly faster than the polyurethanes with built in soft segments from the same diol. Castor oil biodegrades slower than soybean oil.

Infrared and Raman Spectral Signatures of Aromatic Nitration in Thermoplastic Urethanes

The spectral signatures of nitro attack of the aromatic portion of thermoplastic urethanes (TPU) were determined. Eight fragment molecules were synthesized that represent the nitrated and pristine methylenediphenyl section common to many TPUs. Infrared (IR) and Raman (785 nm illumination) spectra were collected and modeled using the B3LYP/6-31G(d)//B3LYP/6-31G(d) model chemistry. Normal mode animations were used to fully assign the vibrational spectra of each fragment. The vibrational assignment was used to develop a diagnostic method for aromatic nitro attack in thermoplastic urethanes. The symmetric NO(2) stretch coupled out of phase with the C-NO(2) stretch (1330 cm(-1)) was found to be free from spectral interferences. Spectral reference regions that enable correction for physical differences between samples were determined. The carbonyl stretch at 1700 cm(-1) was the best IR reference region, yielding a limit of quantitation (LOQ) of 0.66 +/- 0.02 g N/100 g Estane. Secondary IR reference regions were the N-H stretch at 3330 cm(-1) or the urethane nitrogen deformation at 1065 cm(-1). The reference region in the Raman was a ring stretching mode at 1590 cm(-1), giving an LOQ of 0.69 +/- 0.02 g N/100 g Estane. Raman spectroscopy displayed a larger calibration sensitivity (slope = 0.110 +/- 0.004) than IR spectroscopy (slope = 0.043 +/- 0.001) for nitration determination due to the large nitro Raman cross-section. The full spectral assignment of all eight molecules in the infrared and Raman is presented as supplemental material.

Mistura reativa de poliamida 6 e policarbonato: reatividade do copolímero formado "in situ"

As misturas físicas de poliamida 6 (PA6) e policarbonato (PC) processadas a 240 ºC, durante 10, 30 e 60 minutos formam um copolímero de PA6-PC. A alta temperatura e o longo tempo de processamento podem causar modificações nas propriedades dessas misturas e degradar o copolímero, originando grupos isocianato e subseqüentemente CO2 e grupos NH2 terminais. A quantidade de copolímero PA6-PC formado durante o processo de mistura é maior com o aumento da proporção de PC na mistura. As ligações uretânicas de polímeros termoplásticos exibem mais baixas estabilidades térmica e oxidativa, resultando no aumento da concentração de grupos terminais NH2. A reatividade dessas misturas foi investigada através do torque durante o processo de mistura, da titulação potenciométrica dos grupos NH2 terminais e por microscopia eletrônica de varredura.

A Quantum-Chemistry-Based Potential for a Poly(ester urethane)

We have carried out extensive high-level quantum chemistry studies of the geometry, charge distribution, conformational energies, and hydrogen-bonding energies of model compounds for a family of Estane thermoplastic urethanes (TPUs). Upon the basis of these studies, we have parametrized a classical potential for use in atomistic simulations of Estane TPUs that can also be applied directly or with minor extensions to a wide variety of polyesters and polyurethanes.

Thermoplastic Urethanes for Extrusion Injection and Blow Moulding and for Textile Coating

Thermoplastic urethanes behave as crosslinked rubbers when cold, but when heated to moulding temperatures, behave as linear non- crosslinked polymers which flow readily for moulding. The material is inert to most common solvents, has good abrasion resistance, and high elasticity. Being thermoplastic, scrap and sprues may be recycled, while in coatings, the material is finding a natural application in the construction of simu lated leather products.