Properties Of Thermoplastic Polyurethane Elastomers Research Articles

Improved the dielectric properties of thermoplastic polyurethane elastomer filled with MXene nanosheets and BaTiO3 nanofibers

To achieve high deformation under a low electric field intensity is still a big challenge for the dielectric elastomers (DE) potentially used in artificial electronic skin and artificial muscles. Herein, poly-dopamine (PDA) modified 1D barium titanate (BT@PDA) nanofibers and 2D MXene nanosheets with high aspect ratio and large dipole moment were fabricated, and introduced into TPU elastomers. Results showed that the interfacial polarization and micro-capacitor structure formed by MXene sheets lead to the high dielectric constant, and high dielectric loss of MXene/TPU composites with low modulus. The interfacial polarization caused by BT@PDA nanofibers resulting in high dielectric constant and low dielectric loss of BT@PDA/TPU composites with high modulus. Combing the advantages of the two fillers, the MXene/BT@PDA/TPU composites showed high dielectric constant, low dielectric loss, low modulus. The electrical sensitivity factor of 0.5 wt% MXene/5 wt% BT@PDA/TPU composite (11.38) was much higher than the sum of that of 0.5 wt% MXene/TPU (1.73) and 5 wt% BT@PDA/TPU (4.35) composites at a low filler content, showing the 0.5 wt% MXene/5 wt% BT@PDA/TPU dielectric composite had a large deformation under a low electric field. This work can provide an effect strategy to design DE nanocomposites with good deformation performance.

Improved Dielectric Properties of Thermoplastic Polyurethane Elastomer Filled with Core-Shell Structured PDA@TiC Particles.

Insulating interlayer between nanoparticles and polymer matrix is crucial for suppressing the dielectric loss of polymer composites. In this study, titanium carbide (TiC) particles were surface modified by polydopamine (PDA), and the obtained PDA@TiC powders were used to reinforce thermoplastic polyurethane (TPU). The results indicate that the PDA@TiC were homogenously dispersed in the matrix compared with the pristine TiC, and that the PDA@TiC/TPU composites show improved dielectric and mechanical properties, i.e., much lower dissipation factors and obviously enhanced dielectric breakdown strength, as well as higher tensile strength and elongation at break as compared to the raw TiC/TPU. The nanoscale PDA interlayer contributes to the dielectric and mechanical enhancements because it not only serves as an insulating shell that prevents TiC particles from direct contacting and suppresses the loss and leakage current to very low levels, but also enhances the interfacial interactions thereby leading to improved mechanical strength and toughness. The prepared flexible PDA@TiC/TPU with high permittivity but low loss will find potential applications in electronic and electrical applications.

Relationship between structure and dynamic mechanical properties of thermoplastic polyurethane elastomer containing bi‐soft segment

AbstractIn this work, we investigated the microphase separation, mechanical, and dynamic mechanical properties of thermoplastic polyurethane elastomers (TPUs) with one‐soft segment (polypropylene glycol, PPG, or hydroxyl‐terminated polybutadiene, HTPB) or bi‐soft segment (PPG and HTPB) using FTIR, XRD, SAXS and amplitude modulated‐frequency modulated viscoelastic mode of AFM (AM‐FM mode AFM) methods. The results showed that the microphase separation process of hard and soft segments (HS and SS) in TPU containing PPG and HTPB soft segments (PPG‐HTPB‐PU) was restricted by randomly alternated bi‐soft segments, which results in formation of a low content of irregular‐shaped hard domain (HD). In addition, the microphase separation of PPG‐HTPB‐PU induced a triple‐phased structure of HD, HTPB rich phase and mesophase. The mesophase of PPG‐HTPB‐PU was formed of HS, PPG and HTPB segments which were excluded out of HD and HPTB rich domains during microphase separation process. The damping temperature range (at tan δ greater than 0.3) of PPG‐HTPB‐PU was from −14.6 to 32.1°C (46.5°C) which was more broad than that of TPU containing HTPB soft segment (HTPB‐PU). The broad damping temperature range of PPG‐HTPB‐PU is mainly attributed to the enhanced energy consumption caused by the frictional motions of mixed segments of mesophase.

Effect of TBPF Microencapsulated Ammonium Polyphosphate on the Properties of Thermoplastic Polyurethane Elastomer

In our previous work, ammonium polyphosphate (APP) microcapsule with the shell of boron modified phenolic resin (BPF) was prepared, recorded as BPFAPP. However, the compatibility and the flame retardancy of BPFAPP in thermoplastic polyurethane elastomer (TPU) are still not very good due to the brittle and hard shell wall. To improve the brittleness of microcapsules shell and the property reinforcements of APP in TPU, APP was encapsulated with the tung oil and boron modified phenolic resin (TBPF) in this paper, recorded as TBPFAPP. The property reinforcements of TBPFAPP in TPU were studied. The thermogravimetry, limiting oxygen index and cone calorimetry analysis showed that TPU/TBPFAPP composite had higher char yield and better flame resistance. The tensile strength and elongation at break showed that the mechanical properties were also significantly improved due to the introduction of α-Eleostearate.

A simple and versatile method to tailor physicochemical properties of thermoplastic polyurethane elastomers by using novel mixed soft segments

Novel thermoplastic polyurethane elastomers (TPUs) were designed and synthesized using mixtures of poly (tetramethylene ether) glycol (PTMG) and polycaprolactone (PCL) diols as soft segments. Five block polyurethanes with different soft segment composition were studied in order to discover the impact of mixed soft segments on the properties of TPUs. The corresponding properties of these polyurethanes including phase transitions, morphology, microphase separation, hydrogen bonding, rheological and mechanical were investigated by experimental methods. Molecular dynamics simulation was also used to evaluate dynamic of hard and soft segments, hydrogen bonding and segmental interactions at atomic level. Successful synthesizing of the TPUs was evaluated by ATR-FTIR and 13C NMR spectroscopy. The results indicated that polyurethanes with higher PTMG content produce stronger hydrogen bonding, more solid like behavior, higher microphase separation and lower viscosity than polyurethanes with high PCL diol; however the most exciting outcome is the influence that mixed soft segments have on the microphase separation kinetics and mechanical properties. Isothermal and non-isothermal examinations have shown that using mixed soft segments accelerated the microphase separation process comparing samples with one type of polyols and sample containing equal compositions of each polyols has the fastest microphase separation kinetics. Microscopy images showed that this sample has the thread-like hard segment rich regions and its morphology differs from other samples. Mechanical property data indicated that the enhanced elongation at break and overall toughness of TPU at equal ratio of PCL/PTMG is highest in comparison with other samples.

Rheological and mechanical properties of thermoplastic polyurethane elastomer derived from CO2 copolymer diol

ABSTRACTCO2 copolymer diol‐based thermal polyurethane elastomers (PPC‐TPU) were prepared by the reaction of CO2 copolymer diol and methylene diphenyl diisocyanate and chain extender (ethylene glycol/1,4‐butanediol/1,6‐hexanediol) (EG/BDO/HG). The rheological and mechanical properties of PPC‐TPU were analyzed. The effects of shear rate, shear temperature, hard segment content, and variety of chain extender on the properties of PPC‐TPU were studied. The results showed that the apparent viscosity (η) of PPC‐TPU decreased with the increasing shear rate (τ), and the non‐Newtonian index (n) was less than 1. PPC‐TPU exhibited a typical character of pseudoplastic non‐Newtonian rheological behavior. The degradation during the processing was obviously inhibited by adding plasticizer and antioxidant. It was also discovered that the apparent viscosity varied with the content of hard segment and chain extender. Under the same temperature (185 °C) and shear rate (50 s−1), the apparent viscosity increased considerably with the raise of hard segment content, and the apparent viscosity and tensile strength of PPC‐TPU with EG as chain extender was the maximum. It can be seen that with the apparent shear rate increasing, the variation tendency of apparent shear stress levels off, and the nonlinear relationship of τ–γ curve tended to be obvious. PPC‐TPU exhibited a typical character of pseudoplastic non‐Newtonian rheological behavior. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45974.

Electrostrictive properties of thermoplastic polyurethane elastomer: Effects of urethane type and soft–hard segment composition

The electromechanical behavior of thermoplastic elastomer polyurethane (TPE-PU) is investigated under the effects of urethane type (ester and ether-types) and soft–hard segments at various electric field strengths and temperatures. The highest dielectric constant, electrical breakdown strength, and specific conductivity belong to the ester-type polyurethane (LPR matrix), while the lowest values are obtained from the ether-type polyurethane composing predominantly with the soft-segment (E 80A matrix). Under the electric field strength in the range between 0 and 2 kV/mm, the LPR matrix attains the storage modulus sensitivity (ΔG′/G′0) up to 2 at 2 kV/mm. For the temporal response, the polyurethanes behave with good reproductively (number of cycles >105 times) and with very good recoverability. The steady state behavior can be attained at the first actuation and at the electric field strength of 1 kV/mm. Furthermore, the storage modulus (G′) shows linearly negative responses with increasing temperature. In the deflection experiments, the deflection distance and the dielectrophoresis force increase monotonically with increasing electric field strength. All of the TPE-PU possesses very fast response times for activation (<10 s.) and deactivation (<5 s.). TPE-PU material is systematically shown here to be a potentially good actuator material with high efficiency based on the electrostrictive performance data obtained.

Enhancing mechanical properties of thermoplastic polyurethane elastomers with 1,3-trimethylene carbonate, epsilon-caprolactone and L-lactide copolymers via soft segment crystallization

Multiblock thermoplastic polyurethane elastomers based on random and triblock copolymers were synthesized and studied. Dihydroxyl-terminated random copolymers were prepared by ring opening copolymerization of !-caprolac- tone (CL) and 1,3-trimethylene carbonate (TMC). The triblock copolymers were synthesized by using these random copolymers as macro-initiator for the L-lactide (L-LA) blocks. These random and triblock copolymers were further reacted with 1,6-hexamethylene diisocyanate (HMDI) and chain extended by 1,4-butanediol (BDO). The polymer structure and chemical composition were characterized by 1 H NMR 13 C NMR and SEC. Their thermal and mechanical properties were studied by using DSC and Instron microtester. Multiblock polyurethanes based on random PCL-co-PTMC copolymers showed strain recovery improvement with increasing PCL content. However, these polyurethanes were unable to sustain deformation at body temperature due to the melting of PCL crystals and low hard segments content. With the presence of crystallizable PLLA blocks, mechanical properties were improved at body temperature without compromising their good strain recovery.

Control of Mechanical Properties of Thermoplastic Polyurethane Elastomers by Restriction of Crystallization of Soft Segment.

Mechanical properties of thermoplastic polyurethane elastomers based on either polyether or polycarbonate (PC)-glycols, 4,4’-dipheylmethane diisocyanate (1,1’-methylenebis(4-isocyanatobenzene)), 1,4-butanediol, were controlled by restriction of crystallization of polymer glycols. For the polyether glycol based-polyurethane elastomers (PUEs), poly(oxytetramethylene) glycol (PTMG), and PTMG incorporating dimethyl groups (PTG-X) and methyl side groups (PTG-L) were employed as a polymer glycol. For the PC-glycol, the randomly copolymerized PC-glycols with hexamethylene (C6) and tetramethylene (C4) units between carbonate groups with various composition ratios (C4/C6 = 0/100, 50/50, 70/30 and 90/10) were employed. The degree of microphase separation and mechanical properties of both the PUEs were investigated using differential scanning calorimetry, dynamic viscoelastic property measurements and tensile testing. Mechanical properties could be controlled by changing the molar ratio of two different monomer components.

熱可塑性ポリウレタンエラストマーのミクロ凝集構造と物性に及ぼすアニール温度の影響

The effects of annealing temperature on the micro-aggregation structure, the mechanical and melting properties of thermoplastic polyurethane elastomer (TPU) were investigated. TPU was composed of poly{(tetramethylene adipate)-co-(hexamethylene adipate)} glycol, 4, 4′-diphenylmethane diisocyanate and 1, 4-butanediol units. The TPU sheets prepared by injection molding were annealed at various temperatures from 23 to 120°C for 4h. Differential scanning calorimetry, pulsed nuclear magnetic resonance and dynamic viscoelastic measurements revealed that the degree of micro-phase separation of the TPUs became stronger with increasing annealing temperature owing to the progress of the formation of well-organized hard segment domains. Dynamic storage modulus of the rubbery plateau region around room temperature and the termination temperature of the rubbery plateau region decreased and increased with increasing annealing temperature, respectively. The temperature sweep experiments for molten TPUs indicated that the critical gel temperature at intersection between G′ and G″, increased with increasing annealing temperature. In addition, the TPUs showed the strain hardening of uniaxial elongation viscosity with increasing annealing temperature owing to residual hard segment domains at the operating temperature. It was revealed that the formation of well-organized hard segment domains by annealing strongly influences on not only mechanical properties but also melting ones of the TPUs.

ワンショット法により重合した熱可塑性ポリウレタンエラストマーの構造と物性への重合温度の影響

Effects of polymerization temperature on the molecular aggregation structure and the mechanical and melting properties of thermoplastic polyurethane elastomers (TPUs) were investigated. The TPUs were prepared from poly(ethylene adipate)glycol, 4, 4'-diphenylmethane diisocyanate, and 1, 4-butanediol by a one-shot method in bulk at various polymerization temperatures from 140 to 230°C. Glass transition temperature of the soft segment and melting point of the hard segment increased and decreased with increasing polymerization temperature, respectively. The pulsed NMR analyses of the TPUs indicated that the relative proton contents in the interfacial phase between hard and soft phases and its spin-spin relaxation time increased with increasing polymerization temperature. It is conceivable that the degree of microphase-separation of the TPUs became weaker with increasing polymerization temperature. Dynamic storage modulus for the rubbery plateau region of the TPUs prepared at 140 and 170°C were much higher than those at 190 and 230°C. Also, viscosity measurement revealed that the TPUs prepared at lower polymerization temperature bare the non-Newtonian behavior for wide shear rate region owing to the residual hard segment domains at an operated temperature. These results can be attributed to the degree of microphase-separation and melting temperature of the hard segment domain in the TPUs.

プレポリマー法により重合した熱可塑性ポリウレタンエラストマーの構造と物性への重合温度の影響

プレポリマー法により重合した熱可塑性ポリウレタンエラストマーの構造と物性への重合温度の影響

Novel Segmented Thermoplastic Polyurethanes Elastomers Based on Tetrahydrofuran Ethylene Oxide Copolyethers as High Energetic Propellant Binders

AbstractNovel thermoplastic polyurethane (TPU) elastomers based on copolyether (tetrahydrofuran ethylene oxide) as soft segments, isophorone diisocyanate and 1,4‐butanediol as hard segments were synthesized for the purpose of using as propellant binders. In order to increase the miscibility of thermoplastic polyurethane elastomers with nitrate ester, polyethylene glycol (PEG) is incorporated in the co‐polyether (tetrahydrofuran ethylene oxide) as soft segment. When the molecular weight and content of polyethylene glycol are controlled to 4000 and 6% of soft segments, respectively, the properties of thermoplastic polyurethane elastomers are most perfect. If plasticizing ratio of nitrate ester to thermoplastic polyurethane elastomers exceeds 4 no crystallinities are determined at room temperature. The propellant samples were prepared by a conventional absorption‐rolling extrusion process and the mechanical and combustion properties evaluated afterwards. The maximum impulse reaches up to 265∼270 s which is a little bit higher than that of a HTPB propellant. The measured results reveal a promising TPE propellant candidate which shows good processing temperature (&lt;393 K) and excellent mechanical properties. An attracting feature which can be pointed out is that the burning rate pressure exponent reaches as low as 0.36 without the addition of burning rate catalysts. This enables an easy control of propellant combustion.

Properties of thermoplastic polyurethane elastomers chemically modified by rosin

Properties of thermoplastic polyurethane elastomers chemically modified by rosin

Properties of thermoplastic polyurethane elastomers chemically modified by rosin

AbstractThermoplastic polyurethane elastomers (TPUs) are prepared including different amounts of rosin in their composition. Rosin is used either as an additive, mixed in the TPU solutions, or as a reactant in the chain‐extension step of polymer synthesis. The properties of the materials are studied using solution viscosity measurements, size‐exclusion chromatography, stress‐controlled rheometry, differential scanning calorimetry, wide‐angle X‐ray diffraction, and contact angle determinations. Rosin as an additive does not markedly change the polymer properties. On the contrary, the use of rosin in the chain‐extension step leads to sharp increases of viscosity and molar mass as well as improvements of rheological properties and changes in morphology: the crystalline regions are more affected (variations in the softening temperature and enthalpy) than the amorphous ones (quite constant glass‐transition temperature). The conclusion is that rosin acts as an actual chain extender and that it modifies the organization of both the hard and the soft segments of the polymers. Furthermore, the TPUs are used as raw materials of solvent‐based adhesives, which adhesion properties are characterized by T‐peel tests of PVC/TPU adhesive joints. Rosin as an additive cannot improve the low tack (initial adhesive strength) of TPU, although as a chain extender or cochain extender (together with butane diol) rosin allows development of significant initial adhesive strengths, while keeping a high level of actual (maximal) adhesive strength. © 2001 John Wiley &amp; Sons, Inc. J Appl Polym Sci 82: 3402–3408, 2001

Mechanical properties of thermoplastic polyurethane elastomers with mica and aluminum trihydrate

In the present work two types of fillers were incorporated into thermoplastic polyurethane elastomers (TPU): mica and aluminum trihydrate (ATH). In the first stage, mixtures were prepared with TPU and 5, 10, 20, 25 and 30 phr of mica. The optimum amount of filler was evaluated for mechanical properties. In the second stage, ATH was used in mixtures with TPU and mica in the preparation of compositions with good flame retardant. All mixtures were obtained by extrusion and after compression molding they were evaluated through mechanical properties of tensile resistance, Shore A hardness and abrasion resistance. The objective of this work is to obtain good mechanical properties from TPU composites with mica–ATH as fillers and optimum cost-performance balance, in addition to flame retardant characteristics.

Influence of the prepolymerization on the properties of thermoplastic polyurethane elastomers. Part II. Relationship between the prepolymer and polyurethane properties

Influence of the prepolymerization on the properties of thermoplastic polyurethane elastomers. Part II. Relationship between the prepolymer and polyurethane properties

Influence of the prepolymerization on the properties of thermoplastic polyurethane elastomers. Part I. Prepolymer characterization

Thermoplastic polyurethane elastomers (TPUs) are generally synthesized by using the two-step, so-called prepolymer, method. To study the influence of the prepolymer on the properties of the final TPUs, four polyurethane prepolymers were prepared from a diisocyanate and a macroglycol by using different NCO/OH ratios. The prepolymers and the macroglycol used in their synthesis were characterized by using gel permeation chromatography, differential scanning calorimetry, and strain–stress measurements. Additionally, to test the adhesion properties of the prepolymers and the macroglycol, adhesive solutions were prepared, and the T-peel strength of plasticized poly(vinyl chloride)/prepolymer solution joints was determined. It was found that the properties of the prepolymers depend on those of the macroglycol used in their synthesis in such a way that the lower the relative amount of macroglycol units in the prepolymer molecules (higher NCO/OH ratio), the closer the properties of the prepolymer and macroglycol. The maximal theoretical degree of polymerization (DPn) determines the relationship between the macroglycol and prepolymer properties. Finally, the possibility of obtaining good adhesives from prepolymers, using low NCO/OH ratio in the synthesis, is evidenced. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1596–1601, 2000

Influence of the synthesis conditions on the properties of thermoplastic polyurethane elastomers

Thermoplastic polyurethane elastomers (TPUs) of constant composition were prepared by using the prepolymer method and by changing the reaction conditions (prepolymerization and chain-extension time) to study the influence of these conditions on the final TPU properties. The TPUs were characterized by gel permeation chromatography, differential scanning calorimetry, strain–stress measurements, and contact-angle measurements. To test the adhesion properties of the TPUs, poly(vinyl chloride) strips were bonded to each other by using TPU solutions and the T-peel strength of the adhesive joints was measured. It was found that provided a threshold is crossed, the prepolymerization time markedly influences the final properties of the TPUs (viscosity of solutions, molecular weight, mechanical and adhesive behavior), whereas the chain extension time does not. Therefore, it is possible to prepare TPUs with specific properties by playing with the prepolymerization conditions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1590–1595, 2000

Influence of the prepolymerization on the properties of thermoplastic polyurethane elastomers. Part II. Relationship between the prepolymer and polyurethane properties

The synthesis of thermoplastic polyurethane elastomers (TPUs) is generally carried out using the prepolymer method. To study the influence that the properties of the prepolymer may have in the final TPUs, four TPUs were prepared by using different NCO/OH ratios. The prepolymers and the macroglycol used in their synthesis were characterized in the first part of this article. TPUs were characterized by using gel permeation chromatography, strain–stress measurements, differential scanning calorimetry, and contact-angle measurements. To test their adhesion properties, the T-peel strength of PVC/TPU/PVC adhesive joints was determined. It was found that the properties of the prepolymers determine the properties of the TPUs when the amount of hard segments (related to the soft-segments size) is small. In contrast, when the amount of hard segments (related to the soft-segments size) is high, it is the chain extension step that determines the TPUs structure and properties. On the other hand, it was observed that a high amount of ever hard or soft segments gives TPUs with similar properties. This behavior is explained by the structure of the prepolymer (related to the degree of polymerization) and the TPUs. Finally, it was found that the adhesive properties of the finished TPUs are comparable to those of blocked prepolymers prepared with low NCO/OH ratio. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1602–1607, 2000