Preparation of microporous thermoplastic polyurethane by low-temperature supercritical CO2 foaming

2016 ◽  
Vol 53 (2) ◽  
pp. 135-150 ◽  
Author(s):  
Chien-Chia Chu ◽  
Shu-Kai Yeh ◽  
Sheng-Ping Peng ◽  
Ting-Wei Kang ◽  
Wen-Jeng Guo ◽  
...  
Keyword(s):  
Polyurethane Foam ◽  
Supercritical Co2 ◽  
Thermoplastic Polyurethane ◽  
Saturation Temperature ◽  
Phenyl Isocyanate ◽  
Blowing Agent ◽  
Soft Segments ◽  
Hard Segments ◽  
Poly Propylene ◽  
Foam Production

Thermoplastic polyurethane possesses many special characteristics. Its flexibility, rigidity, and elasticity can be adjusted by controlling the ratio of soft segments to hard segments. Due to its versatile physical properties, thermoplastic polyurethane is commonly used in transportation, construction, and biomaterials. However, methods for thermoplastic polyurethane foam production using CO2 are still under investigation. We have previously prepared nanoporous thermoplastic polyurethane foam using commercially available thermoplastic polyurethane; however, in this study, thermoplastic polyurethane was synthesized using 4,4′-methylenebis(phenyl isocyanate), poly(propylene glycol) and 1,4-butanediol, without solvents, using a pre-polymer method. The properties of the synthesized thermoplastic polyurethane were characterized by Fourier transform infrared spectroscopy, thermal analysis, and their mechanical properties were measured. The synthesized thermoplastic polyurethane was foamed by batch foaming using supercritical CO2 as the blowing agent. The effect of saturation temperature and saturation time on the cell morphology of the thermoplastic polyurethane foam was examined.

Rheology of Thermoplastic Polyurethanes

2007 ◽  
Author(s):  
Chang Dae Han
Keyword(s):  
Rheological Behavior ◽  
Thermoplastic Polyurethane ◽  
Complete Characterization ◽  
Chain Extender ◽  
Reaction Sequence ◽  
Molecular Weights ◽  
Soft Segments ◽  
Hard Segments ◽  
A Chain ◽  
Long Chain

Thermoplastic polyurethane (TPU) has received considerable attention from both the scientific and industrial communities (Hepburn 1982; Oertel 1985; Saunders and Frish 1962). Applications for TPUs include automotive exterior body panels, medical implants such as the artificial heart, membranes, ski boots, and flexible tubing. Figure 10.1 gives a schematic that shows the architecture of TPU, consisting of hard and soft segments. Hard segments, which form a crystalline phase at service temperature, are composed of diisocyanate and short-chain diols as a chain extender, while soft segments, which control low-temperature properties, are composed of difunctional long-chain polydiols with molecular weights ranging from 500 to 5000. The soft segments form a flexible matrix between the hard domains. TPUs are synthesized by reacting difunctional long-chain diol with diisocyanate to form a prepolymer, which is then extended by a chain extender via one of two routes: (1) by a dihydric glycol chain extender or (2) by a diamine chain extender. The most commonly used diisocyanate is 4,4’-diphenylmethane diisocyanate (MDI), which reacts with a difunctional polyol forming soft segments, such as poly(tetramethylene adipate) (PTMA) or poly(oxytetramethylene) (POTM), to produce TPU, in which 1,4-butanediol (BDO) is used as a chain extender. There are two methods widely used to produce TPU: (1) one-shot reaction sequence and (2) two-stage reaction sequence. The reaction sequences for both methods are well documented in the literature (Hepburn 1982). It should be mentioned that MDI/BDO/PTMA produces ester-based TPU. One can also produce ether-based TPU when MDI reacts with POTM using BDO as a chain extender. TPUs are often referred to as “multiblock copolymers.” In order to have a better understanding of the rheological behavior of TPUs, one must first understand the relationships between the chemical structure and the morphology; thus, a complete characterization of the materials must be conducted. The rheological behavior of TPU depends, among many factors, on (1) the composition of the soft and hard segments, (2) the lengths of the soft and hard segments and the sequence length distribution, (3) anomalous linkages (branching, cross-linking), and (4) molecular weight.

scholarly journals Excellent Toughening of 2,6-Diaminopyridine Derived Poly (Urethane Urea) via Dynamic Cross-Linkages and Interfering with Hydrogen Bonding of Urea Groups from Partially Coordinated Ligands

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1320 ◽  
Author(s):  
Sun ◽  
Guo ◽  
Zhang ◽  
Li ◽  
Liu ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Hydrogen Bonding ◽  
Thermoplastic Polyurethane ◽  
Tensile Tests ◽  
Ligand Interaction ◽  
Chain Flexibility ◽  
Pyridine Moiety ◽  
Hard Segments ◽  
Poly Propylene ◽  
Metal Ligand

Conventional approaches to synthesize thermoplastic polyurethane (TPU) with excellent robustness are limited by a competing relationship between soft and hard segments for tuning mechanical properties in terms of chain flexibility and micro-phase separation. Herein, we present a facile and effective way of simultaneously improving the tensile strength, elongation, and toughness by constructing dynamic cross-linkages from metal-ligand interaction between Zn2+ and pyridine moiety in backbone of poly(urethane urea) (PUU) derived from 2,6-diaminopyridine and poly(propylene glycol). It was found that a Zn2+/pyridine ratio of 1:4 is the most effective for improving robustness. Specifically, tensile strength, elongation, and toughness could be remarkably increased to 16.0 MPa, 1286%, and 89.3 MJ/m3 with 226%, 29%, and 185% increments compared to uncomplexed PUU, respectively. Results from UV-vis, Fourier transform infrared spectroscopy (FTIR), cyclic tensile tests, and stress relaxation reveal that metal-ligand interaction significantly interferes with the hydrogen bonding of urea groups, thus leading to weakening of stiffness. Furthermore, half of vacant ligands enable dynamic complexation during stretching, which consequently ensures constant noncovalent cross-linkages for constraining mutual chain sliding, contributing to simultaneous improvement of tensile strength, elongation, and toughness. This work provides a promising approach for designing TPU with excellent robustness.

scholarly journals Novel Water Loving Coatings (WLC) Lubricious and Durable Guidewires

2017 ◽  
Author(s):  
Peter A. Edwards ◽  
Michael Price ◽  
Nick Nimchuk ◽  
Jeff Mahon
Keyword(s):  
Phenyl Isocyanate ◽  
Structure Property ◽  
Poly Ethylene Glycol ◽  
Water Dispersible ◽  
Structure Property Relationships ◽  
Soft Segments ◽  
Hard Segments ◽  
Poly Ethylene ◽  
Hydrophilic Coatings ◽  
Glycol Methyl Ether

Hydrophilic coatings applied to guidewires or catheters, lower friction of the device thus improves handling and reduces damage to the vessel walls during access, delivery and retrieval. Peripheral guidewires typically consist of a polymer jacket, basecoat and topcoat. The polymer jacket is highly radiopaque for fluoroscopy visualization. Basecoat adheres to the polymer jacket and hydrophilic topcoat. Basecoat and topcoat play important roles towards coating device durability and lubricity. Water Loving Coatings (WLC) are the first developed 510(k) clearance guidewires utilizing epoxy polyurethane technology. Coatings are non-hemolytic and non-cytotoxic. WLC are advances toward glycidyl carbamate (GC) resins. Linear Glycidyl Carbamates have shown excellent flexibility based off structure property relationships [1]. Water dispersible GC (WD-GC) oligomers have been prepared by additions of poly(ethylene glycol) methyl ether (m-peg) to isocyanurate and biuret, then end capped with glycidol [2]. WLC technologies are lubricious and durable water dispersible polyurethane or polyurea glycidyl carbamates [3]. Modified Hyaluronate with WD-GC oligomers have shown increases in lubricity of Guidewires when used with a catheter [4]. WLC coatings have been applied to a micro-wire to reduce endothelial mechanical lining damage [5]. Common thermoplastic urethanes (TPU), similar to WLC morphology, used in the medical industry, are: Biomer and Lubrizol’s Pellethane®, Tecoflex™ and Estane™. Biomer consists of 4,4′-Methylenebis(phenyl isocyanate) (MDI), Ethylenediamine (EDA), and Polytetramethylene diol (Poly THF). Pellethane consists of MDI, 1,4-Butanediol (BDO) and Poly THF. Tecoflex consists of 4-4′-methylenebis (cyclohexyl isocyanate) (H12MDI), BDO and Poly THF. Medical grade Estane is an ester of adipic acid with BDO for soft segments and MDI and BDO for hard segments. TPU structure and morphology dictates polymeric properties.

scholarly journals Mechano-responsive hydrogen-bonding array of thermoplastic polyurethane elastomer captures both strength and self-healing

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Youngho Eom ◽  
Seon-Mi Kim ◽  
Minkyung Lee ◽  
Hyeonyeol Jeon ◽  
Jaeduk Park ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Thermoplastic Polyurethane ◽  
Healing Process ◽  
Polyurethane Elastomer ◽  
Self Healing ◽  
Static Mode ◽  
Soft Segments ◽  
Hard Segments ◽  
Thermoplastic Polyurethane Elastomer ◽  
Dynamic Exchange

AbstractSelf-repairable materials strive to emulate curable and resilient biological tissue; however, their performance is currently insufficient for commercialization purposes because mending and toughening are mutually exclusive. Herein, we report a carbonate-type thermoplastic polyurethane elastomer that self-heals at 35 °C and exhibits a tensile strength of 43 MPa; this elastomer is as strong as the soles used in footwear. Distinctively, it has abundant carbonyl groups in soft-segments and is fully amorphous with negligible phase separation due to poor hard-segment stacking. It operates in dual mechano-responsive mode through a reversible disorder-to-order transition of its hydrogen-bonding array; it heals when static and toughens when dynamic. In static mode, non-crystalline hard segments promote the dynamic exchange of disordered carbonyl hydrogen-bonds for self-healing. The amorphous phase forms stiff crystals when stretched through a transition that orders inter-chain hydrogen bonding. The phase and strain fully return to the pre-stressed state after release to repeat the healing process.

Gelation of thermoplastic polyurethane/2-butanone solutions

e-Polymers ◽  
2005 ◽  
Vol 5 (1) ◽  
Author(s):  
Sonia Florez ◽  
María Eugenia Muñoz ◽  
Anton Santamaría
Keyword(s):  
Hard Segment ◽  
Critical Concentration ◽  
Thermoplastic Polyurethane ◽  
Crystallization Rate ◽  
Solution Viscosity ◽  
Scanning Calorimetry ◽  
Soft Segments ◽  
Gelation Concentration ◽  
Hard Segments ◽  
Chain Entanglements

AbstractNew features of thermoplastic polyurethane (PUR)/2-butanone gels are investigated, using dynamic viscoelastic measurements and differential scanning calorimetry. The work is focused on the effect of the hard-segments content on the gelation process. In the case of PUR with the highest hard-segment fraction (30%), soft segments are not able to crystallize on cooling from solution; consequently, gels are not formed. The copolymer with the lowest hard-segment content (12%) gives the shortest gel times. This is attributed to the low solution viscosity of this copolymer, which enhances the crystallization rate. All gels melt at 7°C, giving rise to a viscoelastic solution in a thermoreversible process. The critical gelation concentration is below the critical concentration for polymer chain entanglements.

Understanding the shape memory behavior of thermoplastic polyurethane elastomers with coarse-grained molecular dynamics simulations

MRS Advances ◽  
2017 ◽  
Vol 2 (6) ◽  
pp. 375-380 ◽  
Author(s):  
Md Salah Uddin ◽  
Jaehyung Ju
Keyword(s):  
Molecular Dynamics ◽  
Shape Memory ◽  
Shape Recovery ◽  
Thermoplastic Polyurethane ◽  
Coarse Grained ◽  
Polyurethane Elastomers ◽  
Weight Percentage ◽  
Shape Memory Behavior ◽  
Soft Segments ◽  
Hard Segments

ABSTRACTWe perform molecular dynamics (MD) simulations to understand thermally triggered shape memory behavior of a thermoplastic polyurethane (TPU) elastomer with an enhanced coarse-grained (CG) model. Hard and soft phases of shape memory polymers (SMPs) are known as fixed and reversible phase, respectively. Fixity depends on the content of hard segments due to their restricted mobility. On the contrary, recovery depends on the dynamic motion of the soft segments as well the degree of cross-linking, which is also affected by the quantity of hard segment. Several CG models of the TPU are constructed varying the weight percentage of soft segments to observe their effects on shape recovery and fixity. All of the models are equilibrated at 300K (above glass transition, Tg: 200-250 K) and deformed under uniaxial loading with NPT (isothermal-isobaric) ensembles. The deformed state is cooled to 100K (below Tg) and further equilibrated to estimate the shape fixity. Shape recovery is predicted by heating and equilibrating the structures back to 300K. By the end of this study, we may answer how much the shape fixities and recoveries are changed for varying concentration of hard segments from thermomechanical cycles with CGMD simulations.

Study on Properties and Preparation of Thermoplastic Polyurethane Hot-Melt Adhesive

2011 ◽  
Vol 311-313 ◽  
pp. 1071-1076
Author(s):  
Jun Ling Tian ◽  
You Ming Cao ◽  
Xin Qi Zhou
Keyword(s):  
Shear Strength ◽  
Thermoplastic Polyurethane ◽  
Molar Ratio ◽  
Polyurethane Elastomer ◽  
Soft Segments ◽  
Comprehensive Performance ◽  
Hard Segments ◽  
Thermoplastic Polyurethane Elastomer ◽  
Hot Melt ◽  
Scanning Electron

The thermoplastic polyurethane elastomer (TPU) was firstly synthesized by using polybutylene adipate (PBA) as soft segments, methane-4-4’-diisocyanate(MDI) and 1,4–butanediol(BDO) as hard segments. The polyurethane hot-melt adhesive was then prepared by adding the tackifying resin, filler and other auxiliaries into the TPU matrix. The structure of the synthetic products was characterized by Infrared Spectrum and the thermal properties and microstructure of polyurethane hot-melt adhesive was tested by the thermogravimetric(TG) and the scanning electron microscopy(SEM), respectively. The results showed that the thermoplastic polyurethane elastomer had the expected structure, the shear strength of polyurethane hot-melt adhesive increased with the pentaerythritol abietate content increasing when the addition of the pentaerythritol abietate is less than 20 wt%, and decreased with the content of CaCO3 filler and petroleum resin increasing, respectively; the thermal stability was improved, and the char yields of the polyurethane blends increased with adding the filler CaCO3. When the molar ratio of PBA:MDI:BDO was 1:2:1, the addition of pentaerythritol abietate and filler CaCO3 was 20 wt% and 30 wt%, the comprehensive performance of PU hot-melt adhesive was better and the shear strength was 7.37 MPa.

scholarly journals Mechano-responsive hydrogen-bonding array of thermoplastic polyurethane elastomer captures both strength and self-healing

2020 ◽  
Author(s):  
Youngho Eom ◽  
Seon-Mi Kim ◽  
Minkyung Lee ◽  
Hyeonyeol Jeon ◽  
Sung Yeon Hwang ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Thermoplastic Polyurethane ◽  
Healing Process ◽  
Polyurethane Elastomer ◽  
Self Healing ◽  
Static Mode ◽  
Soft Segments ◽  
Hard Segments ◽  
Thermoplastic Polyurethane Elastomer ◽  
Dynamic Exchange

Abstract Self-repairable materials strive to emulate curable and resilient biological tissue; however, their performance is currently insufficient for commercialization purposes because mending and toughening are mutually exclusive. Here, we report a carbonate-type thermoplastic polyurethane elastomer that self-heals at 35 °C and is as strong as footwear elastomers. This elastomer exhibits the highest tensile strength to date (43 MPa). Distinctively, it has abundant carbonyl groups in soft-segments and is fully amorphous with negligible phase separation due to poor hard-segment stacking. It operates in dual mechano-responsive mode through a reversible disorder-to-order transition of its hydrogen-bonding array; it heals when static and toughens when dynamic. In static mode, non-crystalline hard segments promote dynamic exchange of disordered carbonyl hydrogen-bonds for self-healing. The amorphous phase forms stiff crystals when stretched through a transition that orders inter-chain hydrogen bonding. The phase and strain fully return to the pre-stressed state after release to repeat healing process.

scholarly journals Properties of polyurethane foam with fourth-generation blowing agent

e-Polymers ◽  
2021 ◽  
Vol 21 (1) ◽  
pp. 763-769
Author(s):  
Vladimir Yakushin ◽  
Ugis Cabulis ◽  
Velta Fridrihsone ◽  
Sergey Kravchenko ◽  
Romass Pauliks
Keyword(s):  
Thermal Conductivity ◽  
Polyurethane Foam ◽  
Cellular Structure ◽  
Fourth Generation ◽  
Low Density ◽  
Technological Parameters ◽  
Blowing Agent ◽  
Foam Properties ◽  
Rise Direction ◽  
Foam Production

Abstract Climate change makes it imperative to use materials with minimum global warming potential. The fourth-generation blowing agent HCFO-1233zd-E is one of them. The use of HCFO allows the production of polyurethane foam with low thermal conductivity. Thermal conductivity, like other foam properties, depends not only on the density but also on the cellular structure of the foam. The cellular structure, in turn, depends on the technological parameters of foam production. A comparison of pouring and spray foams of the same low density has shown that the cellular structure of spray foam consists of cells with much less sizes than pouring foam. Due to the small size of cells, spray foam has a lower radiative constituent in the foam conductivity and, as a result, a lower overall thermal conductivity than pouring foam. The water absorption of spray foam, due to the fine cellular structure, also is lower than that of pouring foam. Pouring foam with bigger cells has higher compressive strength and modulus of elasticity in the foam rise direction. On the contrary, spray foam with a fine cellular structure has higher strength and modulus in the perpendicular direction. The effect of foam aging on thermal conductivity was also studied.

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