Effects of emulsification on properties of quaternary ammonium ion-based polyurethane anionomer

Summary Quaternary ammonium ion-based Polyether polyurethane anionomer solution and emulsion are studied. In the un-ionized film, the soft segment crystallites are not present. Ionization creates soft segment crystallites and produces increased phase separation between the soft and hard domains, which leads to an increase in both tensile strength and elongation at break. Emulsification of the PU ionomer solution can lead to slightly increased phase mixing. During the emulsification, conductivity and viscosity variations show that water is first adsorbed on the surface of the hard-segment microionic lattices and then enters successively into the more disordered and less disordered hard domains. The morphology of the unionized film shows that the hard domains are dispersed in the soft domains and that the size of hard domain increases greatly after the ionization. After dispersion, the hard segments originally distributed in the dispersed phase can be inverted to become a hard domain network.     

Thermal and mechanical properties of fiber‐forming poly(urethane semicarbazide)s

Fiber‐forming poly(urethane semicarbazide)s were prepared with poly(butylene adipate)glycol as soft‐segment domains and hexamethylene diisocyanate/terephthalic dihydrazide as hard‐segment domains. The hard‐segment content was varied via variations in the polyol/isocyanate molar ratio, and the films were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. The effect of the hard‐segment‐content variation on the properties was studied by differential scanning calorimetry, stress–strain analysis, and dynamic mechanical testing. Differential scanning calorimetry showed that the samples exhibited a very low level of hard/soft‐segment phase mixing. The stress–strain analyses revealed that the elongation at break decreased with an increase in the hard‐segment content and that the mechanical property depended on the overall crystallinity of the samples. Dynamic mechanical tests revealed a high glassy‐to‐rubbery state modulus and a high degree of phase separation between the hard and soft segments. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 86–93, 2002     

The role of diisocyanate structure on microphase separation of solution polymerized polyureas

Three diisocyanates with different symmetry and planarity (2,6-TDI, 2,4-TDI and MDI) were used to synthesize polyureas with the same oligomeric polyetheramine having a molecular weight of ∼1000 g/mol. The influence of diisocyanate symmetry on the phase separated morphology, hydrogen bonding behavior, and molecular dynamics were investigated. Symmetric diisocyanate structures facilitated self-assembly of hard segments into ribbon-like domains, driven by strong bidentate hydrogen bonding. The hard domains for the 2,6-TDI polymer appear to be continuous in AFM images, while the persistence length of the hard domains in the 2,4-TDI and MDI polymers gradually decrease, and fewer hard domains are apparent with decreasing hard segment symmetry. The extent of hard/soft segment demixing, assessed from small-angle X-ray scattering, was very incomplete for all of the polyureas and is significantly influenced by hard segment structure. For the 2,4- and 2,6-TDI polyureas, two segmental relaxations were observed using dielectric relaxation spectroscopy; one arising from relatively unrestricted motion in the soft segment rich phase, and a slower process associated with segments in the soft phase constrained by their attachment to hard domains.     

Microstructural organization of polydimethylsiloxane soft segment polyurethanes derived from a single macrodiol

Segmented polyurethane (PU) block copolymers were synthesized using 4,4′-methylenediphenyl diisocyanate and 1,4-butanediol as hard segments and oligomeric ethoxypropyl polydimethylsiloxane (PDMS) as the soft segments, with hard segment contents ranging from 26 to 52 wt%. The microphase separated morphology, phase transitions, and degrees of phase separation of these novel copolymers were investigated using a variety of experimental methods. Like similar copolymers with mixed ethoxypropyl PDMS/poly(hexamethylene oxide) soft segments, PU copolymers containing only ethoxypropyl PDMS soft segments were found to consist of three microphases: a PDMS matrix phase, hard domains, and a mixed phase containing ethoxypropyl end group segments and dissolved short hard segments. Analysis of unlike segment demixing using small-angle X-ray scattering demonstrates that degrees of phase separation increase significantly as copolymer hard segment content increases, in keeping with findings from Fourier transform infrared spectroscopy measurements.     

Structure-property behaviour of segmented polyether-MDI-butanediol based urethanes: effect of composition ratio

The structure-property relationship of a systematic series of segmented polyurethanes was investigated segment was 4,4′-diphenylmethane diisocyanate (MDI) extended with 1,4-butanediol, and the soft segment was 2000 M_w poly (tetramethylene oxide) ether. X-ray studies reveal that some hard segment segment was 2000 mW poly (tetramethylene oxide) ether. X-ray studies reveal that some hard segment crystallization occurs at high hard segment content (45%). In addition, other morphological changes take place as the hard segment fraction is increased. The texture changes from that in which little such domain content exists at low hard segment levels (15%), to that in which the polymer has an interlocking domain morphology at high hard segment content (35 and 45%). Preferable elastomeric properties (low hysteresis, high extension) can be obtained when isolated hard segment domains exist (25% hard segment). Thermal treatment of the samples results in domain disruption and hard-soft segment mixing. However, this phenomenon, and the consequent time-dependent structure recovery as the material is allowed to age, is composition dependent. In general, crystalline domains, when present, are disrupted the least while the fastest recovery is displayed by samples with noncrystalline domain texture. This behaviour can be explained qualitatively in terms of kinetic diffusion effects relative to the thermodynamic driving forces for phase separation.     

Influence of soft segment composition on phase-separated microstructure of polydimethylsiloxane-based segmented polyurethane copolymers

Segmented polyurethane block copolymers were synthesized using 4,4′-methylenediphenyl diisocyanate (MDI) and 1,4-butanediol (BDO) as hard segments and various soft segments derived from poly(hexamethylene oxide) (PHMO) and poly(dimethylsiloxane) (PDMS)-based macrodiols and mixtures thereof. The microstructure and degrees of phase separation were characterized using a variety of experimental methods. Copolymers synthesized with the PDMS macrodiol and from PDMS/PHMO macrodiol mixtures were found to consist of three phases: a PDMS phase; hard domains; and a mixed phase of PHMO, PDMS ether end group segments and some dissolved hard segments. Two models were used to characterize the small-angle X-ray scattering from these copolymers: pseudo two-phase and core-shell models. Analysis using both methods demonstrates that as the PDMS content in the soft segment mixture increases, the greater the fraction of hard segments involved in hard domains than are dissolved in the mixed phase. Findings from analysis of the carbonyl region of FTIR spectra are also in agreement with greater hard/soft segment demixing in copolymers containing higher PDMS contents.     

Structure–property relationships of thermoplastic polyurethane elastomers based on polycarbonate diols

The phase-separation behavior and morphology of polycarbonate-based polyurethanes were investigated as a function of the soft-segment molecular weight and chemical structure and the 4,4′-diphenylmethane diisocyanate/1,4-butanediol based hard-segment contents. Polarized optical microscopy and atomic force microscopy images showed that the surface morphologies changed as the soft-segment molecular weight and hard-segment content varied and also when the sample preparation conditions were modified. An increase in the soft- and hard-segment lengths led to increased phase separation with respect to the lower molecular weight soft segment, and this showed an interlocked and connected morphology of intermixed soft and hard domains. The surface morphology of phase-separated polyurethanes with hard segments composed of more than four to five 4,4′-diphenylmethane diisocyanate units contained globular hard-segment domains formed by spherulites, in which the size and connectivity between the branched lamellae changed with the hard-segment size. Interlamellar areas related to the soft segment were seen in the spherulites. Variations in the hard-segment spherulites were observed for polyurethanes based on soft segments of different molecular weights. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Morphology and water vapor permeability of temperature‐sensitive polyurethanes

A series of segmented polyurethanes (PUs) were prepared, in which five different polyols and hexamethylene diisocyanate were used as soft segments, and 4,4′‐diphenylmethane diisocyanate, hydrophilic segment poly (ethylene glycol) 200 (PEG 200), and chain extender 1,4‐butanediol were used as hard segment. Morphology of the PUs was investigated using differential scanning calorimetry, wide angle X‐ray diffraction, polarizing microscopy, and transmission electron microscopy. Water vapor permeability of the membranes as a function of temperature was tested accordingly. Results show that the presence of PEG200 interferes the crystallization of hard segment in these PUs, and at the same time, increases phase compatibility between soft and hard segment in the PET‐PU. It leads to a lower crystal melting temperature and degree of crystallinity of soft segment in the segmented PU than those of pure polyols, and no crystallization existing in hard segment. A morphological model is proposed, that is, aggregated soft‐segment‐rich domains can be observed clearly in the PUs with high crystallinity in soft segment, while identifiable hard domains are well‐distributed in the soft segment domains in the PU with low crystallinity. Within the temperature range of crystal melting, water vapor permeability of the PU membranes increases significantly with increase of temperature. Such temperature‐sensitive property is triggered by crystal melting of soft segment. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

粒料法合成聚氨酯分散体及性能的研究

以聚四氢呋喃二醇(PTMG)为软段,异氟尔酮二异氰酸酯(IPDI)和1,4-丁二醇(BDO)为硬段,二羟甲基丙酸(DMPA)为亲水单体,采用粒料法合成了聚氨酯离子聚合物粒料,制备了固含量为40%的聚氨酯分散体(PUD),研究了亲水含量和硬段含量对分散体性能及其胶膜性能的影响。PUD的ζ电位处于30~60 mV,黏度小于1100 mPa s。随着亲水含量增加,平均粒径减小,粒径分布变窄,黏度升高;硬段含量增加,平均粒径增大,粒径分布变宽,黏度降低。透射电镜显示,溶胶粒子呈大小不一的球形结构。PUD胶膜吸水率在3.15%~6.67%。力学性能测试表明硬段含量增加,断裂伸长率降低,拉伸强度增强。DMA测试显示胶膜出现相分离,有硬段和软段两个玻璃化转变温度。随着硬段含量增加,相分离程度提高,软段玻璃化温度降低,硬段玻璃化温度升高。     

Exploring long-range connectivity of the hard segment phase in model tri-segment oligomeric polyurethanes via lithium chloride

The influence of the extent of hydrogen bonding in mediating the long-range connectivity and percolation of the hard segment phase in model tri-segment oligomeric polyurethanes (PU) was explored by using LiCl as a molecular probe. A 22 wt% hard segment containing model PU plaque based on a mono-functional oligomeric polyether, 80:20 2,4:2,6 isomeric mixture of toluene diisocyanate, and water as a chain extender was employed. Samples cast from 20 wt% solutions in dimethyl acetamide were utilized. The tapping-mode atomic force microscopy (AFM) phase image of the solution cast film sample (soft segment T_g −63 °C) without LiCl exhibited the presence of long interconnected ribbon-like hard domains. The long-range connectivity and percolation of the hard phase that arose during plaque formation gave rise to a brittle rigid solid. A systematic break-up of the hard domains was also observed by AFM when the concentration of LiCl was increased from 0.1 to 1.5 wt%. DSC analysis indicated that the samples were able, however, to maintain a microphase separated morphology even at the highest LiCl concentration utilized in the study. FT-IR data confirmed that LiCl interacts with the hard domains of the model PU samples by disrupting the hydrogen bonding capability of the urea hard segments. A systematic softening of the samples was observed with increasing LiCl content as confirmed by thermomechanical analysis. Thus, this study indicates that hydrogen bonding plays an important role in assisting the hard segments in PU to develop long-range connectivity and percolation of this phase through the soft matrix.     

负离子型聚氨酯离聚体水分散过程的相反转

用异佛尔酮二异氰酸酯、聚己二酸新戊二醇酯和二羟甲基丙酸（DMPA）合成了负离子型聚氨酯离聚体．研究了该类离聚体在水分散过程中的相反转变化,讨论了DMPA质量分数和水分散温度对相反转过程的影响。结果表明,DMPA质量分数增加或水分散温度提高,可使相反转所需的时间缩短,分散液粒子粒径变小,粒径分布更均匀,黏度增大。水分散温度的作用较DMPA更为明显。差示扫描量热分析表明,水分散过程破坏了亲水性硬链段的有序性。傅里叶变换红外光谱分析表明,聚氨酯水分散液用乙二胺扩链后．脲羰基的氢键化程度随DMPA质量分数的增加、水分散温度的提高而提高。     

Polyurethane elastomers based on molecular weight advanced poly(ethylene ether carbonate) polyols. III. Effects of diisocyanate modified diols

A series of diisocyanate-modified, molecular weight advanced poly(ethylene ether carbonate) diols has been prepared, characterized, and formulated into polyurethane elastomers using a prepolymer process. Properties were compared to a polyurethane elastomer control in which the only variable was the diisocyanate modification. The diisocyanate modification produces polymers with increased modulus (445–730% at 25°C), improved tensile strength and hardness properties and reduced (improved) coefficients of linear thermal expansion, while still passing the notched Izod impact test. The tensile strength at break increases with increasing number of urethane moieties in the soft segment and the elongation at break also increases. The plaques studied appear to have a three-phase morphology—a soft segment continuous phase containing amorphous hard segment, an amorphous hard segment phase plasticized by about 11% of the soft segment material, and a crystalline hard segment. The polymers based on the diisocyanate modified polyols are significantly more phase mixed than the control due to the increased amount of hard segment-soft segment interactions taking place. The improved properties of the polymers made with the modified polyols are due to their higher hydrogen bonding protential which gives more physically crosslinked polymers.     

Morphology of crystalline polyurethane hard segment domains and spherulites

Chemical staining of the unsaturated hard segment portion of a segmented polyurethane based on poly(propylene oxide)/4,4′-diphenyl methane-diisocyanate/butenediol (PPO/MDI/BEDO) permitted observation of the hard segment domains by electron microscopy. The hard segment phase forms (para)-crystalline domains which are fibrillar in nature. The fibrils are arranged radially into spherulite structures. The concentration of the hard segment is greatest at the centre of the largest spherulites suggesting the preferential agglomeration of molecules with the longest hard segment sequences at the beginning of the phase separation process from solution.     

Morphology of water-blown flexible polyurethane foams

A series of four TDI–polypropylene oxide (PO) water-blown flexible polyurethane foams was produced in which the water content was varied from 2 to 5 pph at a constant isocyanate index of 110. A portion of each foam was thermally compression molded into a plaque. The morphology of both the foams and plaques was investigated using dynamic mechanical spectroscopy (DMS), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), scanning electron microscopy (SEM), swelling, wide angle X-ray scattering (WAXS), and small angle X-ray scattering (SAXS). A high degree of microphase separation occurs in these foams, and its degree is nearly independent of water (hard segment) content. In the foam with the lowest water content the morphology possesses many similarities to that of typical linear segmented urethane elastomers. Small hard segment domains are present with a correlation distance of about 7.0 nm. When the water content is increased a binodal distribution of hard segment material appears. There are the small hard segment domains typical of segmented urethane elastomers as well as larger “hard aggregates” greater than 100 nm in size. The larger domains are thought to be aggregates of rich polyurea that develop by precipitation during the foaming reaction. WAXS patterns of the foams suggest urea and possibly hard segment ordering that may be of a paracrystalline nature but certainly lacking in true 3-dimensional crystallinity.     

Synthesis and characterization of thermoplastic polyurethanes as binder for novel thermoplastic propellant

Two series of thermoplastic polyurethanes (TPUs), which used nitroester plasticiable tetrahydrofuran‐ethylene oxide random copolyether as soft segment and adduction products of isophorone diisocyanate (IPDI) and toluene diisocyanate (TDI) with 1,4‐butanediol as hard segments respectively, were successfully synthesized as binders for novel thermoplastic propellant. Mechanical tests and DSC techniques were applied to make characterizations of the polymers in order to choose candidate materials. Results shown that the TPU based on IPDI with fraction of the hard segment around 45% will meet requirements of propellant in terms of mechanical properties and glass transition of the soft segment phase. The results were further manifested in detail by quantitative studies of the degree of microphase separation as well as hydrogen bonding within the hard segment domain based on the equations established through FTIR and DSC analyses. It was found that mixing of two phases, which mainly referred to the mount of the hard segment dissolving into the soft segment phase, was as little as 10% in IPDI series TPUs, whereas it was almost up to 30% in TDI series. This indicated that better phase separation was achieved in IPDI series TPU. By contrast, studies of hydrogen bonding in domain revealed that the domain of TPUs prepared with TDI was much oriented in comparison with that with IPDI, which indicated higher processing temperatures. The results were raised by the melting index results under required conditions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2961–2966, 2002; DOI 10.1002/app.2324     

Morphology–properties relationship in high‐renewable content polyurethanes

The effect of diisocyanate nature and hard segment content on the morphology and properties of high‐renewable content segmented thermoplastic polyurethanes was studied. Vegetable oil‐based polyether diol and corn sugar derived chain extender were used as renewable reactants together with an aliphatic (1,6‐hexamethylene diisocyanate, HDI) or aromatic (4,4′‐diphenylmethane diisocyanate, MDI) diisocyanate as hard segment. Segmented thermoplastic polyurethanes were synthesized by two‐step bulk polymerization. Morphology and physicochemical, thermal and mechanical properties were analyzed by Fourier‐transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, atomic force microscopy, and mechanical testing. The effect of mechanical deformation over the microstructure was also analyzed. Changes in crystallinity and hard segment hydrogen bonding after mechanical testing were evaluated by Fourier‐transform infrared spectroscopy and differential scanning calorimetry. The increase of physical crosslinking sites by aromatic diisocyanate and chain extender ratio in the polyurethane results in hard segment crystalline domains with spherulitic morphology, which enhance the stiffness and hardness whereas percentage elongation at break diminish. The flexible, linear aliphatic nature of HDI favors the arrangement of urethane groups thus creating strong hard segment interactions and hard segment crystal microdomains composed of fibrillar morphology are observed. POLYM. ENG. SCI., 54:2282–2291, 2014. © 2013 Society of Plastics Engineers     

Effects of aggregation structure on rheological properties of thermoplastic polyurethanes

The effects of the molecular aggregation structure on the rheological properties of thermoplastic polyurethane (TPU) were investigated. The TPU was composed of poly{(tetramethylene adipate)-co-(hexamethylene adipate)} glycol as the soft segments, 4,4′-diphenylmethane diisocyanate and 1,4-butanediol as the hard segments. The TPU sheets prepared by injection molding were annealed at various temperatures from 23 to 120 °C to vary the molecular aggregation structure. Glass transition temperature of the soft segment and melting points of the hard segment domains of the TPUs decreased and increased, respectively, with increasing annealing temperature. The results of DSC, solid-state NMR spectroscopy and dynamic viscoelastic measurements revealed that the degree of micro-phase separation of the TPUs becomes stronger with increasing annealing temperature due to the progress of formation of well-organized hard segment domains. The dynamic temperature sweep experiments for molten TPUs revealed that the temperature at critical gel point, which is defined as the temperature at which the dynamic storage modulus coincides with the loss storage modulus, in the cooling process increased with the progress of aggregation of the hard segments in the TPUs observed in the solid state. The uniaxial elongational viscosity measurements showed that TPUs exhibited an obvious strain hardening behavior with strain rate owing to residual hard segment domains at an operating temperature. It was revealed that the formation of well-organized hard segment domains had a profound effect on the rheological properties of TPUs, in particular on their elongational viscosity.     

Structure and physical properties in crosslinked polyurethanes

Crosslinked polyurethanes based on a mixture of toluene diisocyanate, polypropylene glycol, trimethylol propane (TMP), glycerol (GLY), and desmophen (DES) were synthesized with various ratios of DES and GLY. Chemical crosslinks were introduced through the hard segment (TMP, GLY) and through the soft segment (DES). The effects of the degree of crosslinking on the properties were examined. The crystallinity of the obtained polymers were studied by using modulated differential scanning calorimetry, differential scanning calorimetry, dynamic mechanical analysis and their morphology was studied by atomic force microscopy. It appeared that the degree of crosslinking increased according to the increase of GLY content. Moreover, it was found that chemical crosslinks in the hard segment destroyed the crystallinity of the hard phase and reduced the mobility of the soft phase, improving the heat stability of the hard domains, and modifying the mechanical properties of polyurethane films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermoplastic polyurethane elastomers based on polycarbonate diols with different soft segment molecular weight and chemical structure: Mechanical and thermal properties

A series of thermoplastic polyurethane elastomers based on polycarbonate diol, 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol was synthesized in bulk by two‐step polymerization varying polycarbonate diol soft segment molecular weight and chemical structure, and also hard segment content, and their effects on the thermal and mechanical properties were investigated. Dynamic mechanical analysis termogravimetric analysis, differential scanning calorimetry, Fourier transform infrared‐attenuated total reflection spectroscopy and mechanical tests were employed to characterize the polyurethanes. Thermal and mechanical properties are discussed from the viewpoint of microphase domain separation of hard and soft segments. On one hand, an increase in soft segment length, and on the other hand an increase in the hard segment content, i.e., hard segment molecular weight, was accompanied by an increase in the microphase separation degree, hard domain order and crystallinity, and stiffness. In phase separated systems more developed reinforcing hard domain structure is observed. These hard segment structures, in addition to the elastic nature of soft segment, provide enough physical crosslink sites to have elastomeric behavior. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers     

IPDI／PEPA型热塑性聚氨酯的合成及表征

以异佛尔酮二异氰酸酯(IPDI)、聚己二酸乙二醇丙二醇酯二醇(PEPA)和1,4-丁二醇(BDO)为原料,用熔融预聚合两步法,后聚合温度60-90℃,合成硬段含量为50％的IPDI／PEPA型热塑性聚氨酯。采用凝胶渗透色谱仪测试其数均相对分子质量为78 650,重均相对分子质量为125 446,相对分子质量分布为1．59。红外光谱分析表明聚合较为完全,聚合物不存在支链结构,为热塑性材料。DSC分析表明聚合物软段和硬段的玻璃化转变温度分别为-34℃和48℃,透射电镜照片进一步说明该材料存在一定的相分离。