Synthesis,characterization, and pervaporation properties of segmented poly(urethane‐urea)s

Poly(urethane‐urea)s (PUUs) from 2,4‐tolylene diisocyanate (2,4‐TDI), poly(oxytetramethylene)diols (PTMO) or poly(butylene adipate)diol (PBA), and various diamines were synthesized and characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, and density measurements. Transport properties of the dense PUU‐based membranes were investigated in the pervaporation of benzene–cyclohexane mixtures. It was shown that the pervaporation characteristics of the prepared membranes depend on the structure and length of the PUU segments. The PBA‐based PUUs exhibit good pervaporation performance along with a very good durability in separation of the azeotropic benzene–cyclohexane mixture. They are characterized by the flux value of 25.5 (kg μm m⁻² h⁻¹) and the separation factor of 5.8 at 25°C, which is a reasonable compromise between the both transport parameters. The PTMO‐based PUUs display high permeation flux and low selectivity in separation of the benzene‐rich mixtures. At the feed composition of 5% benzene in cyclohexane, their selectivity and flux are in the range of 3.2 to 11.7 and 0.4 to 40.3, respectively, depending on the length of the hard and soft segments. The chemical constitution of the hard segments resulting from the chain extender used does not affect the selectivity of the PUU membranes. It enables, however, the permeability of the membranes to be tailored. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1615–1625, 1999     

Segmented poly(urethane‐urea) elastomers based on polycaprolactone: Structure and properties

A series of segmented poly(urethane‐urea) polymers have been synthesized varying the hard segments content, based on the combination of polycaprolactone diol and aliphatic diisocyanate (Bis(4‐isocyanatocyclohexyl)methane), using diamine (1,4‐Butylenediamine) as the chain extender. The microstructure and properties of the material highly depend on the hard segments content (from 14 to 40%). These PUUs with hard segment content above 23% have elastomeric behaviors that allow high recoverable deformation. The chemical structure and hydrogen bonding interactions were studied using FTIR and atomic force microscopy, which revealed phase separation that was also confirmed by DSC, dynamic‐mechanical, and dielectric spectroscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and Properties of Poly(urethane‐urea) Crosslinked Coatings from Perfluorocopolyethers and Polyfunctional Isocyanurates

Two model isocyanate terminated resins were synthesized by addition of perfluorocopolyether oligomers (M̄_n ca. 1 000) with cyclic polyisocyanurates of hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI). The resins were characterized by chemical titration, gel permeation chromatography, FT‐IR spectroscopy, and viscosity. The two resins, and some blends of them, were crosslinked through urea bond formation by exposure to atmospheric moisture. The resulting coatings were characterized by dynamic mechanical spectroscopy (DMS), tensile properties, abrasion resistance, adhesion, atomic force microscopy (AFM) and contact angle measurements. Phase separation phenomena and mechanical properties were related to composition and thermal transitions of both hard and soft phase. Adhesion (pull‐off) was poor on inorganic surfaces like glass and aluminium (<1 MPa) and good on organic primers (>5 MPa). The use of organosilane adhesion promoters was successfully investigated. Surface analysis by AFM showed the formation of a chemically heterogeneous very smooth (on a nanoscale) surface. Contact angle determinations with water, diiodomethane and hexadecane were carried out. The total surface energy of coatings was calculated by the harmonic mean approximation and resulted typically low (16.0–17.5 mN/m) and unaffected by the coating bulk composition.     

Preparation of aqueous anionic poly(urethane‐urea) dispersions. Influence of the structure and molecular weight of the macrodiol on the dispersion and polymer properties

Aqueous poly(urethane‐urea) dispersions were prepared by the prepolymer mixing technique, without any organic solvent, using two aliphatic diisocyanates (α,α,α′,α′‐tetramethyl‐1,3‐xylylene diisocyanate and isophorone diisocyanate) and various macrodiols, in conjunction with a fixed proportion of emulsifying agent (dimethylol propionic acid, neutralised with triethylamine) and the same chain extender (1,2‐ethylene diamine). The properties of both the dispersions and the dried polymer films were characterised as a function of the two main parameters studied in this investigation, viz the structure of the macrodiols and their molecular weight, in order to establish criteria leading to optimised performances in terms of dispersion stability, particle size, and polymer film properties. Copyright © 2005 Society of Chemical Industry     

Preparation and properties of MDI/H12MDI‐based water‐borne poly(urethane‐urea)s—Effects of MDI content and radiant exposure

Water‐borne poly(urethane‐urea)s (WBPUs) were prepared by a prepolymer mixing process using aromatic diisocyanate (MDI, 4,4′‐diphenylmethane diisocyanate)/aliphatic diisocyanate (H₁₂MDI, 4,4′‐methylenebis cyclohexyl isocyanate), polypropylene glycol (PPG, M_n = 1000), dimethylol propionic acid, and ethylene diamine as a chain extender, and triethylamine as a neutralizing agent. The effect of MDI on the molecular weight, chemical structure, dynamic thermo, and tensile properties of WBPUs was investigated. The yellowness index (YI, photo‐oxidation behavior) change of WBPUs under accelerated weathering exposure was also investigated. The WBPUs containing higher MDI content showed lower molecular weight, which verified the participation of some high reactive isocyanate groups of MDI into side reaction instead of chain growing reaction. As the MDI content increased, the storage modulus and tensile modulus/strength of WBPUs film increased, and their glass transitions of soft segments (T_gs) and hard segments (T_gh) were shifted to higher temperature. The intensity of tan δ peak of all three samples increased with increasing radiant exposure. The YI of H₁₂MDI‐based WBPU sample (WBPU‐0) was not occurred. The YI of WBPUs containing MDI increased with increasing MDI content and radiant exposure. However, the YI of sample WBPU‐25 containing 25 mol % of MDI at 11.3 MJ/m² (radiant exposure) was 6.6 which is a permissible level for exterior applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and properties of flame retardant poly(urethane‐imide)s containing phosphine oxide moiety

The preparation of new poly(urethane‐imide)s (PUIs) having acceptable thermal stability and higher flame resistance was aimed. Two new aromatic diisocyanate‐containing methyldiphenylphosphine oxide and triphenylphosphine oxide moieties were synthesized via Curtius rearrangement in situ and polymerized by various prepared diols. Four aliphatic hydroxy terminated aromatic based diols were synthesized by the reaction between ethylene carbonate and various diphenolic substances. Chemical structures of monomers and polymers were characterized by FTIR, ¹H NMR, ¹³C NMR, and ³¹P NMR spectroscopy. Thermal stabilities and decomposition behaviors of the PUIs were tested by DSC and TGA. Thermal measurements indicate that the polymers have high thermal stability and produce high char. Polymers exhibit quite high fire resistance, evaluated by fire test UL‐94. The films of the polymers were prepared by casting the solution. Inherent viscosities, solubilities, and water absorbtion behaviors of the polymers were reported in. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structure–property relationships of poly(urethane–urea)s with ultra-low monol content poly(propylene glycol) soft segments. Part II. Influence of low molecular weight polyol components

Segmented poly(urethane–urea)s have been synthesized with mixed soft segments of ultra-low monol content poly(propylene glycol) (PPG) and tri(propylene glycol) (TPG) which allows the fabrication of quality elastomers without crosslinking. The narrow molecular weight distribution of the ultra-low monol content PPG polyols allows for the probing of the influence of the low molecular components of the molecular weight distribution through the inclusion of low molecular homologs of PPG such as TPG. Structure–property relationships for these materials were investigated as average soft segment molecular weight was varied by blending 8000 g/mol PPG with TPG to achieve molecular weights of 2500, 2000, and 1500 g/mol. Morphological features such as microphase separation, interdomain spacing and interphase thickness were quantified and revealed with SAXS. AFM was utilized to verify the microphase separation characteristics inferred by SAXS. The thermal and mechanical behavior was assessed through applications of DMA, DSC, and conventional mechanical tests. It was found that as the average soft segment molecular weight was decreased through the addition of TPG, the interdomain spacing distinctly increased contrary to the trend seen for decreasing soft segment molecular weight in PPG based systems without TPG. Additionally, the inclusion of TPG in the poly(urethane–urea) formulations resulted in the formation of larger hard domains as evidenced by AFM. These results and supporting evidence from DMA, DSC, birefringence, and mechanical testing led to the conclusion that TPG apparently acts more as a chain extender as well as, or in contrast to, a soft segment.     

Synthesis and characterization of poly(urethane‐ester)s based on calcium salt of mono(hydroxybutyl)phthalate

Calcium‐containing poly(urethane‐ester)s (PUEs) were prepared by reacting diisocyanate (HMDI or TDI) with a mixture of calcium salt of mono(hydroxybutyl)phthalate [Ca(HBP)₂] and hydroxyl‐terminated poly(1,4‐butylene glutarate) [HTPBG₁₀₀₀], using di‐n‐butyltin‐dilaurate as catalyst. About six calcium‐containing PUEs having different composition were synthesized by taking the mole ratio of Ca(HBP)₂:HTPBG₁₀₀₀:diisocyanate (HMDI or TDI) as 3:1:4, 2:2:4, and 1:3:4. Two blank PUEs were synthesized by the reaction of HTPBG₁₀₀₀ with diisocyanate (HMDI or TDI). The polymers were characterized by IR, ¹H NMR, Solid state ¹³C‐CP‐MAS NMR, TGA, DSC, XRD, solubility, and viscosity studies. The T_g value of PUEs increases with increase in the calcium content and decreases with increase in soft segment content. The viscosity of the calcium‐containing PUEs increases with increase in the soft segment content and decreases with increase in the calcium content. X‐ray diffraction patterns of the polymers show that the HMDI‐based polymers are partially crystalline and TDI‐based polymers are amorphous in nature. The dynamic mechanical analysis of the calcium‐containing PUEs based on HMDI shows that with increase in the calcium content of polymer, modulus (g′ and g″) increases at any given temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1720–1727, 2006     

Synthesis and thermal properties of poly(urethane‐imide)

The synthesis and thermal properties of thermoplastic poly(urethane‐imide) (PUI) resins were studied. Model reaction studies on the reactions of 4,4′‐diphenylcarbamatodiphenylmethane and 4,4′‐diisocyanatodiphenylmethane with phthalic anhydride were performed. We found that the reaction of anhydrides with urethane groups could take place under certain reaction conditions. According to the model reaction studies, N‐2‐methyl‐pyrrolidone was employed as a solvent, and no catalyst was used in the polymerization. To restrain the side reaction of anhydrides with urethane groups, we adopted a two‐step chain‐extending procedure in a chain‐extending reaction. The inherent viscosity of PUI was 0.83–0.99 dL/g. The prepared polymers not only exhibited improved solubility in organic solvents but also formed flexible films. Thermogravimetric analysis showed that PUI exhibited a two‐step thermal weight‐loss pattern. The first step of the thermal degradation of PUI was attributed to the thermooxidizing cleavage of weak and labile linkage, such as urethane groups, isopropylidene, and methylene, except for imide rings. The polymer inherent viscosity decreased sharply during the first step of thermal degradation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 773–781, 2001     

Miscibility and physical properties of conducting poly(urea‐urethane) thermoplastic elastomers

A series of amine‐terminated polyaniline oligomer (OPA)‐based conducting poly(urea‐urethane) thermoplastic elastomers (PUUs) was synthesized by two‐stage solution polymerization and characterized by FTIR. Various percentages of OPA were introduced into PUUs as chain extenders to form hard segments of PUUs with urea‐linkages. Spectroscopic and differential scanning calorimetry, as well as dynamic mechanical analysis, were conducted to elucidate the interaction and degree of miscibility between hard and soft segments, which were related to the stress–strain properties of PUUs. The hydrogen bonding index (HBI) measured by FTIR was employed to show the degree of interchain hydrogen bonding. Copolymer films with higher OPA content exhibit higher HBI and the degree of miscibility is significantly improved. The resultant conducting copolymers have higher tensile strength, higher Young's modulus, and lower elongation at break, because of the long rigid structure of OPA and the increase in the number of hydrogen bonds among the copolymers blocks. Incorporating OPA in PUUs increases the mass of the residue at temperatures over 600°C, according to thermogravimetric analysis. The conductivity of PUUs is found to range from 0.83 S/cm for neat OPA to 6.11 × 10^?5 S/cm for PUUs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3803–3810, 2007     

Synthesis and characterization of isocyanic acid,m‐phenylenediiso‐propylidene based poly(urethane‐urea) dispersions containing different amount of 2,2‐Bis(hydroxyl methyl)propionic acid

Isocyanic acid, m‐phenylenediiso‐propylidene (m‐TMXDI)‐based anionic poly(urethane‐urea) dispersions were prepared by the prepolymer mixing process. The equivalent ratio of NCO/OH was kept constant at 1.8, while 2,2‐bis(hydroxyl methyl) propionic acid (DMPA) used was varied from 3 to 10 wt %. The colloidal stability of poly(urethane‐urea) dispersions arose entirely from the presence of ionized carboxylic acid groups. The chemical structure of poly(urethane‐urea) dispersions with various amount of DMPA were identified by FTIR and ¹³C NMR analysis. The test results showed that the hydrophilicity of poly(urethane‐urea) dispersions were increased with increase in DMPA content. The degree of chain extension was much lower than the values predicted theoretically due to the side reaction of a small amount of hydrophilic isocyanate‐terminated prepolymer with water. The average particle size of poly(urethane‐urea) dispersions were decreased with an increase in DMPA content, and this lead to an increase in viscosity. Also, the thermal degradation behavior were measured and was shown that the initial degradation temperature shifted to lower temperature with an increase in DMPA content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5737–5746, 2006     

Aqueous poly(urethane–urea) dispersions and cast films based on m‐TMXDL. 1. Structure–property relationships

Aqueous poly(urethane–urea) dispersions were prepared from polycaprolactone diol, α,α,α′,α′‐tetramethyl‐1,3‐xylylene diisocyanate (m‐TMXDI) and α,α‐dimethylol propionic acid (DMPA) using a prepolymer mixing process. In the process, polyurethane prepolymers were neutralised with triethylamine and the chains extended in water with either hydrazine, 1,2‐ethylene diamine or 1,2‐propylene diamine. For comparison, some samples were prepared from a more commonly used diisocyanate, isophorone diisocyanate (IPDI). Dispersion characteristics and basic structure–property relationships of the cast films were determined. m‐TMXDI provided some advantages over IPDI in the preparations since its use gave lower prepolymer viscosities and better resistance to elevated temperatures. Films prepared from m‐TMXDI dispersions exhibited considerably lower values of Young's modulus and hardness and higher elongations at break than those prepared from IPDI‐based dispersions for analogous compositions, whereas differences in the average particle sizes or viscosities of the dispersions were only small. When the DMA content was varied, the dispersions and cast films of m‐TMXDI‐based systems showed similar changes as are known to occur in IPDI‐based systems: as the DMPA content was increased, the average particle size of the dispersions decreased and the viscosity increased, and for the cast films, the Young's modulus and tensile strength increased and the maximum elongation at break decreased. Changing the chain‐extension agent from hydrazine to 1,2‐ethylene diamine, to 1,2‐propylene diamine and had little effect on the particle size of the dispersions, but increased the Young's modulus and hardness of the respective cast films. Molar masses of the chain‐extended polymers were unexpectedly low. DSC analysis of cast films indicated that the degree of crystallisation of the soft or hard domains was low. © 2002 Society of Chemical Industry     

Simple and versatile method for the one‐pot synthesis of segmented poly(urethane urea)s via in situ‐formed AB‐type macromonomers

We present a one‐pot method for the synthesis of poly(urethane urea)s (PUUs) with uniform (monodisperse) hard segments that eliminates tedious approaches to control the exothermic nature of isocyanate–amine reaction, is less sensitive to impurities and involves no isolation of intermediates. Reaction of two moles of hexamethylene diisocyanate with one mole of polycaprolactone of various molecular weights under optimum time and temperature led to NCO‐terminated polyurethane prepolymers. Addition of an equimolar quantity of benzoic acid and excess dimethylsulfoxide at ambient temperature produced quantitative yields of PUUs with high molecular weight. The structure of the PUUs was fully characterized using spectroscopic methods and a reasonable mechanism for the reaction sequences was determined via preparation and characterization of a model compound. Dynamic mechanical thermal analysis data confirmed the phase‐separated structure of the PUUs. Evaluation of stress‐strain curves revealed the wide‐ranging mechanical properties depending on soft‐segment molecular weight. Monitoring the remaining weight and molecular weight of polymers incubated in phosphate‐buffered saline showed hydrolytic degradability with rate depending on soft‐segment molecular weight. Also, a preliminary investigation of the interaction of L929 fibroblast cells with the prepared polymers confirmed no cytotoxicity and acceptable cytocompatibility for the PUUs. Copyright © 2010 Society of Chemical Industry     

Structure–property relationships of poly(urethane‐urea)s with ultralow monol content poly(propylene glycol) soft segments. III. influence of mixed soft segments of ultralow monol poly(propylene glycol), poly(tetramethylene ether glycol), and tri(propylene glycol)

Recent advances in the catalyst technology associated with the production of poly(propylene glycol) (PPG) have allowed for the fabrication of ultralow monol content PPG macrodiols (Acclaim? polyols), which are highly bifunctional and can be produced in substantially higher molecular weights and with narrower molecular weight distributions than previously possible. These factors have enabled the preparation of higher value elastomers and may allow for the first manufacture of economically attractive PPG‐based poly(urethane‐urea) (PUU) fibers. In the past, many performance polyurethane and PUU elastomers used poly(tetramethylene ether glycol) (PTMEG) for the soft segments either alone or in combination with other macrodiols. The work presented here details the investigation of the morphological features of PUU systems with mixed soft segments of PPG, PTMEG, and a low molecular analog of PPG, tri(propylene glycol) (TPG) in an effort to ascertain the influence of structural features on the mechanical and thermal properties of the elastomers. Also of interest was whether the incorporation of PPG and TPG would either prohibit or greatly hinder the formation of strain‐induced PTMEG crystallites. It was found that, even when only 60 wt % of the soft segments consisted of PTMEG, those soft segments were still able to undergo recognizable strain‐induced crystallization as detected by wide‐angle X‐ray scattering. It was also seen that, as the ratio of PPG to PTMEG was varied, there were systematic changes in the soft segment glass transition and cold crystallization characteristics. Inclusion of PPG and TPG resulted in PTMEG's diminished ability to undergo cold and strain‐induced crystallization, as seen with differential scanning calorimetry and wide‐angle X‐ray scattering. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3520–3529, 2003     

Synthesis and properties of novel poly(urethane‐imide) dispersions based on 2,2‐bis[N‐(3‐hydroxyphenyl)phthalimidyl]hexafluoropropane

Imide units are incorporated into thermoplastic and solvent‐based polyurethane (PU) chains to improve the thermal stability of PU. However, these poly(urethane‐imide) (PUI) materials have poor processablity and suffer from solvent emission. To prepare easily processable and environmentally friendly PUI products, some waterborne PUIs are synthesized using a prepolymer process. A series of PUI dispersions with 25 wt % solid content, viscosities of 7.5–11.5 cps, and particle sizes of 63–207 nm was prepared. The composition–property relationship of PUIs, including the solubility behavior of PUI cast films, and their thermal and mechanical properties were established. The solvent resistance and tensile strength of PUI film increased with the number of imide groups. All PUIs exhibited improved thermal stability but not char yield as the temperature increased. The inclusion of a little imide increased the decomposition temperature of PUI while maintaining the elasticity of the polymer, revealing successful translation of PUI into the water‐based form. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The effect of processing routes on the thermal and mechanical properties of poly(urethane‐isocyanurate) nanocomposites

A systematic investigation of four processing routes was implemented so as to evaluate the thermal and mechanical properties of nanosilica (NS) reinforced poly(urethane‐isocyanurate) nanocomposites (NC). The NS dispersion in the Polmix and the Isomix routes was performed in the polyol and the isocyanate precursor, respectively. The Isopol and the Solvmix routes consisted on the dispersion of the filler after the mixing of the precursors and with the aid of solvents, respectively. The NS dispersion, fractography (SEM, TEM), flexural and tensile mechanical properties, thermogravimetric analysis and FTIR analysis of NCs was performed as a function of processing route, isocyanate index, and NS concentration. Each route produced a NC with distinct properties, which were correlated to the NS agglomeration degree and how the NS affected the thermal transitions of the HS and the relative ratio of urethane and isocyanurate chemical groups. For example, the NC prepared with the Polmix route had substantial improvements of σ_t and ε_t of around +40 and +52%, respectively and an improved thermal resistance of the Hard Segments. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42750.     

Effect of annealing on poly(urethane‐siloxane) copolymers

Poly(urethane‐siloxane) copolymers were prepared by copolymerization of OH‐terminated polydimethylsiloxane (PDMS), which was utilized as the soft segment, as well as 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol (1,4‐BD), which were both hard segments. These copolymers exhibited almost complete phase separation between soft and hard segments, giving rise to a very simple material structure in this investigation. The thermal behavior of the amorphous hard segment of the copolymer with 62.3% hard‐segment content was examined by differential scanning calorimetry (DSC). Both the T₁ temperature and the magnitude of the T₁ endotherm increased linearly with the logarithmic annealing time at an annealing temperature of 100°C. The typical enthalpy of relaxation was attributed to the physical aging of the amorphous hard segment. The T₁ endotherm shifted to high temperature until it merged with the T₂ endotherm as the annealing temperature increased. Following annealing at 170°C for various periods, the DSC curves presented two endothermic regions. The first endotherm assigned as T₂ was the result of the enthalpy relaxation of the hard segment. The second endothermic peak (T₃) was caused by the hard‐segment crystal. The exothermic curves at an annealing temperature of above 150°C exhibited an exotherm caused by the T₃ microcrystalline growth. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5174–5183, 2006     

The effect of the soft segment of prepolymers on properties of poly(urethane‐ester) and its biodegradability

The influence of soft‐segment prepolymers prepared through the polymerization of δ‐valerolactone (VL) and 2,2‐dimethyl‐1,3‐propandiol (DP) monomers on the structure and properties of poly(urethane‐ester) as well as its biodegradability were investigated. Poly(urethane‐ester) was prepared in two steps. The first step was the preparation of prepolymers with various chain lengths by polymerizing VL and DP monomers in the presence of a distannoxane catalyst at 100 °C under nitrogen atmosphere. The second step was the preparation of poly(urethane‐ester) by polymerizing 4,4′‐methylene‐bis(phenyl isocyanate) (MDI) and prepolymers with various chain lengths in the absence of catalysts. The poly(urethane‐ester) was characterized through an analysis of functional groups (FTIR), thermal properties (differential thermal analysis/TGA), mechanical properties (tensile tester), crystallinity (XRD) and biodegradability. An increased chain length of the prepolymer used in polymerization with MDI leads to an increase in the thermal properties and crystallinity of poly(urethane‐ester). However, the maximum biodegradability in the activated sludge was observed in the poly(urethane‐ester) prepared by polymerizing MDI and prepolymers with a molar VL/DP ratio of 20/1. The amorphous parts of polymers were more easily decomposed by microorganism enzymes than were the crystalline parts after an incubation period of 30 days. Copyright © 2011 Society of Chemical Industry