Polyurethane dispersions derived from polycarbonatediols by a solvent‐free process

Polyurethanes having shape memory effects

A series of polyether-based thermoplastic polyure thanes, varying in soft segment molecular weight and hard seg ment content was prepared and studied. Poly(oxypropylene- oxyethylene) diols of Mn of 1000, 2000, 3000, and 4000 were the soft segment polyols. The hard segment, 4,4'-diphenyl methane diisocyanate (MDI) extended with 1,4-butanediol (BDO), and also the soft segment content were varied from 20 to 80 weight percent. Physical-mechanical, thermal (DSC) and dynamic-mechanical property data are used to elucidate the mechanical and morphological behavior of these polymers. Two distinct phases are detected in most of the polymers. The Tg of the amorphous soft phase decreases with increasing polyether molecular weight and is relatively unaffected by soft segment content except at very low levels (≤ 30%). Hard segments appar ently separate into ordered structures which melt between 150 and 220°C. The melting points and the heats of fusion generally increase with hard segment content and soft segment Mn. Soft segment molecular weight also has a significant influence on the mechanical properties of the polymers. In general, the ambient flexural moduli and the dynamic moduli (E') increase with in creasing soft segment Mn and the modulus/temperature curve is flattened.

Studies on thermoplastic polyurethanes based on new diphenylethane-derivative diols. II. Synthesis and characterization of segmented polyurethanes from HDI and MDI

This article examines the effects of the soft-segment composition on the structure and physical properties of waterborne polyurethane (WBPU) based on polycaprolactone–poly(ethylene glycol)–polycaprolactone (PCL–PEG–PCL) triblock copolydiol as the soft segment. The molecular weight of PEG in the soft-segment composition and soft-segment content (SSC) are varied in this study. The water-vapor permeability (WVP) for the WBPU-coated nylon fabric is also studied. The results showed that the glass transition temperatures (Tg's) of the soft segment decreased and its temperature range (ΔTg's) narrowed with increase of SSC up to 63 wt % and decrease of the PEG molecular weight. The dynamic mechanical analysis results showed that the α-peak height of the soft segment increased with SSC when the SSC was less than 63 wt %. However, when SSC was more than 63 wt %, the α-peak height became smaller with increasing SSC due to the crystallization of the soft segment. At the same SSC, the number of spherulites was reduced and the spherulites become larger with decrease of the PEG molecular weight. As for the mechanical properties of the WBPU cast film, the breaking stress decreased and the breaking elongation increased with increasing SSC or decreasing PEG molecular weight. For the WBPU-coated nylon fabrics, either higher SSC or higher PEG molecular weight improves the WVP. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:883–892, 1997

Effect of intersegmental interactions on the morphology of segmented polyurethanes with mixed soft segments: A coarse-grained simulation study

Various segmented polyurethanes of different soft segment structure with hard segment content of about 50 wt% were prepared from 4,4′‐diphenylmethane diisocyanate (MDI), 1,4‐butanediol and different polyols with a M n of 2000 by a one‐shot, hand‐cast bulk polymerization method. The polyols used were a poly(tetramethylene ether)glycol, a poly(tetramethylene adipate)glycol, a polycaprolactonediol and two polycarbonatediols. The segmented polyurethanes were characterized by gel permeation chromatography (GPC), UV‐visible spectrometry, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X‐ray diffraction, and their tensile properties and Shore A hardness were determined. The DSC and DMA data indicate that the miscibility between the soft segments and the hard segments of the segmented polyurethanes is dependent on the type of the soft segment, and follows the order: polycarbonate segments > polyester segments > polyether segments. The miscibility between the soft segments and the hard segments plays an important role in determining the transparency of the segmented polyurethanes. As the miscibility increases, the transparency of the segmented polyurethanes increases accordingly. The segmented polyurethanes exhibit high elongation and show ductile behavior. The tensile properties are also affected by the type of the soft segment to some extent. POLYM. ENG. SCI., 47:695–701, 2007. © 2007 Society of Plastics Engineers.

New thermoplastic nonsegmented thiopolyurethanes were obtained from the low-melting aliphatic–aromatic thiodiols 4,4′-bis(2-hydroxyethylthiomethyl)benzophenone (BHEB), 4,4′-bis(3-hydroxypropylthiomethyl)benzophenone (BHPB), and 4,4′-bis(6-hydroxyhexylthiomethyl)benzenophenone(BHHB) as well as hexamethylene diisocyanate (HDI), both by melt and solution polymerization with dibutyltin dilaurate as the catalyst. The effect of various solvents on molecular-weight values was examined. The polymers with the highest reduced viscosities (0.63–0.88 dL/g) were obtained when the polymerization was carried out in a solution of tetrachloroethane, N,N-dimethylacetamide, and N,N-dimethylacetamide or N,N-dimethylformamide for BHEB-, BHPB-, and BHHB-derived polyurethanes, respectively. These polymers with a partially crystalline structure showed glass-transition temperatures (Tg) in the range of −1 to 39 °C, melting temperatures (Tm) in the range of 107 to 124 °C, and thermal stabilities up to 230 to 240 °C. The BHEB-derived polyurethane is a low-elasticity material with high tensile strength (ca. 50 MPa), whereas the BHPB- and BHHB-derived polyurethanes are more elastic, showing yield stress at approximately 16 MPa. We also obtained segmented polyurethanes by using BHHB, HDI, and 20 to 80 mol % poly(oxytetramethylene) glycol (PTMG) of M̄n = 1000 as the soft segment. These are high-molecular thermoplastic elastomers that show a partially crystalline structure. Thermal properties were investigated by thermogravimetric analysis and differential scanning calorimetry. The increase in PTMG content decreases the definite Tg and increases the solubility of the polymers. These segmented polyurethanes exhibit the definite Tg (−67 to −62 °C) nearly independent of the hard-segment content up to approximately 50 wt %, indicating the existence of mainly phase-separated soft and hard segments. Shore A/D hardness and tensile properties were also determined. As the PTMG content increases, the hardness, modulus of elasticity, and tensile strength decrease, whereas elongation at break increases. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4140–4150, 1999

Morphology and properties of thermoplastic polyurethanes with dangling chains in ricinoleate-based soft segments

Effect of the degree of soft and hard segment ordering on the morphology and mechanical behavior of semicrystalline segmented polyurethanes

In this study, a series of nonionic waterborne polyurethanes containing side chain poly(ethylene glycol) monomethyl ether (PEGME) were synthesized using 4,4‐methylene bis(isocyanatocyclohexane), the nonionic dispersing center produced by isophorone diisocyanate, N‐diethanol amine, and PEGME, and a series of soft segments [polyethylene glycol (PEG), polypropylene glycol (PPG), polytetramethylene glycol (PTMG), and polycaprolactone (PCL)] with a different molecular weight. The solution properties of the polyurethane (PU) dispersions, thermal properties of the PU casting films, and the water vapor permeability (WVP) of the PU coated fabrics were investigated. Our results show that the surface tension of PU dispersion and its contact angle to untreated nylon fabric are higher for the ether‐based PU dispersion than for the ester‐based PU dispersion, with a sequence of PEG‐PU ≫ PTMG‐PU ≫ PPG‐PU ≫ PCL‐PU. Both the surface tension and the contact angle between PU dispersion and nylon fabric increase upon increasing the Mw of the soft segment. As for the thermal property of PU film, the Tgs of PCL‐PU is the highest, followed by PEG‐PU, PTMG‐PU, and PPG‐PU, and the Tgs decreases with the increase in the length of the soft segment. The Tms follows the order: PEG‐PU ≫ PCL‐PU ≫ PPG‐PU ≫ PTMG‐PU, and the Tms increases upon increasing the soft segment length. As regard to PU coated fabric, the trend of WVP is PEG‐PU ≫ PTMG‐PU ≫ PPG‐PU ≫ PCL‐PU, which increases with the increasing the soft segment length. With regarding to application for the coating, the Coated‐PU with PEG‐PU has an excellent WVP. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

A series of waterborne polyurethane (WPU) dispersions were prepared by chain-extending a prepolymer made of polyester diol, isophorone diisocyanate, and dimethylol propionic acid using cellulose acetate butyrate (CAB). The particle size and viscosity of the WPU dispersion were measured. In addition, we investigated the effects of CAB on the thermal, mechanical, and optical properties of WPU films. The use of CAB effectively improved the crosslinking degree of the WPUs, increasing the thermal stability and water resistance of the corresponding films. In particular, CAB increased the tensile strength of the WPU films up to 67%, while maintaining their elongation at break unchanged. In addition, CAB improved the optical transmittance by reducing the microphase separation between the soft and hard segments of PU. The rough surface structure of the WPU films formed by CAB led to improved matting properties.

An ionic/nonionic polyurethane dispersion with high solid content and low viscosity with a complex hydrophilic chain-extending agent was prepared using isophorone diisocyanate as a hard segment and propylene oxide glycol as a soft segment. The complex hydrophilic chain-extending agent consisted of DPSA and BDSA. The effects of the molar ratio of DPSA/BDSA on the properties of the resultant polyurethane dispersions were studied. The morphologies and properties of the ionic/nonionic PU dispersions were examined using particle-size, TEM, and viscosity analyses. It was found that the ionic/nonionic dispersions possessed wide particle-size distributions due to the addition of the complex hydrophilic chain-extending agent. The ionic/nonionic PU dispersions possessed higher solid content than conventional WPU dispersions because the number and volume percentage of the large particles and small particles of the ionic/nonionic dispersions met the requirements for high solid content. It was observed that the solid content of the ionic/nonionic dispersion increased and then decreased with an increasing molar ratio of DPSA/BDSA. When the ratio ranged from 4:10 to 5:10, the solid content of the ionic/nonionic PU dispersion reached up to 55%. It was also noticed that the apparent viscosity of the ionic/nonionic polyurethane dispersion decreased with an increasing molar ratio of DPSA/BDSA. The complex hydrophilic chain-extending agent consisting of DPSA and BDSA enhanced the solid content and decreased the viscosity of the ionic/nonionic dispersions, which are very important for improving the properties and expanding the applications of PU dispersions. In addition, the ionic/nonionic polyurethane dispersion had good electrolyte-resistance properties, stability at both high and low temperatures, and storage stability.

Three series of segmented polyurethanes, based on polytetramethylene oxide (PTMO) soft segments, having molecular weights of 650, 1000, and 2000 and MDI/butane diol hard segments, were synthesized and their dielectric properties examined. The effect of the soft segment length, soft segment concentration (ssc) as structural variables, and frequency and temperature as experimental variables, on relative permittivity and tan δ, were examined. The results were discussed in terms of the structural parameters such as the degree of phase separation and soft segment phase state. It was found that both soft segment length and ssc strongly affect dielectric behavior.

Various segmented polyurethanes with a hard segment content of about 50 wt% were prepared from 4,4′‐diphenylmethane diisocyanate (MDI), a poly(tetramethylene adipate) glycol with an Mn of 2000, and various combinations of aliphatic diols as chain extenders by a one‐shot, hand‐cast bulk polymerization method. The segmented polyurethanes were characterized by gel permeation chromatography (GPC), ultraviolet‐visible spectrometry, differential scanning calorimetry (DSC), and X‐ray diffraction, and their tensile properties and Shore A hardness were determined. The DSC data indicate rather good miscibility between the soft segments and the hard segments that accounts for the good transparency. The incorporation of a small amount of a second chain extender into MDI and 1‐4‐butanediol‐based segmented polyurethanes decreases the crystallinity of the hard segment, thus enhancing the transparency. A segmented polyurethane derived from MDI and 1,6‐hexanediol exhibits better transparency due to its relatively lower crystallinity of the hard segment. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:33–40, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20086

Influence of the solids content on the properties of waterborne polyurethane dispersions obtained with polycarbonate of hexanediol