Aliphatic Polyurethane Research Articles

Experimental study of the simulated process of degradation of polycarbonate- and d,l-lactide-based polyurethane elastomers under conditions mimicking the physiological environment

The extent of the hydrolytic degradation of aliphatic polyurethane (PU) films made from polycarbonate-based aliphatic macrodiol (MD), diisocyanate-1,6-hexane, butane-1,4-diol (BD) and d,l-lactide-based oligomeric diol (DLL) was tested in phosphate-buffered saline (PBS) for a period of up to 12 months. Two macrodiols of equal molecular weight (∼2000 Da), differing in chain composition and regularity, and equal MD-to-BD-to-DLL molar ratios were chosen for the PU synthesis. The isocyanate-to-total hydroxyl group ratio was kept constant at 1.05. The functional properties of raw four-component polyurethane films and samples immersed for 1, 3, 6, 9 and 12 months in a model physiological environment (37 °C, pH = 7.4) were studied from the segmental up to the macroscopic level. Tensile testing and water uptake experiments, as well as DSC, SEM, AFM, FTIR and WAXD analyses, were used for the comprehensive characterization of the raw and PBS-treated films. The study shows that the untreated four-component PU films are highly elastomeric materials with very high tensile strength and suitable thermal properties for potential medical coating/film applications. The DLL oligomeric diol turned out to be a very efficiently degradable unit, leading to substantial mechanical property deterioration. The products of more regular macrodiol have higher tendency to the degradation process; 89% or 94% of the original toughness value is lost in just 12 months of immersion. The studied type of PU can be practically used either as fairly stable high-performance elastomers for short-term applications (up to 3 months) or as degradable materials, when the time of exposure to the physiology-mimicking conditions is sufficient.

Studying the effect of organo-modified nanoclay loading on the thermal stability, flame retardant, anti-corrosive and mechanical properties of polyurethane nanocomposite for surface coating

Abstract Clay polyurethane nanocomposite (CPN) coating films were fabricated by uniformly dispersing nanoclay, organically modified with 25–30 wt.% octadecylamine in varying concentrations up to 5 wt.%, in a commercial two component, glossy, acrylic aliphatic polyurethane using ultrasonication. Organo-modified nanoclay was characterized by X-ray diffraction (XRD). The dispersion of the nanoclay into the matrix was investigated by scanning electron microscopy (SEM). CPN coating films were characterized by thermogravimetric analysis (TGA), and flame retardant, corrosion resistance and mechanical properties were also investigated. The XRD measurement indicated that, the organo-modified nanoclay particles were mainly constituted of montmorillonite with traces of quartz and calcite also found to be present. The SEM analysis showed that the nanoclay layers were dispersed and intercalated into the polyurethane coating. Thermogravimetric analysis showed that incorporating 5 wt.% organo-nanoclay into polyurethane considerably enhanced the thermal stability and increased the char residue to 14.11 wt.% relative to 4.58 for the sample without organo-nanoclay (blank polyurethane). The limiting oxygen index (LOI) test revealed that incorporation of organo-nanoclay led to a further increase in LOI values, which indicate an improvement in flame retardancy properties. The corrosion resistance also improved and this improvement increases with increase nanoclay wt.%. The mechanical resistance measurements demonstrated that the gloss of the CPN coating films slightly decreased, although hardness, adhesion and impact resistance of the CPN coating films improved with the incorporation of the organo-nanoclay.

Multifunctional cotton fabrics with graphene/polyurethane coatings with far-infrared emission, electrical conductivity, and ultraviolet-blocking properties

In order to introduce multifunctional properties into flexible cotton fabric, graphene and waterborne anionic aliphatic polyurethane composites were prepared and then deposited on the surface of the fabric substrate through facile pad-dry-cure process. The fabrics thus obtained were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy, and their functional properties such as far-infrared emission, electrical conductivity, and ultraviolet (UV) blocking were studied. The coating process enhanced the far-infrared emissivity up to 0.911 in the wavelength range of 4–18 μm. In addition, the ultraviolet protection factor (UPF) of the fabric with 0.8-wt% graphene could reach 500, up to 60-fold higher than that of pristine cotton fabric (UPF 8.19), and its electrical resistivity was decreased from 1.15 × 107 to 2.94 × 10−1 Ω m, which is almost 8 orders of magnitude. The fabrics have also been found to be stable even after 10 cycles of laundering.

A route toward multifunctional polyurethanes using triple click reactions

The aliphatic polyurethane with pendant alkyne, perfluorophenyl, and anthracene moieties (PU-anthracene) was prepared from polycondensation of anthracene, alkyne, and perfluorophenyl functional-diols with hexamethylenediisocyanate in the presence of dibutyltindilaurate (DBTL) in CH2Cl2 at room temperature for 10 days. Thereafter, the PU-(anthracene-co-alkyne-co-perfluorophenyl) (Mn,GPC = 15,400 g/mol, Mw/Mn= 1.37, relative to PS standards) was sequentially clicked with benzyl azide, octylamine, and 4-(2-hydroxyethyl)−10-oxa-4-azatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione (adduct alcohol) via copper-catalyzed azide-alkyne cycloaddition, active ester substitution and Diels–Alder reactions, respectively, to finally yield PU-(hydroxyl-co-benzyltriazole-co-octylamine). The PUs were characterized using 1H NMR, GPC, and DSC. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 480–486

Role of the interactions between carbonate groups on the phase separation and properties of waterborne polyurethane dispersions prepared with copolymers of polycarbonate diol

Abstract Different aliphatic waterborne polyurethane dispersions (PUDs) were synthesized by using different polyols ( M w : 1000 Da) of randomly copolymerized polycarbonate diols with hexamethylene and pentamethylene (C6–C5), tetramethylene (C6–C4) and trimethylene (C6–C3); these copolymers differed in the length of the methylene groups and the structural regularity due to the combination of even and odd units. Brookfield viscosity, extent of particle crowding and broadening of the particle size distribution of the PUD synthesized with C6–C4 polyol followed a different trend than for the other because of the even number of methylene units in the polyol. The PUDs showed monomodal particle size distribution which was narrower in C6–C4 (i.e. the dispersion with higher structural regularity) and the mean particle size decreased by decreasing the length of the methylene unit of the copolymer. The properties of the polyurethanes were affected by the phase separation between the hard and soft segments, the more regular packing of even methylene units in the copolymer and the crystallized polar segments due to carbonate groups. Thus, the glass transition values of the soft segments in the polyurethanes were similar because of the more regular packing of even methylene units in C6–C4 polyol and the crystallized segments produced by interactions of carbonate groups. PU(C6–C5) and PU(C6–C4) showed similar degree of phase separation, the higher degree of phase separation corresponded to PU(C6–C3). Furthermore, the crystallinity of the polyurethanes increased with decreasing the number of methylene units in the polyol, but PU(C6–C4) was the most crystalline because of the more regularly packed even methylene groups in the polyol chain. The thermal stability of the polyurethanes increased from PU(C6–C5) to PU(C6–C3) because the more net interactions between the carbonate groups in the soft segments. The lower was the number of methylene groups between carbonate units in the copolymer, the higher was the elastic modulus of the polyurethanes. The tensile strength and elongation-at-break values of the polyurethanes increased by increasing the number of methylene groups between carbonate units in the copolymer. Finally, the peel strength was maximal in the joint made with PU(C6–C5) and the shear strength was the highest in the joint made with PU(C6–C3), in agreement with the variation of the viscoelastic and mechanical properties of the polyurethanes.

Effects of organically modified nanoclay particles on the mechanical properties of aliphatic polyurethane/clay nanocomposite coatings

Nano clay particles were modified organically by indole‐3‐carbaldehyde and indole‐3‐acetic acid with the purpose of preparing aliphatic polyurethane nanocomposite coatings. X‐ray diffraction (XRD), thermogravimetric analysis, and Fourier transform infrared spectroscopy (FTIR) analysis confirmed the ion exchange through the silicate layer of nano clay particles. XRD result showed about 5 A° increment in the distance of silicate layers. Transmission electron microscopic images showed good dispersion of modified nanoparticles in polymeric matrix. Mechanical properties of nanocomposites were evaluated using dynamic thermal analysis and tensile techniques. Results illustrated that nanocomposite coatings have higher toughness property and lower brittleness due to the proper nanoparticles dispersion. Morphology of the fractured surface of free films was examined by preparing scanning electron microscopic images; less ruptures and more roughness in the fractured surface of nano composites in comparison to the polyurethane‐free films have been proven. POLYM. COMPOS., 38:1167–1174, 2017. © 2015 Society of Plastics Engineers

Spectral and photophysical properties of phenalenone dyes in aliphatic polyurethane matrix

Spectral and photophysical properties of phenalenone dyes in aliphatic polyurethane matrix

Improvement of the Low-Temperature Property of Aliphatic Polycarbonate Glycols-Based Polyurethane Elastomers

Improvement of the Low-Temperature Property of Aliphatic Polycarbonate Glycols-Based Polyurethane Elastomers

A Processable Shape Memory Polymer System for Biomedical Applications.

Polyurethane shape memory polymers (SMPs) with tunable thermomechanical properties and advanced processing capabilities are synthesized, characterized, and implemented in the design of a microactuator medical device prototype. The ability to manipulate glass transition temperature (Tg ) and crosslink density in low-molecular weight aliphatic thermoplastic polyurethane SMPs is demonstrated using a synthetic approach that employs UV catalyzed thiol-ene "click" reactions to achieve postpolymerization crosslinking. Polyurethanes containing varying C=C functionalization are synthesized, solution blended with polythiol crosslinking agents and photoinitiator and subjected to UV irradiation, and the effects of number of synthetic parameters on crosslink density are reported. Thermomechanical properties are highly tunable, including glass transitions tailorable between 30 and 105 °C and rubbery moduli tailorable between 0.4 and 20 MPa. This new SMP system exhibits high toughness for many formulations, especially in the case of low crosslink density materials, for which toughness exceeds 90 MJ m(-3) at select straining temperatures. To demonstrate the advanced processing capability and synthetic versatility of this new SMP system, a laser-actuated SMP microgripper device for minimally invasive delivery of endovascular devices is fabricated, shown to exhibit an average gripping force of 1.43 ± 0.37 N and successfully deployed in an in vitro experimental setup under simulated physiological conditions.

Influence of graphene on self-assembly of polyurethane and evaluation of its biomedical properties

Novel aliphatic polyurethane (PU) nanohybrids have been prepared using varying amount of graphene by dispersing it in the early stage of polymerization (in situ) and achieved uniform distribution throughout the matrix, required for the improvement of properties. The alteration of self-assembly in presence of graphene have been explored through X-ray diffraction, small angle neutron scattering, atomic force and optical microscopy in the length scale of nanometer, tens of nanometer, hundreds of nanometer and micron range, respectively, indicating the layer by layer self-assembly of polymer and graphene in nanohybrids. The cause of self-assembly has been studied through spectroscopic techniques like FTIR and UV–vis measurements revealing strong interaction between polymer chain (both hard and soft segments) and graphene which is further confirmed from the depression of melting point and decrease in heat of fusion with increasing graphene content in the nanohybrids. The toughness of nanohybrids in solid state improves considerably as compared to pure PU and the mechanical strength in liquid state also dramatically increases with graphene content showing a dip at a particular frequency depending on the strength of self-assembly (greater for higher graphene content nanohybrid) followed by its reformation at higher frequency. Sustained drug release has been achieved in presence of graphene explaining the phenomena from the greater tortuousity in nanohybrids arising from the 2-D graphene and small but uniform cluster size of self-assembly as compared to pure PU. The suitability of the developed nanohybrids has been testified for its use in biomedical arena by checking the complete biocompatibility of the nanohybrids as compared to pure PU using bone marrow derived mesenchymal stem cells.

Effect of dose and temperature on the physical properties of an aliphatic thermoplastic polyurethane irradiated with an electron beam

The electron beam irradiation of a fully aliphatic thermoplastic polyetherurethane was carried out in air at doses ranging from 50 to 4000 kGy at room temperature and 100 °C and a dose rate of 5.1 kGy min−1. The effects of the irradiation on the chemical structure and the physical properties were studied. Gel was obtained already at the lower dose, increasing to almost 100% gel at the higher dose, with cross-linking predominating over chain scission. FTIR and DSC measurements proved that both, soft segment and hard segment, were affected by irradiation. Mechanical properties were adversely affected by irradiation mainly due to the cross-linking produced in the amorphous part of the material. Irradiation temperature did not have any significant effect except at the highest dose of 4000 kGy.

Thermal and mechanical properties of multiple‐component aliphatic degradable polyurethanes

ABSTRACTMacroscopic thermal and mechanical properties of complex aliphatic polycarbonate‐based polyurethane (PU) films containing degradable ester units in PU backbone were studied by a combination of several experimental techniques. Differential scanning calorimetry (DSC) revealed that the synthesized oligomeric diol (DL‐L) contributes (in addition to polycarbonate diol) to the formation of soft‐segment domains, while the hard‐segment domains are formed from 1,6‐diisocyanatohexane (HDI) and butane‐1,4‐diol (BD). Three main phase transitions were detected by DSC and by dynamic mechanical thermal analysis. Thermogravimetric analysis (TGA) of two‐component PUs showed that the PU made from DL‐L and HDI is the least thermostable product, while the PU made from polycarbonate diol and HDI is the most stable one. The differences in the thermal stability of different four‐component PUs are not important. Tensile properties very sensitively reflect the changes in composition and in microstructure of PU samples; the best tensile properties exhibits the degradable sample containing the equimolar ratio of hydroxyl groups of macrodiol, oligomeric diol DL‐L and butane‐1,4‐diol. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41872.

Degradability in vitro of polyurethanes based on synthetic atactic poly[(R,S)-3-hydroxybutyrate

The aim of the present study was to determine the degradability of aliphatic polyurethanes, based on a different amount of synthetic, atactic poly[(R,S)-3-hydroxybutyrate] (a-PHB), in hydrolytic (phosphate buffer) and oxidative (H2O2/CoCl2) solutions. The soft segments were built with atactic poly[(R,S)-3-hydroxybutyrate] and polycaprolactone or polyoxytetramethylenediols, whereas hard segments were the reaction product of 4,4'-methylenedicyclohexyl diisocyanate and 1,4-butanediol.The selected properties - density and morphology of polymer surfaces - which could influence the sensitivity of polymers to degradation processes - were analyzed.The analysis of molecular mass (GPC), thermal properties (DSC) and the sample weight changes were undertaken to estimate the degree of degradability of polymer samples after incubation in environments studied.Investigated polyurethanes were amorphous with the very low amount of crystalline phases of hard segments.The polyurethane synthesized with a poly[(R,S)-3-hydroxybutyrate] and polyoxytetramethylenediol at a molar ratio of NCO:OH=3.7:1 (prepolymer step) appeared as the most sensitive for both degradative solutions. Its weight and molecular mass losses were the highest in comparison to other investigated polyurethanes.It could be expected that playing with the amount of poly[(R,S)-3-hydroxybutyrate] in polyurethane synthesis the rate of polyurethane degradation after immersion in living body would be modeled.

Synthesis and characterization of aliphatic thermoplastic poly(ether urethane) elastomers through a non-isocyanate route

A simple non-isocyanate route synthesizing aliphatic thermoplastic polyurethane elastomers with good mechanical properties is described. A biscarbamate, i.e. di(hydroxyethyl)isophorone biscarbamate (DIBC), was prepared from direct reaction of isophorone diamine with ethylene carbonate without any catalyst. Self melt transurethane polycondensation of DIBC and co-polycondensation with different polyethylene glycols (PEGs) were conducted. Homopolymer of DIBC (PDIBC) and poly(ether urethane)s (PEUs) with high molecular weight were prepared. They were characterized by GPC, FT-IR, 1H NMR, 13C NMR, 2D 13C–1H HSQC NMR, DEPT-135 13C NMR, DSC, TGA and tensile test. PEUs exhibited an Mn up to 31,100, an Mw up to 126,000, Tg between −38.3 °C and 64.1 °C, initial decomposition temperature at over 259.1 °C, tensile strength up to 24.41 MPa with elongation at break of 454.17%, and resilience up to 97.50%.

Cotton Fabric Finished by WPU/LPAA Modified Nano-ZnO for Antibacterial Applications

An antibacterial agent (ZPU) was prepared by surface modification of nanoZnO with aliphatic aqueous polyurethane (WPU) and polyacrylates sodium of lower molecular weight (LPAA). Then two kinds of cotton fabrics were dipped in ZPU and finally finished by paking-baking process. ZPU and the finished cotton fabrics were characterized by SEM, TEM and DLS. The antimicrobial properties of the cotton fabrics were investigated. The results indicated that ZnO retained nanosize with little aggregation on the fabric surface. The finished cotton fabrics showed obviously antibacterial activity againstS. aureusandE. coliwith the 24 h antibacterial rate of 99%.

Synthesis and Characterization of Biomedical Aliphatic Polyurethane Material

Biomedical transparent poly(carbonate-urethane) elastomers were synthesized by melting pre-polymer method, using 4,4’-methylenebis (cyclohexyl isocyanate)(H12MDI) and chain extender (butadiene)(BDO) as hard segment, poly(1,6-hexanediol) carbonate diols(PCDL) as soft segment, and dibutyltin dilaurate as catalyst.The effects of molar ratio of the reactants on mechanical properties of PCU were studied and the relationship between micro-phase separation structure and properties was analyzed by the contact angle determination, total reflection fourier transform infrared spectrography(ATR-FTIR), differential scanning calorimeter(DSC),gel permeation chromatograph (GPC), mechanical property test. The comparative analysis was made between the prepared material and commercial medical polyurethane materials, showing the prepared poly(carbonate-urethane) elastomers was better in mechanical properties. As a elastic biomedical material, it has a great potential for developments and applications in biomedical materials.

Polymer grafting onto polyurethane backbone via Diels-Alder reaction

The aliphatic polyurethane with pendant anthracene moieties (PU-anthracene) was prepared from polycondensation of anthracen-9-yl methyl 3-hydroxy-2-(hydroxymethyl)-2-methylpropanoate (anthracene diol), 1 with hexamethylenediisocyanate in the presence of dibutyltindilaurate in CH2Cl2 at room temperature for 10 days. Thereafter, the PU-anthracene (Mn,GPC = 12,900 g/mol, Mw/Mn = 1.87, relative to PS standards) was clicked with a linear α-furan protected-maleimide terminated-poly(methyl methacrylate) (PMMA-MI) (Mn,GPC = 2500 g/mol, Mw/Mn = 1.33), or -poly(ethylene glycol) (PEG-MI) (Mn,GPC = 550 g/mol, Mw/Mn = 1.09), to result in well-defined PU-graft copolymers, PU-g-PMMA (Mn,GPC = 23800 g/mol, Mw/Mn = 1.65, relative to PS standards) or PU-g-PEG (Mn,GPC = 11,600 g/mol, Mw/Mn = 1.45, relative to PS standards) using Diels–Alder reaction in dioxane/toluene at 105 °C. The Diels–Alder grafting efficiencies were found to be over 93–99% using UV spectroscopy. Moreover, the structural analyses and the thermal transitions of all copolymers were determined via 1H NMR and DSC, respectively. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 521–527

Biological evaluation of porous aliphatic polyurethane/hydroxyapatite composite scaffolds for bone tissue engineering.

Biomaterial scaffolds meant to function as supporting structures to osteogenic cells play a pivotal role in bone tissue engineering. Recently, we synthesized an aliphatic polyurethane (PU) scaffold via a foaming method using non-toxic components. Through this procedure a uniform interconnected porous structure was created. Furthermore, hydroxyapatite (HA) particles were introduced into this process to increase the bioactivity of the PU matrix. To evaluate the biological performances of these PU-based scaffolds, their influence on in vitro cellular behavior and in vivo bone forming capacity of the engineered cell-scaffold constructs was investigated in this study. A simulated body fluid test demonstrated that the incorporation of 40 wt % HA particles significantly promoted the biomineralization ability of the PU scaffolds. Enhanced in vitro proliferation and osteogenic differentiation of the seeded mesenchymal stem cells were also observed on the PU/HA composite. Next, the cell-scaffold constructs were implanted subcutaneously in a nude mice model. After 8 weeks, a considerable amount of vascularized bone tissue with initial marrow stroma development was generated in both PU and PU/HA40 scaffold. In conclusion, the PU/HA composite is a potential scaffold for bone regeneration applications.

Multiscale approach to the morphology, structure, and segmental dynamics of complex degradable aliphatic polyurethanes

ABSTRACTA multiscale approach spanning from the segmental (subnanometer) up to micrometer level was applied for detailed study of the self‐assembly of aliphatic block polyurethane (PU) elastomers. To understand the principles of the self‐organization of hard and soft segments in the complex multi‐component systems, several two‐component model PU samples, that is, the products of 1,6‐diisocyanatohexane (HDI) with three diols differing in the length and constitution were also prepared, characterized, and investigated: (i) polycarbonate‐based macrodiol (MD), (ii) biodegradable oligomeric diol (DL‐L; product of butane‐1,4‐diol and D,L‐lactide), and (iii) butane‐1,4‐diol (BD). The study (particularly 13C‐1H PILGRIM NMR spectra) reveals complex internal organization and interesting (application appealing) behavior of multi‐component PUs. Hard segments (HDI+BD products) feature self‐assembled and significantly folded chain conformations with interdomain spacing 15–22 nm (small‐angle X‐ray scattering analysis). The small domains are hierarchically assembled in various structural formations of µm size (spherulites) depending on PU composition, as detected by transmission electron microscopy and atomic force microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41590.

Investigation of accelerated aging behaviour of high performance industrial coatings by dynamic mechanical analysis

• Dynamic mechanical analysis (DMA) was used to study four different industrial topcoats. • T g varies widely depending on cure chemistry, composition and crosslink density. • Creep recovery is a critical factor for improved durability in topcoats. • Crosslink density and T g change considerably after artificial weathering. • DMA study gives valuable indications about the long-term performance properties. Dynamic mechanical analysis (DMA) represents one of the most important methods for understanding mechanical behaviour of surface coatings providing a valuable link between chemistry, morphology, and performance properties. In this work, dynamic mechanical properties of several high performance industrial coatings were studied extensively. Four commercially available topcoats namely alkyd modified polyurethane (PU), economy aliphatic PU, high performance aliphatic PU and epoxy modified polysiloxane were selected based on their cure chemistries, volume solids, and overall performance. DMA was used to determine elastic modulus, glass transition temperature ( T g ), crosslink density and creep behaviour of these coatings. DMA data were substantiated with mechanical and performance properties. Among the coatings, epoxy modified polysiloxane showed the highest T g of 65.6 °C as well as crosslink density value of 2.24 × 10 −3 mol/cc which was attributed to its superior mechanical and performance properties. In addition, topcoats were also subjected to artificial aging process in accelerated cyclic corrosion cabinet and QUV-weatherometer, respectively. The consequent changes in their physico-mechanical properties post exposure were also evaluated using DMA and correlated with other performance properties. After aging, the T g increased substantially for all the coatings irrespective of their exposure type. For example, T g of economy aliphatic PU increases from 38.4 °C to 52.9 °C and 51 °C after cyclic corrosion and UV-B weathering, respectively. However, crosslink densities either increased or decreased depending on the type of exposure and cure chemistries. These changes were corroborated using the Fourier transform infrared spectroscopy findings. The outcome of this study is expected to generate new insights into the behaviour of these coatings under dynamic mechanical stress and its relation with long term performance properties.