Aliphatic Polyurethane Elastomers Research Articles

Structure, morphology, and properties of aliphatic polyurethane elastomers from bio‐based 1,3‐propanediol

AbstractThe utilization of biomass resources in the production of bio‐based or bio‐recycled polyurethanes (PUs) enhances the sustainable development and eco‐friendliness of PU. Herein, a series of new bio‐based aliphatic poly(propylene dicarboxylate) diols were synthesized using bio‐based 1,3‐propanediol (bio‐PDO) and aliphatic dicarboxylic acids with different chain lengths. These bio‐based polyester diols and 1,4‐butanediol (BDO) reacted with 4,4′‐dicyclohexylmethane diisocyanate to produce aliphatic PU elastomers (PUEs). The study aimed to evaluate the impact of the structure of poly(propylene dicarboxylate) diols on the architecture, morphology, mechanical properties, and degradation of PUEs, thereby expanding the application of bio‐PDO. The results indicate a strong correlation between the degree of microphase separation, tensile properties, and degradation behavior of the synthesized PUEs and the number of methylene groups in the repeating unit of the poly(propylene dicarboxylate) diols. Notably, the PUE derived from poly(propylene pimelate) diol demonstrates the highest level of microphase separation and superior elasticity properties because of the high flexibility of the polyester. On the other hand, PUE prepared from poly(propylene succinate) diol exhibits the fastest degradation performance due to its high density of ester groups. Bio‐PDO based polyester diols show significant potential as raw materials for PUEs with biodegradable and adjustable mechanical properties.Highlights Poly(propylene dicarboxylate) diols were prepared from bio‐based 1,3‐propanediol. The poly(propylene dicarboxylate) diols based polyurethane elastomers (PUEs) have high tensile strength (>22 MPa) and elongation at break (>920%). The morphology, mechanical properties and degradation of PUEs are highly related to the structure of the poly(propylene dicarboxylate) diols. The increasing repeating unit length of the poly(propylene dicarboxylate) diols increases elastic recovery of PUEs.

Strength Enhancement of Polyurethane Film by Solution Annealing.

Recently, polyurethane elastomer (TPU) has attracted more and more attention depending on its excellent optical, mechanical, and retreatment properties. The high strength of polyurethane has always been pursued, which can enable its application in more fields. In this work, an aliphatic polyurethane elastomer membrane (HRPU6) was successfully synthesized, and its strength was obviously improved by solvent annealing technology. The tensile strength and adhesion strength can reach 64.56 and 2.58 MPa, but 36.55 and 1.57 MPa only before solvent annealing, respectively. The impact strength of laminated glass based on HRPU has also been significantly improved after solvent annealing, confirmed through drop ball impact testing. It has been confirmed that the increase in strength of HRPU6 is attributed to the enhancement of hydrogen bonding and the improvement of the phase separation degree.

Aliphatic Polyurethane Elastomers Quaternized with Silane-Functionalized TiO2 Nanoparticles with UV-Shielding Features.

The design of high-performance nanocomposites with improved mechanical, thermal or optical properties compared to starting polymers has generated special interest due to their use in a wide range of targeted applications. In the present work, polymer nanocomposites composed of polyurethane elastomers based on polycaprolactone or polycaprolactone/poly(ethylene glycol) soft segments and titanium dioxide (TiO2) nanoparticles as an inorganic filler were prepared and characterized. Initially, the surface of TiO2 nanoparticles was modified with (3-iodopropyl) trimethoxysilane as a coupling agent, and thereafter, the tertiary amine groups from polyurethane hard segments were quaternized with the silane-modified TiO2 nanoparticles in order to ensure covalent binding of the nanoparticles on the polymeric chains. In the preparation of polymer nanocomposites, two quaternization degrees were taken into account (1/1 and 1/0.5 molar ratios), and the resulting nanocomposite coatings were characterized by various methods (Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, contact angle, thermogravimetric analysis, dynamic mechanical thermal analysis). The mechanical parameters of the samples evaluated by tensile testing confirm the elastomeric character of the polyurethanes and of the corresponding composites, indicating the obtaining of highly flexible materials. The absorbance/transmittance measurements of PU/TiO2 thin films in the wavelength range of 200–700 nm show that these partially block UV-A radiation and all UV-B radiation from sunlight and could possibly be used as UV-protective elastomeric coatings.

Multiphase Structure and Electromechanical Behaviors of Aliphatic Polyurethane Elastomers

Understanding the relationship between multiphase structure and electromechanical property of thermoplastic dielectric elastomers is significantly important in the developments of high-performance and novel dielectric elastomers. In this work, we fabricated a series of aliphatic polyurethane elastomers (PUEs) based on hydroxyl-terminated butadiene-acrylonitrile copolymer (HTBN), hexamethylene diisocyanate (HDI), and various lengths of linear aliphatic diols and investigated effect of their microstructure and morphology on dielectric and electromechanical properties. The FTIR, WAXS, SAXS, and viscoelastic AFM results showed that the PUEs existed in crystalline phase, hard domain (HD) and soft domain (SD) phases composed HD-rich region and few HDs and SD composted SD-rich region by crystallization and microphase separation. Also, the crystal morphology and crystallinity of PUEs are strongly influenced by the length of chain extender due to the chain extender adopting various conformations by hydrogen bondin...

Synthesis, Characterization and Mechanical Properties of Hydroxyl-Terminated Hyperbranched Polymer Graft Polyether-Based Aliphatic Polyurethane Elastomer

Hydroxyl-terminated hyperbranched polyurethane elastomer (HBPU) was synthesized by graft copolymerization of hyperbranched poly (amine-ester) polyols(HPAE) and polyether-based aliphatic polyurethane prepolymer(PPU), and the PPU was synthesized by step polymerization of isophorone diisocyanate(IPDI) with polyethylene glycol(PEG) and dibutyltin dilaurate(DBTDL) as catalyst. The FT-IR spectroscopy, TGA and XRD were used to characterize the structure, thermal properties and crystallinity of HBPU. The mechanical properties of the elastomers were conducted on a testing machine. Microphase separation of HBPU film surface was studied by atomic force microscopy (AFM). The experimental results showed that the HBPU took on excellent hydrogen bonding and mechanical properties. The tensile strength of HBPU elastomer reached to 20.6MPa, which increased by 41.2 times than that of PPU elastomer. And the elongation at break was as high as 251.3%.

Synthesis of cross-linked polyurethane elastomers with fluorescein linkages

The reaction of polyurethane prepolymers with fluorescein (free acid) and glycerin or castor oil-cross-linker has been performed in N,N-dimethylformamide and in such way a cross-linked elastomer material has been obtained. Polyurethane prepolymers were prepared by reaction of the poly(1,4-butane)diols (Terathane 1400) with aliphatic 1,6 hexamethylene diisocyanate. The above polymerization reactions lead to the formation of novel aromatic–aliphatic polyurethane elastomers having fluorescein moieties in the main chain. The resulting novel cross-linked polyurethanes have excellent mechanical properties, especially in the castor oil polyurethane elastomer formulations and show light-violet fluorescence property and could be used as photoactive polymers for labeling materials. These polyurethanes were characterized through IR, TGA, DSC, and mechanical analyses. Some aspects of the fluorescent emission in fluorescein-polyurethane elastomers were studied.

Synthesis, characterization and mechanical properties of polyester-based aliphatic polyurethane elastomers containing hyperbranched polyester segments

Aliphatic polyester-based polyurethane (PU) elastomers with hyperbranched polyester segments were synthesized from polyester diol, hydroxyl-terminated hyperbranched polyester (HB-20), isophorone diisocyanate (PDI) and 1,4-butanediol. The crosslinking density of the PU elastomer was calculated by using Flory–Rehner equation. The degree of hydrogen bonding, the microstructure and the morphologies of these PU materials were characterized by means of FT-IR, WAXD and DSC, respectively. The experimental results showed that the PU elastomers containing small amount of HB-20 exhibited the enhanced hydrogen bonding and mechanical properties. As compared with the comparable PU specimen, the tensile strength of the polyester-based aliphatic PU containing 6 wt% HB-20 increased by 71.2 times, up to 36.1 MPa, and the elongation at break was still as high as 333.1%, resulting from the dual effects of the hydrogen bonding and the crosslinking density in the PU system.

Highly Stretchable and Conductive Polymer Material Made from Poly(3,4‐ethylenedioxythiophene) and Polyurethane Elastomers

AbstractA highly elastic and stretchable conductive polymer material resulted from blending the conductive polymer poly(3,4‐ethylenedioxythiophene):p‐tosylate and an aliphatic polyurethane elastomer. The blend inherited advantageous properties from its constituents, namely high conductivity of 120 S cm–1 from its conductive polymer component, and elastomeric mechanical properties resembling those of the polyurethane, including good adhesion to various substrates. Stretching of the blend material by up to 50 % resulted in increased conductivity, while subsequent relaxation to the unstretched state caused a decrease of conductivity compared to the pristine blend. These initial changes in conductivity were reproducible on further cycling between 50 % stretching and the unstretched state for at least 10 cycles. Stretching beyond 50 % resulted in decreasing conductivity of the blend but with substantial conductivity remaining even when stretched by 200 %. Optical, mechanical, and thermal properties of the blend, as well as high resolution electron microscopy of bulk cross‐sections, suggest that the system is a single phase and not two separate phases. Ageing experiments indicate that the material retains substantial conductivity for at least a few years at room temperature.

Regeneration of bicortical defects in the iliac crest of estrogen‐deficient sheep, using new biodegradable polyurethane bone graft substitutes

Porous scaffolds for cancellous bone graft substitutes were prepared from new experimental biodegradable aliphatic polyurethane elastomers with varying hydrophilicity. The ratios of the hydrophilic-to-hydrophobic content in the polymers were 30-70, 50-50, and 70-30%, respectively. The hydrophilic component consisted of poly(ethylene oxide) diol and the hydrophobic component of poly(epsilon-caprolactone) diol. To promote the materials' biological performance, the calcium complexing moiety, the polysaccharide, and vitamin D(3) were incorporated into the polymer chain upon synthesis. The scaffolds had an interconnected porous structure with an average pore size in the range of 300-2,000 microm and pore-to-volume ratios of (85 +/- 5)%. The bone substitutes were implanted (press-fit) in biocortical 10 x 10 mm(2) defects created in the tuber coxae of 21 skeletally mature Warhill ewes, which were ovariectomized 12 months prior to implantation. At the time of euthanasia at 18 and 25 months, all the defects in the ilium implanted with polyurethane bone substitutes had healed with new bone. The extent of bone healing depended on the chemical composition of the polymer from which the implant was made, although for the same material there were animal-related differences in healing. The structure of the newly formed cancellous bone was radiographically and histologically similar to the native bone. The implants from polymers with the incorporated calcium-complexing additive were the most effective promoters of bone healing, followed by those with vitamin D(3) and polysaccharide-containing polymer. There was no bone healing in the control defects.

Quartz Microbalance Microcalorimetry: A new method for studying polymer-solvent thermodynamics

We have developed a sensitive method of determining enthalpy changes for gas-surface interactions: quartz microbalance microcalorimetry. We mount in an isoperibol environment both sample and reference combinations of a quartz crystal microbalance (QCM) in intimate thermal contact with a heat flow sensor. We coat the sample QCM with a thin (∼1 µm) polymer film. By exposing the film to ethanol vapor, we measure simultaneously the change in mass per unit area (to ±0.25 ng cm−2) and the resulting heat flows (to ±50 nW) when the polymer adsorbs or desorbs ethanol. The molar enthalpies of sorption of ethanol vapor in Tecoflex, an aliphatic polyurethane elastomer, are ΔadsorptionH= −53±8 kJ mol−1 and ΔdesorptionH=52±3 kJ mol−1.

Effect of chain extender structure on the properties and morphology of polyurethanes based on H12MDI and mixed macrodiols (PDMS–PHMO)

The effect of chain extender structure on properties and morphology of α,ω-bis(6-hydroxyethoxypropyl) polydimethylsiloxane (PDMS) and poly(hexamethylene oxide) (PHMO) mixed macrodiol-based aliphatic polyurethane elastomers was investigated using tensile testing, differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA). All polyurethanes were based on 50 wt % of hard segment derived from 4,4′-methylenecyclohexyl diisocyanate (H12MDI) and a chain extender mixture. 1,4-Butanediol was the primary chain extender, while one of 1,3-bis(4-hydroxybutyl)tetramethyldisiloxane (BHTD), 1,3-bis(3-hydroxypropyl)tetramethyldisiloxane (BPTD), hydroquinonebis(2-hydroxyethyl)ether (HQHE), 1,3-bis(3-hydroxypropyl)tetramethyldisilylethylene (HTDE), or 2,2,3,3,4,4-hexafluoro-1,5-pentanediol (HFPD) each was used as a secondary chain extender. Two series of polyurethanes containing 80 : 20 (Series A) and 60 : 40 (Series B) molar ratios of primary and secondary chain extenders were prepared using one-step bulk polymerization. All polyurethanes were clear and transparent and had number-average molecular weights between 56,000 and 122,100. Incorporation of the secondary chain extender resulted in polyurethanes with low flexural modulus and high elongation. Good ultimate tensile strength was achieved in most cases. DSC and DMTA analyses showed that the incorporation of a secondary chain extender disrupted the hard segment order in all cases. The highest disruption was observed with HFPD, while the silicon-based chain extenders gave less disruption, particularly in Series A. Further, the silicon chain extenders improved the compatibility of the PDMS soft segment phase with the hard segment, whereas with HFPD and HQHE, this was not observed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2979–2989, 1999

Aliphatic polyurethane elastomers with high performance properties

AbstractA new diisocyanate, 1,4‐eyclohexane diisocyanate (CHDI), has been used in a series of polyether‐based polyurethane elastomers. The slightly opaque samples are semicrystalline in nature with high performance properties, including high softening temperature, very good thermal stability, high tensile and tear strengths, excellent solvent resistance, and low hysteresis in compressive fatigue. Polymer properties are in part due to the small, compact, symmetrical structure of the aliphatic CHDI. Comparison of the physical, mechanical, and thermal properties of polyurethanes prepared from the aliphatic diisocyanate 4,4′‐dicyclohexylmethane dilsocyanate (H12MDI) reveal the H12MDI polymers to be more flexible and transparent elastomers with lower softening temperatures and tensile moduli and higher hysteretic heat build up. They are generally soluble in organic solvents.

A Study of Aliphatic Polyurethane Elastomers Prepared from Diisocyanate Isomer Mixtures

Abstract Linear polyurethane elastomers are block copolymers which are elastomeric because they are phase separated. The soft block is derived from a hydroxy terminated telechelic polymer, frequently a polyether or polyester of a molecular weight less than 3000 and a glass transition temperature well below room temperature. The hard block, having a Tg above room temperature, consists of a diisocyanate and a diol. Most frequently the diisocyanate is aromatic and the diol is 1,4-butanediol. The elastomers produced are frequently opaque and then yellow in storage due to the presence of the aromatic rings. For applications where transparency and nonyellowing are important, aliphatic diisocyanates are the compounds of choice. One such diisocyanate is methylene bis(4-cyclohexyl-isocyanate), which is conveniently called H12MDI. It is prepared from the same diamine as methylene dianiline diisocyanate (MDI), but the aromatic rings are hydrogenated before phosgenation. The hydrogenation leads to a mixture of three aliphatic diamine isomers. Phosgenation leads to a diisocyanate which is a mixture of the three isomers shown in Figure 1. The isomer content is adjusted by the manufacturer, and the product received is a liquid. Another example of a diisocyanate which is marketed as a mixture is toluene diisocyanate, an 80:20 mixture of the 2,4:2,6 isomers being the most common. The aromatic diisocyanates are planar molecules or bent planar molecules like MDI. The H12MDI is also bent, but does not contain planar rings. Even if polymers from one pure diisocyanate isomer are examined, the cycloaliphatic compounds are much less likely to form highly ordered or crystalline regions in the hard-segment phase due to the greater difficulty in packing correctly. A desire to know the isomer composition of the diisocyanate and what effect the isomer composition has on the properties of the elastomers led to this study. Mixtures of the isomers varying from approximately 10% of the trans-trans isomer up to 95% (t-t) have been prepared and the properties of polyurethanes prepared from them have been studied.