Series Of Polyurethane Elastomers Research Articles

Molecular engineering and morphology of polyurethane elastomers containing various molecular weight of macrodiol

A series of polyurethane elastomers (PUEs) based on 4,4′-cyclohexamethylene diisocyanate (H12MDI)/1,2-ethanediol as hard segment with the soft segments having different molecular weights of polycaprolactone diols, were effectively polymerized by two step technique. The structural characterization was performed by FT-IR spectroscopy. The X-ray diffraction (XRD) technique was used to study the crystallinity and hydrophilicity of the prepared polymer films. It was found that crystallinity and hydrophilicity increased with increasing the chain length of soft segments. The effect of molecular weight of polyols on the contact angle, water absorption (%) and swelling behavior of the synthesized polyurethanes were also studied. Moreover, the scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques revealed that the degree of micro-phase separation increases with increasing molecular weight of polyol which confirmed the results pattern shown by XRD diffractogram.

Influences of Polyol on the Chemical, Thermal, and Mechanical Properties of Polyurethane Elastomers Crosslinked by <i>β</i>-Cyclodextrin

A series of polyurethane elastomers (PUEs) were synthesized from an aromatic diisocyanate (4, 4’-diphenylmethane diisocyanate); a polyether polyol (polytetramethylene glycol, molecular weight: 1000), polyester polyol (poly-caprolactonediol, molecular weight: 1000, or polycarbonate diol, molecular weight: 1000); and β-cyclodextrin (β-CD) as a cross-linker. The effect of the polyol on the morphologies and chemical, thermal, and mechanical properties of the resultant β-CD-based PUEs were investigated in this study. The obtained films were characterized via solubility and swelling tests (chemical properties), differential scanning calorimetry (crystallinity degree), dynamic mechanical analysis (thermal stability), thermogravimetric analysis (thermal stability), tensile testing (mechanical properties), nuclear magnetic resonance spectroscopy, infrared spectroscopy, atomic force microscopy (morphology), contact angle determination (morphology), and scanning electron microscopy (morphology).

Influence of β-cyclodextrin on morphologies and chemical, thermal, and mechanical properties of non-chain extended polyurethane elastomers

A series of polyurethane elastomers (PUEs) were synthesized from an aromatic diisocyanate (4,4′-diphenylmethane diisocyanate (MDI)), a polyether polyol (polytetramethylene glycol; molecular weight: 1000 Da (PTMG1000)), and using β-cyclodextrin (β-CD) as the cross-linker. In this study, we investigated the effects of the addition of β-CD on the morphologies and chemical, thermal, and mechanical properties. The introduction of β-CD in the main chain of PUEs was verified using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and swelling test. The morphology was analyzed through SEM and confocal laser scanning microscopy (CLSM). The results show that the PUEs containing β-CD units exhibited an incompatible microstructure that was improved by the addition of β-CD. The tensile strength of PUEs decreased with the addition of β-CD; however, the elasticity was maintained for <5 % β-CD content. The dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) were used to prove the existence of a chemically cross-linked structure and evaluate the thermal stability of PUEs having different β-CD content.

Influence of Diisocyanate on Polyurethane Elastomers Which Crosslinked by &amp;lt;i&amp;gt;β&amp;lt;/i&amp;gt;-Cyclodextrin

A series of polyurethane elastomers (PUEs) were synthesized by using β-cyclodextrin (β-CD) as cross-linker from aliphatic, alicyclic, aromatic diisocyanates, and polyol. The PUEs were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), swelling test, hardness test and tensile test. The influence of diisocyanate on microphase separation and properties of PUEs was evaluated.

Synthesis and investigation of properties of thiacalix[4]arene-based polyurethane elastomers

A series of polyurethane elastomers (PUEs) derived from three thiacalix[4]arene derivatives (TC4As), namely p-tert-butylthiacalix[4]arene, tetrasodium thiacalix[4]arenetetrasulfonate and thiacalix[4]arenetetrasulfonic acid, as a portion of chain extender in a mixture with glycerol were synthesized. The effects of the chemical structure of TC4As used as chain extenders on the various properties of the prepared PUEs were investigated and compared with PUE extended with only glycerol as chain extender using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy and a universal tensile tester. Moreover, the effect of the introduction of TC4As as a portion of chain extender on the hydrophobicity of the PUEs was also evaluated. DSC, FTIR spectroscopy and XRD revealed that the degree of phase separation and crystallinity in TC4A-based PUEs was much higher than that of the glycerol-based ones. Thus, it was concluded that the presence of TC4As in TC4A-based PUEs seems to favour the formation of a more ordered structure due to an increase in the degree of phase separation. The TGA results also showed that, with incorporation of TC4As into the polyurethane backbone, the thermal stability of PUEs was improved. © 2014 Society of Chemical Industry

New Polyurethane Elastomers with Enhanced Thermal Stability

A series of polyurethane elastomers with enhanced thermal stability was prepared and their physical and thermal properties were studied. For this purpose in the first step, an excess amount of methylene diphenyl diisocyanate was reacted with poly(tetramethylene ether) glycol to produce isocyanate-terminated polyurethane pre-polymer. In the second step, a new imide-based diol chain extender was synthesized via reaction of benzophenonetetracarboxylic dianhydride with 5-amino-1-naphthol. Finally, reaction of the pre-polymer with chain extender resulted in preparation of polyurethane elastomers. Presence of imide unit in the polymer backbone improved their properties and enhanced thermal stability of polyurethane.

Effect of the hard segment structure on properties of resorcinol derivatives-based polyurethane elastomers

Two series of polyurethane elastomers were obtained from poly(1,4-butylene adipate) diol and 1,6-diisocyanatohexane, which were then chain extended with resorcinol derivatives such as benzene-1,3-diol, 2,4-dihydroxybenzaldehyde, or 1-(2,4-dihydroxyphenyl) hexan-1-one. This article investigates the effects induced in polyurethane elastomer properties by varying the hard segment composition through changing the amount of aliphatic diisocyanate and through the influence of the chemical structure of the resorcinol derivatives’ chain extenders. The different chemical composition and the presence of different dangling chains on the chain extender structure influenced hard segment cohesion, resulting in important effects on the polyurethane elastomer properties. The incorporation of aliphatic diisocyanate alongside the aromatic chain extender leads to changes in the physical and mechanical properties of the polyurethane elastomers compared with aromatic rigid diisocyanates. These polyurethane elastomers were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and mechanical measurements. We synthesized resorcinol-based polyurethane elastomers with aliphatic–aromatic hard segment structures, with the resorcinol addition making it unnecessary to transform phenolic OH groups into aliphatic OH groups.

Synthesis and characterization of polydimethyl siloxane-based polyurethane elastomers using toluene diisocyanate

A series of polyurethane elastomers (PUEs) were prepared by the reaction of hydroxyl-terminated polybutadiene (HTPB) and toluene diisocyanate (TDI), the resultant PU prepolymer was extended with polydimethyl siloxane (PDMS). The conventional spectroscopic characterization of the synthesized samples using Fourier transform infrared spectrophotometer confirmed the structure of the proposed PDMS-based PU. Thermogravimetric analysis (TGA) was carried out to determine the thermal stability of the prepared PU samples. Surface properties of the synthesized material were studied determining the percentage of water absorption and equilibrium degree of swelling. The results revealed that by increasing the mole ratio of PDMS, the synthesized PUEs showed hydrophilic behavior while placing them in water and dimethyl sulfoxide solvent.

Synthesis and Characterization of Linear and Cross-Linked Cyclodextrin Polyurethane Elastomers

Cyclodextrin-based polyurethane elastomers were synthesized to obtain network matrices with good mechanical properties apt for being used as films with scavenging properties. A series of polyurethane elastomers were obtained by chain extension of polyurethane prepolymer with cyclodextrin and butane diol or with the addition of glycerin or castor oil. Toluene, menthone and linalool were introduced as air or water contaminants. The thermal, mechanical and wetting properties of the crosslinked polyurethane films were evaluated. The improved scavenging properties, studied by static headspace chromatography were associated with polyurethane films synthesized with butane diol/cyclodextrin and castor oil/cyclodextrin blends as chain extenders.

Mechanical and Thermal Properties of Polyurethane Elastomers Synthesized with Toluene Diisocyanate Trimer

A series of polyurethane elastomers (PUE) incorporating TDI (toluene diisocyanate) trimer were synthesized via an in-situ polymerization and prepolymer process. It was found that for the sample with 10 wt% or less TDI trimer, the stress–strain curves of PUE exhibited the characteristics of a ductile failure with relatively high tensile strength and elongation at break. However, with incorporation 20∼30 wt% of TDI trimer, the samples changed to brittle fracture. All PUE samples exhibited a loss peak corresponding to the glass transition temperature (Tg ) of the soft-segments, which shifted to higher temperature and decreased in peak height by incorporation of the three-functional isocyanurate rings. Although the TDI trimer modified PUE showed only slightly higher onset and peak degradation values than that of PUE in the absence of TDI trimer, there were still big differences in the end temperatures of the second stage. The value of activation energy and frequency factor fluctuated for varying samples, indicating that the thermal stability of PUE can be improved to a certain degree by incorporation of TDI trimer, but not so remarkably.

Effect of resorcinol-based chain extenders chemical structure on the enhanced properties of polyurethane elastomers

Two series of polyurethane elastomers with resorcinol derivatives in the polymer backbone were synthesized by chain extending isocyanate end-capped prepolymers with resorcinol, 2,4-dihydroxybenzaldehyde or 1-(2,4-dihydroxyphenyl)-hexanone-(1). Chain extenders are differentiated from each other by the structure of the side chain attached to the resorcinol rings. Isocyanate-terminated prepolymers were obtained from poly(1,4-butylene adipate) diol and 4,4′-diphenylmethane diisocyanate. These polyurethane elastomers were characterized using Fourier transform infrared spectroscopy, thermo-gravimetric analysis, differential scanning calorimetry, and mechanical measurements. The effects of the chemical structure of resorcinol-derivative chain extenders on the properties of polyurethane elastomers were investigated. A significant increase in maximum stress–strain properties and in thermal stability was observed for the samples with free carbonyl in the side chain of the resorcinol ring. All the polymers showed 5% weight losses above 300 °C and glass transition temperature values in the range of −39 and −23 °C. The aim was to enhance the mechanical properties and thermal behavior by varying the chemical structure of the resorcinol moieties from the hard segment domain, without transform phenolic OH groups in aliphatic OH groups.

Preparation and Mechanical Properties of Polyurethane Elastomer with Two Soft Segments of HTPB/PTMG

In this paper, a series of polyurethane elastomers (PUE) were prepared employing casting method using toluene diisocyanate (TDI), hydroxy-terminated butadiene-acrylonitrile copolymer(HTBN) and polytetrahydrofuran glycol (PTMG) as the main raw materials, and using 2,4- and 2,6- dimethylthioaromatic diamine (DMTDA) as a chain extender. The effects of the content of NCO in PUE (NCO%), mass ratio of HTBN/PTMG, molecular weight of PTMG, dosage of chain extender and heat treatment on the mechanical properties of PUE were studied. The results showed that the lower molecular weight of PTMG and the higher heat treatment temperature were both favorable for increasing the mechanical properties of PUE. When the mass ratio of HTBN/PTMG was 35:65, NCO% was 6.0%, molar ratio of NCO/NH2 was 1.20 and heat treatment time was 2h at 115 , the mechanical properties of PUE were best.

The effect of chain extenders structure on properties of new polyurethane elastomers

Two series of polyurethane elastomers were synthesized to investigate what effect does the incorporation of various new chain extenders have on the mechanical and thermal properties of polyurethane elastomers. The polyurethane soft segments were based on poly(e-caprolactone) polyol. The hard segment was based on 1,6-hexamethylene diisocyanate in combination with 2,5-dimethyl-3-hexine-2,5-diol (DHD), hexaethylene glycol, glycerin, or castor oil. The results showed that the degradation rate and mechanical properties of the final products can be controlled through the structure of diol chain extenders or/and hard segment cross-linking present in the polyurethane elastomers. The DHD-based polyurethane displayed a relatively low glass transition temperature of −57 °C and a tensile strength of 11–14 MPa and elongation at break of 600–700%. These kinds of materials have potential application in many domains.

Thermo-mechanical characteristics of UV-irradiated polyurethane elastomers extended with α, ω-alkane diols

A series of polyurethane elastomers were prepared by the reaction of poly ε-caprolactone and 4,4′-diphenylmethane diisocyanate. The prepolymer was extended using α, ω-alkane diols as chain extenders having 2–10 methylene units in their structure. The synthesized samples were irradiated for 50, 100 and 200 h in an ultra violet (UV) exposure unit. Modifications in the chemical structure before and after irradiation were characterized using Fourier Transform Infrared spectroscopy. The thermal and mechanical properties were affected by the ultra violet irradiation time and the number of methylene units in the chain extenders. The experimental results indicated that the morphological structure changed during irradiation as a consequence of hard segment and soft segment degradation.

Synthesis and Characterization of Polyurethane Elastomers

This study reports the synthesis and characterization of polyurethane (PU) elastomers, with emphasis on the effect of different methods and order for raw materials feeding. First, a series of PU elastomers is synthesized using polyether glycol, TDI, and extender chain reagent. The results show that after diisocyanate is dipped into the dried polyether, the elastomers synthesized using extender chain reagent exhibit the best properties. The subsequent characterization and measurements further show that by an optimum synthetic route, considerable hard segments can be formed uniformly in the soft segments, and the extent of micro-phase separation is relatively perfect. Moreover, it is demonstrated that the relative molecular weight of polyether glycol has an important effect on the properties of the synthesized PU elastomers. The more the relative molecular weight, the more soft segments are contained, and the smaller the tensile strength, rupture strength, and rigidity. In addition, the investigation on the effect of different raw materials indicates that the prepared polyether-type elastomers exhibit an excellent water/solvent resistance.

Thermoplastic biodegradable polyurethanes: The effect of chain extender structure on properties and in-vitro degradation

Biodegradable polyurethanes are typically prepared from polyester polyols, aliphatic diisocyanates and chain extenders. We have developed a degradable chain extender (DCE) based on dl-lactic acid and ethylene glycol to accelerate hard segment degradation. Three series of polyurethane elastomers were synthesised to investigate the effect of incorporating DCE on synthesis, mechanical and thermal properties and in-vitro degradation. Polyurethane soft segments were based on poly( ε-caprolactone) (PCL) polyol. The hard segment was based on either ethyl lysine diisocyanate or hexamethylene diisocyanate in combination with ethylene glycol or DCE. Polyurethanes were characterised by gel permeation chromatography, tensile testing (Instron) and differential scanning calorimetry. Polymer degradation in-vitro (phosphate buffered saline) was tested by measuring mass loss, change in molecular weight and amine concentration in degradation products at three different time points over a 1 year period. Incorporation of DCE did not affect thermal or mechanical properties but had an influence on the in-vitro degradation. All polyurethanes exhibited considerable molecular weight decrease over the test period, and DCE-based polyurethanes showed the highest mass loss. The presence of the DCE and the initial molecular weight of the polyurethane are the key factors responsible for high mass losses. Differential scanning calorimetry, amine group analysis and the observation that mass loss was directly proportional to hard segment weight percentage, strongly supported that the polyurethane hard segment is the most susceptible segment to degradation in these polyurethanes. The PCL-based soft segment appears to undergo little or no degradation under these test conditions.

Photoinduced Birefringence and Surface Relief Gratings in Polyurethane Elastomers with Azobenzene Chromophore in the Hard Segment

A series of polyurethane elastomers containing aromatic azobenzene chromophore in the hard segment was synthesized by a one-step method. AFM surface study showed that particles on the order of 100 nm to several micrometers appeared after annealing the polymer films. Birefringence was induced in these polymer elastomers. The stability of the photoinduced birefringence could be improved significantly by annealing the polymer films. This also induced microphase separation. The effects of azo contents and molecular weight of soft segments were investigated. Dynamic study shows that photoinducing rate decreased while relaxation rate increased after annealing. Surface relief gratings could be induced only on the pure polyurethane and the elastomer containing 75% bis(azo)−diol. Only a reversible volume hologram was observed for the other elastomers.

The effect of stoichiometry on the fracture toughness of a polyurethane-urea elastomer

The fracture toughness of a series of polyurethane elastomers based on polytetramethylene glycol (PTMEG) soft segment, a toluene diisocyanate (TDI) and a dimethyl-thio-toluenediamine (Ethacure E300) curative with different ratios of isocyanate to amine groups has been studied. The fracture toughness required to initiate crack growth was found to be invariant with stoichiometry but the degree of stable crack growth was found to vary with stoichiometry. This behaviour has been discussed in terms of the molecular and physical structure of the polymers, particularly the extent of cross-linking which varied with the isocyanate/amine ratio.

Synthesis and characterization of a series of poly(alkylene carbonate) macrodiols and the effect of their structure on the properties of polyurethanes

A series of polycarbonate and copolycarbonate macrodiols was prepared by using an ester interchange reaction with ethylene carbonate and diols such as 1,6-hexanediol, 1,10-decanediol, 2,2-diethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, and 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane. The diols were chosen to prepare a series of macrodiols with different structural features including linear, branched, rigid, and flexible. The macrodiols were characterized by 1H- and 13C-NMR spectroscopy and DSC. The commercial macrodiol based on 1,6-hexanediol exhibited a high level of crystallinity, while with the exception of 1,10-decanediol–based copolycarbonates all the others were completely amorphous. 1,10-Decanediol–based materials showed partial crystallinity under subambient conditions. A series of polyurethane elastomers with a constant hard segment percentage (40 wt %) was prepared using 4,4′-methylenediphenyl diisocyanate and 1,4-butanediol as the hard segment. Tensile test results and Shore hardness measurements demonstrated that polyurethanes based on polycarbonate macrodiols prepared from 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane had the lowest modulus and hardness of the series of polyurethanes. The remaining polyurethanes had high tensile strength with poor elasticity. The morphology of the polyurethanes, as determined by DSC analysis, varied from completely phase-mixed to well phase-separated structures. Polyurethanes based on macrodiols prepared from 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane showed good phase-separated morphology, with sharp hard segment melting endotherms and soft segment glass transitions close to that of the pure soft segment. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1621–1633, 1998

Synthesis and characterization of a series of poly(alkylene carbonate) macrodiols and the effect of their structure on the properties of polyurethanes

A series of polycarbonate and copolycarbonate macrodiols was prepared by using an ester interchange reaction with ethylene carbonate and diols such as 1,6-hexanediol, 1,10-decanediol, 2,2-diethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, and 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane. The diols were chosen to prepare a series of macrodiols with different structural features including linear, branched, rigid, and flexible. The macrodiols were characterized by 1H- and 13C-NMR spectroscopy and DSC. The commercial macrodiol based on 1,6-hexanediol exhibited a high level of crystallinity, while with the exception of 1,10-decanediol–based copolycarbonates all the others were completely amorphous. 1,10-Decanediol–based materials showed partial crystallinity under subambient conditions. A series of polyurethane elastomers with a constant hard segment percentage (40 wt %) was prepared using 4,4′-methylenediphenyl diisocyanate and 1,4-butanediol as the hard segment. Tensile test results and Shore hardness measurements demonstrated that polyurethanes based on polycarbonate macrodiols prepared from 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane had the lowest modulus and hardness of the series of polyurethanes. The remaining polyurethanes had high tensile strength with poor elasticity. The morphology of the polyurethanes, as determined by DSC analysis, varied from completely phase-mixed to well phase-separated structures. Polyurethanes based on macrodiols prepared from 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane showed good phase-separated morphology, with sharp hard segment melting endotherms and soft segment glass transitions close to that of the pure soft segment. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1621–1633, 1998