Chain-extended polyurethanes—Synthesis and characterization

Thermoset polyurethane (PU) elastomers were prepared using hydroxyl-terminated polybutadiene (HTPB), toluene diisocyanate (TDI) and hexamethylene diisocyanate (HMDI). The effects of various diamines and diols on the mechanical and thermal properties of polyurethanes are discussed. The average molecular weight between crosslinks (M?/_c) was determined by swelling studies. The properties imparted by the extenders are explained on the basis of the groups present in the diamines and the number of methylene carbons in the diols.     

Chain‐extended polyurethane–acrylate ionomer for UV‐curable waterborne coatings

Conventional and chain‐extended UV‐curable waterborne polyurethane–acrylate (PUA) ionomers were prepared from diisocyanate, polyethylene glycol (PEG), dimethylolpropionic acid, and hydroxyethyl methacrylate, and identified with FTIR spectra and 500‐MHz ¹H‐NMR spectra. The number‐average molecular weight (M_n) and polydispersity of chain‐extended PUA were determined by gel permeation chromatography. For the synthesis of chain‐extended PUA, water was employed as the chain extender. The two kinds of PUA prepolymer could be easily dispersed in water in the form of self‐emulsified latex after the carboxyl group attaching to the backbone of PUA was neutralized with tertiary amine. The effects of M_n of PEG, carboxyl content, and type of diisocyanate on the interfacial tension and rheological behavior of PUA dispersions were investigated. The chain‐extended PUA prepolymer could photopolymerize to a greater extent than the conventional PUA, as indicated by differential photocalorimetry. The photopolymerization kinetics of chain‐extended PUA, based on different substrates, were also investigated. The differential scanning calorimetry analysis for the photo‐cured films from PUA dispersions suggested that lower M_n of PEG tended to favor phase mixing between soft and hard segment phases, and higher M_n of PEG would provoke phase separation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1818–1831, 2002; DOI 10.1002/app.10384     

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     

Synthesis and characterization of novel chain‐extended bismaleimides containing fluorenyl cardo structure

Novel fluorenyl cardo chain‐extended bismaleimides (FCCEBMIs) were synthesized by reacting maleic anhydride with fluorenyl cardo diamine and different dianhydrides. FCCEBMIs were characterized by FT‐IR spectra (FT‐IR), ¹H NMR, and elemental analysis. All FCCEBMI monomers were readily soluble in a variety of organic solvents, such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethyl acetamide, chloroform (CHCl₃), methylene chloride (CH₂Cl₂), dimethyl sulfoxide, and tetrahydrofuran when compared with 9,9‐bis(4‐maleimidophenyl) fluorene. Curing process was investigated by differential scanning calorimetry. Thermal properties of the cured FCCEBMIs were characterized by thermogravimetry analysis, the cured products are stable up to 430°C. The results show that the FCCEBMIs with imide structure improve significantly the solubility of bismaleimide (BMI) in organic solvents without sacrificing thermal properties of cured BMIs. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Structure–property relationship of starch‐filled chain‐extended polyurethanes

Chain‐extended polyurethane (PU) elastomers were prepared using castor oil with 4,4′‐methylene bis (phenyl isocyanate) (MDI) as a crosslinker and 4,4′‐diamino diphenyl sulphone (DDS) as an aromatic diamine chain extender. A series of starch‐filled (from 5 to 25% wt/wt) diamines chain‐extended PUs have been prepared. The starch‐filled PU composites were characterized for physico‐mechanical properties viz, density, surface hardness, tensile strength, and percentage elongation at break. Thermal stability of PU/starch have been carried out by using thermogravimetric analyzer (TGA). Thermal degradation process of PU/starch were found to proceed in three steps. TGA thermograms of PU/starch shows that all systems were stable upto 235°C, and maximum weight loss occur at temperature 558°C. The microcrystalline parameters such as crystal size (〈N〉) and lattice strain (g in %) of PU/starch have been established using wide‐angle X‐ray scattering (WAXS) method. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2945–2954, 2003     

Thermal degradation of biomedical polyurethanes—A kinetic study using high‐resolution thermogravimetry

The kinetics of thermal degradation of polyurethanes (PUR) has been studied by means of high‐resolution and constant heating rate thermogravimetry (TG), under nitrogen and synthetic air atmospheres. The high‐resolution TG provided a way to increase resolution with decreasing the time of data acquisition. In this mode, the heating rate is dynamically varied to maximize resolution. A method to calculate the kinetic parameters from this technique was used. The TG curves showed two or three decomposition steps, depending on the atmosphere employed. The parameters calculated for the PUR decomposition were the activation energy, reaction order, and preexponential factor. A method to estimate the polymer lifetime was also used. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 910–919, 2001     

Synthesis and characterization of novel thermoplastic poly(oligophosphazene‐urethane)s

BACKGROUND: Polyurethanes are some of the most popular polymers used in a variety of products, such as coatings, adhesives, flexible and rigid foams, elastomers, etc. Despite the possibility of tailoring their properties, polyurethanes suffer a serious disadvantage of poor thermal stability. Many attempts have been made in order to improve the thermal stability of polyurethanes. RESULTS: A new hydroxyl‐terminated oligomer containing sulfone groups, 2,2‐bis(4‐hydroxy‐4,4‐sulfonyldiphoneloxy)tetraphenoxyoligocyclotriphosphazene (HSPPZ), was synthesized. HSPPZ was characterized using Fourier transform infrared (FTIR), NMR and gel permeation chromatography analyses. A series of novel thermoplastic poly(oligophosphazene‐urethane)s were then synthesized via the reaction of NCO‐terminated polyurethane prepolymer with HSPPZ containing chain‐extender diols. Their structure and properties were investigated using FTIR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, X‐ray diffraction, water contact angle measurement and tensile measurements. CONCLUSION: Compared to conventional thermoplastic polyurethanes, poly(oligophosphazene‐urethane)s exhibit better thermal stability, low‐temperature resistance and hydrophobicity, but their mechanical properties are slightly poorer. Copyright © 2009 Society of Chemical Industry     

异丁烯-对甲基苯乙烯无规共聚物的合成与表征

以二枯基氯/四氯化钛/2,6 -二叔丁基吡啶为引发体系,在-80℃条件下采用正离子聚合法合成了异丁烯-对甲基苯乙烯无规共聚物(IB -co -p - MeSt),研究了不同单体投料比(摩尔比)下聚合反应的特征,并通过示差折光指数仪/多角激光光散射仪/紫外检测器、核磁共振氢谱、差示扫描量热法和热重分析对无规共聚物进行了表...     

Synthesis and characterization of butan‐1‐ol modified toluene diisocyanate trimer

Butan‐1‐ol modified toluene diisocyanate tri mer (TDI‐trimer) was synthesized and characterized with Fourier transform infrared spectroscopy, gel permeation chromatography, and thermal gravimetry analysis techniques. The modified TDI‐trimer showed good dissolvable ability with hydroxy resin and can be used to produce paints with acrylic polyol resin. The thermal stability of the modified TDI‐trimer was improved by simply increasing both the amount of catalyst and the ratio of ? NCO/? OH, less depended on the kind of catalyst. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4958–4962, 2006     

Synthesis and molecular weight characterization of rubber seed oil‐modified alkyd resins

Alkyd resins of 40% (I), 50% (II), and 60% (III) oil length (OL) were prepared with rubber seed oil (RSO), phthalic anhydride (PA), and glycerol (GLY), employing the two‐stage alcoholysis method. Changes in the physical characteristics of the reaction medium were monitored by determination of the acid value and the number‐average molecular weight, M_n , of in‐process samples withdrawn at different stages of the reaction. The mode of variation of these properties denotes that the preparation of RSO alkyds is complex. Molecular weight averages and the molecular weight distribution (MWD) of the finished alkyds were determined by GPC, cryoscopy, and end‐group analysis. Molecular weight averages and the MWD vary with differences in the formulation, with sample II exhibiting the narrowest size distribution. Values of M_n with the corresponding polydispersities in brackets are 3234 (1.91), 1379 (1.56), and 3304 (2.56) for samples I, II, and III respectively. M_n values obtained by cryoscopy are comparable to those obtained by gel permeation chromatography (GPC), while end‐group analysis seems to grossly overestimate their molecular weights. Correlation of M_n and the MWD with the quality of the finished alkyds shows that the narrower the size distribution the better the quality of the alkyd. Properties such as the rate of drying and resistance of the alkyds are optimum at 50% OL. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2431–2438, 2001     

Synthesis of Block Copolymers containing Chain‐Controlled Aramid and Fluoroethylene Segments

Summary: Novel block copolymers containing aromatic polyamide (aramid) and fluoroethylene segments were synthesized by a two‐step solution polycondensation. This synthetic method could control the chain‐length of aramid segments and these copolymers could have high structural regularity. The number‐average molecular weight ( ) of one of these polymers is over 2.0 × 10⁴. Incorporating fluoroethylene segments improves the solubility of the resulting polymer compared with conventional aramids.

The synthesis of the fluoroethylene‐aramid block copolymers.     

Light scattering characterization of poly(tetrafluoroethylene‐co‐perfluoromethyl vinyl ether) copolymer

Static and dynamic light scattering experiments were performed to characterize the copolymer of tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE). Solvents of perfluoro‐2‐butyltetrahydrofuran (FC‐75) and Flutec PP11 (PP11) were used to dissolve the TFE‐PMVE copolymer. By taking advantage of the solvent properties of FC‐75 and PP11, homogeneous TFE‐PMVE copolymer solutions were specially prepared in a FC‐75/PP11 mixed solvent. Such prepared solutions could provide a strong enough scattered intensity for light scattering studies. The molecular weight, molecular weight distribution, chain dimensions, and conformation were determined for the TFE‐PMVE copolymer in the FC‐75/PP11 mixed solvent. A combination of viscosity and molecular weight measurements enabled the calculation of the k value in the relation of η₀ = k (M_w)^3.4 and thus the prediction of the molecular weight of a given TFE‐PMVE copolymer with the same composition by using only the simpler and more readily available rheological measurements. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 733–739, 2000     

Synthesis and characterization of a novel siloxane‐imide‐containing polybenzoxazine

A novel siloxane‐imide‐containing polybenzoxazine based on N,N′‐bis(N‐phenyl‐3,4‐dihydro‐2H‐benzo[1,3]oxazine)‐5, 5′‐bis(1,1′,3,3′‐tetramethyldisiloxane‐1,3‐diyl)‐bis(norborane‐2,3‐dicarboximide) (BZ‐A1) was successfully synthesized. The thermal properties of BZ‐A1 are superior to those of conventional polybenzoxazines lacking siloxane groups. Polymerized BZ‐A1 possesses extremely low surface free energy (γ_s = 15.1 mJ m^?2) after curing at 230 °C for 1 h. Moreover, the surface free energy of polymerized BZ‐A1 is more stable than conventional bisphenol A‐type polybenzoxazine during thermal curing and annealing processes, indicating that polymerized BZ‐A1 is more suitable for applications requiring low surface free energy materials for high temperatures over long periods of time. Copyright © 2010 Society of Chemical Industry     

Synthesis and characterization of crosslinked polyurethane dispersions based on hydroxylated polyesters

Stringent environmental regulation has endowed dispersible coatings with excellent property profiles in industrial applications. In this aspect, aqueous polyurethane dispersions (PUDs) are of special interest. The present study reports on the synthesis of hydroxylated polyester (HP) based polyurethane polyols containing internal carboxyl group with different diisocyanates. These polyurethane polyols were partly acetoacetylated with ethyl acetoacetate to incorporate β‐ketoester in the polyurethane polyol backbone. The synthesized polyols were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and differential scanning calorimetry. Polyurethane polyols and their acetoacetylated cousins were used to develop PUDs. Particle size of the reactive PUDs was evaluated by a particle size analyzer. PUDs were crosslinked with hexamethoxy methyl melamine and their film properties were studied by dynamic mechanical and thermal analyzers and thermogravimetric analyses. The effects of different diisocyanate and acetoacetylation on the stability of reactive dispersion and properties of the crosslinked films were evaluated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 368–380, 2006     

Low‐modulus siloxane‐based polyurethanes. I. Effect of the chain extender 1,3‐bis(4‐hydroxybutyl)1,1,3,3‐tetramethyldisiloxane (BHTD) on properties and morphology

A series of eight polyurethane elastomers was prepared using a two‐step bulk polymerization procedure to investigate the effect of the siloxane chain extender 1,3‐bis(4‐hydroxybutyl)1,1,3,3‐tetramethyldisiloxane (BHTD) on polyurethane properties and morphology. All polyurethanes were based on 40 wt % hard segment derived from 4,4′‐methylenediphenyl diisocyanate (MDI) and a mixture of 1,4‐butanediol (BDO) and BHTD in varying molar ratios. The soft segment was based on an 80 : 20 (w/w) mixture of the macrodiols α,ω‐bis(6‐hydroxyethoxypropyl)polydimethylsiloxane (PDMS, MW 965) and poly(hexamethylene oxide) (PHMO, MW 714). Polyurethanes were characterized by size‐exclusion chromatography, tensile testing, differential scanning calorimetry, dynamic mechanical thermal analysis, and FTIR spectroscopy. Clear and transparent polymers were produced in all cases with number‐average molecular weights in the range of 90,000 to 111,000. The ultimate tensile strength decreased only slightly (15%), but Young's modulus and flexural modulus decreased by 76 and 72%, respectively, compared with that of the pure BDO extended polyurethanes as the amount of BHTD was increased to 40 mol %. This change resulted in “softer” and more elastic polyurethanes. Polyurethanes with BHTD contents above 40 mol % were more elastic but had poor tensile and tear strengths. A 60 : 40 molar ratio of BDO : BHTD produced a “soft” polyurethane, which combined good tensile strength and flexibility. The DSC and DMTA results confirmed that the incorporation of BHTD as part of the hard segment yielded polyurethanes with improved compatibility between hard and soft segments. IR data indicated that the amount of hard segments soluble in the soft‐segment phase increased with increasing BHTD, contributing to the improved phase mixing. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 736–746, 2002     

Differential scanning calorimetry analysis of silicon‐containing and phosphorus‐containing segmented polyurethane. I—Thermal behaviors and morphology

This article investigated thermal transition and morphology utilizing differential scanning calorimetry (DSC), which was performed on silicon‐containing and phosphorus‐containing segmented polyurethane (Si‐PU and P‐PU). The hard segments of those Si‐PU and P‐PU polymers investigated consisted of 4,4′‐diphenylmethane diisocyanate (MDI) and diphenylsilanediol (DSiD), MDI, and methylphosponic (MPA), respectively. The soft segment of those polymers comprised polytetramethylene ether glycol, with an average molecular weight of 1000 or 2000 (PTMG 1000 and PTMG 2000, respectively). Several thermal transitions appeared for on the Si‐PU and P‐PU polymers, reflecting both the soft‐segment and hard‐segment phases. The Si‐PU and P‐PU polymers with a lower hard‐segment content exhibited a high degree of phase separating as indicated by the constancy of both the soft‐segment glass transition temperature (T_gs) and the breadth of transition zone (ΔB). The polymers in which PTMG 2000 was used as the soft segment generally exhibited a crystalline melting endotherm about 10°C, while crystallization usually disappeared upon melt quenching. The hard segments of the Si‐PU and P‐PU polymers displayed multiple endotherms. The first endotherm was related to a short‐range ordering of the hard segment domain (Region I), and the second endotherm was ascribed to a long‐range ordering of the domain (Region II). The wide‐angle X‐ray demonstrated that the structure in Region I and Region II was almost completely amorphous. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3489–3501, 2001     

Synthesis and characterization of biodegradable non-toxic poly(ester-urethane-urea)s based on poly(ε-caprolactone) and amino acid derivatives

Non-toxic biodegradable linear poly(ester-urethane-urea)s with different hydrophilic character were synthesized from poly(ε-caprolactone) as macrodiol, l-lysine diisocyanate (LDI) and ethyl ester l-lysine or l-ornithine as chain extenders. Linear segmented polymers were synthesized by the prepolymer method with a tertiary amine playing a critical role in the chain extension in heterogeneous conditions. The prepared segmented polymers were fully chemically and physically characterized, including water uptake and hydrolytic stability measurements. Depending on the poly(ε-caprolactone) length, the segmented polymers were amorphous or semicrystalline. The crystallinity degree strongly affected the mechanical properties and water uptake behaviour.     

Synthesis,characterization, and thermal properties of tris (3‐aminophenyl) phosphine oxide‐based nadimide resins

This article describes the synthesis, characterization, and thermal properties of nadimides obtained by reacting endo‐5‐norbornene‐2,3‐dicarboxylic acid anhydride (nadic anhydride) (NA), 4,4′‐oxodiphthalic anhydride (ODA), 1,4,5,8‐naphthalene tetra carboxylic dianhydride (NTDA) in glacial acetic acid/DMF. Structural characterization of the resins was done by elemental analysis, IR, ¹H‐NMR, and ¹³C‐NMR. The DSC scan showed the endothermic transition in the temperature range of 120–270°C. Multistep decomposition was observed in the TG scan of uncured resins in nitrogen atmosphere. Isothermal curing of the resins was done at 250 and 300°C for 1 h in an air atmosphere. These cured resins were stable to (350 ± 30)°C and decomposed in a single step above this temperature. This may be due to the retro Diels Alder (RDA) reaction. The char yield of the resins increased significantly on curing. The char yield was highest for P‐2N resin and this could be due to the presence of rigid skeleton i.e. naphthalene. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of UV‐curable acrylic resin containing fluorine groups

A novel fluorine‐containing acrylic resin, 4‐trifluoromethylphenyl glycerol dimethacrylate (TPGD), was synthesized and the structure was characterized by FTIR, ¹³C NMR, ¹H NMR, and ¹⁹F NMR spectroscopy. The conversion of cure reaction, thermal stability, glass transition temperature (T_g), and electrical properties of the TPGD acrylic resin cured with UV radiation were investigated. The thermal stability and T_g of the UV‐cured specimens show a maximum value at 1 wt% photoinitiator, due to the formation of advanced network structures. The cured specimens had a relatively low dielectric constant, attributed to the decreased deformation polarizability of segment motion in the fluorine‐containing resin. Copyright © 2004 Society of Chemical Industry