Kinetics of urethane formation from isophorone diisocyanate: The alcohol nature effect

The kinetics of the noncatalytic reactions of isophorone diisocyanate with n-propanol, isopropanol, 1,3-diazidopropan-2-ol, propargyl alcohol, and phenol in toluene in the temperature range from 20 to 90°C at the stoichiometric ratio of reactive groups has been investigated by IR spectroscopy. The apparent rate constants for the reactions of the aliphatic and cycloaliphatic isocyanate groups of isophorone diisocyanate with all of the alcohols have been measured. The activation parameters of the reactions of isophorone diisocyanate with n-propanol, isopropanol, and 1,3-diazidopropan-2-ol have been determined. The data obtained are considered in terms of the alcohol structure and molecular organization of solutions.     

DSC study on the effect of isocyanates and catalysts on the HTPB cure reaction

The urethane forming cure reactions of hydroxyl terminated polybutadiene (HTPB) binder with three different isocyanate curatives, viz., toluene diisocyanate (TDI), isophorone diisocyanate (IPDI) and 4,4-methylene bis(cyclohexyl isocyanate) (MCHI), were investigated by differential scanning calorimetry (DSC). The effect of two cure catalysts, viz., dibutyl tin dilaurate (DBTDL) and ferrric tris-acetylacetonate (FeAA) on the cure reactions was also studied. Cure kinetics was evaluated using the multiple heating rate Ozawa method. The reactivities of the three isocyanates and catalytic efficiencies were compared based on the DSC reaction temperatures, activation energies and rate constants. Viscosity build-up in these systems at isothermal temperature was also studied and compared with the results from DSC.     

Poly(siloxane‐urethane) crosslinked structures obtained by sol‐gel technique

Poly(siloxane‐urethane) crosslinked structures were prepared from isophorone diisocyanate, α,ω‐bis(hydroxybutyl)oligodimethylsiloxane and a new hybrid diol containing hydrolysable Si? OC₂H₅ groups besides OH groups. The latest was synthesized by the acid‐catalyzed reaction between 1,3‐bis(3‐glycidoxypropyl)tetramethyldisiloxane and 3‐aminopropyltriethoxysilane. The formations of the urethane groups along the polymer backbone as well as the formation of the silica domains were first confirmed by the presence of the specific bands in Fourier transform infrared spectra. The resulted materials were characterized using differential scanning calorimetry, thermogravimetric analysis and scanning electron microscopy. The results of the dynamic mechanical analysis (DMA) performed at various frequencies revealed shape memory capabilities for some of the obtained structures. The silica formed because of the hydrolysis‐condensation reactions proved to have reinforcing effect upon siloxane‐urethane structure also evidenced by DMA and increasing water vapor sorption capacity as was measured by dynamic vapor sorption. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Fluoropolyethers end‐capped by polar functional groups. I. Kinetic approach to the reaction of hydroxy‐terminated fluoropolyethers with cycloalyphatic and aromatic diisocyanates

Urethane reactions of cycloaliphatic and aromatic diisocyanates with hydroxy‐terminated fluoropolyethers (FPEs) of various molecular weights and structure, at NCO : OH = 2, have been studied by monitoring, by IR analysis, the rate of decrease in NCO absorbance at 2264–2268 cm⁻¹. Different diisocyanates have been tested, among them the following: 4,4′‐dicyclohexylmethane diisocyanate (H₁₂MDI); 5‐isocyanato‐1,3,3‐trimethylcyclohexylmethyl isocyanate or isophorone diisocyanate (IPDI); 2,4‐toluene diisocyanate (TDI). Ethyl acetate (EA), methyl isobutyl ketone (MIBK), and hexafluoroxylene (HFX) have been used as solvents in presence of dibutyltin dilaurate (DBTDL) or 1,4‐diazabicyclo[2.2.2]octane (DABCO) as catalysts. These reactions gave rise to NCO‐end‐capped FPE–oligourethanes. Preliminary solubility tests for HO‐terminated FPEs in various solvents made it possible to select proper candidates for carrying out reaction in homogeneous conditions at high concentrations of reagents (30–50% w/w). The second‐order kinetic mechanism was shown to be valid. Positive deviations from linearity for the second‐order kinetics around 40–80% conversion, found for most of the FPE diols, were attributed to the autocatalysis of the isocyanate–hydroxyl reaction by the arising urethane groups. Uncatalyzed reactions with cycloaliphatic diisocyanates are very slow at 40°C. The tertiary amine DABCO is a much less effective catalyst than DBTDL. FPEs having terminal OH groups separated from the perfluorinated main molecular chain by  (OCH₂CH₂)_n segments (n = 1–2) are generally more reactive than FPEs with end  CH₂OH groups. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 557–570, 1999     

Synthesis and characterization of hyperbranched poly(urea‐urethane)s based on AA* and B2B* monomers

Hyperbranched aromatic and aliphatic poly(urea‐urethane)s were prepared by the one‐pot method using 2,4‐toluylene diisocyanate (TDI), isophorone diisocyanate, and 2(3‐isocyanatopropyl)cyclohexyl isocyanate as AA* monomers and diethanol amine and diisopropanol amine as B₂B* monomers. The characteristics of the resulting polymers were very sensitive to slight changes in the reaction conditions, such as temperature, concentration, and type of catalyst used, as can be seen from the results of gel permeation chromatography and differential scanning calorimetry. The structures were analyzed in detail using ¹H and ¹³C NMR spectroscopy. By using model compounds, the different isomeric structures of the TDI polymers were deduced, their percentages of their linear, terminal, and dendritic subunits were calculated, and their degree of branching (DB) was determined. DB values up to 70% were reached depending on the reaction conditions and stoichiometry of the monomers. The number of terminal groups decreased significantly when dibutylamine was used to stop the reaction instead of B₂B*, indicating the presence of a significant number of unreacted isocyanate groups in the hyperbranched product when the polyaddition reaction was stopped. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3062–3081, 2004     

水溶性封闭异氰酸酯单体的解封动力学

采用热失重分析(TGA)法研究了水溶性封闭型异佛尔酮二异氰酸酯(IPDI)的热分解过程, 利用傅里叶变换红外光谱法(FTIR)考察了谱图中40 与140 ℃两种温度下的异氰酸酯特征峰. TGA与FTIR的结果表明失重阶段即对应封闭异氰酸酯的解封闭反应. 用Friedman-Reich-Levi (FRL)和Flynn-Wall-Ozawa (FWO)两种动力学模型研究了解封反应的表观活化能E, 所得平均表观活化能分别为125.0和124.5 kJ·mol-1. 采用双等双步法对解封过程进行表观机理函数判断, 结果符合Jander方程, 反应机理为三维扩散, 结合FWO方程确定了反应级数n和指前因子对数lnA的范围.     

Synthesis and characterization of polyurethane-g-chitosan

The present work presents a study on the grafting of polyurethane onto chitosan. Prepolymers (polyurethanes) were obtained by condensation reactions between poly(ethylene glycol) of two different molar masses and isophorone diisocyanate. Characterization of graft copolymers was performed by infrared spectroscopy (IR) and ¹³C Nuclear Magnetic Resonance in the solid state (¹³C NMR). Evidences of grafting were obtained by IR from the absorbance increase of relative intensity of NH and CO bands, with respect to chitosan. The degree of NH₂ substitution by urea groups observed from 0.12 to 0.59 was estimated from NMR data. The graft copolymers exhibited different solubility behavior as a function of degree of substitution, such as partial solubility, gelation or swelling in diluted acetic acid, and swelling in water, dimethylsulfoxide and acetic acid/sodium acetate.     

Synthesis and characterization of yellow water-borne polyurethane using a diol colorant as extender

<正>A novel and facile method toward a series of yellow water-borne polyurethane was developed by using an intrinsically colored diol in this paper.The yellow aqueous dispersion PCLD-HENA-PU was synthesized based on isophorone diisocyanate(IPDI), polycaprolactonediol(PCLD) and 2,2-dimethylol propionic acid(DMPA) using a yellow diol N,N-bis(2-hydroxyethyl)-4-nitroaniline (HENA) as a chain extender.Due to the complete reaction of OH group in colorant HENA with NCO group in diisocyanate,a series of stable yellow polyurethanes could be obtained conveniently and easily.The structure of PCLD-HENA-PUs was confirmed by means of Fourier transform infrared spectroscopy.The UV-visible absorption analysis showed a blue shift effect of about 7 nm when HENA was blocked into polyurethane chain.The absorption intensity of PCLD-HENA-PUs increased with increasing HENA content.It was found that the tensile strength enhanced from 8.6 to 19.6 MPa with HENA content increased from 0 to 18.0%,while the extensibility decreased from 449 to 300%.The thermal gravimetric analysis presented that the initial decompose temperature began from about 250℃,and had a little increase with increasing the HENA content.     

Studies on allophanate-urethane networks based on hydroxyl terminated polybutadiene: effect of isocyanate type on the network characteristics

Polyurethane networks containing allophanate groups, based on hydroxyl terminated polybutadiene and various diisocyanates, such as toluene diisocyanate, 4,4^′ di(isocyanatocyclohexyl) methane and isophorone diisocyanate were synthesized at various NCO/OH equivalence ratios (r-values) ranging from 1.0 to 1.5. Mechanical properties such as tensile strength, stress at 100% elongation, equilibrium relaxation modulus increase and % elongation at break decreases with r-value. Crosslink density (ν_e) for the networks was determined using swell methods. Crosslink density values calculated from equilibrium relaxation modulus were found to be close to those obtained from swell data. Crosslink density (ν_t) was theoretically calculated assuming complete reaction between the functional groups. The ratio, ν_e/ν_t decreases with r-value. Linear fits with good correlation coefficients were obtained between network parameters and mechanical properties. Dynamic mechanical studies show that the r-value does not influence the glass transition temperature. Thermal decomposition studies using thermogravimetric technique indicate that the decomposition is in multiple stages.     

Kinetics and thermodynamics of the blocking reaction of several aliphatic isocyanates

The oxime-blocking reaction of several aliphatic isocyanates, such as 1,6-Hexane diisocyanate (HDI), isophorone diisocyanate (IPDI), and dicyclohexylmethane-4,4′-diisocyanate (H₁₂MDI), is investigated. The reaction is carried on in various solvents that are divided into two categories: aromatic solvents and oxygen-contained solvents. In situ FT-IR is used to monitor the reaction and show the large difference of solvent and the structure of isocyanate. Kinetic studies indicate that the reaction rate appears faster in aromatic solvents although the polarity of aromatic solvents is lower. Then, thermodynamic parameters of the blocking reaction, such as activation energy (E_a), enthalpy (ΔH*) and entropy (ΔS*), are determined from the Arrhenius and Eyring equations. It is found that activation energy in aromatic solvents is higher, but the reaction rate is much faster, all of which are discussed corresponding to the reaction mechanism.     

不同硬段含量脂肪族聚脲的结构与性能研究

通过端氨基聚醚、异佛尔酮二异氰酸酯和异佛尔酮二胺反应 ,合成了一系列不同硬段含量的脂肪族聚脲 ,并用DSC和FTIR等考察了硬段含量对聚脲的微观结构与力学性能的影响 .研究结果表明 ,聚脲呈现部分微观分相的形态 ,随硬段含量增加 ,聚脲中软段和硬段间的相容性提高 ,脲羰基的氢键化程度增加 ,但软段的玻璃化转变温度变化不大 ;此外 ,材料的拉伸强度、撕裂强度和硬度等也随着硬段含量的增加而显著提高 .     

不同异氰酸酯固化的蓖麻油／酚氧树脂聚氨酯的力学性能

以ＢＦ３·ＯＥｔ２为催化剂，４，４－二羟基二苯基丙烷与环氧氯丙烷反应，生成端羟基的酚氧树脂（Ａ），Ａ与蓖麻油（Ｂ）混合，用３种异氰酸酯（ＴＤＩ、ＩＰＤＩ和ＨＤＩ）作为固化剂，制得交联聚氨酯。研究了这３种聚氨酯的力学性能及形态与组成和二异氰酸酯结构的关系；改变ＮＣＯ／ＯＨ摩尔比及Ｂ与Ａ的质量比，可以制得具有较好力学性能的聚氨酯材料。蓖麻油，酚氧树脂，聚氨酯，力学性能     

Fluoropolyethers end‐capped by polar functional groups. II. Effect of catalyst and reagents concentration,solvent nature,and temperature on reaction kinetics of α,ω‐bis(hydroxy)‐terminated fluoropolyethers with cycloalyphatic and aromatic diisocyanates

A comparative kinetic study of the dibutyltin dilaurate (DBTDL) and 1,4‐diazabicyclo[2,2,2]octane (DABCO) catalyzed reactions of α,ω‐bis(hydroxy)‐terminated fluoropolyethers (FPEs)—Z‐DOLs and Z‐DOL TXs—of various molecular weights and purity, with 4,4′‐dicyclohexylmethane diisocyanate (H₁₂MDI), isophorone diisocyanate (IPDI) and 2,4‐toluene diisocyanate (TDI) was carried out in different solvents. An analytical method was used to follow the kinetics of the reactions at four different temperatures. The rate of NCO disappearance measured by two independent methods—IR spectroscopy and chemical titration were found to be very close. Straight proportionality between rate constants k_cat and catalyst concentration was found. But in some cases for the DBTDL catalyzed reactions effect of catalyst saturation along with appearance of the limiting DBTDL concentration C_lim below which the rate of reaction was close to zero were observed. Reactivity of Z‐DOLs in the tin‐catalyzed urethane reactions was found to decrease with their storage time at RT due to the slow hydrolysis of the end  COOR groups impurities, which give the corresponding acids that act as a strong inhibitor of the DBTDL activity. These acid admixtures have no influence on the DABCO catalyzed reactions. For the DBTDL and DABCO catalyzed reactions of Z‐DOLs with IPDI the dependence of effective rate constants k_eff (where k_eff = k_cat · 0.01/[DBTDL] and catalyst concentration is taken in mol % based on IPDI) on total reagents concentration were found to be described by curves with a maximum. Critical reagents concentration, after which the relationship k_eff = f (C) changes from proportional to inverse proportional, seems do not substantially depend on the solvent nature. Hydrogenated analog poly(ethylene glycol) MW 400 (PEG‐400) differs greatly from Z‐DOLs: only steady decrease of k_eff was observed with increase of reagents concentration C from 5 up to 95 wt %. Activation energies for all the studied reactions are within the range of 10.8–16.7 kcal/mol. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2579–2602, 2000     

Synthesis and Fluorescent Performance of Fluorescein-functionalized Waterborne Polyurethane

A novel yellow fluorescent diisocyanate 3,6-di(hexamethylene urethano)spiro[xanthene-9,3′-phthalide] diisocyanate (DIX) was synthesized by the reaction of fluorescein with hexamethylene diisocyanate first. Using DIX to substitute partially isophorone diisocyanate (IPDI), a kind of yellow fluorescent waterborne polyurethane DIX-WPU was prepared by blocking the fluorophore of DIX into the polyurethane chain using IPDI, polytetramethylene ether glycol and 2,2-dimethylol propionic acid. The molecular structure of DIX and DIX-WPU was confirmed by means of Fourier transform infrared spectroscopy. The fluorophore is fixed permanently in the polyurethane chain and is difficult to migrate due to the covalent bonding with other component during the synthesis. The fluorescence intensity of DIX-WPU fluorescent dispersion was enhanced greatly comparing with that of fluorescein in a wide range of fluorophore content between 1 × 10^–7 and 1 × 10^–3 mol/L. The fluorescence of DIX-WPU dispersion is very stable not only for the long term storage but also for the fluorescence quencher. It was found that the fluorescence intensity of DIX-WPU increased with the increase of temperature.     

Diisocyanate route as a convenient method for the preparation of novel optically active poly(amide-imide)s based on N-trimellitylimido-S-valine

A new class of optically active poly(amide-imide)s based on an α-amino acid was synthesized via direct polycondensation reaction of different diisocyanates with a chiral diacid monomer. The step-growth polymerization reactions of N-trimellitylimido-S-valine (TISV) (1) with 4,4′-methylene-bis(4-phenylisocyanate) (MDI) (2) was performed under microwave irradiation, as well as solution polymerization under graduate heating and reflux conditions. The optimized polymerization conditions for each method were performed with tolylene-2,4-diisocyanate (TDI) (3), hexamethylene diisocyanate (HDI) (4), and isophorone diisocyanate (IPDI) (5) to produce optically active poly(amide-imide)s via diisocyanate route. The resulting polymers have inherent viscosities in the range of 0.02-1.10 dL/g. Decomposition temperatures for 5% weight loss (T₅) occurred above 300 °C (by TGA) in nitrogen atmospheres. These polymers are optically active, thermally stable and soluble in amide-type solvents. Some structural characterization and physical properties of this new optically active poly(amide-imide)s are reported.     

Biofunctional rapid prototyping for tissue-engineering applications: 3D bioplotting versus 3D printing

Two important rapid-prototyping technologies (3D Printing and 3D Bioplotting) were compared with respect to the computer-aided design and free-form fabrication of biodegradable polyurethane scaffolds meeting the demands of tissue-engineering applications. Aliphatic polyurethanes were based on lysine ethyl ester diisocyanate and isophorone diisocyanate. Layer-by-layer construction of the scaffolds was performed by 3D Printing, that is, bonding together starch particles followed by infiltration and partial crosslinking of starch with lysine ethyl ester diisocyanate. Alternatively, the 3D Bioplotting process permitted three-dimensional dispensing and reactive processing of oligoetherurethanes derived from isophorone diisocyanate, oligoethylene oxide, and glycerol. The scaffolds were characterized with X-ray microtomography, scanning electron microscopy, and mechanical testing. Osteoblast-like cells were seeded on such scaffolds to demonstrate their potential in tissue engineering. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 624–638, 2004     

Preparation and Properties of Frost-Resistant Room-Temperature-Curable Compounds Based on Oligoethertetraurethane Diepoxides of Various Chemical Structures

New polytetraurethane diepoxides were prepared from oligo(tetramethylene oxide)diols of various molecular masses, various diisocyanates, and glycidol. High-strength frost-resistant cold-curable elastic compounds were prepared on their basis. The use of aminoethylpiperazine as a curing agent allows the cured materials to be prepared in 24 h at room temperature. The elastomers based on isophorone diisocyanate exhibit higher mechanical and thermal characteristics than those based on 2,4-toluene diisocyanate, which is due to higher degree of microphase segregation of soft and hard blocks of elastomers based in isophorone diisocyanate.     

Effect of the diisocyanate on the structure and properties of polyurethane acrylate prepolymers

In this study, we investigated the role of diisocyanate on the properties of polyurethane acrylate (PUA) prepolymers based on polypropylene oxide (M̄_n = 2000 g · mol⁻¹). The diisocyanates studied were isophorone diisocyanate, 4‐4′dicyclohexylmethane diisocyanate, and toluene diisocyanate (pure 2,4‐TDI, pure 2,6‐TDI, and a TDI mixture, TDI_tech). The molecular structure of the diisocyanate had a major role on the course of the polycondensation and, more precisely, on the sequence length distribution of the final prepolymer. Moreover, the structural organization of the prepolymer also strongly depended on the nature of the diisocyanate. Two types of behaviors were particularly emphasized. On the one hand, the PUA synthesized from 2,4‐TDI displayed an enhanced intermixing between soft polyether segments and hard urethane groups, as revealed by the analysis of hydrogen bonding in Fourier transform infrared. Consecutively, the glass transition shifted to higher temperatures for these polymers. On the other hand, strong hard–hard inter‐urethane associations were observed in 2,6‐TDI‐based prepolymers; these led to microphase segregation between polyether chains and urethane groups, as revealed by optical microscopy. This inhomogeneous structure was thought to be responsible for the unusual rheological behavior of these PUA prepolymers. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2750–2768, 2000     

A novel method for preparation of exfoliated UV-curable polymer/clay nanocomposites

The half adduct of isophorone diisocyanate and 2-hydroxyethyl acrylate (IPDI-HEA), as a reactive organic modifier, was used to functionalize Na-montmorillonite (Na-MMT) clay. Unlike the electronic interaction in the conventional cation-exchange method, the driving force for the organic modification came from the chemical reaction between IPDI-HEA and framework hydroxyl groups on the surface of clay. With high degree of organic modification (48%), the d-spacing of clay layer was greatly enlarged to 3.32 nm, and the clay became more organophilic. After in situ photopolymerization among the IPDI-HEA grafted MMT clay, monomers and oligomers, the exfoliated polymer/clay nanocomposites were obtained. X-ray diffraction and transmission electron microscopy were used to detect the structure and morphology of the clay dispersed in the polymer matrix. Compared with the pure polymer materials, the exfoliated polymer/clay nanocomposites exhibited enhancements in mechanical and thermal properties.     

2-Ethy-4-methylimidazole terminated polyurethane prepolymer as functional latent curing agents for epoxy resin crosslinking

Three kinds of 2-ethyl-4-methylimidazole (EMI)-terminated polyurethane prepolymer were prepared through the reaction between diethylene glycol (DEG), polyethylene glycol 400 (PEG-400) and different isocyanates (toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), hexamethylenediisocyanate (HDI)). The storage stability, curing temperature and curing time of diglycidyl ether of bisphenol A (DGEBA) with EMI derivatives have been investigated by viscometer, DSC, and FTIR, respectively. It was proved that DGEBA/EMI derivatives exhibited superior storage stability than that of DGEBA/EMI. And the DGEBA can be effectively cured by the EMI derivatives at 120–140?°C without the generation of harmful species. Moreover, the higher impact strength and lower glass transition temperature (Tg) suggested an improvement of stiffness. The results of tensile test and TGA indicated that the excellent bonding strength with steel and unconspicuous compromise in thermal stability were simultaneously achieved.