New insight into the kinetics of diisocyanate‐alcohol reactions by high‐performance liquid chromatography and mass spectrometry

The uncatalyzed reactions of 2,4‐TDI (2,4‐ toluenediisocyanate ) and MDI (4,4 ′ ‐ diphenylmethane‐diisocyanate ) with alcohols including butan‐1‐ol, butan‐2‐ol, diethylene glycol monomethylether (DEGME) were studied by high ‐ performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI‐MS). The reactions were carried out at different temperatures from 22°C to 75°C using high molar ratios of alcohols to diisocyanates. It was found that the first isocyanate group of the MDI reacts about 1.5 times faster with the alcohols than the second one. The relative reactivities of the isocyanate groups (para and ortho) of 2,4‐TDI as a function of the temperature was also deduced. From the temperature dependence of the rate constants the apparent activation energies were determined. Furthermore, the dependence of the apparent rate constant on the concentration of alcohols was also investigated and a mechanism was proposed for the reaction of diisocyanates with alcohols. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42127.     

Rheo‐kinetic evaluation on the formation of urethane networks based on hydroxyl‐terminated polybutadiene

Rheo‐kinetic studies on bulk polymerization reaction between hydroxyl‐terminated polybutadiene (HTPB) and di‐isocyanates such as toluene‐di‐isocyanate (TDI), hexamethylene‐di‐isocyanate (HMDI), and isophorone‐di‐isocyanate (IPDI) were undertaken by following the buildup of viscosity of the reaction mixture during the cure reaction. Rheo‐kinetic plots were obtained by plotting ln (viscosity) vs. time. The cure reaction was found to proceed in two stages with TDI and IPDI, and in a single stage with HMDI. The rate constants for the two stages k₁ and k₂ were determined from the rheo‐kinetic plots. The rate constants in both the stages were found to increase with catalyst concentration and decrease with NCO/OH equivalent ratio (r‐value). The ratio between the rate constants, k₁/k₂ also increased with catalyst concentration and r‐value. The extent of cure reaction at the point of stage separation (x_i) increased with catalyst concentration and r‐value. Increase in temperature caused merger of stages. Arrhenus parameters for the uncatalyzed HTPB‐isocyanate reactions were evaluated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1869–1876, 2001     

Kinetics of glycidyl azide polymer‐based urethane network formation

Reactions between hydroxyl‐terminated glycidyl azide polymer (GAP) and different isocyanate curatives such as toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), and methylene diicyclohexyl isocyanate (MDCI) at various temperatures viz. 30, 40, 50, and 60°C were followed by Fourier transform infra red spectroscopy. The reactions were found to follow second‐order kinetics. With TDI and IPDI at 30°C, a two‐stage reaction was observed. For GAP‐TDI system, the second stage was slower than the first while for GAP‐IPDI system, the second stage was faster than the first indicating dominance of autocatalytic effect. The stage separation occurred due to the difference in reactivity of the isocyanate groups and was found to narrow down with increase in temperature. The viscosity build up due to the curing reaction was followed for GAP‐TDI system for comparison. The stage separation was evident in the viscosity build up also. Rheokinetic analysis done based on data generated showed a linear correlation between viscosity build up and fractional conversion. The kinetic and activation parameters evaluated from the data showed the relative difference in reactivity of the three diisocyanates with GAP. Both the approaches suggested that the reactivity of the isocyanates employed for the present study could be arranged as TDI > IPDI ? MDCI. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Urethane‐forming reaction kinetics and catalysis of model palm olein polyols: Quantified impact of primary and secondary hydroxyls

Model palm olein natural oil polyols (NOPs) with varying ratios of primary to secondary hydroxyls were synthesized, characterized, and evaluated in reaction kinetics study with isocyanate in formation of polyurethanes. Reaction rate constants and activation energies associated with primary and secondary hydroxyls of NOPs were quantified. The kinetic study in toluene shows that the NOP containing primary hydroxyls have three times higher reaction rate constants in noncatalyzed reaction with 4,4′‐diphenylmethane diisocyanate (4,4′‐MDI) compared to the model NOP containing only secondary hydroxyls, which is associated with higher activation energy of secondary hydroxyls. However, the difference in reaction rate constants of primary and secondary hydroxyls in NOPs diminished in the reactions catalyzed with dibutyltin dilaurate. Bulk polymerization reaction confirms the kinetics results in toluene, showing that the model NOP containing primary hydroxyls reached gel time at a faster rate. Evaluation of elastomers from bulk polymerization shows low degree of phase separation of hard and soft segments for elastomers based on the model NOPs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42955.     

Preparation of polystyrene/toluene‐2,4‐ di‐isocyanate–modified montmorillonite hybrid

A novel selective interlamellar modification of cetyltrimethylammonium bromide‐exchanged montmorillonite (MMT) by toluene‐2,4‐di‐isocyanate (TDI) has been successfully obtained, and a polystyrene/TDI‐modified MMT hybrid has been prepared. After the interlamellar modification, TDI was grafted to hydroxyl groups of the MMT, and the orientation of cetyltrimethylammonium in the interlayer space changed from a bilayer lying flat structure to a double‐layer inclined one. The structures of the TDI‐modified MMT and the hybrid were characterized by Fourier transform infrared (FTIR) spectra, powder X‐ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. A schematic model of the TDI‐modified MMT structure was also presented. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2201–2205, 2000     

Effects of chemical structure of polyurethane‐based low‐profile additives on the miscibility,curing behavior,volume shrinkage,glass transition temperatures,and mechanical properties for styrene/unsaturated polyester/low‐profile additive ternary systems. II: Glass transition temperatures and mechanical properties

The effects of three series of thermoplastic polyurethane‐based (PU) low‐profile additives (LPA) with different chemical structures and molecular weights on the glass transition temperatures and mechanical properties for thermoset polymer blends made from styrene (ST), unsaturated polyester (UP), and LPA have been investigated by an integrated approach of static phase characteristics‐cured sample morphology‐reaction conversion‐property measurements. The three series of PU used were made from 2,4‐tolylene di‐isocyanate (2,4‐TDI) and varied diols, namely polycaprolactone diol (PCL), poly(diethylene adipate) diol (PDEA), and poly(propylene glycol) diol (PPG), respectively, while the two UP resins employed were synthesized from maleic anhydride (MA) and 1,2‐propylene glycol (PG) with and without modification by phthalic anhydride (PA). Based on the Takayanagi mechanical models, factors that control the glass transition temperature in each phase region of cured samples, as identified by the method of thermally stimulated currents (TSC), and mechanical properties will be discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 558–568, 2000     

Polymer networks based on the diepoxide–diisocyanate reaction catalyzed by tertiary amines

Reactions taking place in a system consisting of a diepoxide (DGEBA, diglycidylether of bisphenol A) and a diisocyanate (TDI 80 : 20, toluene diisocyanate), catalyzed by a tertiary amine (BDMA, benzyldimethylamine), were followed by differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), and chemical titration of isocyanate groups in the pre-gel stage. It was found that the main reactions took place in series, in steps of increasing temperature: (i) isocyanurate formation, (ii) epoxy-isocyanate reaction leading to oxazolidone rings, and (iii) isocyanurate decomposition by epoxy groups producing oxazolidone rings. Isocyanurate rings were stable in the presence of epoxides and an isocyanate excess [reaction (ii) was faster than (iii)]. Epoxy homopolymerization (secondary reaction) occurred in parallel with steps (ii) and (iii). Step (i) took place by two different mechanisms and led to a maximum conversion, possibly limited by topological restrictions. A kinetic study of TDI trimerization in the presence of an equimolar amount of DGEBA and variable amounts of BDMA led to a third-order regression with an activation energy E = 43 kJ/mol. © 1995 John Wiley & Sons, Inc.     

Poly(dimethylsiloxane)urethane‐co‐poly(methyl methacrylate) with 2,4‐toluene diisocyanate and m‐xylene diisocyanate. I. Compatibility and impact strength of copolymers

In this study, slightly crosslinked poly(dimethylsiloxane)urethane‐co‐poly(methyl methacrylate) (PDMS urethane‐co‐PMMA) graft copolymers based on two diisocyanates, 2,4‐toluene diisocyanate (2,4‐TDI) and m‐xylene diisocyanate (m‐XDI), were successfully synthesized. Glass‐transition behaviors of the copolymers were investigated. Results confirm that PDMS–urethane and PMMA are miscible in the 2,4‐TDI system, but are only partially miscible in the m‐XDI system. The methylene groups adjoining the isocyanate in the m‐XDI system show increased phase‐separation behavior over the 2,4‐TDI system, in which the benzene ring adjoins the isocyanate. The functional group of PDMS–urethane improves the impact strength of the copolymers. The toughness depends on the compatibility of PDMS–urethane and PMMA segments in the copolymers. In the m‐XDI system, the impact strength of the copolymer containing 3.75 phr macromonomer achieves a maximum value (from 13.02 to 22.21 J/m). The fracture behavior and impact strength of the copolymers in the 2,4‐TDI system are similar to that of PMMA homopolymer, although they are independent of the macromonomer content in the copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1875–1885, 2002     

Grafting hydroxy‐terminated polybutadiene onto nanosilica surface for styrene butadiene rubber compounds

Hydroxy teminated polybutadiene (HTPB) was grafted onto the surface of nanosilica particles via toluene di‐isocyanate (TDI) bridging to reduce filler–filler interactions and improve dispersion of nanosilica in rubber. Also, this prepolymer as modifier contains double bonds which participate in sulfur curing of styrene butadiene rubber (SBR) matrix to enhance filler/polymer interaction and reinforcement effects of silica. The reactions were characterized by titration and Fourier transforms infrared spectroscopy. Thermogravimetric analysis was utilized to evaluate the weight percentage of grafted TDI and HTPB. About 60% of the hydroxyl sites of silica were reacted with excess TDI in the first reaction. In the second reaction, HTPB as desired reactive coating was grafted on the functionalized nanosilica to constitute about 24 wt % of the final modified silica. The sedimentation experiments showed good suspension stability for the modified nanosilica in the organic media. Scanning electron microscopy revealed nanoscale dispersion of modified silica aggregates in the SBR matrix at concentration of about 14 phr. Also, vulcanization characteristics and mechanical properties of compounds demonstrated that HTPB grafting improved dispersion of nanosilica as well as its interaction to the rubber matrix as an efficient reinforcement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Kinetic and Technological Analysis of Dimethyl Toluene‐2,4‐Dicarbamate Synthesis

The synthesis of dimethyl toluene‐2,4‐dicarbamate from 2,4‐toluene diamine and dimethyl carbonate is a complex reaction system. First, the reaction enthalpies, the Gibbs function changes, and the equilibrium constants of the reactions were calculated by several methods of group contribution. Secondly, the kinetics of the synthesis reaction over a zinc acetate catalyst was investigated in a batch autoclave. The kinetic model equations were established by parameter estimation based on experimental data, and the model met the requirements of the statistical test. The calculated results based on the model agreed well with the experimental data. According to the results of both thermodynamic calculation and kinetic analysis, the influence of some technological parameters, such as content of methanol in the feed and reaction temperature, on the synthesis reaction was discussed.     

Kinetics of reaction of n-butanol and triaminononane trisisocyanate measured via 13C solution NMR

The model reaction kinetics of a novel trifunctional isocyanate 4-aminomethyl-1,8-diaminooctane [informally referred to as triaminononane trisisocyanate (TTI) with n-butanol is described. Butanol is used in place of the normal polyols used in actual coatings formulations in order to simplify the system for kinetic analysis. Using ¹³C-NMR, the differences in reactivity of each isocyanate group was studied in real-time measurements. There is little difference in the second-order rate constants between the three TTI isocyanate groups in the uncatalyzed systems at 25, 35, or 45°C. The dibutyl tin dilaureate (DBTDL) catalyzed system exhibits similar second-order rate constants for the medium-and long-branch systems, and a smaller rate constant for the short-branch system. The activation energies increase with increasing chain length in the uncatalyzed system, while for the catalyzed system the long and medium branches have identical activation energies, and the short-branch system has the lowest activation energy. The addition of chloroform or increasing the butanol: TTI ratio results in an increase of the measured rate constant. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of novel sulfobetaines derived from 2,4‐tolylene diisocyanate

Novel sulfobetaines were synthesized from two urethanes derived from 2,4‐tolylene diisocyanate (TDI) blocked with 2‐hydroxyethyl methacrylate (HEMA) and either N,N‐dimethylaminopropylamine (DMAPA) or N,N‐dimethylaminoethanolamine (DMAEA). The first‐stage reaction of TDI with HEMA was carried out in petroleum ether heterogeneously with the precipitation of the intermediate monoadduct product in the reaction solution. The second stage is a homogeneous reaction of the monoadduct with the blocking agent, DMAPA or DMAEA, in tetrahydrofuran (THF). In both reactions, an inhibitor, hydroquinone, and a catalyst, dibutyltin diacetate (DBDAc), were used. The tertiary amine urethanes were quaternized by 1,3‐propane sultone to form the two novel sulfobetaines. The results of the elemental analysis of those products along with their ¹H‐NMR and IR spectra indicated that these materials were, indeed, the compounds expected. The products dissolved in strongly polar organic solvents. The copolymerization of these two monomers with comonomers such as styrene, methyl methacrylate, acrylamide, and HEMA was investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3447–3459, 2001     

Monitoring of the Synthesis of Hyperbranched Poly(urea‐urethane)s by Real‐Time Attenuated Total Reflection (ATR)‐FT‐IR Spectroscopy

Summary: The reaction of 2,4‐TDI and DEA, as an A₂ + B^*B₂ polymerization system towards hyperbranched HPUs was followed using in situ ATR‐FT‐IR spectroscopy. The decrease in intensity of the NCO absorption band of the reactive isocyanate group of 2,4‐TDI along with the formation and growth of the new characteristic bands of urethane and urea groups were detected. The reactivity difference of both NH and OH groups towards the NCO group at low temperatures was proven. The rate of the reaction was found to be affected by changing the temperature, the rate of addition of the B^*B₂ monomer and the type of solvent. Moreover, the increase of the carbonyl vibration and the amide II bands of urea was very obvious during the addition of the stopper DEA. Thus, it was possible to verify the individual reaction steps of this complex polyreaction and to correlate these with the structural development of the resulting macromolecules.

Characteristic vibration bands of urethane and urea groups in the IR spectra (1 780–1 480 cm^?1) during the polymerization reaction.     

Synthesis and application of CDA‐beta‐CD in controlling release of drug

To chemically attach beta‐cyclodextrin (beta‐CD) molecules to cellulose diacetate (CDA), an isocyanate containing preformed polymer was synthesized by prepolymerization of CDA and toluene‐2,4‐diisocyanate (TDI), which was then grafted with beta‐CD. Effects of reaction temperature, time, and mixture ratio on reactions were observed. The structure of CDA‐beta‐CD was characterized by ¹H‐ and ¹³C‐NMR spectra; the release of CDA‐beta‐CD with medicament naproxen by dynamic dialysis in the artificial simulated intestinal fluid (pH = 7.4) was studied in vitro. Results indicated that the release time could reach more than 8 h at a graft ratio of 68.7%, which showed a good controlled‐release drug effect. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of new polyureas derived from 4‐cyclohexylurazole

4‐Cyclohexylurazole (1) R = cyclohexyl (CHU) was prepared from cyclohexyl isocyanate in two steps. Polycondensation reactions of compound CHU with hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), and toluene‐2,4‐diisocyanate (TDI) were performed in DMAc/chloroform and DMAC in the presence of pyridine as a catalyst. The resulting novel polyureas have an inherent viscosity in the range of 0.044–0.206 g/dL in DMF at 25°C. These polyureas were characterized by IR, ¹H–NMR, elemental analysis, and TGA. The resulting polymers are soluble in most organic solvents. Some physical properties and structural characterization of these novel polyureas are reported. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1335–1341, 2001     

Isothermal kinetics of (E)‐4‐(4‐metoxyphenyl)‐4‐oxo‐2‐butenoic acid release from a poly(acrylic acid‐co‐methacrylic acid) hydrogel

A kinetic study of the release of the drug (E)‐4‐(4‐metoxyphenyl)‐4‐oxo‐2‐butenoic acid (MEPBA) from a poly(acrylic acid‐co‐methacrylic acid) (PAA‐co‐MA) hydrogel was performed. The isothermal kinetic curves of MEPBA release from the PAA‐co‐MA hydrogel in bidistilled water at different temperatures ranging from 20 to 40°C were determined. The reaction rate constants of the investigated process were determined with the initial rate, the saturation rate, and Peppas's semiempirical equation. Also, a model‐fitting method for the determination of the kinetics model of drug release was applied. The influence of α at the values of the kinetic parameters and the presence of a compensation effect was established. A procedure for the determination of the distribution function of the activation energies was developed. This procedure was based on the experimentally determined relationship between the activation energy and α. The mechanism of active compound release is discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of novel azo‐containing polyureas derived from 4‐[4′‐(2‐hydroxy‐1‐naphthylazo)phenyl]‐1,2,4‐triazolidine‐3,5‐dione

4‐[4′‐(2‐Hydroxy‐1‐naphthylazo)phenyl]‐1,2,4‐triazolidine‐3,5‐dione ( HNAPTD ) ( 1 ) has been reacted with excess amount of n‐propylisocyanate in DMF (N,N‐dimethylformamide) solution at room temperature. The reaction proceeded with high yield, and involved reaction of both N? H of the urazole group. The resulting bis‐urea derivative 2 was characterized by IR, ¹H‐NMR, elemental analysis, UV‐Vis spectra, and it was finally used as a model compound for the polymerization reaction. Solution polycondensation reactions of monomer 1 with Hexamethylene diisocyanate ( HMDI ) and isophorone diisocyanate ( IPDI ) were performed in DMF in the presence of pyridine as a catalyst and lead to the formation of novel aliphatic azo‐containing polyurea dyes, which are soluble in polar solvents. The polymerization reaction with tolylene‐2,4‐diisocyanate ( TDI ) gave novel aromatic polyurea dye, which is insoluble in most organic solvents. These novel polyureas have inherent viscosities in a range of 0.15–0.22 g dL^?1 in DMF at 25°C. Some structural characterization and physical properties of these novel polymers are reported. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3177–3183, 2001     

Catalytic synthesis of toluene‐2,4‐diisocyanate from dimethyl carbonate

The process for catalytic synthesis of toluene‐2,4‐diisocyanate (TDI) from dimethyl carbonate (DMC) consists of two steps. Starting from the catalytic reaction between toluene‐2,4‐diamine (TDA) and DMC, dimethyl toluene‐2,4‐dicarbamate (TDC) is formed, and then decomposed to TDI. For the first step, the yield of TDC is 53.5% at a temperature of 250 °C, over Zn(OAc)₂/α–Al₂O₃ catalyst. For the second step, the yield of TDI is 92.6% at temperatures of 250–270 °C and under pressure of 2.7 kPa, over uranyl zinc acetate catalyst, when di‐n‐octyl sebacate(DOS) is used as heat‐carrier, and a mixture of tetrahydrofuran (THF) and nitrobenzene is used as solvent. © 2001 Society of Chemical Industry     

Kinetics of water-isocyanate reaction in N,N-dimethylformamide

The uncatalyzed reaction of p-tolyl isocyanate (p-TI) with water in N,N-dimethylformamide (DMF) was investigated by high performance liquid chromatography (HPLC).The reactions were carried out at different temperatures from 293 K to 323 K,using various molar ratios of water to p-TI.DMF,as a special amide,was proved to be an efficient catalyst for water-isocyanate reaction.Under the reaction conditions in this study,substituted urea was the only final product observed.An appreciable amount of intermediate p-toluidine was detected.Concentrations of the isocyanate group as well as the amine and urea were determined as a function of time.New kinetic equations were deduced for each of the substance on the basis of a multistep mechanism,instead of a simple second order reaction as usual.Kinetic constants were calculated using the software MATLAB.Furthermore,the effects of temperature and concentrations of reactants on the reaction rate and amine content were discussed.The activation energy of each step was also determined.