Presence Of Dibutyltin Dilaurate Research Articles

Hyperbranched polycyclocarbosiloxane

A new cross-linkable naphthalene-cyclocarbosiloxane was synthesised starting from bis[1,4-bis(methylhydrosiloxanyl)-dihydronaphthalene] via catalytic addition of the Si–H reactive groups to the unsaturated bond of triethoxyvinylsilane. Hyperbranched polycyclocarbosiloxane networks were formed by condensation of the alcoxyl groups in the presence of dibutyltin dilaurate as catalyst. The cross-linking process was studied in order to obtain information concerning the values of the reaction parameters and to determine the position of the gelation point relative to conversion. GPC analysis, IR, and 1 H-NMR spectral analysis techniques were used to investigate the chemical structures of the intermediates and of the product.

Synthesis and Characterization of Ordered Polyurethanes from Tolylene 2,4-Diisocyanate and Ethylene Glycol

An ordered polyurethane with a head-to-head or tail-to-tail (H–H or T–T) content of 90% was prepared by polyaddition reaction of a nonsymmetric monomer, tolylene 2,4-diisocyanate (1) with a symmetric monomer, ethylene glycol (2). The polymerization was conducted in toluene in the presence of dibutyltin dilaurate (DBTL) at 0°C by slow addition of a half amount of 2 to 1, followed by removing toluene and then adding the rest of 2 in DMF at once at room temperature in the presence of DBTL. Furthermore, the authentic ordered and random polymers were prepared to verify the structure of the ordered polymer and it was found that the polymer had the expected structural regularity. The constitutional regularity of polymers influenced on their thermal properties.

Synthesis and characterization of ordered polyurethanes from nonsymmetric diisocyanate and ethylene glycol

An ordered polyurethane with a head-to-head (H-H) or tail-to-tail (T-T) content over 95% was prepared by polyaddition reaction of a nonsymmetric monomer, p-isocyanatobenzyl isocyanate (1) with a symmetric monomer, ethylene glycol (2). The model reactions were studied in detail to demonstrate the feasibility of polymer formation. The polymerization was conducted in THF in the presence of triethylamine (TEA) at 0 °C by slow addition of a half amount of 2 to 1, followed by removing THF and then adding the rest of 2 in DMF at once at 30 °C in the presence of dibutyltin dilaurate (DBTL). The microstructure of the polymer obtained was investigated by 13C NMR spectroscopy, and it was found that the polymer had the expected structural regularity. The constitutional regularity of polymers influenced their thermal properties. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2106–2114, 2000

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

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

Preparations and properties of new monomeric light stabilizers

Six new monomeric light stabilizers have been synthesized by a two-step controlled isocyanation. In the first step methacrylic acid (MAA) or acrylic acid (AA) reacts with toluene-2,4- diisocyanate (TDI) or hexamethylene diisocyanate (HMDI) at a mole ratio of 1 to 1 to form an intermediate. In the second step this intermediate was directly added to 2,2,6,6-tetramethyl-4-piperidinol (TMP) or 2,4-dihydroxy benzophenone (DHBP) at a 1 to 1 mole ratio at a given temperature in the presence of dibutyltin dilaurate (DBTDL) catalyst. These six new monomeric stabilizers are 2,2,6,6-tetramethyl-4-piperidinyl, (4-methacryloyl amino) tolyl carbamate-2 ( A); 2,2,6,6-tetramethyl-4-piperidinyl, (4-acryloyl amino) tolyl carbamate-2 ( B); 2,2,6,6tetramethyl-4-piperidinyl, (6-methacryloyl amino) hexyl carbamate-1 ( C); 2-hydroxy-4-benzophenonyl, (6-methacryloyl amino) hexyl carbamate-1 ( D); 2,2,6,6-tetramethyl-4-piperidinyl, (6-acryloyl amino) hexyl carbamate-1 ( E) and 2-hydroxy-4-benzophenonyl, (6-acryloyl amino) hexyl carbamate-1 ( F). These new monomeric light stabilizers were characterized by IR, NMR, UV and elemental analysis. Their stabilizing action for protecting polypropylene (PP) against photo-oxidation and polymerizability were examined.

Synthesis and performance of new bifunctional stabilizers

Six new bifunctional stabilizers have been synthesized by a two-step controlled isocyanation. In the first step a compound containing a stabilizing functional group, 2,4-dihydroxy benzophenone (DHBP) or 2,2,6,6-tetramethyl-4-piperidinol (TMP), reacts with toluene-2,4-diisocyanate (TDI) or hexamethylene diisocyanate (HMDI) at a mole ratio of 1 to 1 to form an intermediate I. In the second step I was directly added to another compound containing a different stabilizing functional group such as TMP or 2,6-di-tert-butyl-4-hydroxy methyl phenol (DBHMP) at a 1 to 1 mole ratio at a given temperature in the presence of dibutyltin dilaurate (DBTDL) catalyst. These six new stabilizers are 2-hydroxy-4-benzophenonyl, 2,2,6,6-tetramethyl-4-piperidinyl hexamethylene dicarbamate ( A, MW=540); 2-hydroxy-4-benzophenonyl, 3,5-di- tert-butyl-4-hydroxyl benzyl hexamethylene dicarbamate ( B, MW=619); 3,5-di- tert-butyl-4-hydroxyl benzyl, 2,2,6,6-tetramethyl-4-piperidinyl hexamethylene dicarbamate ( C, MW=562); 2,2,6,6-tetramethyl-4-piperidinyl, 2-hydroxy-4-benzophenonyl toluene 2,4-dicarbamate ( D, MW=546); 3,5-di- tert-butyl-4-hydroxyl benzyl, 2-hydroxy-4-benzophenonyl toluene 2,4-dicarbamate ( E, MW=625) and 3,5-di- tert-butyl-4-hydroxyl benzyl, 2,2,6,6-tetramethyl-4-piperidinyl toluene 2,4-dicarbamate ( F, MW=568). Their structures have been characterized by IR, NMR, UV and elemental analysis. The photostabilizing and thermal stabilizing effectiveness of these new stabilizers for polypropylene (PP) had been examined. Experimental results show that these new bifunctional stabilizers are effective in protecting PP against photo-oxidation and thermal-oxidation. The effectiveness in relation to the structures of these new bifunctional stabilizers is discussed.

Enhanced adhesion and chemoattraction of zoospores of the fouling alga enteromorpha to some foul‐release silicone elastomers

Significantly higher numbers of zoospores of the fouling, green alga Enteromorpha adhered to silicone elastomers cured by dibutyltin dilaurate (DBTDL) than to identical polymers cured by dibutyltin diacetate (DBTDA). Enhanced zoospore adhesion was shown to be due to the presence of DBTDL and the effect was concentration‐dependent. Further experiments revealed that enhanced zoospore adhesion also occurred to glass coverslips coated with lauric acid (C12) and other saturated fatty acids. The possibility that fatty acids may act as chemical cues (chemoattractants), guiding motile zoospores to the substratum for settlement in the natural environment is discussed. Settlement of other fouling organisms to DBTDL‐cured silicone elastomers is currently being investigated.

Synthesis and Characterization of new Monomers and Polymers Containing Hindered Piperidine Groups

Two new methacryloyl ureas, 1-(2-methylacryloyl)-3-(2,2,6,6-tetra-methylpiperidin-4-yl)-urea and 1-butyl-3-(2-methylacryloyl)-1-(2,2,6,6-tetramethylpiperidin-4-yl)-urea (monomer I and monomer II), were prepared by the addition reaction of 2-methylacryloyl iso-cyanate with 2,2,6,6-tetramethylpiperidin-4-yl-amine or butyl-(2,2,6,6-tetramethylpiperidin-4-yl)-amine in a molar ratio of 1:1 at low or room temperature. In a similar way, the syntheses of two new methacryloyl carbamates, 1-(2,2,6,6-tetra-methylpiperidin-4-yl)-3-(2-methylacryloyl)-carbamate and l-(1,2,2,6,6-pentamethyl-piperidin-4-yl)-3-(2-methylacryloyl)-carbamate (monomer III and monomer IV), were completed by the reaction of 2,2,6,6-tetra-methylpiperidin-4-ol or 1,2,2,6,6-pentamethylpiperidin-4-ol with 2-methylacryloyl isocyanate in the presence of dibutyltin dilaurate as catalyst at 60°C. The four new monomers were homopolymerized, and copolymerized with styrene by AIBN as initiator at 70°C. The structures of the new monomers and their polymers were characterized by FT-IR and NMR spectroscopy and by GPC.

Low molar mass polybutadiene made crosslinkable by the introduction of silane moities via urethane linkage: 1. Synthesis and kinetic study

Polybutadiene crosslinkable under moisture was synthesised by modification of hydroxy telechelic functions of low molecular weight polybutadiene with isocyanato propyl triethoxy silane. At 50°C and with dibutyl tin dilaurate (DBTL) as catalyst, silane moities were introduced quantitatively at the rate of 1.2, 2 and 2.4 per polymer chain. Two analytical methods ( FTi.r. spectroscopy and volumetric titration) were used to follow isocyanate consumption. Two kinetic treatments were investigated (2nd and 3rd order) and influence of catalyst concentration and temperature were studied. A 2nd order kinetic seems to be better fitted for our experimental results. Nevertheless, in each case, Arrhenius law suggests an entropically controlled reaction with probably ethoxy silane groups participating in a transition state in the presence of DBTL.

Polyurethane macroazoinitiators based on 2,2?-azobis (2-cyanopropanol) kinetic studies

2,2'-Azobis(2-cyanopropanol) (ACP) was used to react with 4,4'-methylene diphenyl diisocyanate (MDI) and α,ω-hydroxy polycaprolactone (PCL) in the presence of dibutyltin dilaurate (SnDBDL) as a catalyst in a two-stage polycondensation to produce a polyurethane macroazoinitiator (PUMAI). The kinetics of the reaction of ACP with a monoisocyanate (para-tolylisocyanate, p-TI) was followed using high performance liquid chromatography. The condensation reaction was performed in 2-butanone, with SnDBDL as catalyst. Kinetic models were suggested to calculate rate constants. The experimental results showed an autocatalytic effect of the reaction by urethane groups and a different reactivity of the second OH group of ACP after the reaction of the first one. The kinetics of the reaction of MDI with ACP and PCL were studied using size exclusion chromatography. Polycondensation was performed under the same conditions used for the model system. The reaction rates of MDI with ACP and PCL were compared. ACP was shown to be slightly more reactive with MDI than PCL. The first stage of PUMAI synthesis (reaction of ACP with a large excess of MDI) was studied. Some side reactions with isocyanates occured. Finally, a typical PUMAI was synthesized.

Polyurethane macroazoinitiators based on 2,2′‐azobis (2‐cyanopropanol) kinetic studies

2,2′-Azobis(2-cyanopropanol) (ACP) was used to react with 4,4′-methylene diphenyl diiso-cyanate (MDI) and α,ω-hydroxy polycaprolactone (PCL) in the presence of dibutyltin di-laurate (SnDBDL) as a catalyst in a two-stage polycondensation to produce a polyurethane macroazoinitiator (PUMAI). The kinetics of the reaction of ACP with a monoisocyanate (para-tolylisocyanate, p-TI) was followed using high performance liquid chromatography. The condensation reaction was performed in 2-butanone, with SnDBDL as catalyst. Kinetic models were suggested to calculate rate constants. The experimental results showed an autocatalytic effect of the reaction by urethane groups and a different reactivity of the second OH group of ACP after the reaction of the first one. The kinetics of the reaction of MDI with ACP and PCL were studied using size exclusion chromatography. Polycon-densation was performed under the same conditions used for the model system. The reaction rates of MDI with ACP and PCL were compared. ACP was shown to be slightly more reactive with MDI than PCL. The first stage of PUMAI synthesis (reaction of ACP with a large excess of MDI) was studied. Some side reactions with isocyanates occured. Finally, a typical PUMAI was synthesized. © 1996 John Wiley & Sons, Inc.

Influence of thermal stabilizers on diffusion of poly(?-caprolactone) in poly(vinyl chloride)/poly(?-caprolactone) blends

The influence of thermal stabilizers on the poly(ϵ-caprolactone) (PCL) diffusion in poly(vinyl chloride) (PVC)/PCL blends was studied with the addition of various concentrations of dibasic lead phthalate and dibutyltin dilaurate. The rate of PCL diffusion was followed by differential scanning calorimetry and IR spectroscopy in three series of experiments: the migration of PCL at the surface of the sample; the extraction of PCL in a fluid surrounding the sample; and the sorption of liquid PCL in the blend. In the last two series, mass losses and mass uptakes were measured as a function of time. As compared to the blend without additive, dibutyltin dilaurate induces an increase of the PCL rate of diffusion whereas dibasic lead phthalate gives a decrease. These trends are explained by: first, the formation of an associative complex between dibutyltin dilaurate and PVC, which can compete with the PVC/PCL interactions in the blend and thus favor the PCL migration; and, second, the modification of the Tg of the blend induced by the addition of a third component, which can modify the diffusion rate by changing the free volume fraction at the diffusion temperature. Tg decreases slightly in the presence of dibutyltin dilaurate but increases with dibasic lead phthalate. © 1996 John Wiley & Sons, Inc.

Surface modification of ethylene-vinyl alcohol (EVOH) copolymer films by the attachment of triethoxysilane functionality

Triethoxysilane groups were covalently attached onto the surface of ethylene-vinyl alcohol (EVOH) copolymer film via a urethane linkage through reaction between the hydroxyl groups in EVOH and 3-isocyanatopropyltriethoxysilane in the presence of dibutyltin dilaurate as catalyst. This reaction was confirmed by ATR-IR and XPS analysis. XPS results also indicated that this reaction was not surface sensitive and the modified layer was at least 40 A in depth. The modified film samples were further reacted with tetramethoxysilane (TMOS) for partial hydrolysis and condensation and XPS results showed a significant increase in the contents of oxygen and silicone on the surface which confirmed the above reaction.

Synthesis and characterization of new monomers containing UV-absorber function

Two new monomers, 2-hydroxy-4-benzophenonyl allyl carbamate and 2-hydroxy-4-benzophenonyl m-isopropenyl-α,α′-dimethyl-benzyl carbamate, were synthesized by the direct addition reaction of 2,4-dihydroxybenzophenone (DHBP) to allyl isocyanate (AI) or m-isopropenyl-α,α′-dimethylbenzyl isocyanate ( m-TMI) in the presence of dibutyltin dilaurate (DBTDL) catalyst at 80°C. The structure of these two monomers was characterized by FT-IR, 1H-NMR, UV-spectra, XPS, MS and elemental analysis. The properties of these two monomers are also described.

Damping materials based on simultaneously grafted interpenetrating polymer networks from castor oil

AbstractFour kinds of grafted interpenetrating polymer networks (IPNs) were synthesized from castor oil (CAS), toluene diisocyanate (TDI), monohydroxy terminated acrylic (or methacrylic) prepolymer and/or acrylic (or methacrylic) monomer in the presence of dibutyltin dilaurate and redox initiators. Formation rates of soluble and insoluble polymers were investigated in the course of synthesis of the grafted IPN from NCO‐terminated CAS precursor, butyl acrylate prepolymer, CAS and ethyl methacrylate monomer. Mechanical properties of the IPNs were studied as well. Studies of the dynamic mechanical properties of the various grafted IPNs showed that certain IPNs (from CAS/TDI/butyl methacrylate and butyl acrylate prepolymers, CAS/TDI/butyl acrylate monomer/ethyl methacrylate prepolymer, CAS/TDI/ethyl methacrylate monomer/butyl methacrylate prepolymer) exhibit high damping behavior over wide temperature ranges for tan δ ≥ 0.3 (ΔThd from 88°C up to 133°C) and maximum tan δ values higher than 1.1.

Synthesis and characterization of uv‐curable acrylated urethane prepolymers, I. Effects of reactive diluents and relative humidity on physical properties

AbstractA UV‐curable acrylated urethane prepolymer was synthesized from tolylene‐2,4‐diisocyanate (TDI), a polyether polyol (Arcol 1131) and endcapped with 2‐hydroxyethyl methacrylate (HEMA) by addition reaction in the presence of dibutyltin dilaurate as catalyst. UV curing was performed with either diethylene glycol diacrylate or thiodiethylene glycol diacrylate as reactive diluent.The effects of reactive diluent types, their concentrations and the humidity of environment on mechanical properties of cured films were investigated. Changes in the tensile strength, elongation and Young's modulus values of the cured films upon addition of reactive diluents with different concentrations were related to the effect of the diluent on the crosslinking density of cured films.The increase of relative humidity from 50 to 95% caused a decrease of tensile strength and Young's modulus values of cured films. It is proposed that the decrease of these physical properties in high relative humidity is due to the formation of hydrogen bonding in polymer chains caused by water molecules.

Transesterification reaction of poly(ethylene‐co‐vinyl acetate) with alcohols: A kinetic study in solution and in the bulk

AbstractThe chemical kinetics of the transesterification reaction of poly(ethylene‐co‐vinyl acetate) (EVA) with aliphatic alcohols were investigated, both in solution and in bulk, in the presence of dibutyl tin dilaurate (DBTDL) as the catalyst. A Fourier Transform infrared spectrometer (FTIR) was utilized for the measurement of the extent of the reaction. Experimental results showed that the reaction carried out in solution and in the bulk follows the same mechanism, namely, a reversible second order reaction of which the equilibrium only slightly increases with temperature. Additionally, the overall forward and reverse rate constants are proportional to the square root of the concentration of the catalyst. This study has also revealed that the intrinsic rate constants in solution and in the bulk are the same, regardless of the differences in the physical conditions encountered in the bulk and solution media, in particular, the reactant concentrations and viscosity of the reacting mixture. The effects of mechanical mixing are unimportant, since the reaction rate is relatively slow as compared with the rate of diffusion.

Synthesis and test of styrene?Cyclosiloxane and butadiene-cyclosiloxane block copolymers containing ultraviolet (UV) absorber and antioxidant groups

Block copolymers of polystyrene and poly(dimethylsiloxane) or of polybutadiene and poly(dimethylsiloxane) with nonhydrolyzably bound 2-hydroxybenzophenone and 2,6-di-tert-butylphenol residues were prepared by terminating the “living” block copolymers with glacial acetic acid to form siloxanol end groups, followed by condensation with diethoxysilyl derivatives of the stabilizers in the presence of dibutyltin dilaurate. The polymeric UV absorbers were proved to be nonextractable from polystyrene. At Xenotest aging (40°C) the polymeric UV absorbers were less effective than 2-hydroxy-4-octyloxybenzophenone. The polymeric antioxidants were superior to antioxidants of low molecular weight both in thermooxidative aging of vulcanized polybutadiene films at 70°C and in oxygen-uptake studies with stabilized polypropylene at 180°C over long periods.

Synthesis of PS-PEG and PMMA-PEG Branched Block Copolymers by Macroinimers

Abstract A new type of macroinimers were synthesized by the capping reaction of hydroxyl groups of polyazoesters with isocyanato ethyl, methacrylate in the presence of dibutyl tin dilaurate. Macroinimers having PEG-400 and PEG-1500 units were used in the polymerization of methyl methacrylate (MMA) or styrene (S) to obtain PS-PEG or PMMA-PEG branched block copolymers at 60°C. Longer polymerization times or higher macroinimer concentrations led to cross-linked block copolymers. Similarly neat homopolymerization of macroinimers also led to the cross-linked polyethyleneglycols. The products were characterized by IR and NMR spectroscopy, viscosity measurements and fractional precipitation.