H. Kothandaraman

The Thermal Dissociation of Phenol-Blocked Toluene Diisocyanate Crosslinkers

Abstract The thermal dissociation reaction of different phenol-blocked toluene diisocyanate crosslinkers has been studied by the use of differential scanning calorimetry. It was found that dissociation occurs after melting of the adduct. The dissociation reaction rate constants, activation energies, and the heat of reaction values are reported. Adducts with orthosubstituted phenols dissociate at a faster rate than those with para isomers. The regeneration of isocyanate functionality was identified by an infrared spectrophotometer.

Catalysis of Blocked Isocyanate-Hydroxyl-Terminated Polybutadiene Cure Reaction

The catalytic activity of three tertiary amines and three organotin compounds in the cure reaction of blocked isocyanate with hydroxyl-terminated polybutadiene was investigated. It was found that the steric factor determines the catalytic activity of the compound. The tin compounds showed higher catalytic activities than the amine compounds. The deblocking catalytic activity of the amine and tin compounds was confirmed by the identification of isocyanate functionality using infrared spectroscopy. The synergistic effect of amine and tin mixed catalysts systems in the deblocking reaction was reported for the first time.

Synthesis and Properties of Phenol-Blocked Toluene Diisocyanate Crosslinkers

Abstract Phenol, 2,4-di-t-butylphenol, and 3-methyl-4-nitrophenol blocked TDI adducts were prepared and characterized by elemental analysis and IR and 1H-NMR spectra. The dissociation temperatures were determined by the carbon dioxide evolution method and extrapolation of TG curves. It was found that the adducts based on 2,4-di-t-butylphenol and 3-methyl-4-nitrophenol dissociate at a lower temperature than the adduct based on phenol. It was also found that the 3-methyl-4-nitrophenol-blocked TDI adduct shows a low curing time compared to other adducts. The kinetic parameters are reported. The dissolution temperatures of the blocked TDI adducts were determined in four different polyols having different molecular weights.

The Kinetics of the Polymerization Reaction of Toluene Diisocyanate with Polyether Polyols

Abstract The uncatalyzed and catalyzed polymerization of polypropylene glycols (MW 400-2000) with toluene diisocyanate has been studied in toluene solution at three different temperatures. Discontinuity was observed in the second-order plots of uncatalyzed reactions in contrast to the catalyzed reactions which showed straight-line plots. The rate constants (k1, k 2) and the activation parameters (Ea 1 Ea2, δS# 1, δS# 2) for the isocyanate groups in the 4- and 2-positions were calculated. In the uncatalyzed and diethylcyclohexylamine-catalyzed reactions, the rate constants were found to decrease with increasing molecular weight of the polyols, whereas in the dibutyltin-dilaurate-catalyzed reactions the rate constants and the activation parameters were found to be independent of the molecular weight of the polyols.

Preparation and characterization of poly(ethylene/tetramethylene terephthalate) copolyesters

Abstract Random copolyesters were prepared from dimethyl terephthalate (DMT), ethylene glycol (EG) and butane 1,4-diol (BD) by melt-polycondensation techniques, using varying amounts of EG and BD. Compositions have been established by 1H n.m.r. spectroscopy. Intrinsic viscosity and number average molecular weight ( M n ) were measured. Thermal properties have been studied by differential thermal analysis. Melting and crystallization temperatures and thermodynamic parameters are discussed in terms of structural differences, particularly the effect of composition and chain flexibility. The degree of crystallinity from differential thermal analysis, i.r. and wide angle X-ray scattering (WAXS) are discussed.

A comparative study of the kinetic and thermodynamic approaches to the glass transition phenomenon in high polymers

Abstract The effect of thermal history on the glass transition temperature Tg of polystyrene, polyvinylchloride and polyethyleneterephthalate was studied using differential scanning calorimetry (DSC). Parameters such as the hole energy Eh, the activation energy Ej for the disappearance of holes, the activation enthalpies Δh1∗ and Δh2∗ for structural relaxation and the activation energy E for the glass transition process were calculated. The increase in Eh value with increasing Tg showed that there exists a distribution of hole sizes. The Ej value calculated according to Wunderlichs treatment, the Δh1∗ parameter obtained using Moynihans procedure and the E value derived from Barton and Critchleys method agreed with one another for polystyrene and polyvinylchloride. The Δh2∗ quantity obtained using Moynihans formula increased as the rate of heating was increased, a result similar to the variation in Eh value with heating rate. The validity of the ΔCp-Tg criteria proposed by Wunderlich and by Simha and Boyer were also investigated for the three polymers concerned. The variations in kinetic parameters such as ΔHa, the cohesive energy density (CED) and the thermodynamic quantity Δμ (Adam-Gibbs) were also calculated and their variation is discussed in the light of structure-property relationships.

Metal-containing polyurethanes

SummaryMetal-containing polyurethanes were prepared from cobalt and copper mono(hydroxyethyl) phthalate with hexamethylene diisocyanate and tolylenediisocyanate and characterized. The presence of ionic links in the polymers was shown by IR spectra, solution viscosity and conductance measurements.

Kinetics of polymerization of 1-octene with the catalyst systems VO(acac)2-AlEt3 (or AlEt2Br)

Abstract The kinetics of 1-octene polymerization by the catalyst systems VO(acac) 2 -AlEt 3 (I) and VO(acac) 2 -AlEt 2 Br (II) was investigated. A linear dependence of the rate of polymerization on the monomer and catalyst concentrations as well as the overall activation energy of 44.5 kJ/mol for both the catalyst systems was found. The dependence of the rate of polymerization on aluminium alkyl concentration is explained by Langmuir-Hinshelwood adsorption of the monomer and the aluminium alkyl. Characterization of the structure of the polymer by 13 C-NMR spectra revealed the isotactic content. The mechanism of polymerization is discussed in relation to the kinetic data obtained.

Electron Impact Mass Spectra of Phenol Blocked Isocyanates

The electron impact mass spectra of a series of substituted phenol blocked toluene diisocyanate crosslinkers were analyzed and a suitable dissociative pathway proposed.

Synthesis and characterization of polyestermaleamides

SummaryPolyestermaleamides have been synthesized from N,N′-bisisomaleimide, p-aminophenol, iso-and tere-phthaloyl chlorides. Through ring-opening addition reaction, a bisphenolamide was first formed; it was then polycondensed with acid chlorides to produce Polyestermaleamides, with an ordered sequence. The polymers were fully characterized by elemental analysis, infrared and electronic spectra, solubility in various solvents as well as inherent viscosity measurements. Thermal behaviour of the polymers were determined by thermogravimetric analysis in nitrogen atmosphere.