Kinetics of fast (RIM) urethane polymerization

Richter, E.; Macosko, Chris

doi:10.1002/pen.760181308

Cited by 107 publications

(56 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…36 A similar mechanism that deals with an equilibrium involving active ion intermediates was proposed by Richter and Macosko for the poly(-caprolactone)/MDI/DBTDL system. 37 In view of the results for acrylic OH/NCO/DBTDL reaction system examined in this study, reaction rate is proportional to the NCO concentration and the square root of DBTDL concentration, which agrees with the literature data. 36 However, in contrast to the literature, 36 the reaction rate is not proportional to the OH concentration but to its square root.…”

supporting

confidence: 78%

Kinetics and mechanisms of catalyzed and noncatalyzed reactions of OH and NCO in acrylic polyol–1,6‐hexamethylene diisocyanate (HDI) polyurethanes. VI

Han

Urban

2002

J of Applied Polymer Sci

View full text Add to dashboard Cite

Fourier transform infrared spectroscopy was used to study the kinetics of noncatalyzed and catalyzed polyurethanes. These studies show that for noncatalyzed acrylic polyol-hexamethylene diisocyanate (HDI) trimer reactions, the reactions between OH and NCO of HDI exhibit second-order kinetics, with first-order kinetics with respect to NCO and OH. On the other hand, when dibutyltin dilaurate (DBTDL) is used as a catalyst in acrylic polyol-HDI trimer reactions, the reaction rate is first order with respect to NCO and 0.5 order in OH and DBTDL concentrations. A mechanism for the catalyzed acrylic polyol-HDI trimer crosslinking reactions is proposed and it appears that an equilibrium involving associations between OH and DBTDL exists, resulting in the formation of an active anion, which interacts with NCO to generate polyurethanes. To further verify this mechanism, the influence of acidity on the reaction rate constant was investigated. When the acidity of the system is increased, retardation of urethane formation occurs.

show abstract

supporting

confidence: 78%

Kinetics and mechanisms of catalyzed and noncatalyzed reactions of OH and NCO in acrylic polyol–1,6‐hexamethylene diisocyanate (HDI) polyurethanes. VI

Han

Urban

2002

J of Applied Polymer Sci

View full text Add to dashboard Cite

show abstract

“…Equation ( 1 ) by taking both equations and equalizing the conversions; in other words, a1 = a,, so ( 4 ) In this way the activation energy can be evaluated, although neither the reaction order nor the Arrhenius prefactor can be determined.…”

Section: Theorymentioning

confidence: 99%

Determination of the kinetic parameters for the polymerization of a polyurethane using an improved method of differential scanning calorimetry

Hernández-Sánchez

Vera‐Graziano²

1992

J of Applied Polymer Sci

View full text Add to dashboard Cite

The kinetic parameters for the polymerization reactions of two polyurethane systems were determined by using an improved method of differential scanning calorymetry (DSC ) . The calculated activation energy, reaction order, and Arrhenius prefactor show good correlation with the experimental results. The method used here shows several improvements as respects to other DSC methods: the three kinetic parameters can be calculated directly; it is more accurate than other DSC methods; and it requires only one heating rate, during the calorimetric experiments, to determine the activation energy.

show abstract

“…9 A comparison between the adiabatic temperature rise method and the chemical technique for determining the kinetics is shown in Figure 3 …”

Section: Kineticsmentioning

confidence: 99%

Kinetic and Viscosity Relations for Thermosetting Polyurethanes

Reboredo

Rojas

Williams

1983

Polym J

View full text Add to dashboard Cite

ABSTRACT:Kinetic and viscosity relations for polyurethane network polymerization were analyzed. A rigid foam formulation consisting of a polymeric isocyanate (functionality ca. 2.7) and a polyether polyol (functionality ca. 4.5), was selected. The kinetics were studied with adiabatic temperature rise and chemical techniques. An overall second-order reaction and an activation energy, E= 5!.2 kJ mol-1 , were obtained. The viscosity rise was correlated with the reaction extent and the weight average molecular weight.· The dependence of viscosity on the latter was of mth order, with m greater than 3.4. This high parametric sensitivity is associated with the formation of branched structures from the beginning of the reaction.KEY WORDS Thermosetting Polyurethanes I Polyurethane Kinetics I Polyurethane Viscosity I Kinetic-Viscosity Relations I Polyurethane Foams IThe processing of thermosetting materials requires a kinetic-viscosity characterization of the system. This is particularly relevant to the analysis of flow through ducts and the filling of molds. 1 • 2 The viscosity (I]) of the polymerizing mixture is best characterized by the weight-average molecular weight (Mw), since both IJ and Mw become infinite at the gel point. 3 On the other hand, an empirical expression relating the viscosity to the extent of reaction (x) and also accounting for the fact that IJ becomes infinite at the gel point (xg) is adequate for design purposes. 4 Several studies on rheological changes during polymerization for polyurethanes have been reported in literature. 4 -7 All of them deal with reaction injection molding (RIM) formulations. The purpose of this paper is to present and discuss the results for rigid foam formulations. There is a significant difference between both kinds of formulations which is the average functionality of reactants. Rigid foams are usually made with reactants (one or both) of high functionality to attain a sufficient rigidity at a relatively low reaction extent. That is to say, the gel conversion for foam-* To whom all correspondence should be addressed.ing is lower than for reaction mJection molding. This may have a bearing on the rheological behavior. On the other hand, a kinetic-viscosity characterization of a rigid foam formulation might be useful for a detailed analysis of the foaming process. EXPERIMENTALA typical formulation for rigid foams was selected. The polymeric isocyanate was a polymethylenepolyphenyl isocyanate (PAPI 135, Upjohn), with an average functionality f..= 2. 7 as reported by the supplier. The NCO content was determined by dissolving a sample in a solution of dibutylamine in toluene and back titrating with HCl in the presence of bromocresol green (ASTM-D-1638-70). The resulting equivalent weight was 154.7 gjeq. It was reacted with a polyether polyol based on sorbitol (NIAX LS 490, Union Carbide) with an OH value of 490mg KOH g-1 polyol. The polyol was dehydrated under vacuum for 4 hours at 65°C. A number-average molecular weight of 521 was determined by cryoscopy in dioxane. The res...

show abstract

Kinetics of fast (RIM) urethane polymerization

Cited by 107 publications

References 7 publications

Kinetics and mechanisms of catalyzed and noncatalyzed reactions of OH and NCO in acrylic polyol–1,6‐hexamethylene diisocyanate (HDI) polyurethanes. VI

Kinetics and mechanisms of catalyzed and noncatalyzed reactions of OH and NCO in acrylic polyol–1,6‐hexamethylene diisocyanate (HDI) polyurethanes. VI

Determination of the kinetic parameters for the polymerization of a polyurethane using an improved method of differential scanning calorimetry

Kinetic and Viscosity Relations for Thermosetting Polyurethanes

Contact Info

Product

Resources

About