The curing of phenol‐formaldehyde resins III

Abstract

A kinetic investigation has been made of the curing process of phenol-formaldehyde resins by the method of adiabatic heat measurements. The applicability of rate equations related to adiabatic reactions for the given process has been examined. It was found that the curing of phenol-formaldehyde resins in closed system cannot be considered as an unidirectional reaction. In circumstances analogous to practical application the curing of resins takes place parallel to the evaporation of water. Adding a further term to the rate-equation of the strictly adiabatic reaction taking into account the evaporation, this process also can be described with an accuracy meeting the requirements of the practice. ZUSAMMENFASSUNG:Die Aushiirtung von Phenol-Formaldehyd-Harzen wurde durch adiabatische Messung der Reaktionswiirme untersucht. Dazu wurde die Verwendbarkeit von Geschwlndigkeitsgleichungen, die fur adiabatisch verlaufende Reaktionen abgeleitet wurden, gepriift. Die Phenolharzhartung kann in geschlossenen Systemen nicht als in nur eine Richtung verlaufende Reaktion angesehen werden. Unter den Bedingungen der Praxis verlauft die Hirtung parallel zur Verdampfung von Wasser. Deshalb muB in die genannte Geschwindigkeitsgleichung ein weiteres Glied aufgenommen werden, das die Verdampfung berucksichtigt ; dann kann der ProzeB mit hinreichender.Genauigkeit beschrieben werden.In the course of studying the curing of phenol-formaldehyde resins, in our previous experiments 1 . we tried to follow the process by viscosimetric, dilatometric and calorimetric methods. In our present paper we describe the method ofadiabatic reaction heat measurements. In a previous publication we derived equations expressing adiabatic reactions of different order, presented the function of an adiabatic calorimeter constructed by us, and described the application of the method in the case of polyurethane resins. The choice fell on polyurethane as the first model as the measurement of polyaddition

A mixing model for multicomponent reactions in twin screw extruders applied to the polymerization of urethanes

“…32, NO. 7 geometrical constants A , B , and K , the screw speed N , the amount of leakage flow and therewith the actual throughput of the extruder.…”

“…Few studies have been made of the reaction kinetics of the polyurethane synthesis in bulk (7)(8)(9)(10)(11)(12). These studies have been investigating both the catalyzed and uncatalyzed polymerization of the urethanes.…”

“…The mixing deJciency as a function of the reciprocal die resistance of the experimental extruder.POLYMER ENGINEERING AND SCIENCE, MID-APRIL 1992, VOl. 32, NO 7. The mixing deficiency as a function of the screw speed of the experimental extruder.…”