Effects of cellulosic fibers on the polymerization of a polyurethane

• Published in: Polymer engineering and science 1988-10, Vol.28 (20), p.1334-1341
• Main Authors: De J. Aguilar-Vega, M., Cruz-Ramos, C. A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Forms of application and semi-finished materials; Polymer industry, paints, wood; Reinforced plastics; Technology of polymers
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.760282008

The effects that the inclusion of low concentrations (0 to 0.6 percent by Volume) of cellulosic fibers have on the polymerization of a polyurethane was tested by monitoring the viscosity of a reacting diol‐diisocyanate system under isothermal conditions. An increase in viscosity due to the presence of the cellulosic fibers is observed, in addition to the expected rise related to polymer formation. However, a slackening effect appears as more cellulosic fibers are added to the polymerizing medium, in contrast to a system with comparable concentrations of glass fibers. On the basis of reaction kinetics arguments, it is suggested that the hollow nature of the cellulosic fibers and their sorbency play important roles in the effect observed, by reducing the effective concentrations of one of the monomers in the reacting phase, thereby diminishing the overall reaction rate. If similar portions of both monomers are extracted from the bulk of the reacting mass, the reaction is not affected as markedly as when only part of one of the monomers is ed. The results found illustrate the type of constraints that arise when certain types of polymerizations are carried out in situ to obtain cellulosic fiber composites.