Accessible Requires Authentication Published by De Gruyter June 22, 2020

Microcellular Thermosetting Polyurethane Foams

C. Brondi, M. R. Di Caprio, E. Di Maio, T. Mosciatti, S. Cavalca, V. Parenti and S. Iannace

Abstract

Thermosetting polyurethane foams are nowadays produced with typical bubble size, d > 150 μm, with plenty of room for improvement towards the cellular structure refinement, to gain, among others, in the thermal insulation performances. We herein report a first example of a microcellular thermosetting polyurethane foam, i. e. with bubble size below 5 μm, produced via the gas foaming technology. In particular, high-pressure CO2, N2 and their mixtures were utilized as blowing agents: solubilized separately into the polymer precursors, they were brought into a supersaturated state by a pressure reduction to induce the bubble nucleation and growth. To achieve microcellular foams, we made use of a novel two-stage pressure reduction program, concurrent to the polymer curing. The first stage is a pressure quench O (10–2 s) from the saturation pressure to an intermediate pressure to induce the nucleation of a large amount of dense bubbles. The second stage is a slow O (102 s) further pressure decrease to ambient pressure, allowing for a slow bubble growth, designed to reach ambient pressure exactly when the curing reached completion.


*Correspondence address, Mail address: Ernesto Di Maio, Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, University of Naples Federico II, P.le Tecchio 80, 80125 Naples, Italy, E-mail:

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Received: 2020-01-21
Accepted: 2020-02-12
Published Online: 2020-06-22
Published in Print: 2020-07-03

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