Abstract
The requirements for structural foams for aerospace applications include high mechanical strength properties and service temperatures as high as 150°C, moisture resistance and foam isotropy. A comparison was made of isocyanatebased foams incorporating isocyanurate, urea and oxazolidone moieties in various combinations with or without the presence of urethane groups. Major emphasis was placed on the cell geometry with regard to the distribution of the polymer matrix between the cell windows (faces) and cell struts (edges). For that reason, a basic study was undertaken with polyoxazolidones to determine parameters for foaming, gel time-temperature dependence and viscosity relationships, as well as dynamic viscoelastic properties. Foaming techniques included conventional water-blown foams, as well as foaming using chemical blowing agents.
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