TABLE OF CONTENTS Polymer polyols are defined as very fine and stable dispersions of solid polymers (vinylic polymers and copolymers, polyurea, polyurethanes) in liquid polyethers. Currently polymer polyols represent one of the most important group of polyolic intermediates for elastic polyurethanes [1-10].
The experience of flexible foam manufacture using polyols containing inorganic fillers (BaSO 4, CaCO 3), leads to the observation that fillers act as nucleating agents during the foaming process and aid cell opening at the end of the rise process, and the hardness or load bearing properties of the resulting filled flexible PU foams are markedly improved. Generally the inorganic fillers substantially increase the flexible foam density.
As with the inorganic fillers, the organic polymers can be successfully used as fillers. The preferred method is the synthesis of polymeric filler in situ, by radical polymerisation, polycondensation or polyaddition processes, developed in liquid polyether media [1-10].
These kind of polyether polyols containing polymeric fillers are called polymer polyols and are produced on a large industrial scale, because they are one of the most important group of polyols used for high performance flexible polyurethane (PU) foams and PU elastomers [8-12].
Polymer polyols are divided, by the nature of the polymer finely dispersed in the polyether matrix, into the following categories [8-10]:
Graft polyether polyols (the dispersed polymer is a carbocatenary vinylic polymer or copolymer obtained by radical polymerisation),
Poly Harnststoff Dispersion (PHD polyols; dispersions of polyurea),
Polyisocyanate poly addition (PIPA) polyols (polyurethane dispersions), and
Other...
