Chemistry of a Silicone Surfactant in Flexible Slabstock Foam Production

4 Chemistry of a Silicone Surfactant in Flexible Slabstock Foam Production 

As outlined previously the main reason for the interest in optimised surfactants for the liquid carbon dioxide processes lies in their role as nucleation promoters. 

The silicone surfactants can be viewed as PDMS-polyether-copolymers which are mainly based on a combination of just three structural units the methyl substituted siloxane backbone as well as a sophisticated ratio and arrangement of ethylene oxide and/or propylene oxide forming the attached polyethers and, in some cases, additional modifications. 

The Si-O-C products resulting from the reaction of chlorosiloxanes and hydroxyl groups of polyethers provide an extremely good processing and superior consistency combined with being hydrolytically stable under the water-amine conditions found in polyurethane foaming. The Si-C products offer a more beneficial access to high activity and lead to an easier production of flame retardant foams. These products are derived from the addition of an Si-H functionality at the siloxanes to a double bond, a process called hydrosilylation. 

Examples of how this variety of structural parameters affects the development of silicone surfactants especially for liquid carbon dioxide blown foams, are many [39,40,41, 42] and this latest drive in surfactant development provides good examples of the important performance issues and how they can be addressed. 

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