Room-Temperature-Foaming Silicone Rubbers

Room-Temperature-Foaming Silicone Rubbers Liquid silicone rubber prepolymers that foam and cure at room temperature are available. These products are foamed by the liberation of hydrogen from the reaction  

Zimmerman, R.L. and BaUey, H.R., Chapter 4, Sponge Rubber and Latex Foam, in Plastic Foams, Part 1, eds. Frisch, K.C. and Saunders, J.H., Marcel Dekker, New York (1972). 

ASTM D 1056-85, Standard Specification for Flexible Cellular Materials—Sponge or Expanded Rubber, in Vol. 09. 02, Annual Book of ASTM Standards. 

Morford, R.H., The Flammability of Neoprene Cushioning Foam, Journal of Fire and Flammability, 8 279-298 (July 1977). 

---

While unaffected by water, styrofoam is dissolved by many organic solvents and is unsuitable for high-temperature applications because its heat-distortion temperature is around 77°C. Molded styrofoam objects are produced commercially from expandable polystyrene beads, but this process does not appear attractive for laboratory applications because polyurethane foams are much easier to foam in place. However, extruded polystyrene foam is available in slabs and boards which may be sawed, carved, or sanded into desired shapes and may be cemented. It is generally undesirable to join expanded polystyrene parts with cements that contain solvents which will dissolve the plastic and thus cause collapse of the cellular structure. This excludes from use a large number of cements which contain volatile aromatic hydrocarbons, ketones, or esters. Some suitable cements are room-temperature-vulcanizing silicone rubber (see below) and solvent-free epoxy cements. When a strong bond is not necessary, polyvinyl-acetate emulsion (Elmer s Glue-All) will work. 

Silicones are well known for their versatility, which makes them ideally suitable for a variety of applications. The fluids can be used as solvents, as foam-control systems, or as release agents (20% of the total volume). High-molecular-weight silicones are mainly used in rubber applications such as High Temperature Vulcanisable (HTV) and Room Temperature Vulcanisable (RTV) (43%), resins (4%), or specialties (15%). Other applications for silicones are masonry protection (8%), textiles (7%), and paper coatings (3%). Silicones can be uniquely tailored for each application area by substitution by reactive groups, allowing them to be cured by different mechanisms. 

---