Silsesquioxane (POSS)

Polyhedral oligomericsilsesquioxanes (POSS) are a kind of inorganic–organic hybrid materials which nanostructures have become attractive because of their environmental neutrality, good heat resistance as well as excellent thermoxidative stability. Many attentions were directed to the use of POSS, as a great potential for producing materials characterized by improved fire retardance along with superior physical properties. POSS exert astonishing effects on some fire properties of polymers, because they can act as stand-alone fire retardants or as synergistic fire retardant in important regulatory fire tests.

Silsesquioxane are Cage Structure- like hybrid molecules of silicon and oxygen with similarities to both silica and silicone. When mixed with virtually any ordinary polymer, they bond to the organic molecules and to one another, forming large chains that weave through the polymer. The result is a nanostructured organic-inorganic hybrid polymer.

The POSS chains act like nanoscale reinforcing fibers, producing extraordinary gains in heat resistance. POSS molecules can be thought of as the smallest particles of silica.Unlike silica or modified clays, each POSS molecule contains covalently bonded reactive functionalities suitable for polymerization or grafting POSS monomers to polymers chains. Each POSS molecule contains nonreactive organic functionalities for solubility and compatibility of the POSS segments with various polymer systems.

Enhancements in the physical properties of polymers incorporating POSS segments results from POSS’S ability to control the motions of the chains while still maintaining the processability and mechanical properties of the base resin.

POSS incorporation increases modulus and hardness while maintaining stress & strain characterstics of the base resin. Compared to common fire retared plastics, polymers containing POSS show delayed combustion and major reductions in heat evolution.