Читать книгу Green Nanomaterials - Siddharth Patwardhan - Страница 34

Silica is another widely used nanomaterial in applications such as toothpastes, tyres and cosmetics. One of the key properties in its success is its inertness under most conditions of use. Silica is resistant under acidic conditions and most organic reagents—it can only be degraded by strong caustic solutions (pH > 10) or hydrofluoric acid. As silica can withstand high temperatures similar to glass, it provides excellent improvement in thermal properties when blended with polymers. This, coupled with its added mechanical strength, means silica is an ideal component in tyre and composite applications. Further, silica (in most forms) has been ‘generally regarded as safe (GRAS)’ by regulating bodies in the USA and Europe, and hence is widely used in food and cosmetics. In those applications, silica improves the rheological (flow) properties of food and cosmetic products. Finally, its specific porous structure and the ability to absorb water/moisture makes it highly useful in desiccant applications where even a small amount of moisture needs to be avoided (e.g. electronics packaging and table salt).