ABSTRACT
Most polymeric materials are not a single polymer, but they contain chemicals that modify
some physical and=or chemical behavior. These additives are generally added to modify properties, assist in processing, and introduce new properties to a material. Coloring
agents, colorants, are added giving a product or component with a particular color often
for identification or ecstatic purposes. Antibacterial agents are added to protect the
material from certain microbial attack. Composites contain a fiber and continuous polymer
phase resulting in a material that has a greater flexibility and strength than either of
the two components. Some of these additives are polymeric while others are not. They
may be added as gases, liquids, or solids. Often, some combination of additives is present.
A typical tire tread recipe has a processing aid, activator, antioxidant, reinforcing filler,
finishing aid, retarder, vulcanizing agent, and accelerator as additives (Table 15.1). A typical
water-based paint has titanium dioxide as the white pigment, China clay as an extender, a
fungicide, a defoaming agent, a coalescing liquid, a surfactant-dispersing agent, and calcium
carbonate as another extender. In total, additives are essential materials that allow the poly-
meric portion(s) to perform as needed. Some of these additives are present in minute amounts
and others are major amounts of the overall composition. Some additives are expensive,
whereas others that are added simply to give bulk are inexpensive. While the identity,
amount, and action of many additives were not totally developed on a scientific basis,
adequate scientific knowledge is available so that there exists a rational for the use of
essentially all additives.
