Page 544 - Carrahers_Polymer_Chemistry,_Eighth_Edition

15 Additives

Most polymeric materials are not wholly a single polymer, but they contain chemicals added to
them to modify some physical, biological, and/or chemical behavior. These added chemicals, or
additives, are generally added to modify properties, assist in processing, and introduce new prop-
erties to a material. Coloring agents, colorants, are added giving a product or component with a
particular color often for identifi cation or ecstatic purposes. Antibacterial agents are added to pro-
tect the material from certain microbial attack. Composites contain a fiber and continuous polymer

phase, resulting in a material that has a greater fl exibility and strength than either of the two com-
ponents. 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 fi ller, 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 essen-
tial materials that allow the polymeric 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 and others are added to simply give bulk and thus are inexpensive. While the identity,
amount, and action of many additives were developed on less than a scientific basis, today adequate

scientific knowledge is known so that there exists a rational for the use of essentially all additives.
Typical additives include the following:
Antiblocking agents Lubricants
Antifoaming agents Mold release agents
Antifogging agents Odorants or fragrances
Antimicrobial agents Plasticizers
Antioxidants Preservatives
Antistatic agents Reinforcements
Blowing agents Slip agents
Coloring agents Stabilizers, including
Coupling agents Radiation (UV, VIS)
Curing agents Heat
Fillers Viscosity modifi ers
Flame retardants Flow enhancers
Foaming agent Thickening agents
Impact modifi ers Antisag agents
Low-profi le materials

In this chapter, we will look at a variety of additives.

15.1 PLASTICIZERS

Flexibilizing of polymers can be achieved through internal and external plasticization. Internal
plasticization can be produced through copolymerization giving a more flexible polymer backbone

or by grafting another polymer onto a given polymer backbone. Thus, poly(vinylchloride-covinyl
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