Blends and Additives - Fundamentals of Industrial Chemistry: Pharmaceuticals, Polymers, and Business - page 149

part performance and sometimes safety. Antistatic agents dissipate surface
charges which form during manufacture and use. Another advantage to the
use of antistatic agents is that dust particles are attracted to a lesser extent,
and the dust buildup on the plastic article is reduced. For some applications,
especially transparent articles which rely on optical properties, dust can be a
problem. Migrating antistats diffuse to the polymer surface over time, creat-
ing a thin layer that attracts water molecules. The water molecules provide a
conductive pathway that prevents build-up of static electricity and reduces the
polymer's surface resistivity [14]. There are many additives that function as
antistatic agents. Examples include glycerol monostearate, ethoxylated fatty
acid amines such as ethoxylated stearylamine, and diethanolamides such as
diethanol stearamide.

O

C 17 H 35

O

OH

OH

C 17 H 35

C 18 H 37 N

N

OH

O

OH OH

OH

Diethanol stearamide

Glycerol monostearate Ethoxylated stearylamine

For some applications, such as trays of conveyer belts for electronic
components, copiers and printers, or even artificial turf, more permanent
antistats are desired. One approach is the use of polymers such as polyether
amide copolymers or ethylene ionomers. Highly conductive graphite and
metal fibers such as nickel fiber are also used to lower the resistivity of
polymer articles [15]. For high performance materials that can tolerate the
added cost impact, carbon nanotubes can also be used.

9.5 PEROXIDES

Peroxides have many uses in polymer manufacture. They are used as ini-
tiators in radical polymerization processes such as the formation of PVC,
polystyrene, and low density polyethylene. They can also be added in a poly-
mer formulation for various reasons. Sometimes this is to crosslink an unsatu-
rated polymer such as unsaturated polyesters used in fiberglass formulations.
Other times it is to graft one polymer to another chemical or polymer by a rad-
ical reaction. The choice of the peroxide is dictated by considerations such as
storage stability, solubility, and decomposition to form radicals at a tempera-
ture near the desired reaction. Common peroxides include benzoyl peroxide,
di-t-butylperoxide, and dicumylperoxide (DICUP).