Page 201 - Engineering Plastics Handbook

174 Engineering Plastics

potential variables involved with hydrolysis, part testing at end-use con-
ditions is the best method to evaluate a resin’s fitness for use in a given
part design and specific application.
PEI resins are made from high-purity intermediates and have very low
ion content. With proper handling and isolation, total extractable inor-
ganic ions are below 100 ppb. Sulfate and chloride ion content can be below
20 ppb. This high purity is useful for preparation of film and handling
equipment to make semiconductor wafers and chips for microprocessors,
as well as burn-in test sockets.

Uses of Polyetherimide Resins
There are two different types of performance needs that must be con-
sidered when one is discussing melt-processable polyetherimides. These
two types of performance needs are those of the molders or extruders
who fabricate the articles and those of the design engineers and the users
of the articles made from the PEI resins.
The molders or extruders are most interested in the melt processing
of the resin. Some of their concerns include
■ Viscosity
■ Molecular weight changes in the melt
■ Part appearance
■ Time needed to make the parts
■ Yield of good parts
■ Ability to recycle resins

The other families of users who need to be accommodated when one
is developing a polymer (or blend) are the design engineers and end
users, the people interested in the performance of the molded part or
devices made from it. Their concerns can include the following.
■ Is it stiff enough for the application?
■ Will it hold up to temperature without deforming?
■ How will it hold up to environmental factors such as water, light,
heat, and solvent exposure?
The answers to these types of questions are often complex, being
influenced by part design, molding, polymer type, and exact end-use
conditions.
The concerns of both groups of users have to be accommodated in the
molecular structure of the polyetherimides or their blends.