Page 314 - Engineering Plastics Handbook

274 Engineering Plastics

Other PAI producers
The majority of isocyanate-produced polyamide-imide solutions are con-
sumed within the wire enamel marketplace, where Altana AG and
Hitachi are known. Other producers with polyamide-imide solution
®
products include Bayer Material Science with Resistherm , while
®
Huntsman has Rhodeftal .
Due to the specialty nature and niche applications for polyamide-
imide parts, many of these low-volume pieces are machined from
preformed stock shapes. Toray, based in Japan, is producer of polyamide-
imide resin that it converts to polyamide-imide parts and stock shapes,
largely for the Asian markets. In the United States, Quadrant EPP sup-
plies extruded Torlon polyamide-imide rod and plate stock as well as
compression-molded ingots and shapes. Drake Plastics extrudes custom
profiles in addition to standard shapes from Torlon resins. Injection-
molded Torlon polyamide-imide stock shapes are available through
Parkway Products.

Physical Properties
As seen from the application examples, polyamide-imides possess a
unique blend of high-performance properties. An overview of polyamide-
imide properties for compounded materials is shown in Table 12.1.

Mechanical properties
Polyamide-imides posses excellent mechanical properties over a broad
temperature range that are virtually unmatched. The polymer chemistry
responsible for this performance is the fully aromatic backbone, which
offers stiffness, high-temperature capability, and thermal and oxida-
tive resistance. Further stiffening the polymer backbone is the imide
linkage driving the glass transition temperature to 280°C in its cured
state. The amide and ether linkages provide processability, ductility, and
toughness.
The room temperature tensile strength of an unfilled polyamide-imide
is greater than 25,000 psi. Mechanical properties of polyamide-imides are
higher than those of other related high-performance polymer compounds,
especially at elevated temperatures (Figs. 12.17 and 12.18). Their mechan-
ical properties at 204°C are greater than those of other engineering poly-
mers at room temperature. Because of this, glass- or carbon-fiber reinforced
polyamide-imides are utilized in critical metal replacement parts and
demanding applications. At low strain levels, polyamide-imides behave as
hookean solids with a very high modulus. At high strain levels, polyamide-
imides do not yield, but instead rupture or break.