Page 274 - Engineering Plastics Handbook

236 Engineering Plastics

At least 356°F (180°C) is required for predrying in order to keep less
than 100 ppm, which is needed to obtain appropriate molded parts. An
exposure to air even after drying can result in moisture absorption that
affects molded parts. Before molding, resin should be removed from
conditions of moisture.

Hopper dryer. It is necessary to seal the top of the hopper to avoid con-
tamination and humidity. A hot air circulation type of dryer with dehu-
midifier is recommended for high drying efficiency and lower running cost.

Molding condition
See Table 10.9.

Molding temperature. Resin melt temperature is required to be 752 to
788°F (400 to 420°C). Filler grades such as JCL3030 should be set at
788°F (420°C) while neat resin can be molded at 752 to 770°F (400 to
410°C).

Mold temperature. A temperature of 356°F (180°C) or preferably 392°F
(200°C) is recommended.

Injection machine. Part volume should be more than 20% of the maxi-
mum injection capacity of the injection machine.

Purging
PEI (Ultem) should be used as the purging material before and after
molding.

™
SuperAurum
In the early 2000s, another new thermoplastic polyimide entered the
™
market, called SuperAurum, an in-mold crystallizable polyimide, which
has an excellent HDT of 752°F (400°C) with carbon fiber filler. The
enhancing crystallization speed enables a crystalline state even during

TABLE 10.9 Typical Molding Conditions

Cylinder temperature, °F
Grade Hopper side Center, nozzle Mold temperature, °F
Natural 752 752 338–356
GF, CF filled 752 788 374–410