Page 324 - Engineering Plastics Handbook

282 Engineering Plastics

TABLE 12.4 Aqueous Formulation
of Torlon AI-30
AI-30 20 g
Dimethylaminoethanol 4 g
Water 76 g

reference guide is indicated in Table 12.5. It is critical to use modern
injection-molding presses, which are the correct size. Torlon polyamide-
imide compounds are still reactive, as evidenced by the need for an
additional cure cycle. If the resin has excessive residence time in the hot
equipment, the viscosity can increase, leading to flow problems, mold-
ing defects, and black specks. The shot size should conform to a mini-
mum of 50% of the barrel size, but not to exceed 80%. The clamp tonnage
2 2
should be a minimum of 6 tons/in of the part area, while 12 tons/in is
recommended to improve dimensions at the part line.
As with any injection-molded polymer, mold design is critical to match-
ing the characteristics of the polymer with desired part specifications.
Due to the flow characteristics of polyamide-imides, the mold gates and
vents need to be placed strategically, along with emphasis on smooth
ejection. Steel selection is based on the length of the run, and mold plat-
ing is not necessary and is discouraged.

TABLE 12.5 Torlon Setup

Torlon injection-molding setup table
Machine Modern injection-molding press with microprocessor
closed-loop controls
Shot size 50–80% of barrel capacity
2
Clamp tonnage Minimum 6, recommend 12 tons/in of projected part area
Screw design 1:1 to 1.5:1 compression, L/D of 18:1 to 24:1, smooth
constant taper, no check ring
Tool design Steel
Cavity Prototype P-20 prehardened or S-7 (28–32 Rc)
Production H-13 air-hardened (50–52 Rc)
1
Ejection Smooth positive linear ejection with generous draft ( /2° to 1°)
and polishing
Undercuts These should be avoided due to brittle nature of polymer out
of the mold. Movable in-mold features may be incorporated
Shrinkage rates (molding and curing total)
Grade Percent
4203L 0.60–0.85
4275 0.25–0.45
4301 0.35–0.60
4435 0.06–0.18
5030 0.1–0.15
7130 0.00–0.15