BPADA-MPD polyetherimide

BPADA is reacted with a more or less equimolar amount of a diamine, for instance, m-phenylene diamine (MPD), to make the polyamide acid. Water is removed by heating to form the polyetherimide (PEI). In this case, after removal of water and solvent, the added flexibility of the polyimide allows the molten resin to be extruded into strands. Strands of the BPADA-MPD polyetherimide [Eq. (8.5)] are cooled and chopped into pellets, which can subsequently be remelted to form parts or film. PEI powder can be made by grinding pellets or through precipitation methods. Special processes have been developed to make small-particle (15- 0,m) PEI powders. 

Figure 7.5 Chemical structure of BPADA-MPD polyetherimide (Ultem 1000 series).

Polyetherimides are amorphous polymers with excellent dimensional stabihty. They are transparent with useful optical properties [12], but aU thermoplastic polyetherimides are a yellow amber color (as are almost aU polyimides). The yellowness index (YI) of a 3.2-mm (0.130-in) BPADA-MPD PEI injection-molded part is usually > 50. 

Combinations of the thermoplastic polyetherimides with 10 to 40 wt% fiberglass reinforcement are very effective for increasing strength and modulus, as shown in Table 8.3. Heat resistance is shghtly increased too. The increase in stiffness is shown in Fig. 8.3, which compares modulus versus temperature for an unfilled BPADA-MPD-based PEI resin and blends with 10 and 30% short-chopped fiberglass. 

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