Page 199 - Engineering Plastics Handbook

172 Engineering Plastics

TABLE 8.4 Comparative Properties for BPADA-MPD PEI:PCE Blends
Blend ratio ~ 85:15 PCE:PEI ~ 25:75 PCE:PEI
Melt flow rate, g/10 min, at 295°C (563°F) 6.0 2.8
Tg, °C (°F) PCE = 174 (345) PCE = 174 (345)
PEI = 215 (419) PEI = 215 (419)
HDT, 1.9 MPa (264 psi), °C (°F) 157 (315) 191 (376)
HDT, 0.5 MPa (66 psi), °C (°F) 169 (336) 205 (401)
Tensile strength Y, MPa (kpsi) 69 (10) 97 (14)
Flexural modulus, MPa (kpsi) 2537 (368) 3172 (460)
Flexural strength, MPa (kpsi) 107 (15.5) 145 (21.0)
Unnotched Izod, J/m (ft⋅lb/in) > 2083 (> 39) 2083 (39)
Notched Izod, J/m (ft⋅lb/in) 427 (8.0) 53 (1.0)
Specific gravity 1.21 1.26

on a microscale [39, 40]. When the polyamide is the continuous phase, the
PEI acts as a melt-processable reinforcement, improving heat capability
under load above nylon’s T . The PEI also provides better dimensional sta-
g
bility due to its reduced shrink, as well as lower water absorption com-
pared to the polyamide. As opposed to PEEK blends, the PEI-nylon blends
usually show rapid crystallization as injection-molded. The crystalline
polyamide phase provides high flow, higher ultimate heat resistance, and
excellent solvent resistance. Presence of polyamide in the blend is usu-
ally detrimental to PEI’s ignition resistance and thermal color stability.
PEI can also be combined with amorphous polyamides.
PEI blends have also been further modified with silicone polyether-
imide copolymer to improve impact strength, especially at lower temper-
atures. Use of a silicone polyetherimide as an impact modifier has the
added benefit of retaining or even improving flame retardance, as it has
a lower fuel value than traditional rubbery impact modifiers. The sili-
cone-PEI copolymer also has the stability needed to survive high PEI pro-
cessing temperatures without decomposition. These PEI-silicone copolymer
blends are hazy or opaque, phase-separated systems.
Lubricants such as fluoropolymers [e.g., polytetrafluoroethylene
(PTFE)], molybdenum disulfide, or graphite have also been blended
with PEI polymers to achieve enhanced tribological properties, partic-
ularly improved lubricity, and reduced friction and wear.
With all blends, changes in the ratio of the constituent polymers will
yield a range of resins. These blends can also be combined with fiber,
fillers, colorants, and other additives to produce a full family of prod-
ucts for differing applications. Some blends may contain several differ-
ent types of polymers.
Thermoplastic PEI resins are often colored with various pigments.
Titanium dioxide (TiO 2 ) and carbon black are both widely used. Care must