Page 180 - Handbook of Plastics Technologies

THERMOSETS

3.50 CHAPTER 3

TABLE 3.47 Vespel Polyimide Moldings
Specific gravity 1.55
o
Flexural modulus, 23 C, kpsi 550
o
260 C 305
o
Flexural strength, 23 C, kpsi 15
o
260 C 8.3
o
Tensile strength, 23 C, kpsi 8.8
o
260 C 4.6
o
Elongation, %, 23 C 6
o
260 C 4
Compressive modulus, kpsi 386
Notched impact strength, fpi 1.1
o
Heat deflection temperature, C 360
Oxygen index, % 51
Volume Resistivity, Ω-cm 10 14
Dielectric constant 3.6
Dissipation factor 0.003
Water absorption, % 0.2

TABLE 3.48 Pyralin Lacquer Properties
Density 1.4
Tensile strength, kpsi 18
Elongation, % 18

Decomposition temperature, °C 560
Volume resistivity, Ω-cm 10 16
Dielectric constant 3.5
Dissipation factor 0.002
Dielectric strength, V/mil 4000

3.1.6.3.1 Bis-Maleimides. Reaction of maleic anhydride with diamines leads to two
reactions. First, the amine reacts with the dianhydride groups and produces bis-maleim-
ides (Fig. 3.45). Then, the amine adds across the double bonds (“Michael reaction”), thus
lengthening the oligomer chain. These oligomers are easily impregnated into glass cloth,
“catalyzed” by high-temperature peroxide such as dicumyl peroxide, stacked to the de-
sired thickness, and press-cured or vacuum-bag cured, for example at 75 to 210 psi and

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