Volume 4 - Loctite.ph

Polyimide (PI)ThermoplasticTrade Names• Envex• Kapton• Kinel• Matrimid• Meldin• NEW-TPI• VespelManufacturerRogers CorporationE.I. DuPontRhone Poulenc, Inc.Ciba - GeigyFuronMitsui ToastuE.I. DuPontGeneral DescriptionPI is an aromatic, linear polymer typically produced by a condensationreaction, such as polymerizing aromatic dianhydride and aromaticdiamine. The polymer can then either be cast with solvent evaporationto form a thermoplastic, such as Kapton films, or precipitated to form a“pseudo-thermoplastic”, such as Vespel. This pseudo-thermoplastic isnot a true thermoplastic because it thermally degrades before its glasstransition temperature and it is not a true thermoset because it is notcrosslinked. Specialty grades of PI include antistatic, thermallyconductive, corona resistant, and glass, carbon, molybdenum disulfideand PTFE filled. In 2004, the price of Vespel, which is sold as moldedparts or machinable stock, ranged approximately from $225 to $365 fora 1 ⁄4" diameter, 38" long rod or $950 for a 10" by 10" by 1 ⁄8" plaque. Inaddition, the price of Kapton films ranged from $63 (5 mil thickness) to$687 ( 1 ⁄3 mil thickness) per pound.General PropertiesThe most notable properties of PI are its solvent resistance, barrierproperties, and performance at both high and low temperatureextremes. For example, Kapton films have performed outstandinglyin field applications at temperatures as low as -452°F (-269°C) andas high as 752°F (400°C). Moreover, unfilled PI has a glass transitiontemperature of 590°F (310°C), heat deflection temperatures up to660°F (349°C), a maximum recommended continuous servicetemperature as high as 500°F (260°C), and can withstand short-termexposures at temperatures up to 700°F (371°C). PI naturally has anextremely low flammability, with a limiting oxygen index of 44 and aUL 94 flammability rating of V-0. PI also has good dielectric properties,which remain constant over a wide range of frequencies, goodelongation (up to 10%), and good abrasion resistance. PI is chemicallyresistant to most organic solvents and dilute acids. However, PI isattacked by strong acids and bases, and is soluble in highly polarsolvents. PI is very resistant to radiation, but long-term exposure tocorona discharge or combinations of ultraviolet radiation, oxygen,and water have a negative effect on its mechanical and physicalproperties. The major disadvantages of PI are that it is very expensive,very difficult to process, and most types of PI have volatiles or containsolvents which must be vented during curing. A minor disadvantage ofPI is that it is only available in dark colors.Typical Properties of Polyimide (PI)American EngineeringProcessing Temperature 350°F to 465°F 177°C to 241°CLinear Mold Shrinkage 0.001 to 0.004 in./in. 0.001 to 0.004 cm/cmMelting Point – –Density 82.4 to 106.8 lb./ft. 3 1.32 to 1.71 g/cm 3Tensile Strength, Yield 4.7 to 12.6 lb./in. 2 x 10 3 3.3 to 8.9 kg/cm 2 x 10 2Tensile Strength, Break 2.8 to 16.0 lb./in. 2 x 10 3 2.0 to 11.2 kg/cm 2 x 10 2Elongation, Break 0.5 to 10.0% 0.5 to 10.0%Tensile Modulus 1.5 to 3.7 lb./in. 2 x 10 5 1.1 to 2.6 kg/cm 2 x 10 4Flexural Strength, Yield 1.1 to 3.7 lb./in. 2 x 10 3 0.8 to 2.6 kg/cm 2 x 10 2Flexural Modulus 0.9 to 28.0 lb./in. 2 x 10 5 0.6 to 19.7 kg/cm 2 x 10 4Compressive Strength 2.0 to 35.1 lb./in. 2 x 10 3 1.4 to 24.7 kg/cm 2 x 10 2Izod Notched, R.T. 0.3 to 1.8 ft.-lb./in. 1.4 to 9.7 kg cm/cmHardness M100 - M125 Rockwell M100 - M125 RockwellThermal Conductivity 1.5 to 4.4 BTU-in./hr-ft. 2 -°F 0.22 to 0.63 W/m-°KLinear ThermalExpansionDeflection Temperature@ 264 psiDeflection Temperature@ 66 psiContinuousService Temperature0.7 to 2.9 in./in.-°F x 10 -5 1.3 to 5.2 cm/cm-°C x10 -5460°F to 660°F 238°C to 349°CTypical Applications• Nuclear – Valve seats, thermal and electrical insulators,x-ray fluorescent sample holders• Fibers – Flame retardant clothing and filters forhot/corrosive liquids and gases• Miscellaneous – Washers, wear strips, compressor valves,ultrasonic transmitting componentsSI– –480°F to 550°F 249°C to 288°CDielectric Strength 200 to 700 V/10 -3 in. 0.8 to 2.7 V/mm x 10 4Dielectric Constant@ 1 MHzDissipation Factor@ 1 MHzWater Absorption,24 hr.3.0 to 5.2 3.0 to 5.20.001 to 0.010 0.001 to 0.0100.27 to 0.97% 0.27 to 0.97%54The Loctite ® Design Guide for Bonding Plastics, Volume 4