New method for producing high-performance thermoplastic polymeric foams

Brandom, Don K.; Desouza, José P.; Baird, Donald G.; Wilkes, Garth L.

doi:10.1002/(sici)1097-4628(19971121)66:8<1543::aid-app15>3.0.co;2-4

Cited by 10 publications

(11 citation statements)

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“…Consequently, considerable research has been focused on lowering the dielectric constant of polyimides through modification of their chemical structures and introduction of pores into the polyimide film. [16][17][18] In this method, low dielectric constant polymer can be prepared by introducing air voids (with dielectric constant of 1) into the film. For example, incorporation of hexafluoroisopropylidene linkages and pendant trifluoromethyl groups produced films with dielectric constants below 3.0.…”

Section: Introductionmentioning

confidence: 99%

New Polyimide and Nanoporous Structures with Low Dielectric Constant

Mehdipour‐Ataei

Aram

2013

Adv Polym Technol

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A diamine containing pyridine ring, amide, and ether groups was prepared via two-step reactions from 6-chloronicotinoyl chloride. A novel polyimide was prepared from polycondensation of pyromellitic dianhydride with the diamine. In addition, nanoporous polyimide films were prepared from graft copolyimides. A thermally labile oligomer, poly(propylene glycol) (PPG), was incorporated into the polyimide backbone to obtain graft copolyimides that left voids into the polymer matrix through thermolysis of the labile PPG blocks. The properties of polyimide and nanofoams were compared. The dielectric constant of nanofoams was reduced, whereas their thermal stability and mechanical properties were almost maintained in comparison to the homopolyimide. C INSTRUMENTSMelting pointswere measured in capillaries on a Buchi apparatus (model Buchi 535). FT-IR spectra were recorded in the

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Section: Introductionmentioning

confidence: 99%

New Polyimide and Nanoporous Structures with Low Dielectric Constant

Mehdipour‐Ataei

Aram

2013

Adv Polym Technol

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“…The need for polymeric foams with advanced functionalities is increasing especially for applications in aerospace, electronics, construction, automotive and energy . Important foam properties include low foam density, adequate mechanical properties typically represented by a good strength‐to‐weight ratio , high thermal resistance with dimensional stability , and resistance to aggressive solvents and other chemicals .…”

Section: Introductionmentioning

confidence: 99%

“…Numerous high‐performance engineering plastics provide opportunities for foaming and attainment of superior properties particularly on the basis of their relatively high glass transition temperatures and thus their ability to sustain their mechanical integrity at elevated temperatures . Among various high‐performance engineering plastics, the polyimides offer ease of processing, high heat resistance and general chemical stability and are used in such demanding applications like fabrication of aircraft cabins, space vehicles, and automotive applications . Among the polyimides, poly(ether imide) (PEI) is widely used because of its relatively high modulus of elasticity , tensile strength , and low flammability .…”

Section: Introductionmentioning

confidence: 99%

“…Among the polyimides, poly(ether imide) (PEI) is widely used because of its relatively high modulus of elasticity , tensile strength , and low flammability . It has a high glass transition temperature range of around 215–220°C that is affected by cooling rate and pressure applied during solidification and a relatively low coefficient of thermal expansion at glassy state, i.e., 7.7 × 10 −8 m 3 /(kg K) . PEI is used in compression molding, gas assist molding, extrusion, thermoforming and injection molding .…”

Section: Introductionmentioning

confidence: 99%

“…Although such techniques provide good control of temperature and pressure, they are not suitable for high‐throughput operations since their control of the depressurization rate is limited . Continuous processors with Archimedean screws, i.e., single and twin screw extrusion technologies offer alternative foam processing methodologies that are easily tailorable , and cost effective . Furthermore, extrusion methodologies can provide mixing at relatively high deformation rates, promote enhanced diffusivity and generate high pressure loss rates at the die (pressure drop over the residence time at the die) .…”

Section: Introductionmentioning

confidence: 99%

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Extrusion of poly(ether imide) foams using pressurized CO₂: Effects of imposition of supercritical conditions and nanosilica modifiers

Aktaş

Gevgilili

Küçük

et al. 2013

Polymer Engineering & Sci

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Foams of an engineering plastic, poly(ether imide), were extruded using a single screw extruder employing pressurized CO 2 as the blowing agent. The porosity, pore size distributions, and the density of the foams were especially affected by the pressure drop, the pressure loss rate, and temperature at the die. Significant increases in porosity and pore size and corresponding decreases in density were observed when the pressure imposed on CO 2 became greater than the critical pressure values of CO 2 (i.e., the temperature was always greater than the critical temperature of the CO 2 in the extruder and the die). The viscoelastic material functions of the extruded foams depended especially on the density of the foam, with the elastic modulus increasing with density. The incorporation of nanosilica particles in the 0.08-0.6% by weight range increased only the density of the foam and did not provide any benefits in controlling of the nucleation rate and the pore size distribution, presumably due to their poor dispersibility and agglomerated state in the single screw extruder. POLYM. ENG. SCI., 54:2064-2074, 2014

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