Engineering topics

Gerber, Margaret K.

Publications and source records attributed to Gerber, Margaret K..

7 records

NASA NTRS1995

Polyimides Made From 3,5-Diaminobenzotrifluoride

Polyimides synthesized from 3,5-diaminobenzotrifluoride (DABTF). One monomer of major importance in preparing these high-temperature polymers is 1,3-phenylenediamine (mPDA). Fluorinated polyimides exhibit characteristics potentially attractive for aerospace and electronic applications. Includes optical transparency, solubility in common polar solvents, enhanced thermo-oxidative stability, low dielectric constants, and high glass-transition temperatures. Polyimides also used to form free-standing films, coatings, and moldings.

St. Clair, Terry L.↗

NASA NTRS1994

Oligomers Terminated By Maleimide And Acetylene

Oligomeric molecules terminated with maleimide and acetylene groups synthesized and thermally treated to form cross-linked polymers exhibiting high or undetectable glass-transition temperatures and high thermo-oxidative stabilities. Compounds used to make thermally stable, glassy polymers.

St. Clair, Terry L.↗

NASA NTRS1993

Polyimides prepared from 3,5-diamino benzo trifluoride

High performance, thermooxidatively stable polyimides are prepared by reacting aromatic diamines with pendant trifluoromethyl groups and dianhydrides in an amide solvent to form a poly(amic acid), followed by cyclizing the poly(amic acid) to form the corresponding polyimide.

Gerber, Margaret K.↗

NASA NTRS1993

High temperature polymer from maleimide-acetylene terminated monomers

Thermally stable, glassy polymeric materials were prepared from maleimide-acetylene terminated monomeric materials by several methods. The monomers were heated to self-polymerize. The A-B structure of the monomer allowed it to polymerize with either bismaleimide monomers/oligomers or bis-acetylene monomers/oligomers. Copolymerization can also take place by mixing bismaleimide and bisacetylene monomers/oligomers with the maleimide-acetylene terminated monomers to yield homogenous glassy polymers.

Gerber, Margaret K.↗

NASA NTRS1993

Crosslinked polyimides prepared from N-(3-ethynylphenyl)maleimide

The compound N-(3-ethynylphenyl)maleimide (NEPMI) was used to prepare thermally stable, glassy polyimides which did not exhibit glass transition temperatures below 500 C. NEPMI was blended with the maleimide of methylene dianiline (BMI) and heated to form the polyimide. NEPMI was also mixed with Thermid 600 R, a commercially available bisethynyl oligomeric material, and heated to form a thermally stable, glassy polyimide. Lastly, NEPMI was blended with both BMI and Thermid 600 R to form thermally stable, glassy polyimides.

Gerber, Margaret K.↗

NASA NTRS1988

Isomeric oxydiphthalic anhydride polyimides

Much of the polyimide research at Langley Research Center has focused on isomeric modification of the diamine component; polyimides having considerably improved processability and adhesion have resulted. The present structure-property study was designed to investigate how isomeric attachment of the three oxydiphthalic anhydride (ODPA) polyimides affects their properties. Each dianhydride, 3,4,3',4'-oxydiphthalic anhydride (4,4'-OPDA,I), 2,3,2',3'-oxydiphthalic anhydride (3,3'-ODPA,II), and 2,3,3',4'-oxydiphthalic anhydride (3,4'-OPDA,III), was reacted with p-phenylenediamine, 4,4'-oxydianiline, 3,3'-diaminodiphenylsulfone, 3,3'-diaminobenzophenone, and 4,4'-bis(3-aminophenoxy)benzophenone in DMAc. The inherent viscosities of the resulting poly(amic acids) were determined. Thermally imidized films were studied for their creasability and solubility, as well as by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and wide angle X-ray scattering (WAXS). A comparison of these properties will be made.

Gerber, Margaret K.↗

NASA NTRS1988

A study of thermal transitions in a new semicrystalline thermoplastic polyimide

A polyimide derive from 4,4'-isophthaloyl diphthalic anhydride (IDPA) and 1,3-bis (4-aminophenoxy 4'-benzoyl) benzene (1,3-BABB) having semicrystalline behavior was prepared and characterized by differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS). Thus a poly(amic acid) film cured in air for one hour each at 100 and 200 C displayed an endotherm at 286 C, followed by a crystallization exotherm at 317 C, and a second melting transition at 350 C. The 286 C melting point appeared to result from earlier solvent-induced crystallization. Films cast from DMAc, air dried, and soaked in methylene chloride could not be induced into semicrystallinity. The fully cured polyimide has a Tg of 216 C. Films heated to temperatures as high as 100 C for one hour in air were transparent and light yellow in color. Those films heated to or above 125 C were translucent. Polarized light microscopy revealed the presence of spherulites 608 micrometers in diameter in a sample cured to 275 C in air. Two film samples, one cured to 275 and the other to 325 C, were evaluated for tensile and ultimate strength, modulus, and percent elongation at 25 and 200 C. These values remained essentially constant at each test temperature.

Pratt, J. Richard↗