Engineering topics

St. Clair, Terry L.

Publications and source records attributed to St. Clair, Terry L..

46 records · Page 3

NASA NTRS1987

High temperature polyimide blends

In a continuing effort to synthesize polymers that are readily processable and that exhibit state-of-the-art characteristics, LARC-TPI (Mitsui) and polyimidesulfone (PISO2) were blended and subjected to a limited melt flow and thermal properties characterization. Mitsui Toatsu of Japan, working under a licensing agreement with NASA, synthesized an imidized version of LARC-TPI molding powder that exhibited an extraordinarily high level of softening when heated to 300 C. Subsequently, a study of the calorimetric and rheological properties was accomplished by NASA-Langley on that material. The thermoplastic polyimidesulfone that possesses processability similar to polysulfones and the solvent resistance of the polyimides was synthesized and characterized at NASA-Langley in the early 1980's.

Burks, Harold D.↗

NASA NTRS1987

Acetylene-Terminated Polyimide Siloxanes

Siloxane-containing addition polyimides yield toughened high-temperature adhesives and matrix resins. Addition polyimide made by reaction of aromatic tetracarboxylic acid dianhydride with aromatic diamine in presence of ethynyl-substituted aromatic monoamine. Acetylene-terminated siloxane imide cured by heating to yield acetylene-terminated polyimide siloxane.

St. Clair, Terry L.↗

NASA NTRS1987

A DSC study on crystalline LaRC TPI powder - A new version with higher initial molecular weight

A new version of crystalline Langley Research Center Thermoplastic Polyimide (LaRC-TPI) imidized powder, which possesses a higher initial molecular weight (MW), has been prepared and characterized. The scheme used for cyclodehydration during the synthesis of this material is described. Evidence of a higher initial MW for the subject LaRC-TPI is supported by both measurements of the inherent viscosity and the DSC thermograms. An initial melting peak at 295 C is noted in the freshly-synthesized sample. The powder can be recrystallized at any elevated temperatures below 340 C, and a single crystalline endothemic peak is always observed after various thermal histories. The heat of fusion for the fresh sample, as represented by the area under the melting peak in the directional scanning calorimeter thermogram, is about 3.9 cal/gm. Comparisons of thermal properties for the subject material are made to those exhibited by the commercial LaRC-TPI powder.

Hou, Tan-Hung↗

NASA NTRS1987

Processable Polyimides Containing ATBN Elastomers

Void-free moldings obtained without serious sacrifice in other properties. New synthesis produces high-temperture linear aromatic polyimide processed in imide form to yield tough, void-free components without serious sacrifice in other properties. Linear aromatic condensation polyimides are materials of prime choice for use as adhesives, composite matrix resins, films, coatings, and/or moldings where durability at temperatures as high as 200 to 300oC needed. Finding increasing use in aircraft and spacecraft applications.

St. Clair, Anne K.↗

NASA NTRS1987

Copolyimides With Flexibilizing Groups

Copolymers improved flexibility, processability and melt-flow characteristics. Copolyimide of new type exhibits synergistic improvements in flow properties due to flexibilized diamine-derived units incorported into polymer backbone. Technique produces copolyimides with combination of flexible linkage that cause polymers to exhibit flow properties particularly well suited for use in wide range of products including adhesives, molding resins, laminating resins, dielectric and protective coatings. Improved properties make copolymers especially useful as thermoplastic hot-melt adhesives.

St. Clair, Terry L.↗

NASA NTRS1987

High-Temperature Copolyimide Adhesive

Random Copolyimide, called STPI/LARC, prepared from commercially available materials. Being investigated for use as adhesive or matrix resin for aircraft applications.

Progar, Donald J.↗

NASA NTRS1987

Thermoplastic matrix composites - LARC-TPI, polyimidesulfone and their blends

Composites were fabricated from unidirectional unsized AS-4 carbon fiber and two baseline polyimides: benzophenone dianhydride-3,3'-diaminodiphenylsulfone (PISO2) and benzophenone dianhydride-3,3'-diaminobenzophenone (LARC-TPI). In addition, each polymer solution prior to prepregging was doped with various amounts of crystalline LARC-TPI powder to enhance melt flow during press molding. The 2:1, 1:1, and 1:2 ratios of crystalline to amorphous resin, respectively, were studied in the LARC-TPI system and the 1:2 ratio in the PISO2 system. Matrix characterization, prepreg fabrication/characterization and composite fabrication and physical/mechanical properties are described. The latter include three point short beam shear and flexure, dry and wet, as well as fracture toughness properties in selected compositions.

Johnston, Norman J.↗

NASA NTRS1987

Siloxane-modified polyethersulfideimide

BDSDA/APB, a novel linear polyethersulfideimide, was synthesized using siloxane units as flexible linkages in the backbone in an attempt to improve use properties and processability. The effect of these flexible linkages on molecular weight buildup, flexural strength and modulus, glass transition temperature, and melt-flow properties was determined.

Burks, Harold D.↗

NASA NTRS1987

Soluble aromatic polyimides for film and coating applications

The effect of changing isomeric points of attachment of phenoxy units in the diamine portion of several all-aromatic polyimide systems on the solubility of these materials were investigated. It was found that solubility could be enhanced by the presence of meta and ortho isomer links in the diamine portion of the molecule. The soluble phenoxy-linked polyimides yield tough flexible colorless to pale-yellow transparent films from solutions of chlorinated solvents, with high potential for use in electronic applications.

St. Clair, Anne K.↗

NASA NTRS1985

Enhancement of molecular weight build up in polyimides using ether solvents

Two linear polyimides were prepared in various ether and amide solvents. The inherent viscosity was then monitored as a function of time. The polymers made in the ether solvents consistently gave higher inherent viscosities, and thus molecular weights, than the same polymers made in the amide solvents. This molecular weight buildup is attributed to the unique solvation mechanism of the ether solvents which enhances the basicity of the amines via hydrogen bonding.

Egli, Annemarie H.↗