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  • 1
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    The development of aerospace polyimide adhesives (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Few materials are available which can be used as aerospace adhesives at temperatures in the range of 300 C. The Materials Division at NASA-Langley Research Center developed several high temperature polyimide adhesives to fulfill the stringent needs of current aerospace programs. These adhesives are the result of a decade of basic research studies on the structure property relationships of both linear and addition aromatic polyimides. The development of both in house and commercially available polyimides is reviewed with regards to their potential for use as aerospace adhesives.
    Keywords: NONMETALLIC MATERIALS
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    NASA TECHNICAL REPORTS
  • 2
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    Polyimide adhesives - Modified with ATBN and silicone elastomers (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A series of studies evaluating the effects of added elastomers on the properties of a high-temperature addition polyimide adhesive is reviewed. First, thermoset polyimides containing various butadiene/acrylonitrile and silicone elastomers were synthesized either as physical polybends or by chemically reacting the elastomers directly onto the polymer backbone. The modified adhesive resins were characterized for thermomechanical properties, fracture toughness and adhesive strength. A second series of elastomer-containing polyimides was also prepared in order to study the effects of the elastomer chain length on polymer properties. Aromatic amine-terminated silicone rubbers with repeat units varying from n = 10 to 105 were reacted onto the polyimide backbone, and the resulting polymers were characterized for their adhesive properties.
    Keywords: NONMETALLIC MATERIALS
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    NASA TECHNICAL REPORTS
  • 3
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    Soluble aromatic polyimides for film and coating applications (1987)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: 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.
    Keywords: NONMETALLIC MATERIALS
    Type: Polymers for high technology: Electronics and photonics; Sept. 7-12, 1986; Anaheim, CA; United States
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    NASA TECHNICAL REPORTS
  • 4
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    Lanthanide-containing polyimides (1987)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The preparation of a variety of lanthanide-containing polyimide films is described, and results of their characterization are presented. The properties investigated include the glass transition temperature, thermooxidative stability, magnetic susceptibility, and electrical conductivity of the polymer. Films containing lanthanide chlorides, fluorides, and sulfides are flexible, but those containing lanthanide nitrates are extremely brittle. The addition of lanthanide acetates and acetylacetonates caused immediate gelation of two of the synthesis-mixture ingredients. It was found that, in general, the addition of lanthanide to the polyimide increases the density and glass transition temperature of the polymer but slightly decreases the thermooxidative stability.
    Keywords: NONMETALLIC MATERIALS
    Type: ; : TABES 93 - Annual
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    NASA TECHNICAL REPORTS
  • 5
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    Low coefficient of thermal expansion polyimides containing metal ion additives (1992)
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    Publication Date: 2011-08-24
    Description: Polyimides have become widely used as high performance polymers as a result of their excellent thermal stability and toughness. However, lowering their coefficient of thermal expansion (CTE) would increase their usefulness for aerospace and electronic applications where dimensional stability is a requirement. The incorporation of metal ion-containing additives into polyimides, resulting in significantly lowered CTE's, has been studied. Various metal ion additives have been added to both polyamic acid resins and soluble polyimide solutions in the concentration range of 4-23 weight percent. The incorporation of these metal ions has resulted in reductions in the CTE's of the control polyimides of 12 percent to over 100 percent depending on the choice of additive and its concentration.
    Keywords: NONMETALLIC MATERIALS
    Type: SAMPE Quarterly (ISSN 0036-0821); 23; 4, Ju
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    NASA TECHNICAL REPORTS
  • 6
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    Melt flow properties of LARC-TPI 1500 series mixtures (1992)
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    Publication Date: 2011-08-24
    Description: This study examines the melt-flow properties of 50/50 mixtures of high flow grade/medium flow grade LARC-TPI 1500 series pellets and a new form (94/6), of medium flow grade material which contains 6 percent of a low molecular weight imide additive. The flow properties are compared with previously reported flow properties of mixtures of earlier batches of high and medium flow grade TPI 1500 materials. Unlike the earlier batches of materials, the later materials were synthesized and mixed at Mitsui Toatsu Chemicals, Inc., Japan, and made into pellets before NASA received them for characterization. They exhibited a lower melt viscosity as well as improved melt stability.
    Keywords: NONMETALLIC MATERIALS
    Type: SAMPE Quarterly (ISSN 0036-0821); 24; 1; p. 50-53.
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    NASA TECHNICAL REPORTS
  • 7
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    Characterization of medium and high flow series 1500 LARC-TPI (1990)
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    Publication Date: 2011-08-19
    Description: An imidized version of LARC-TPI was developed on NASA's request for use by both aerospace and electronic industries. Two batches of LARC-TPI 1500 Series, consisting of medium-flow and high-flow pellets with different inherent viscosities, are characterized for their dynamic and isothermal melt flow properties at 340 C, mechanical properties of extrudates, extrudate porosity, and degree of crystallinity. The Series shows significantly better melt flow properties than previosly examimed forms of this polymer.
    Keywords: NONMETALLIC MATERIALS
    Type: SAMPE Journal (ISSN 0091-1062); 26; 59-64
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    NASA TECHNICAL REPORTS
  • 8
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    High temperature polyimide blends (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: 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.
    Keywords: NONMETALLIC MATERIALS
    Type: SAMPE Quarterly (ISSN 0036-0821); 19; 1-6
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    NASA TECHNICAL REPORTS
  • 9
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    LARC-TPI 1500 series controlled molecular weight polyimide (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: LARC-TPI, a linear high temperature thermoplastic polyimide, was developed several years ago at NASA Langley Research Center. This material has been commercialized by Mitsui Toatsu Chemicals, Inc., Tokyo, Japan, as a varnish and powder. More recently, a melt-extruded film of a controlled molecular weight of this same polymer has been supplied to NASA Langley Research Center for evaluation. This new form, called LARC-TPI 1500 series, has been prepared in three molecular weights - high, medium and low flow polymers. The subject of this investigation deals with the rheological properties of the high and medium flow powders and the adhesive properties of the medium flow melt-extruded film. Rheological studies indicate that the high and medium flow forms of the polymer fall in the flow range of injection moldable materials. Adhesive data generated on the medium flow extruded film shows this form to be well suited for structural adhesive bonding. The data are as good or better than that for LARC-TPI data of previous studies.
    Keywords: NONMETALLIC MATERIALS
    Type: SAMPE Journal (ISSN 0091-1062); 26; 53-58
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    NASA TECHNICAL REPORTS
  • 10
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    Flexible backbone aromatic polyimide adhesives (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Continuing research at Langley Research Center on the synthesis and development of new inexpensive flexible aromatic polyimides as adhesives has resulted in a material identified as LARC-F-SO2 with similarities to polyimidesulfone, PISO2, and other flexible backbone polyimides recently reported by Progar and St. Clair. Also prepared and evaluated was an endcapped version of PISO2. These two polymers were compared with LARC-TPI and LARC-STPI, polyimides research in our laboratory and reported in the literature. The adhesive evaluation, primarily based on lap shear strength (LSS) tests at RT, 177 C and 204 C, involved preparing adhesive tapes, conducting bonding studies and exposing lap shear specimens to 204 C air for up to 1000 hrs and to a 72-hour water boil. The type of adhesive failure as well as the Tg was determined for the fractured specimens. The results indicate that LARC-TPI provides the highest LSSs. LARC-F-SO2, LARC-TPI and LARC-STPI all retain their strengths after thermal exposure for 1000 hrs and PISO2 retains greater than 80 percent of its control strengths. After a 72-hr water boil exposure, most of the four adhesive systems showed reduced strengths for all test temperatures although still retaining a high percentage of their original strength (greater than 60 percent) except for one case. The predominant failure type was cohesive with no significant change in the Tgs.
    Keywords: NONMETALLIC MATERIALS
    Type: Journal of Adhesion (ISSN 0021-8464); 30; 185-198
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    NASA TECHNICAL REPORTS
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