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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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14 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Hot melt adhesive attachment pad

A hot melt adhesive attachment pad for releasably securing distinct elements together is described which is particularly useful in the construction industry or a spatial vacuum environment. The attachment pad consists primarily of a cloth selectively impregnated with a charge of hot melt adhesive, a thermo-foil heater, and a thermo-cooler. These components are securely mounted in a mounting assembly. In operation, the operator activates the heating cycle transforming the hot melt adhesive to a substantially liquid state, positions the pad against the attachment surface, and activates the cooling cycle solidifying the adhesive and forming a strong, releasable bond.

Fox, R. L.↗
NASA NTRS1984

Hot melt adhesive pad surface attachment assembly concept for on-orbit operations

The use of a hot melt adhesive concept to develop a Surface Attachment Assembly (SAA) for on-orbit attachment and detachment operations for the Manned Maneuvering Unit (MMU) was investigated. The concept involved impregnation of the hot melt adhesive into a fiberglass covered pad which contained electrical heating and thermoelectric cooling devices. The polyamide hot melt adhesive selected can be repeatedly heated to its melting point in a vacuum and provide good adhesion to various surfaces, i.e., reusable surface insulation tiles, metals, and composites, when cooled. After a series of adhesive screening tests, Jet-Melt 3746 was selected from a group of commercially available thermoplastic adhesive candidates which met or exceeded many of the criteria established for the SAA system. The SAA system was designed and fabricted with the goal of proving the concept with a working model rather than attempting to optimize all facets of the system. This system evolved by investigating alternate attachment concepts, designing and fabricating electronic systems to heat and cool the adhesive, and then fabricating electronic systems to heat and cool the adhesive, and then fabricating and testing two prototype full-size units.

Progar, D. J.↗
NASA NTRS1983

Recharging "Hot-Melt" Adhesive Film

Technique for recharging surface with "hot-melt" film makes use of one sided, high-temperature, pressure-sensitive adhesive tape. Purpose of the one-sided tape is to hold hot-melt charge in place until fused to surface. After adhesive has fused to surface and cooled, tape is removed, leaving adhesive on surface.

Progar, D. J.↗
NASA NTRS1983

Hot-Melt Adhesive Attachment System

Adhesive system is as effective on Earth as in space. Fiberglass cloth mounted in head assembly. When adhesive reaches melt temperature head is attached to metals composites, ceramics, and other materials. Once attached, head cooled rapidly for quick stick. Used to tether tools or attach temporary scaffolding to walls, buildings, or beams.

Fox, R. L.↗
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 NTRS1978

Low density bismaleimide-carbon microballoon composites

A process is described for constructing for a composite laminate structure which exhibits a high resistance to heat and flame provides safer interior structures for aircraft and submarine compartments. Composite laminate structures are prepared by the bismaleimide resin preimpregnation of a fiberglass cloth to form a face sheet which is bonded with a bismaleimide hot melt adhesive to a porous core structure selected from the group consisting of polyamide paper and bismaleimide-glass fabric which is filled with carbon microballoons. The carbon microballoons are prepared by pyrolyzing phenolic micro-balloons in the presence of nitrogen. A slurry of the carbon microballoons is prepared to fill the porous core structure. The porous core structure and face sheet are bonded to provide panel structures exhibiting increased mechanical capacities and lower oxygen limit values and smoke density values.

Kourtides, D. A.↗
NASA NTRS1983

Hot melt recharge system

A package assembly is described for pecisely positioning a charge of hot melt adhesive onto an attachment pad or point of use. The adhesive is heated to softening or melt temperature (280 F to 325 F) and thereafter cooled to resolidifying temperature. A single sided pressure sensitive polyimide film tape serves with another film strip to protect a sandwiched adhesive strip until use and to hold the adhesive in precise position until thermally bonded to its point of use. Tab ends serve as aids in stripping tapes and from the adhesive charge.

Progar, D. J.↗
NASA NTRS1989

Copolyimide with a combination of flexibilizing groups

Copolyimides are prepared by reacting one or more aromatic dianhydrides with a meta-substituted phenylene diamine and an aromatic bridged diamine. The incorporation of meta-substituted phenylene diamine derived units and bridged aromatice diamine derived units into the linear aromatic polymer backbone results in a copolyimide of improved flexibility, processability, and melt-flow characteristics. The copolyimides are especially useful as thermoplastic hot-melt adhesives.

Stclair, Terry L.↗
NASA NTRS1988

Evaluation of a thermoplastic polyimide (422) for bonding GR/PI composite

A hot-melt processable copolyimide previously studied and characterized as an adhesive for bonding Ti-6Al-4V was used to bond Celion 6000/LARC-160 composite. Comparisons are made for the two adherend systems. A bonding cycle was determined for the composite bonding and lap shear specimens were prepared which were thermally exposed in a forced-air oven for up to 5000 h at 204 C. The lap shear strengths (LSSs) were determined at RT, 177, and 204 C. After thermal exposure at RT, 177, and 204 C the LSS decreased significantly; however, a slight increase was noted for the 204 C tests. Initially the LSS values are higher for the bonded Ti-6Al-4V than for the bonded composite, however, the LSS decreases dramatically between 5000 and 10,000 h of 204 C thermal exposure. Longer periods of thermal exposure up to 20,000 h results in further decreases in the LSSs. Although the bonded composite retained useful strengths for exposures up to 5000 h, based on the poor results of the bonded Ti-6Al-4V beyond 5000 h, the 422 adhesive bonded composites would most likely also produce poor strengths beyond 5000 h exposure. Adhesive bonded composite lap shear specimens exposed to boiling water for 72 h exhibited greatly reduced strengths at all test temperatures. The percent retained after water boil for each test temperature was essentially the same for both systems.

Progar, Donald J.↗
NASA NTRS1988

Evaluation of a thermoplastic polyimide (422) for bonding GR/PI composite

A hot-melt processable copolyimide previously studied and characterized as an adhesive for bonding Ti-6Al-4V was used to bond Celion 6000/LARC-160 composite. Comparisons are made for the two adherend systems. A bonding cycle was determined for the composite bonding and lap shear specimens were prepared which were thermally exposed in a forced-air oven for up to 5000 h at 204 C. The lap shear strengths (LSSs) were determined at RT, 177, and 204 C. After thermal exposure at RT, 177, and 204 C the LSS decreased significantly; however, a slight increase was noted for the 204 C tests. Initially the LSS values are higher for the bonded Ti-6Al-4V than for the bonded composite, however, the LSS decreases dramatically between 5000 and 10,000 h of 204 C thermal exposure. Longer periods of thermal exposure up to 20,000 h results in further decreases in the LSSs. Although the bonded composite retained useful strengths for exposures up to 5000 h, based on the por results of the bonded Ti-6Al-4V beyond 5000 h, the 422 adhesive bonded composites would most likely also produce poor strengths beyond 5000 h exposure. Adhesive bonded composite lap shear specimens exposed to boiling water for 72 h exhibited greatly reduced strengths at all test temperatures. The percent retained after water boil for each test temperature was essentially the same for both systems.

Progar, Donald J.↗
NASA NTRS1986

Evaluation of a novel thermoplastic polyimide for bonding titanium

A novel hot-melt processable polyimide has been synthesized and characterized as an adhesive for a titanium alloy. This system shows potential for applications with service temperatures near 200 C. A bonding cycle was developed from preliminary processing studies. The bonded specimens were tested at room temperature, 177 C and 204 C both before and after aging in air at 204 C for times up to 1000 hours. There was no appreciable change in strength after aging. Bonded specimens were exposed to boiling water continuously for a 72 hour period. These specimens exhibited some loss in strength due to this rather severe exposure.

Progar, D. J.↗
NASA NTRS1994

Making Semicrystalline Polyimide Powders

Semicrystalline polyimides with controlled molecular weights synthesized in process that yields polyimides in powder form. Powders with desirable melt-flow properties formed in reaction vessels, without grinding. Commercially attractive for fabrication of adhesive bonds, compression molding of shaped parts, and deposition onto reinforcing fibers for subsequent hot pressing into polyimide-matrix/fiber composites.

St. Clair, Terry L.↗
NASA NTRS1981

Hot forming graphite/polyimide structures

Hot forming process has been developed in which structural shapes and panels are fabricated directly from stabilized graphite/polyimide preforms. Process can be used with thermosetting polymers that have high-temperature melt phase just before final cure. This phase allows fibers to move without destroying matrix-to-fiber adhesion. One of key advantages of this process is that prestages preforms are very stable and do not require refrigerated storage.

Baucom, R. M.↗
NASA NTRS1978

Bismaleimide resins for flame resistant honeycomb sandwich panels

Bismaleimide resins are prime candidates for nonflammable aircraft interior panels. Three resin types with different structures and processing characteristics were formulated. Resin M 751 was used to fabricate 100 kg of glass fabric prepregs which were used for the preparation of face sheets for honeycomb sandwich panels. Prepreg characteristics and curing cycles for laminate fabrication are provided. In order to advance beyond the current solvent resin technology for fibre and fabric impregnation, a hot melt solvent-less resin system was prepared and characterized. Preliminary tests were performed to develop a wet bonding process for the fabrication of advanced sandwich honeycomb panels by use of polybismaleimide glass fabric face sheets and polybismaleimide Nomex honeycomb core. B-stage material was used for both the core and the face sheet, providing flatwise tensile properties equivalent to those obtained by the state-of-the-art 3-step process which includes an epoxy adhesive resin.

Stenzenberger, H. D.↗