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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Novel polyamide-imines

An account is given of tough, thermally stable linear polyimides containing amide linkages that recommend themselves for use in high temperature-resistant films and coatings as well as matrix resins for graphite-reinforced structures. Four such polymers were synthesized from unsubstituted amide diamines, and two others from N-substituted amide diamines. High inherent viscosities and glass transition temperatures were obtained. The films exhibit good resistance to organic solvents. Films of the 4,4-prime-isomer polyamide-imide yielded exceptionally high modulus and toughness during impact evaluation.

Dezern, James F.↗
NASA NTRS1988

Synthesis and characterization of BTDA-based polyamide-imides

Several thermally stable tough linear polyimides containing amide linkages were synthesized which have application as matrix resins in graphite reinforced structures. Isomers of diaminobenzanilide were reacted with 3,3-prime,4,4-prime-benzophenonetetracarboxylic dianhydride, and then thermally converted to the polyamide-imide. Polymers prepared from unsubstituted amide diamines and from N-substituted amide diamines exhibited high inherent viscosities and glass transition temperatures. The mechanical properties of these polymers were found to be superior to those of LARC-TPI.

Dezern, James F.↗
NASA NTRS1989

Initial evaluation of novel polyamide-imides and their copolymers as adhesives

Continued interest by the research community in thermally stable, tough, high temperature adhesives has resulted in the investigation by Langley Research Center of two linear aromatic polyamide-imide (PAI) homopolymers and two linear aromatic PAI copolymers. The homopolymers were made with either 3,3'=DABA or 4,4'-DABA and BTDA. The two polymers were prepared with a monomer ratio of 0.75 DABP:0.25 DABA:1.00 BTDA. These aromatic PAIs possess high thermal stability because of intermolecular hydrogen bonding and chain stiffness. Lap shear strength (LSS) was the main criteria used to evaluate the polymers as adhesives. LSS of bonded Ti-6Al-4V was determined at room temperature (RT), 177, 204 and 232 C. The glass transition temperature and the type of bond failure were also determined. The best LSS values of the four adhesive systems investigated were obtained with the PAI copolymer identified in the report as LARC-TPI (25 percent 3,3'-DABA); however, it did not produce LSSs nearly as high as LARC-TPI. The poor flow properties observed appear to be due to a combination of high molecular weight and the increased interchain electronic interactions associated with the amide group.

Progar, Donald J.↗
NASA NTRS1990

Synthesis and characterization of polyamide-imides

The synthesis and characterization of polyamide-imides (PAI) derived from four different dianhydrides and three isomers of diaminobenzanilide are discussed with emphasis on the effect of combining an amide linkage in the diamine portion with other bridging groups in the dianhydride portion of the polymer backbone. It is noted that all of the amide-imide polymers exhibit high-glass transition temperatures, high thermooxidative stability, and a relatively good solvent resistance. These aromatic PAIs are characterized by high thermal stability due to chain stiffness, crystallinity, and intermolecular hydrogen bonding, and are considered to be good candidates as high-temperature films, coatings, and fibers for aerospace applications.

Dezern, James F.↗
NASA NTRS2017

Graphene Oxide Reduces the Hydrolytic Degradation in Polyamide-11

Graphene oxide (GO) was incorporated into polyamide-11 (PA11) via in-situ polymerization. The GO-PA11 nano-composite had elevated resistance to hydrolytic degradation. At a loading of 1 mg/g, GO to PA11, the accelerated aging equilibrium molecular weight of GO-PA11 was higher (33 and 34 kg/mol at 100 and 120 °C, respectively) compared to neat PA11 (23 and 24 kg/mol at 100 and 120 °C, respectively). Neat PA11 had hydrolysis rate constants (kH) of 2.8 and 12 ( × 10(exp -2) day(exp -1)) when aged at 100 and 120 °C, respectively, and re-polymerization rate constants (kP) of 5.0 and 23 ( × 10(exp -5) day(exp -1)), respectively. The higher equilibrium molecular weight for GO-PA11 loaded at 1 mg/g was the result of a decreased kH, 1.8 and 4.5 ( × 10(exp -2) day(exp -1)), and an increased kP, 10 and 17 ( × 10(exp -5) day(exp -1)) compared with neat PA11 at 100 and 120 °C, respectively. The decreased rate of degradation and resulting 40% increased equilibrium molecular weight of GO-PA11 was attributed to the highly asymmetric planar GO nano-sheets that inhibited the molecular mobility of water and the polymer chain. The crystallinity of the polymer matrix was similarly affected by a reduction in chain mobility during annealing due to the GO nanoparticles' chemistry and highly asymmetric nano-planar sheet structure.

Samuel J A Hocker↗
DOE OSTI2022

Tailoring compatibilization potential of maleic anhydride–grafted polypropylene by sequential rheochemical processing of polypropylene and polyamide 66 blends

Reactive compatibilization of immiscible polymer blends using a preferred compatibilizer leaves the following question: How much loading of a compatibilizer is good enough and what maximum properties can be achieved? A good understanding of the process can help solve the reutilization of mixed waste plastics. Here, the reactive compatibilization of polypropylene-graft-maleic anhydride (PP-g-MAH) on polypropylene/polyamide 66 (PP/PA66) blends is quantitatively assessed using thermorheological, microoptical, spectroscopic, and x-ray scattering-based characterization tools. The overall compositions of all PP(60%)/PA66(30%)/PP-g-MAH(10%) blends are kept constant while systematically controlling the degree of the chemical reaction by varying the sequential addition of PP-g-MAH to the melt mixture. The first feeding of PP-g-MAH (x%, 0 ≤ x ≤ 10) is conducted at 280°C and the second feeding of (10–x)% is at 200°C. During the first step, a larger amount of chemical activity is observed up to 4%–6% addition of PP-g-MAH. Furthermore, the constant chemical composition allows a systematic comparison of the compatibilizer-dependent thermal, rheological, morphological, and mechanical properties. With an increased degree of interfacial reaction, the size of dispersed PA66 domains decreases to register improved interfacial adhesion with the PP matrix, yielding enhanced Young's modulus and absolute failure strength of the isotropic matrix.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Substitution of virgin carbon fiber with low-cost recycled fiber in automotive grade injection molding polyamide 66 for equivalent composite mechanical performance with improved sustainability

Recycled carbon fiber has historically proven challenging to integrate into composite manufacturing due in no small part to the low-density, randomly oriented, discontinuous fiber format that results from typical recycling. Discontinuous fiber requires the use of alternative technologies than those traditionally applied to continuous fiber (e.g., hand lay-up, winding). Extrusion compounding is one such applicable technology, but material transfer into the system requires alternative feeding equipment or the use of an altered procedure as trialed in this research. In this study, an injection molding compound for automotive applications was prepared with recycled carbon fiber and compared against an existing commercial compound. Input fibers and molded compound were evaluated for mechanical performance, while relevant variables such as compounded fiber alignment and aspect ratio were compared to the existing baseline material to confirm a like-for-like composite material structure. Overall, analysis indicates that recycled fiber performs similarly to virgin fiber reinforcement, demonstrating that recycled fiber may be a viable drop-in replacement for short-fiber discontinuous applications.

42 ENGINEERING↗
DOE OSTI2024

Literature Review of Recycling Polypropylene and Polyamide 12 Powders for Selective Laser Sintering

Additive manufacturing (AM) is the creation of three-dimensional parts by adding material layer-by-layer based on two dimensional “slices” of a CAD file, without molds or tooling. AM has broken the relationship between part complexity and manufacturing cost. As a general rule, for conventional manufacturing, the more complex the part produced, the more costly its manufacturing. For example, in the production of a bracket for a satellite, moving from conventional manufacturing to AM allowed the part to be consolidated from 4 parts to just one, as well as reducing the weight of the part by 35%. A further benefit, AM can be more cost effective for small lot sizes. To illustrate, consider a case study of white board marker caps presented by Klahn et al. The cost to produce 1,000 units of a new design using SLS was about an order of magnitude lower than conventional manufacturing, as shown in Figure 1.

36 MATERIALS SCIENCE↗
NASA NTRS1970

Chemical treatment makes aromatic polyamide fabric fireproof in oxygen atmosphere

Organic fabric is reacted first with vapors of a phosphorus oxychloride, phosphorus oxybromide solution and then with bromine vapor, after neutralization it is flameproof in pure oxygen atmosphere. Soaking the fabric with mixture of ammonium polyphosphates increases flame resistance, but the polyphosphates are leached out during laundering.

Cardwell, R. O.↗
NASA NTRS1975

High-performance vessels from an aromatic polyamide fiber/epoxy composite

The investigation reported is concerned with the development of a filament-wound, ultralightweight composite vessel for the containment of cryogenic propellants and pressurant gases. The vessels are to be used within an operational temperature range from -253 C to ambient temperature. The fiber used for the process is Kevlar 49. The design and the fabrication of specimens and vessels are discussed along with the results obtained in a testing program.

Chiao, T. T.↗
NASA NTRS1991

Polyamide-Imides Made From BTDA

New synthesis results in improved class of tough, thermally stable polyimides containing amide linkages. Linear, aromatic, polyimide/amides synthesized from isomers of DABA with 3, 3', 4, 4'- BTDA. Mechanical properties better than those of LARC-TPI polyimide. Potentially useful as matrix resins in graphite-reinforced structures, and as fibers or coating films withstanding high temperatures.

Dezern, James F.↗