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Serafini, T. T.

Publications and source records attributed to Serafini, T. T..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Status review of PMR polyimides

In the NASA developed PMR (polymerization of monomer reactants) the reinforcing fibers are impregnated with a solution containing a mixture of monomers dissolved in a low boiling point alkyl alcohol solvent, with the monomers reacting in situ at elevated temperatures to form a thermo-oxidatively stable polyimide matrix. The current status of first and second generation PMR polyimides is reviewed, considering synthesis and properties, processing, and applications. It is concluded that the PMR approach offers various significant advantages, especially superior high temperature properties and processing versatility, to fabricators and users of polyimide/fiber composites.

Serafini, T. T.↗
NASA NTRS1979

High char imide-modified epoxy matrix resins

The synthesis of a class of bis(imide-amine) curing agents for epoxy matrix resins is discussed. Glass transition temperatures and char yield data of an epoxy cured with various bis(imide-amines) are presented. The room temperature and 350 F mechanical properties, and char yields of unidirectional graphite fiber laminates prepared with conventional epoxy and imide-modified epoxy resins are presented.

Serafini, T. T.↗
NASA NTRS1979

High char imide-modified epoxy matrix resins

Studies were performed to synthesize a novel class of bis (imide-amine) curing agents for epoxy matrix resins. Glass transition temperatures and char yield data of an epoxy cured with various bis (imide-amines) are presented. The room temperature and 350 F mechanical properties, and char yields of unidirectional graphite fiber laminates prepared with conventional epoxy and imide-modified epoxy resins are presented.

Serafini, T. T.↗
NASA NTRS1978

PMR Polyimide prepreg with improved tack characteristics

Current PMR Polyimide prepreg technology utilizes methanol or ethanol solvents for preparation of the PMR prepreg solutions. The volatility of these solvents limits the tack and drape retention characteristics of unprotected prepreg exposed to ambient conditions. Studies conducted to achieve PMR 15 Polyimide prepreg with improved tack and drape characteristics are described. Improved tack and drape retention were obtained by incorporation of an additional monomer. The effects of various levels of the added monomer on the thermo-oxidative stability and mechanical properties of graphite fiber reinforced PMR 15 composites exposed and tested at 316 C (600 F) are discussed.

Serafini, T. T.↗
NASA NTRS1978

Status review of PMR polyimides

The current status of first and second generation PMR polyimides are reviewed. Synthesis, processing, and applications were considered, using prepreg materials based on processable, high temperature resistant polyimides.

Serafini, T. T.↗
NASA NTRS1977

Second-generation PMR polyimides

Continuing research has resulted in development of polyimides with improved thermo-oxidative stability at 589 K. Polyimides are based on dimethyl ester of 4,4'-(hexafluoro-isopropylidene)-bis(phthalic acid) (HFDE) and p-phenylenediamine (PPDA) and NE.

Serafini, T. T.↗
NASA NTRS1976

PMR polyimide prepreg with improved tack characteristics

Current PMR Polyimide prepreg technology utilizes methanol or ethanol solvents for preparation of the PMR prepreg solutions. The volatility of these solvents limits the tack and drape retention characteristics of unprotected prepreg exposed to ambient conditions. Studies conducted to achieve PMR 15 Polyimide prepreg with improved tack and drape characteristics were described. Improved tack and drape retention were obtained by incorporation of an additional monomer. The effects of various levels of the added monomer on the thermo-oxidative stability and mechanical properties of graphite fiber reinforced PMR 15 composites exposed and tested at 316 C (600 F) were discussed.

Serafini, T. T.↗
NASA NTRS1975

Processable high temperature resistant polymer matrix materials

A review is presented of studies conducted with addition-cured polyimides, giving particular attention to an improved method involving in situ polymerization of monomer reactants (PMR) on the surface of the reinforcing fibers. The studies show that the PMR approach provides a powerful method for fabricating high performance polymer matrix composites. Significant advantages of the PMR approach are related to the superior high temperature properties of the obtained material, lower cost, greater safety, and processing versatility.

Serafini, T. T.↗
NASA NTRS1975

PMR polyimides: Processable high temperature composite matrix resins

Processing reproducibility and versatility were demonstrated for producing addition-cured polyimide/graphite fiber composites using an in situ polymerization of monomeric reactants directly on the fiber surface. The polymers so derived, designated PMR polyimides, can be fabricated into composite structures by laminating, random fiber molding or autoclave curing. Composites were determined to be thermally stable and retain useful properties after extended exposures at 550 F to 650 F. The material and fabrication capability were demonstrated by the fabrication and evaluation of prototype complex fan blades.

Winters, W. E.↗
NASA NTRS1975

Composites for fans and compressors

The composites research being conducted at Lewis for the application of composite materials to fan and compressor blades, is reviewed. The major areas discussed include the development of improved materials and fabrication methods, recent progress in providing composite fan and compressor blades with improved resistance to foreign object damage, and the development of advanced design and analysis procedures for composite blades.

Serafini, T. T.↗
NASA NTRS1975

Tailor making high performance graphite fiber reinforced PMR polyimides

Studies performed to demonstrate the feasibility of using the polymerization of monomer reactants (PMR) approach in order to 'tailor-make' processable polyimide matrix resins are described. Monomeric reactant solutions containing the dimethyl ester of 3, 3', 4, 4'-benzophenonetetracarboxylic acid, 4, 4'-methylenedianiline and the monomethyl ester of 5-norborene-2, 3-dicarboxylic acid were used to impregnate Hercules HTS graphite fiber. Six different monomeric reactant stoichiometries were studied. The processing characteristics and elevated temperature mechanical properties of the PMR polyimide/HTS graphite fiber composites are described.

Serafini, T. T.↗
NASA NTRS1975

PMR polyimides - Processable high temperature composite matrix resins

Processing reproducibility and versatility were demonstrated for producing addition-cured polyimide/graphite fiber composites using a unique in situ polymerization of monomeric reactants directly on the fiber surface. The polymers so derived, designated PMR polyimides, can be fabricated into composite structures by laminating, random fiber molding or autoclave curing. Composites were determined to be thermally stable and retain useful properties after extended exposures at 550 to 650 F. The material and fabrication capability were demonstrated by the fabrication and evaluation of prototype complex fan blades.-

Winters, W. E.↗
NASA NTRS1974

Criteria for selecting resin matrices for improved composite strength

Area under matrix of typical stress-strain diagram bounded by one percent strain is good index for priority assessment of matrix contribution to composite strength. Initial tangent modulus to stress-strain curve is useful parameter in translating matrix properties to composite properties.

Chamis, C. C.↗
NASA NTRS1974

Tailor making high performance graphite fiber reinforced PMR polyimides

Studies performed to demonstrate the feasibility of using the polymerization of monomer reactants (PMR) approach to tailor make processable polyimide matrix resins are described. Monomeric reactant solutions containing the dimethyl ester of 3,3',4,4' -benzophenonetetracarboxylic acid, 4, 4' -methylenedianiline and the monomethyl ester of 5-norbornene-2, 3-dicarboxylic acid were used to impregnate Hercules HTS graphite fiber. Six different monomeric reactant stoichiometries were studied. The processing characteristics and elevated temperature mechanical properties of the PMR polyimide/HTS graphite fiber composites are described.

Serafini, T. T.↗
NASA NTRS1974

In situ polymerization of monomers for polyphenylquinoxaline/graphite fiber composites

Methods currently used to prepare fiber reinforced, high temperature resistant polyphenylquinoxaline (PPQ) composites employ extremely viscous, low solids content solutions of high molecular weight PPQ polymers. An improved approach, described in this report, consists of impregnating the fiber with a solution of the appropriate monomers instead of a solution of previously synthesized high molecular weight polymer. Polymerization of the monomers occurs in situ on the fiber during the solvent removal and curing stages. The in situ polymerization approach greatly simplifies the fabrication of PPQ graphite fiber composites. The use of low viscosity monomeric type solutions facilitates fiber wetting, permits a high solids content, and eliminates the need for prior polymer synthesis.

Serafini, T. T.↗