Novel Novolac-Phthalonitrile and Siloxane-Phthalonitrile Resins cured with low melting Novolac Oligomers for Flame Retardant Structural Thermosets
dc.contributor.author | Hardrict, Shauntrece Nicole | en |
dc.contributor.committeechair | Riffle, Judy S. | en |
dc.contributor.committeemember | Esker, Alan R. | en |
dc.contributor.committeemember | McGrath, James E. | en |
dc.contributor.department | Chemistry | en |
dc.date.accessioned | 2014-03-14T20:29:58Z | en |
dc.date.adate | 2004-01-15 | en |
dc.date.available | 2014-03-14T20:29:58Z | en |
dc.date.issued | 2003-12-18 | en |
dc.date.rdate | 2004-01-15 | en |
dc.date.sdate | 2004-01-01 | en |
dc.description.abstract | The chemical modification of low molecular weight novolac oligomers and siloxane/silane-containing monomers has led to novel phthalonitrile derivatives with low glass transition temperatures, ranging from -25 to 75 ºC. Multi-functional, low molecular weight phenol-formaldehyde novolac resins were blended with these novel phthalonitrile derivatives to achieve low viscosity resin blends. Moderate temperatures and rapid curing cycles were employed (200 ºC, 1 h and 225 ºC, 4h) to produce networks with high glass transition temperatures (> 250 ºC). A decrease in the sharp band at 2230 cm⁻¹, attributed to the nitrile functionality of the phthalonitrile resin, was monitored in FTIR studies and indicated the progress of the reactions. Ninety percent conversion was achieved within ~ 30 min. Thermal analysis of siloxane-phthalonitrile/novolac networks cured for 1h at 200 ºC and 4h at 225 ºC did not exhibit glass transition temperatures below 250 ºC. In dynamic TGA studies, 5% weight loss temperatures up to 418 ºC were observed, and the materials exhibited 50 to 56 % char at 800 ºC in nitrogen. Networks prepared from a resin blend containing 50 weight% of a phthalonitrile derivative of a 260 g mol⁻¹ novolac oligomer, 50 weight% of the 260 g mol⁻¹ novolac oligomer, and 1.5 mol % triphenylphosphine (based on novolac) (NOV/NOV/TPP) cured at 200 ºC for 1h, did not exhibit a Tg below 250 ºC via DSC. These networks exhibited a 5% weight loss temperature of 350 ºC, and 70 % char at 800 ºC in TGA studies under nitrogen. This degree of char formation makes these materials appealing for use in carbon-carbon composites. Post-curing these networks at 200 ºC for 1h, and then at 225 ºC for 4h, resulted in high thermo-oxidative stability, with a 5% weight loss observed at 447 ºC and 50 % char at 800 ºC. Blending tetramethyldisiloxane phthalonitrile monomers with 260 g mol⁻¹ novolac oligomers afforded prepolymer resins with low melt viscosities, 560 mPa s at 80 ºC. Such viscosities may allow these resins to be processed via vacuum assisted resin transfer molding (VARTM) at low temperatures and heated at elevated temperatures to produce flame resistant three-dimensional networks. | en |
dc.description.degree | Master of Science | en |
dc.identifier.other | etd-01012004-153124 | en |
dc.identifier.sourceurl | http://scholar.lib.vt.edu/theses/available/etd-01012004-153124/ | en |
dc.identifier.uri | http://hdl.handle.net/10919/9669 | en |
dc.publisher | Virginia Tech | en |
dc.relation.haspart | Hardrict_MS_ETD.pdf | en |
dc.rights | In Copyright | en |
dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
dc.subject | novolac | en |
dc.subject | phenolic networks | en |
dc.subject | phthalonitrile | en |
dc.subject | flame retardance | en |
dc.subject | composite matrix | en |
dc.title | Novel Novolac-Phthalonitrile and Siloxane-Phthalonitrile Resins cured with low melting Novolac Oligomers for Flame Retardant Structural Thermosets | en |
dc.type | Thesis | en |
thesis.degree.discipline | Chemistry | en |
thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
thesis.degree.level | masters | en |
thesis.degree.name | Master of Science | en |
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