Poly(pheny1ene sulfide) (PPS) and poly(ether etherketone) (PEEK) are high performance engineering thermoplastics with a unique combination of excellent environmental, mechanical, and thermal properties. Research on the thermal and rheological properties of PPS and PEEK resins and carbon fiber reinforced prepregs are described. Experimental studies of the dynamic viscoelasticity and thermal properties of these materials are summarized. The effects of processing cycles and environment on the thermal and rheological properties are discussed. The effects of the processing environment and the addition of carbon fiber on the thermal stability are reported. Crosslinking of poly(pheny1ene sulfide) in air, enhancing thermal stability, is also investigated.
SYNOPSISGlycidol was used to convert the isocyanate-terminated polyurethane prepolymer to glycidylterminated polyurethane prepolymer. The modified polyurethane not only offers some distinct advantages over the commercial polyurethane prepolymer, but also enhances the properties of the epoxy resins. The glycidyl-terminated polyurethane modified epoxy resin proved to be superior to conventional epoxy resins in improving impact strength, fracture energy, and adhesion properties. The compatibility of the compounds in this glycidylterminated PU/epoxy system was investigated using different preparation procedures. It was found that the synthesized glycidyl-terminated polyurethane prereacted with curing agents, exhibited a lesser degree of phase separation, and can influence the mechanical properties of polymer blends. The results coincide with the phenomena observed in dynamic mechanical analysis and scanning election microscopy. 0 1994 John Wiley & Sons, Inc. INTRODUCTIONIt is known that epoxy resins have high glass-transition temperatures ( T,) , are rigid and brittle in nature, and have poor crack re~istance.'-~ In order to overcome these problems, a considerable amount of study has been done in the direction of toughening epoxies, with some research focused on introducing a rubber phase into epoxy networks.'-7 Polyurethane resin possesses high impact strength and exhibits excellent low-temperature performan~e.~.' This study is based on a blending technique, introducing a second reactive polyurethane polymer into the epoxy resins, to make up for the deficiencies of the existing material.Although polyurethane resins possess excellent low temperature properties, chemical and environmental resistance, and high impact properties, com- CCC 0021-8995/94/081137-15 mercial polyurethanes contain free isocyanate groups, which lead to some limitations.'0-" Small amounts of moisture will interfere with proper curing, which limits the amount of materials used to comparatively large quantities. Another class of compound is that in which the isocyanate groups are "blocked" or "capped" with an "active hydrogen" c~mpound.'~-'~ These products show little or no reaction at room temperature. Some of the disadvantages of employing blocked isocyanates are that a high temperature or a long period of time are required for unblocking, as well as the difficulty in removing the blocking agents during the process. In the previous study, l4 a modified polyurethane was prepared which could overcome these disadvantages. Glycidol was used to transfer the isocyanateterminated polyurethane prepolymers to glycidylterminated polyurethane prepolymers. Crosslinking in these cases occurs primarily through the epoxide groups, and the modified system offers some distinct advantages over the commercial polyurethane resins, for example, good storage stability and room temperature curing. Polymer blends encompass many different kinds of materials containing two or more polymer components; the most important parameter that affects the properties of polymer ...
2,3-Epoxy-l -propano1 has been introduced into isocyanate-terminated polyurethane to form glycidyl-terminated polyurethane resins. A series of glycidyl-terminated polyurethanes based on hydroxyterminated poly(oxypropy1ene) (poly(oxypropylene)glycol, PPG), toluene diisocyanate (TDI), and 1 ,4-butanediol (BD) was synthesized with various PPG soft segment lengths (MW 700, 1000 and 2000) and soft segment concentrations (30, 50 and 70 wt.-Vo). The effect of glycidyl-terminated polyurethane on the adhesion properties and the phase separation were investigated. The adhesion properties at liquid nitrogen temperature coincide with the phenomenon observed in the phase separation behavior of polyurethane. Differential scanning calorimetry (DSC) and infrared technique (IR) were used to assess the phase separation content. The enthalpy jump at the glass transition temperature (AC,) and the unique spectroscopic features in the N-H and C=O stretching regions were applied to characterize the phase separation behavior. It was found that the modified resins do not only show superior adhesion at liquid nitrogen temperature but also exhibit some unique properties, e. g., room temperature curing and good storage stability. ZUSAMMENFASSUNG:Die Klebeeigenschaften und das Phasentrennungsverhalten von Polyurethanen aus ,,weichen" Poly(oxypropy1en)-Einheiten (PPG) und ,,harten" Segmenten aus Toluoldiisocyanat (TDI) und 1,4-Butandiol (BD) wurden untersucht. Die Lange der PPG-Weichsegmente (PPG mit MW 700, 1 OOO bzw. 2000) sowie deren Konzentration (30, 50 and 70 Gew.-Vo) wurden variiert. Die Isocyanat-Endgruppen dieser PU-Harze wurden mit 2,3-Epoxy-l-propanol zu Glycidyl-Endgruppen umgesetzt. Die Klebeeigenschaften bei der Temperatur flussigen Stickstoffs folgen dem Phasentrennungsverhalten der Polyurethane. Die Phasentrennung wurde mit DSC-(Enthalpiesprung bei der Glasternperatur) und IR-Messungen (Veranderungen im Bereich der N-H-und C=O-Streckschwingungen) untersucht. Die rnodifizierten PU-Harze weisen neben verbesserter Haftung bei tiefen Temperaturen auch gute Lagerungseigenschaften sowie die Fahigkeit der Hartung bei Raumtemperatur auf.
SYNOPSISGlycidol has been introduced into isocyanate-terminated polyurethane to form glycidylterminated polyurethane resin. A series of glycidyl-terminated polyurethanes, based on PTMEG, PPG, and polyester soft segments, having different molecular weights were synthesized and their adhesion properties on aluminum were evaluated. The effect of the softsegment structure, soft-segment length, and temperature on adhesion were examined. It was found that the resin showed superior adhesion at cryogenic temperatures. The results coincide with the phenomenon observed in dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). In addition, the modified system also offered some distinct advantages over the commercial polyurethane adhesives, e.g., good storage stability and room-temperature curing.
Polyphenylene sulfide (PPS) and Polyetherether ketone are high performance engineering thermoplastics with a unique combination of excellent thermal, mechanical and environmental properties. This paper presents the thermogravimetric properties of PPS and PEEK resins and carbon fiber reinforced composites. The addition of carbon fiber and the effects of environment on the thermal stability are presented. Crosslinking of Polyphenylene sulfide in air enhances thermal stability is discussed. PEEK resin and its composite show higher thermal stability than PPS by 70°C to 100°C is also described.
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