Processable PMR-Type Polyimides: Process-Property Relationships, Curing Kinetics, and Thermooxidative Stability

Abstract

The rheological and structural characteristics of polyimides with enhanced melt flow have been investigated. The polyimides were based on 2,3,3 1 , 4 1 -biphenyltertracarboxylic dianhydride (PBDA) and a mixture of a diamine, 4,4 1 (1,4-phenylene-bismethylene) bisaniline (BAX) and a triamine, 1,3,5-Tris (4-aminophenoxybenzene), TAB, where the amount of TAB was 4 and 8%. Melt viscosities of these polymers suggest that they are processable by resin infusion methods. Although curing occurs through the phenylethynyl endcap, the steric and electronic differences of the three amines results in different cure kinetics and heterogeneous crosslinking. This is manifested in multiple T g values in the differential scanning calorimetry (DSC) scan of the cured samples. Rheological and DSC kinetic studies of the cure behavior indicate that the sample with 4% TAB cures more quickly than the system with 8% TAB and it has a lower activation energy (147 versus 185 kJ mole 21 ). Thermal gravimetric analysis (TGA) scans indicate that both TAB based samples are more thermally stable than PMR-15. The lower activation energy for 8% TAB , relative to 4% TAB (147.0 versus 170.2 kJ mole 21 ) suggests the additional branching present decreases the thermal stability.

Star‐shaped silicon‐containing arylacetylene resin based on a one‐pot synthesis using zinc powder catalysis with improved processing and thermal properties

“…The thermal cure behavior of SSA resin is displayed in Figure and the results reveal the following trends: (1) The exothermic peak of the thermal cure reaction occurred in the range of 120–245 °C, peaking at 203 °C, (2) the thermal curing peak was lower than those observed for PSA resins (normally in the range of 190–280 °C with a peak at ~240 °C) and much lower than that of polyimide and phthalonitrile (normally in the range of 250–400 °C with a peak at >300 °C), and (3) the enthalpy of uncured SSA resin was 665 J g −1 . The accelerated curing process led the liquid resin to solidify at moderate temperature upon heating, making SSA resin suitable for processing into various shapes (Table ).…”

“…Among the thermosetting resins discovered over the past few decades, the most typical species include polyimides, phthalonitrile resin, polyarylacetylene (PAA) resin, and silicon‐containing polyarylacetylene (PSA) resin . Although these existing resins have been widely used, they also have a degree of limitation for further practical application due to their high melting point and curing temperature.…”

Sustainable, fire‐resistant phthalonitrile‐based glass fiber composites

“…These viscosity data show that the system can be processed effectively at temperatures around 175–200 °C, due to the low viscosity of the resin and that the PN resin polymerization will occur at temperatures >175 °C. When compared to typical polyimide composite fabrication where resin viscosities of 10,000 to 30,000 cP are common, PN resin 1 appears more practical to process under a variety of composite processes such as resin infusion and resin transfer molding.…”

Oligomeric phthalonitriles and tetrakis(phenylethynyl)benzene blends with improved processing and thermal properties

“…For thermal characterizations and preparation of resin blends, RES was staged for 50 min ( η * = 112.7 P). Not only does this staging procedure for RES produce a prepolymer that has not gelled, but the RES prepolymer exhibits a viscosity that falls within the ideal window (100–300 P) for processing composites . Like its counterpart, a TPEB prepolymer was also formed by staging for 37 min which showed a viscosity of 16.5 P according to isothermal characterization.…”

“…Thermosetting polymers for composite structures require specific capabilities if they are to succeed as matrix materials in high‐performance applications . To be useful at elevated temperatures, a resin must be thermoxidatively stable at operating temperatures to limit the evolution of volatile compounds, while also maintaining their mechanical performance over a wide temperature regime . Given these stringent requirements, only a small subset of resin families exhibits the necessary characteristics to be viable high‐temperature materials.…”