Processing and Properties of IM7/LARC ™ -RP46 Polyimide Composites

Abstract

LARC™-RP46 resin system is a PMR type polyimide and is prepared by replacing methylenedianiline in the PMR-15 composition with 3,4′-oxydianiline. This resin system retains the same processing characteristics as PMR-15 but also offers enhanced fracture toughness. Rheological measurements were conducted on pre-imidized LARC™-RP46 moulding powder subjected to various ramp and hold temperature schemes. Adequate flow properties were found with theoretical (formulated) molecular weight 6 ≤1500 g mol−1. Critical transition temperatures for optimizing the process cycle were identified. They included the resin softening point, the imidization reaction peak, the isomerization reaction peak and the gelation point. Utilizing this information, 1.72 × 10 6 Pa (250 psi) cure cycles were designed for B-staged (dry) and unstaged (wet) prepregs. Composite laminates were fabricated which exhibited excellent consolidation and a void content below 0.1–0.2% as measured by image analysis. IM7/LARC™-RP46 exhibited higher composite mechanical properties than IM7/PMR-15. Short-beam shear strength, flexural strength and flexural modulus were measured at room temperature, 93, 150 and 177 °C. Composite engineering properties were also obtained including longitudinal tension, logitudinal compression, interlaminar shear, short block compression, open hole compression (OHC) and compression strength after impact (CAI). Excellent longitudinal tensile and compressive strengths were obtained and the CAI strength was 40% higher than that for PMR-15. Over 80% retention of all RT strengths were noted at 177 °C.

Study of the processing chemistry of polyimides with thermogravimetry/Fourier transform infrared/mass spectrometry techniques

“…On the basis of the TG/FTIR/MS and DSC information, for RP46/IM7 prepreg curing, the overall analysis seemed to suggest the following: (1) the release of methanol and water between 100 and 280°C with a peak at 138–140°C for both, indicating the loss of absorbed moisture and residual methanol as well as that from the formation of imidized prepolymer, and (2) the formation of cyclopentadiene between 200 and 400°C with a peak within 310–350°C. Thus, the prepolymerization and thermal crosslinking reaction sequence proposed by the National Aeronautics and Space Administration (NASA) LARC group11 was confirmed by this real‐time evolved‐gas analysis. They essentially followed the curing reaction paths of the AFR700B/T650‐35 prepreg.…”

Synthesis and characterization of a high temperature thermosetting polyimide oligomer derived from a non-toxic, sustainable bisaniline

“…11 Pater and co-workers studied lower toxicity PMR formulations based on 3,4 0 -oxydianiline. 12,13 However, many of these early replacements had lower T g s and thermal oxidative stability than PMR-15. To address these issues, researchers studied and patented the utilization of mixtures of non-toxic, exible, multi-ring bisanilines in combination with single ring bisanilines.…”

High Temperature Thermosets With a Low Coefficient of Thermal Expansion

“… The chemical structures of the matrix materials investigated in this work. The reaction scheme for LaRC‐RP46 was adapted from ref 6…”

“…Most material names are registered trademarks, which are not additionally denoted in the text. Three thermoset materials were selected based on their high temperature performance: Matrimide 5292 (Vantico), a two‐component bismaleimide (BMI) resin consisting of 4,4′‐bismaleimidodiphenyl methane (A) and 3,3″‐diallyl bisphenol‐A (B); AroCy XU371 (Vantico), an experimental novolac cyanate ester, catalyzed by 2 wt.‐% of a mixture of 3 wt.‐% Co(acac) 3 in nonylphenol (Arcos Chemicals); and LaRC‐RP46,6–8 a B‐staged molding powder, based on polyimide and bisnadimide chemistry. Subsequently AroCy XU371 has been discontinued, but Lonza sells a similar resin as Primaset PT30.…”