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.

Get full access to this article

View all access options for this article.

References

[1] Serafini T T , Delvigs P and Lightsey G R 1972

Thermally stable polyimides from solutions of monomeric reactants

J. Appl. Polym. Sci. 16 905–915

[2] Delvigs P, Serafini T T and Lightsey G R 1972 Addition-type polyimides from solutions of monomeric reactants NASA TN D-6877

[3] Serafini T T and Vannucci R D 1975 Tailor making high performance graphite fiber reinforced PMR polyimides Reinforced Plast./compo. Instit., 30th Anniv. Confer., Reinforced Plastics - Milestone 30 (Proc. Soc. of the Plastics Indus.) sect. 14-E pp 1–5

[4] Vannucci R D 1977

Effect of processing parameters on autoclaved PMR polyimide composites

Proc. National SAMPE Tech. Conf. 9 177–199

[5] Pater R H 1981 SAMPE J. 17 (6) 17–25

[6] Pater R H and Morgan M D 1988 SAMPE J. 24 (5) 25–32

[7] 1986 Current Intelligence Bulletin 47 (NIOSA) 25 July

[8] Hoyle N D et al 1990 Proc. 22nd Int. SAMPE Tech. Conf. 22 198–212

[9] Baggett R B , Gupta H K and Kantz M R 1990 Proc. 35th Int. SAMPE Tech. Conf. 35 1555–1565

10.

[10] Scola D A 1990 Proc. High Temple Workshop (Cocoa Beach, FL, 29 January–1 February)

11.

[11] Pater R H 1991 Proc. 36th Int. SAMPE Symp. and Exhibition p 78–78

12.

[12] Johnston N J , Srinivasan K and Pater R H 1992 Proc. 37th SAMPE Symp. and Exhibition pp 690–704

13.

[13] Hay J N , Boyle J D , James P G , Walton J R , Konarski M and Wilson D 1989 High Perform. Polym. 1 145–145

14.

[14] Preston P N , Soutar I , Woodfine B and Hay J N 1989

Investigation of the curing mechanism in PMR polyimide resin

High Perform. Polym. 1 161–175

15.

[15] Wilkinson S P , Marchello J M , Dixon D and Johnston N H 1993 A new NASA LARC multi-purpose prepregging unit Proc. 38th SAMPE Int. Symp. and Exhibition pp 1–15

16.

[16] Wilkinson S P , Machello J M and Johnston N J 1993

Composite material impregnation unit

NASA Technical Memorandum TM-107751

17.

[17] SP Systems, Inc 1993 private communication

18.

[18] Rohr Industries, Inc 1993 private communication

19.

[19] Hou T H , Johnston N J and St Clair T L 1994 Polymer 35 4956–4956