Investigation of readily processable thermoplastic-toughened thermosets. III. Toughening BMIs and epoxy with a comb-shaped imide oligomer

✍ Scribed by A. Gopala; H. Wu; P. Heiden

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 120 KB
• Volume: 70
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19981031)70:5<943::aid-app15>3.0.co;2-u

✦ Synopsis

This is the third in a five-part series describing the preparation of tough, high-performance thermosets from low viscosity, autoclave-processable prepolymers. The first 2 articles described toughening of bismaleimides (BMI) and epoxy with linear imide thermoplastics of ϳ 1000 g/mol. Highly processable prepolymers were obtained, which resulted in increases in fracture toughness for BMI of ϳ 75-100%, while the fracture toughness of epoxy was increased by up to 220%. This article describes the preparation of a low-molecular-weight comb-shaped imide oligomer (ϳ 4100 g/mol) and the effect of the oligomer architecture and end-group on BMI and epoxy prepolymer viscosity and fracture toughness. When an unreactive comb-shaped oligomer was incorporated in a BMI prepolymer (10% thermoplastic loading in the thermoset), the fracture toughness increased by 67% over that of an untoughed control, while a reactive oligomer increased the fracture toughness by 150% over an untoughened control. At 55°C, the viscosity of the solution of the reactive comb-shaped imide in B was only 6.2 Pa ⅐ S. When the oligomer was dissolved in epoxy resin, the viscosity was less than 0.2 Pa ⅐ S at 90°C, and the fracture toughness increased by 110 and 133% (at ϳ 13% loading in the thermoset), relative to an untoughened control, depending on the reactivity of the end group. The T g and high-temperature modulus of BMI and epoxy remained approximately the same relative to the untoughened controls.