JEC COMPOSITES MAGAZINE - Issue #48 - May 2009 - 45

Application The positive properties of benzoxazine have long been known but their practical application was hampered by their long curing times and high curing temperatures. We have now succeeded in adapting the curing time and temperature to the current requirements of the aerospace industry, with an onset of the reaction occurring around 100°C (Fig. 2). The aerospace industry uses two main processes to manufacture interior parts. In classical composite processes, the component curing temperatures range from 120 to 140°C, whereas in the second process, known as the crushed core process, curing temperatures of 155°C are used. In the classical processes, the curing time is about 45 to 90 min. This cycle is used for pressing flat sandwich panels, producing components in a vacuum bag and curing parts in an autoclave. Typical components are air ducts, galleys and bins. The crushed core cycle is an isothermal press process for complex sandwich structures. Here, the curing cycle is at most 15 min at 155°C and is typically used for the production of sidewall panels and ceiling panels (Fig. 3). Due to its modified curing behaviour, PB1000 can be used in both classical and crushed core processes, and component manufacturers do not have to change their current tooling or curing process. Due to the good compatibility of benzoxazine with other thermosets and its chemical similarity to phenolic resins, it can be used with all common Fig. 3: "A320 enhanced" sidewall panel made ancillary products such as of PB1000 prepreg. paints, adhesives and potting compounds. PB1000 also features lower shrinkage than conventional phenolic resins and, as no condensation occurs, lower processing pressures can be used to provide significantly improved component surface quality without cavities or foam accumulation. The current phenolic prepreg technology produces many pinholes and other surface defects that require costly rework. Such additional processing can account for more than 50% of the total cost of interior aerospace components. The use of the PB1000 can therefore significantly reduce the manufacturing costs of complex components. The fire properties of PB1000 meet the highest requirements for modern aerospace interior components. Many of these fire safety requirements are based on the excellent fire properties of phenolic resins and can only be met by much more expensive More information PB1000 modified benzoxazine Low-cost material No VOC release during cure Excellent flame retardant properties Low water adsorption / moisture pick-up Excellent mechanical properties (modulus) Near-zero resin shrinkage Storage stability at room temperature Compatible with various thermosetting resins materials such as PEEK or cyanates. In addition to these excellent fire properties, PB1000 has significantly higher mechanical properties than today’s phenolic prepregs. This enables the design engineer to save additional weight by reducing the amount of material in a component (Table). Table: Properties of PB1000 prepreg compared with an aerospace phenolic prepreg. Typical mechanical values (US7781 fabric / 40% resin) Standard Flexural strength Flexural modulus Interlaminar Shear strength Climbing drum Peel strength RT 80°C RT 80°C RT 80°C RT ISO 178 ISO 178 AITM 1.0019 EN 2243-3 PB1000 Aerospace Phenolic Unit 470 320 19 16 20 16 90 MPa GPa MPa N/75 mm Values 700 550 25 22 35 28 110 The PB1000 resin formulation fully meets the requirements of the Airbus AP2091 standard. Therefore, the user has a long-term certainty that the material will not be restricted by any statutory regulations such as REACH and that cost-intensive health and safety extraction equipment will not be required for processing. Due to the excellent mechanical and fire properties, the low cost and the low toxicological impact of its formulation, PB1000 is also suitable for other applications in mass transport vehicles, more particularly in the railway sector. This unique material performance combined with a competitive price level makes PB1000 an advantageous choice for aircraft interior applications and any other interior application in mass transport vehicles. PB1000 is clearly capable of replacing the established phenolic systems. Contact: axel.braun@gurit.com More information: www.gurit.com No48 May 2009 / jec composites magazine 45

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JEC COMPOSITES MAGAZINE - Issue #48 - May 2009

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