JEC COMPOSITES MAGAZINE - Issue #59 - August/September 2010 - 55

USERS’ PLATFORM
Buses & Trucks

Tougher fire-rated bus parts thanks to intumescent topcoat
Wright Composites manufactures a range of passenger vehicle FRP parts to demanding quality standards, high mechanical performance levels and stringent fire resistance specifications. To achieve all these key criteria, Wright Composites only uses Scott Bader’s Crystic® Class 1 and 2 fire retardant and HDT resin systems in combination with the Crystic® Fireguard 75PA Excel intumescent topcoat and a variety of woven and CSM reinforcements and Airex® foams.

he laminate structure of each part is designed in-house to match the needs of the application as cost effectively as possible. The Wright Composites (part of the Wright Group, located in Galgorm, Ballymena, Northern Ireland) team discovered that using Crystic Fireguard 75PA Excel enables them to produce much tougher BS 476 Class 1 fire-rated bus parts, such as electrical enclosures, interior floor sections, roof panels, engine and driver cab panels. These parts are then supplied to the sister company, Wrightbus, as well as other vehicle manufacturing customers.

minutes without the laminate behind catching fire. This is a significant period of time to contain a fire and prevent it from rapidly spreading, which can help to avoid catastrophic fire damage and save lives. The new intumescent topcoat is a product upgrade. The long-established Crystic 75PA has been reformulated by Scott Bader’s R&D team (Fig. 1). The new “Excel” version offers better fire

Passive fire protective barrier
When applied to a cured FRP laminate surface, an intumescent topcoat such as Crystic Fireguard 75PA Excel provides a passive barrier to block the path of a fire. Fire protection is ensured by its unique chemistry and its reaction when exposed to a direct flame. In simple terms, when fire attacks the intumescent topcoat, it causes a chemical reaction which makes the topcoat expand to form a nonflammable protective layer that insulates the surface over which it has been applied. While it will not protect indefinitely from an unchecked fire, the topcoat can withstand a direct flame at a temperature of 700°C for over 60

retardant (FR) properties and significant handling improvements, yet is still cured with a standard MEKP catalyst (2% addition by weight). The original Crystic 75PA has been specified for over 30 years in critical internal applications which need to meet BS 476 Part 6 Class 0 or BS 476 Part 7 Class 1 FR test standards. It has been used for interior parts in buildings, rail and other public transport vehicles, as well as in the marine sector where it is used to protect the engine compartments of both pleasure craft and working boats. The most recent successful new applications, now with Crystic Fireguard 75PA Excel, have been produced by Wright Composites for a range of different Wrightbus parts which can go up to 10 sq. metres in size.

Raising quality standards
Established since 2005, Wright Composites has developed into a significant stand-alone business with a dedicated workforce of 120 employees operating from their modern, purposebuilt 4,800 sq. m production facilities. This ISO 9001-2008 accredited company manufactures components for the Wrightbus vehicle range, currently meeting approximately 70% of the Group’s OEM passenger vehicle composites needs, as well as supplying the bus aftermarket customer base and

Fig. 1: The fire in the unprotected right side box raging after 4 minutes, clearly shows the effective fire protection barrier properties of Crystic® Fireguard 75PA Excel topcoat used in the left side box

No59 August - September 2010 / jec composites magazine

JEC COMPOSITES MAGAZINE - Issue #59 - August/September 2010

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #59 - August/September 2010