Introduction
Phenolic Resins
Processing
Fire Performance
Rail Transportation
Costing
Offshore/Sea Vessels
Construction
Conclusions

ABSTRACT

Composites are used in many industries as an alternate to metals, wood and concrete because they provide weight reduction (high strength to weight ratio), low maintenance costs, easier installation and easier fabrication (part consolidation).

The most commonly used thermoset resins for composites are unsaturated polyesters, vinyl esters and epoxies. Although these resins perform well, they may not be the ideal product to use for certain applications. These include passenger rail cars, sea vessels, offshore platforms, aircraft, construction and mining, where a fire can result in devastating damage and loss of life.

In a fire, composites will burn, with most of them emitting high levels of heat, smoke and toxic fumes, which prevent quick egress. An alternate thermoset resin, Phenolic, which is inherently fire retardant without the use of fillers, halogens or additives, can produce Fire Hard composites with excellent Fire / Smoke / Smoke Toxicity properties.

This paper will review the increasing use of Phenolics in recent years as the processability and properties of Phenolic composites are continually improved.
 
 

INTRODUCTION

Although still not as prevalently used as in Europe, the use of Phenolics in the US has significantly increased in the last 10 years.

A new generation of low viscosity Phenolic resins which can be processed via common techniques such as Hand Lay-up, Spray-up, RTM, SCRIMP, Filament winding, Pultrusion and Press molding have made Phenolics the logical choice to achieve the benefits of composites, without sacrificing fire safety.

The recent development of a Phenolic compatible polyester gel coat eliminates any finishing concerns, thus further reducing any barriers to the extensive use of Phenolics.
 
 

PHENOLIC RESINS

Phenolic resole resins used for the manufacture of composites are water soluble and thermosetting. Resoles are prepared by the reaction of phenol and formaldehyde under alkaline conditions, with an excess of formaldehyde, to produce a water based polymer capable of cross-linking (condensation reaction) or curing merely with the addition of heat. Acid catalysts are used to increase the cure rate and lower the cure temperature.

Various acid catalysts are available that provide a pot life ranging from 5 minutes to 5 hours. Resins of varying viscosity and thixotropy are available, to accommodate the process.

(See Table 1)

PROCESSING

The Processing of Phenolics is very similar to polyester with some notable differences:

• PVA or other water-soluble release agents should not be used.
• Aluminum or soft steel tooling or equipment should be avoided because of the acid catalysts being used.
• Catalyzed resins can cure at 25° C but need to be postcured on or off the mold at 60 to 80° C for 2 to 3 hours.
• A Surface Paste is available, that provides a smooth, porosity free surface that is ready for painting.
• The handling and ventilation methods used for polyesters are adequate for working with Phenolic resins and acid catalysts.
• Modified polyester gelcoats that are compatible with Phenolic are processed just like standard gel coats.

FIRE PERFORMANCE

When fully cured, the high cross-link density of the matrix formed provides an exceptional level of fire performance and high temperature resistance. Phenolic composites are rated for over 200° C continuos service. They will not burn readily and if they do burn, they will provide very low flame spread and emit very low smoke levels and toxic fumes. These factors make Phenolic the product of choice in areas where public safety is important, allowing more time to escape in a fire.

Fire test data are provided in Table 2.
 
 

RAIL TRANSPORTATION

Phenolic is ideal for use in bus and rail transportation applications, especially for those that travel in tunnels. In most European countries, where fire/smoke requirements are very stringent, Phenolic is the only composite that will meet specifications. In the US, polyester is still used extensively. Table 3 illustrates the current US rail car requirements compared to what Phenolic can provide.

The Federal Railroad Administration (FRA) and Volpe Transportation Center are sponsoring a multi-phase fire research program, whereby the use of ASTM 1354 Cone Calorimeter data is being considered as an alternate to ASTM E 162 (Flame Spread) and

E 662 (Smoke Density). This is because the Cone Heat Release Rate (HRR) data can be used to provide computer modeling information to assess the performance of composites in a fire. Table 4 provides Cone Calorimeter data for Phenolic. The HRR data is much better than what can be achieved with polyester.

The fact that Phenolics do not require the use of fillers such as ATH for fire retardation, means that the strength to weight ratio remains high. This is demonstrated in Table 5, comparing the mechanical properties of Phenolic composites with Polyester and metals.

Some examples of Phenolic use in rail cars are the DFW Airport People Movers built in 1984. Following the Kings Cross station fire in London Underground, Phenolic has been required and used since 1985. Other examples include London’s new Heathrow Airport express trains, making use of Phenolic for interior and exterior panels.

The interior panels on the new BART C-cars in San Francisco are hand laid Phenolic, built by Texstar. As a result of an extensive fire risk assessment (following a fire at BART) run by Professor Brady Williamson of the University of California, Berkeley, Fire/Smoke requirements exclude the use of polyester or vinyl ester. The interior panels on VIA RAIL in Canada are Phenolic. The Chunnel Tunnel train locomotive and club car panels are Phenolic. A more recent project was the fabrication of 32 airport express Tilt trains in Norway, built using the SCRIMP process, licensed by Hardcore DuPont.

Hand laid trash bins produced by Fiberglas Engineering & Design have been used on Amtrak trains for several years. Milwaukee Composites Inc. produces flooring for trains and buses, using the RTM process and meeting the ASTM E 119 requirement, to replace plymetal (plywood with a metal skin). A weight reduction of almost 50% is achieved.
 
 

COSTING

Although there may be a 10-15% price penalty in producing Phenolic composites compared to Polyester, one must consider the added advantage of weight reduction.

An unfilled Phenolic composite (no fillers required) with 35-40% fiberglass would have a Specific Gravity of 1.4 – 1.5 g/ml. A comparable filled polyester composite (filler required to provide fire retardance) would have a Specific Gravity of 1.8 – 1.9 g/ml. This is a weight savings of about 20%, which would result in considerable life cycle fuel savings, more than offsetting the possible initial higher cost.
 
 

OFFSHORE / SEA VESSELS

Filament wound pressure pipe, produced by Ameron, using proprietary polysiloxane technology, which meets UKOOA jet-fire testing requirements, is used for deluge systems on offshore platforms. Pultruded grating is also extensively used. The corrosion resistance of Phenolic, especially against salt water and hot chlorinated solvents is the reason why Phenolic has replaced Furan in the manufacture of tank linings, thermal oxidizers and scrubbers, produced by Industrial Pipe & Plastics.

In Europe, Phenolic is used extensively in Cruise Ships, High Speed Ferry Boats and military craft. Low maintenance costs and design flexibility in manufacture, while meeting stringent International Maritime Organization (IMO) and Safety Of Life At Sea (SOLAS) requirements allows the increasing use of Phenolics in the Marine market. In the US, consoles produced by Advanced Materials Inc. have been used on Ferry Boats for Pequot River Shipworks. Programs involving the US Coast Guard are underway to possibly increase the use of Phenolic composites in US ships and Ferry Boats.

CONSTRUCTION

Design flexibility and the ability to manufacture complex parts in a one-shot process is very cost effective. The high temperature resistance and fire properties of Phenolic, have made it the ideal material to use for the production of several balsa wood cored domes at the new Law School of Quinnipiac College. The fabricator, New England Boatworks also refurbished the Clock Tower at City Hall in New York City, using Phenolic.

Specially developed Phenolic resins are used by Alderley Materials Ltd of the UK, to produce Contratherm, a reinforced syntactic foam that has the thermal advantages of Phenolic, is low density (about 28 lb/ft³), tough, ambient curable and has a friability (weight loss) of less than 1%.

Phenolic ducting is the ideal product for use in the mining industry. Another fast growing market is Factory Mutual approved ducting for use in Clean Rooms in the semiconductor industry, as produced by Composites USA.

CONCLUSIONS

In summary, it has been demonstrated that where fire, smoke and smoke toxicity are critical parameters, Phenolic is the material of choice for the fabrication of composite parts.

Products in service since 1984, demonstrate that Phenolic composites can retain performance levels over extended time periods as well as other materials being used in the passenger rail car, sea vessel, offshore, construction and mining industries. With the development of easily processable Phenolic resin and finishing systems, the use of Phenolic should dramatically increase in the new Millenium.
 
 

References:
1.    Grigoriou, T. ‘Phenolic Composites: The Use Of Fire Safe Materials’, Composites in Fire Conference, University of Newcastle, 1999

2.    Brown, D. ‘Glass Reinforced Phenolic Mouldings in railway Rolling Stock – A Specifier’s View’, 18^th International BPF Composites Congress, 1992

3.    Brown, D. ‘The Impact of Composites on railway Rolling Stock’, Composites in the Rail Industry Conference, 1997

4.    Seitz, G. ‘GRP Plays Central Role in Innovative Railway Concept’, reinforced Plastics, May 1997.
 
 

Aram Mekjian is President of Mektech Composites Inc. He is the exclusive Distributor (in North America) of Cellobond Phenolic Resins (now owned by Borden Chemical Inc.), which he introduced to the US market in 1990 as Business Manager for BP Chemicals. Prior to that, Aram was the Technical Director and Product Manager for Aristech Polyesters for 13 years. He received a BS in Chemistry from Valdosta State College, a MS in Chemistry and MBA in Marketing from Fairleigh Dickinson University.

Table 1 – Selection of Standard Cellobond Resin/Catalyst by Process

Process	Resin	Catalyst
Hand lay-up	J2018L, J2027L or J2042L (Thixed)	P10, P381 or P382
Spray-up	J2042L or J2018L	P15, P381 or P382
Warm Press Moulding	J2018L or J2033L	P10, P15, P381 or P382
Resin Transfer Moulding	J2027L or J2033L	P15, P381 or P382
Pultrusion	J20/1256L or J2041L	None
SCRIMP or Vacuum Bag	J2027L	P381 or P382
Continuous Panel	J2027L	P10, P381 or P382