Phenolic Applications

The Society of the Plastics Industry, Inc. * the phenolic division

FALL 1997

The Phenolic Advantage

This issue of Phenolic Applications is the second in a continuing series of reports on the use of phenolics. The field of thermoset plastics has evolved considerably from the early 1900s when Dr. Leo Baekeland discovered that a hard, infusible polymer made from phenol-formaldehyde could lend itself to hundreds of applications. With phenolics' excellent properties, products made with phenolic resins are increasingly being developed, manufactured, and distributed throughout North America and the world. This report outlines the development of phenolic resins from phenol through its use in industrial and consumer products. As a result of continual modification and improvement, new applications for phenolic resins are continually being found.

Phenol and formaldehyde are among the most basic building blocks in polymer chemistry. The condensation reaction may be initiated by a number of alkali or acidic catalysts, resulting in a polymer. This polymer, in conjunction with various organic and inorganic reinforcing systems, offers a variety of unique properties and characteristics. The polymer acts as a matrix for binding together a number of substrates such as wood; paper; fibers (e.g., fiberglass); or particles (e.g., wood flour, foundry sand) to form a highly crossed-linked composite.

ATTRIBUTES OF
PHENOLIC-BASED PRODUCTS

* Dimensional stability at elevated temperatures

* Creep resistant

* Excellent fire performance

* Cost effective

* Outstanding durability

* Excellent strength-to-weight ratio

* Excellent thermal insulation properties

* Excellent sound-damping properties

* Corrosion resistant

* Water resistant

CONTENTS

From phenol to Phenolic Resins 2

End Uses and Applications 3

Commercial Information 5

Phenolic Molding Compounds 6

Transportation Application: Locomotive of the Chunnel Train (Le Shuttle)From phenol to Phenolic Resins

Phenol (C6H5OH) is a reactive organic chemical used in a variety of chemical products vital to the economy of the world. Phenolic resins are one such class of compounds that take advantage of these reactive properties.

Phenol, the key raw material in phenolic resins, was originally isolated from coal tar streams. Advances in technology have now allowed phenol to be produced almost entirely by synthesis. The dominant process used today is the oxidation of cumene (a product of benzene and propylene reaction) and the subsequent cleavage of cumene hydroperoxide, which forms phenol and acetone.

Phenol has a melting point of 42.5°C to 43.0°C. Below that point, it is a hygroscopic crystalline mass, which is white in color. (Impurities cause a color shift to pinkish to red.) In its molten state, phenol is a colorless, mobile liquid that will darken on exposure to light. It exhibits a strong, persistent, sweet odor.

Phenol is reacted in various ways with aldehydes to form what are commonly known as phenolic resins. Other aromatic hydrocarbons used in these reactions include cresols, xylenols, and substituted phenols. The aldehydes are usually formaldehyde, paraformaldehyde, and furfural.

Resins that are produced by employing an alkaline catalyst and that are reacted with sufficient formaldehyde to completely cure are referred to as single-stage resins or resole resins. Resins that are produced by employing an acid catalyst and that are reacted with insufficient formaldehyde to completely cure are referred to as two-stage resins or novolac resins. The two-stage resins require the addition of another material to provide the proper mole ratio of phenol-to-aldehyde to completely cure. Hexamethylenetetramine (hexa) is usually the curing agent added to the novolac resins.

The characteristics of these intermediate products are engineered to satisfy a wide array of processing and finished product requirements. When cured, the resins are transformed from the fusible, thermoplastic state to a densely, cross-linked thermoset matrix. Methylene bridges join the phenol molecules in three dimensions. The resulting structure provides a number of advantages over other materials. The strong, rigid polymers that are produced have superior resistance to a wide range of chemicals; high heat resistance; and excellent flame, smoke, and toxicity properties. They satisfy critical requirements for diverse applications in a cost-effective manner.

Phenolic Applications

End Uses and Applications For Phenolic Resins

Molding Compounds

Phenolic resin, reinforcements, and curing agents are blended and processed together to form phenolic molding compounds. When subjected to molding pressure and temperatures of 300°F or higher, products made by curing the molding compounds will retain their original dimensions and strength values. The engineering properties of phenolics such as heat resistance, dimensional stability, and electrical resistance make them the product of choice in applications ranging from appliance parts and electrical devices to automotive parts such as drive pulleys.

Wood Products

The wood industry uses phenolic resins extensively. They are used as binders in the manufacture of hardboard, plywood, particle board, and oriented strandboard. These products are the forerunners of the more advanced composites in which both the resin and the
reinforcements have become more sophisticated.

Fiberglass-Reinforced Plastics (FRP)

Recently developed low viscosity phenolic resins can be processed via commonly used techniques such as hand lay-up; spray-up; filament winding; resin transfer molding (RTM); SCRIMP (Seemann Composite Resin Infusion Molding Process); pultrusion; and press molding to produce composites with excellent strength-to-weight ratios.

Advanced Composites (PFRP)

In the field of advanced composites, phenolic fiberglass-reinforced plastic (PFRP) has remarkable fire performance (flammability, smoke generation, and smoke toxicity). The aerospace industry uses it as a material of construction because of its ablative properties. In addition, the transportation industry uses phenolic resins in vehicle panels and seats due to increasing concerns about the safety of both drivers and passengers.

Other Applications

Phenolic resins are used in several other applications, e.g., as a binder, adhesive, or bonding agent. A large volume is used in insulation. The building industry uses phenolic resins in roofing and walls (fiberglass), and the industrial market uses phenolic resins in pipe insulation (fiberglass and/or mineral wool).

Laminates

In the laminate industry, kraft paper is saturated with phenolic resin, then cured at high temperature and pressure. Several layers of the cured, resin-impregnated papers are pressed together to form decorative laminates used in, for example, kitchen countertops and vertical panel applications.

Foundry Molds

Phenolics are used in the foundry industry to produce resin-bonded sand molds and sand cores. The automotive industry is the largest single consumer of resins for these products. Phenolics are the resin of choice due to their high temperature performance properties and cost-competitive nature.

Friction Products

For the friction industry, phenolics are used as the bonding agent to manufacture brake blocks and pads, brake linings, and clutch facings. Phenolics give friction products excellent heat resistance and thermostability as well as good friction characteristics such as wear, fade, and noise reduction.

Abrasives

The abrasive market uses phenolics to bond the abrasive grains in place, so grinding wheels will have the required strength. Several different types of modified phenolics are used in parts such as cut-off wheels, snag wheels, and polishing wheels.

Products Containing Phenolics:

BUILDING & CONSTRUCTION

* Wood Products

* Roofing & Walls

* Insulative Foam

* Decorative Laminates

* Pipe Insulation

* Sealing Agents

FOUNDRY

* Sand Mold

* Sand Cores

FRICTION

* Brake Blocks & Pads

* Brake Linings

* Clutch Facings

ABRASIVE

* Cut-off Wheels

* Polishing Wheels

* Snag Wheels

* Scouring Pads

* Coated Abrasives

COMPOSITE

Aerospace

* Aircraft Cabin Liners & Flooring

* Helicopter Rotor Blades

* Radar Array Domes

Commercial/Industrial

* Corrosion-resistant pipes, scrubbers, tank liners

* Office Buildings

* Utility Pole Repair

Marine

* Ferry Boats

* Decking

* Ducting

* Wall Panels

* Cruise Ship Interiors

* Off-Shore Platforms: grating, piping

* Boat Decking

Military

* Lightweight Barracks

* Transportable Aircraft Hangars

Transportation

* Auto Panels & Seats

* Bus/Subway/Train: seat pans,
interior panels, doors, door jackets,
floor panels

COMMERCIAL INFORMATION

North American demand for phenolic resins is expected to be over 4 billion pounds by the year 2000. Although wood products will lead the way in growth, phenolics (particularly its use in applications requiring excellent fire performance) will be in strong demand in automotive, mass transit, and industrial markets.

Phenolic Molding Compounds

Phenolic resin (either the novolac or resole type) is combined with 50-60% fillers, reinforcements, pigments, and additives to produce phenolic molding compounds. Phenolic molding compounds are available in general purpose, heat resistant/electrical, impact, and glass-reinforced grades. The properties of these compounds and their associated applications follows.

The Phenolic Advantage

* High Heat Resistance

* Excellent Dimensional Stability

* Excellent Fire Performance

Applications

These properties enable phenolics to be used in household appliances, business equipment, wiring devices, automotive electrical systems, and mass transit.

The Phenolic Advantage

* Strength at High Temperatures

* Creep Resistance Under Load

* Chemical and Corrosion Resistance

Applications

The automotive industry has capitalized on these properties and used phenolics in drive pulleys, fuel rails, intake manifolds, and water pump housings. In the corrosion industry, phenolics are used for tank liners, scrubbers, ducting, and piping, especially for salt water and hot chlorinated solvents.

The Phenolic Advantage

* Excellent Electrical Resistance

* Dimensional/Thermal Stability

Applications

Commutators, switches, and wiring devices are some of the many applications in the electrical/electronic markets.

The Phenolic Advantage

* Nuclear and Electromagnetic Radiation Resistance

Applications

Phenolic products have been used in nuclear facilities for more than 30 years as a result of these attributes.

The Phenolic Advantage

* Cost-Effective

* Recyclable

Applications

Being cost-effective enables phenolic compounds to compete with aluminum, steel, other thermoset compounds, and high-heat thermoplastics in a number of applications. Phenolics have been effectively recycled for years in Europe and North America, despite the perception to the contrary.

ELECTRICAL

* Terminal Blocks

* Household Appliance Components

* Wiring Devices

* Switches

* Fuse Holders

* Distribution Systems

* Capacitors

* Motor Components

* Business Equipment Components

AUTOMOTIVE

* Drive Pulleys

* Fuel Rails

* Intake Manifolds

* Motor Housings

* Commutators

* Ashtrays

* Stators (AC)

* Brake Parts (AC)

* Solenoids

ADDITIONAL

* Wall Plates

* Bearing Seals

* Cookware Handles

* HVAC Controls

Phenolics are high-performance, cross-linked polymers that can be recycled in a number of ways. The Department of Energy's National Renewable Energy Laboratory (NREL) has recently developed technologies for the recycling of phenolics by pyrolysis. These technologies allow for the conversion of waste phenolics to the basic building blocks used in the production of the original polymer. The technologies will allow for the inclusion of a recycled content in phenolic resin products.

Publisher: The Society of the Plastics Industry, Inc. (SPI), The Phenolic Division

Division Director: Allen Weidman, The Society of the Plastics Industry, Inc.

Editor: Barbara Disckind, BBD Communications

Editorial Office: SPI, 1801 K Street, N.W., Suite 600K, Washington, D.C. 20006-1301. Phone: (202) 974-5233.
Fax: (202) 293-0005.

Copyright © 1997 by The Society of the Plastics Industry, Inc., 1801 K Street, N.W., Suite 600K, Washington, D.C.
20006-1301. All rights reserved.

Publication of any information is not an endorsement by SPI of any particular company, individual, product, or process. Any Division member may submit material for inclusion in Phenolic Applications, addressed to the attention of the Division Director. Submissions will be accepted only from members of SPI's Phenolic Business Unit and will be drawn only from publicly available material. Submissions may be edited by the newsletter staff to satisfy space limitations and cannot be returned.

SPI is not responsible for any statement, claim, opinion, or viewpoint expressed in Phenolic Applications. The content is and remains the sole responsibility of the member who submits the material for publication. Submission for publication is an acceptance of these terms, and the member agrees to hold SPI and its agents and employees harmless for any changes made. Inclusion of any materials submitted for use by SPI is at the sole discretion of SPI.

Phenolic Applications welcomes comments and suggestions from members. Contact Allen Weidman, Division Director, SPI, 1801 K Street, N.W., Suite 600K, Washington, D.C. 20006-1301, Phone: (202) 974-5233, Fax: (202) 293-0005.