OAR Box 1413 

Prepped by Ollie Stewart 

Document Number: 

2) 11-1-2 

Docket Number: 

A-94-52 

Printed 7/9/2008 3:11:20 PM Sheet 2 of 114 

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A-94-52 

APPLICATIONS FOR PULTRUDED PRODUCTS 

Author 

ROBERT DILLNER 

Creative Pultrusions, Inc. 

Pleasantville Industrial Park 

Alum Bank, Pennsytvania 15521 

Pultrusion is a continuous manufacturing process utilizing glass or fibrous reinforcement in a 

polyester or other thermosetting resin matrices. Pre-selected reinforcement materials like fiberglass 

roving, mat or cloth are drawn through a resin bath where all the materials are thoroughly 

impregnated with a liquid thermosetting resin. The wet-out fibrous laminate is formed to the 

desired geometric shape and pulled into the heated steel die. Once in the die. the resin cure is 

initiated by controlling precise elevated temperatures. The laminate solidifies in the exact shape 

of the die cavity as it is being continuously pulled by the pultrusion machine. Specific strength 

characteristics can be designed into the composite optimizing laminate performance for a 

particular application by strategic placement of high performance reinforcements. Color is 

uniform throughout the cross section of the part, eliminating the need for many painting 

requirements. 

The pultrusion process produces parts with constant cross-section shapes. Many forms of 

reinforcing material (examples: rovings, continuous strand mats, woven and nonwoven fabrics, 

and a variety of surfacing veils) plus a wide selection of resin systems allow the designer versatility 

in engineering the pultruded structural composite to meet the end-use requirements in the most 

cost-effective way. Cost of the product is also minimized by low tooling cost and the low labor 

content of the pultrusion process. Because the reinforcing materials are processed in continuous 

forms, product properties are very consistent. Last, the length of the pultruded part is limited only 

by shipping considerations. 

Pultrusion is a continuous process making constant cross-section profiles. The process is designed 

to pull flexible reinforcements through a liquid resin bath into a heated die. A pultrusion process 

line is long and narrow with lengths from 40' to over 80' with the width being 5' to over 20'. The 

overall space requirement depends primarily on the size and number of the creels used to hold 

the reinforcements. 

A typical pultrusion line consists of six basic stations: 

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• Reinforcement dispensing 

%s Resin impregnation 

4 Performing 

f Heated die curing 

• Clamp/puller 

•> Cut-off. 

For reinforcement dispensing background, in the first station, continuous fiberglass roving is 

dispensed from center-pull packages that sit on shelves called creels. The roving is guided 

through porcelain eyelets that eliminate static buildup and fuzzing. The roving then passes i hrough 

a carding index that orients the fibers prior to entering the resin bath. Other reinforcements such 

as mat. veils, carbon fiber tows. etc.. are routinely used and are dispensed on the rolls. 

Resin impregnation is a reinforcement package that passes through the wet-out tank. Pan guides 

function within the resin bath to keep the roving separate and to maintain tension on the strands 

to permit the resin to wet-out each fiber. The resin bath can be of the standard dip tank design 

or the straight-through resin pan as for hollow sections or complex profiles. Pressure impregnation 

is a third method used for unique application. In this method, the resin polymerization all occurs 

inside a closed die. This-area is the main concern for VOC release in the form of fugitive styrene 

vapors. However, because of the closed die. processing/pultrusion is typically lower than spray 

up or winding processes (with the profile chops having releases of 3% to 5% and rod producers 

approaching 0.8%). 

When the reinforcement package exits the resin bath, it then passes through a series of bushings 

or forming guides that are designed to strip off excess resin and guide the uncured composite into 

the final composite shape. This is called the performing section. 

The heart of the pultrusion process is the curing die. After the resin-impregnated reinforcement 

package leaves the final pre-shaping section, it enters a heated steel die or dies that are in the 

shape of the finished composite. The dies range in length from 30 to 60 inches and are heated 

either by electric strip heaters or plates on the top and bottom of the die surfaces. The interior 

die surfaces are generally chrome plated for increased die life and improved surface finish. 

The term "pultrusion" comes from the fact that the composite is pulled through the entire process 

by a gripper/puller system. There are two different types of gripper/pull systems used, the 

reciprocating clamp design and the opposed tread caterpillar-tractor type. The former method 

utilizes two identical pullers that operate in tandem to alternately grip and continuously pull the 

profile through the process. The puller process is mainly used for mat/roving composites in which 

urethane cleats grip the part and pull it through the mold. 

The final station is the cut-off station of the pultrusion process. This station consists of a diamond 

abrasive cut-off saw. This saw is synchronized with the movement of the pullers and is activated 

by a preset cut-to-length limit switch. 

The raw materials that make up the bulk of pultruded products consist mainly of reinforcement 

and matrix. The reinforcements include glass fibers in the form of continuous roving, continuous 

strand mats, knitted and woven fabrics, tapes and cloths. More exotic reinforcements include 

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Applications for Pultruded Products 

carbon fiber, aramid. boron and several new thermoplastic fibers and veils. 

Fibers are formed from several glass compositions, the most common of which are A (alkaline), 

C (chemical), E (electrical), and S (strength). Continuous roving ofthe E-glasstype comprises the 

bulk of the reinforcement used in pultrusion. Continuous roving is a collection of filaments coated 

with a sizing that, is compatibJe with the resin system and brought together into a single strand 

called an end. 

Bulk roving is also used in pultrusion. This product form is designed to improve the transverse 

properties in localized areas of pultruded composites where mat cannot be formed. 

C-glass. A-glass and thermoplastic are some ofthe surfacing materials used in pultrusion. Polyester 

veils are the most commonly used surfacing fabrics and provide an 8- to 11-mil resin-rich barrier 

that improves corrosion resistance, reduces fiber exposure on the surface, and improves resistance 

. to UV attack. Surface veils have been processed which withstood 4,000 hours accelerated 

weathering with only a slight loss of gloss. 

The two major families of resin matrices are thermoset and thermoplastic. Today the majority of 

resin matrices used in pultrusion are thermoset. Several thermoset resin types are used in pultrusion 

with standard polyester and flame-retardant polyester resins being the most widely used. 

However, new applications and processing technologies are increasing the demands for 

vinylesters, epoxies. flame-retardant vinylesters, low shrink systems and even thermoplastic resins. 

The choice of the resin will determine the degree of corrosion resistance, the upper operating 

temperature limit, performance in fatigue applications, and to a limited degree, the mechanical 

properties of the pultruded laminate. The reinforcement primarily determines the strength and 

electrical properties ofthe pultruded laminate. Fillers may be added to improve flame retardancy 

and processability and to reduce cost. 

Pultruded composites are generally divided into two parts. One being all unidirectional roving 

parts (rod and bar stock), and two being continuous strand mat/unidirectional roving parts 

(shapes and flat sheet). Typically, all unidirectional roving parts have superior mechanical 

properties in the longitudinal direction, where glass contents range from 65% to 85% by weight. 

These values for shapes, flat sheet and rod/bar stock are taken from ASCE's Structural Plastic 

Design Manual and tell you the range of properties one might expect with fiberglass polyester 

pultrusions. 

The reinforcements in flat sheet are mat and roving. Flat sheet is commonly produced in thickness 

up to 1" and-widths up to 56". with 48" being standard. 

Pultrusions are used in a variety of markets, the first being the electrical industry. This is one of the 

largest markets for pultruded composites because of their high strength-to-weight ratio and 

excellent dielectric insulation properties. The use of pultruded side rails have almost completely 

antiquated the wooden ladder and the electrical nonconductivity of fiberglass has allowed almost 

complete replacement of the aluminum ladder by electrical utilities. The color in the ladder 

channel is molded through the laminate. Orange and yellow are safety colors and can be seen 

on almost any utility truck today. Usage of pultruded products are found in pole line hardware 

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where pultruded tubes and rods are used for tools for work on high power lines because of the 

added benefit of being electrically nonconductive. 

Also, the pultrusion process is used to manufacture structural components which will withstand 

severe corrosive environments. All fiberglass products can be considered to be corrosion resistont 

with the choice of the resin determining the degree of corrosion resistance. Grating 

manufactured with pultruded components is also the strongest fiberglass grating on the market. 

The method of construction of the pultruded shapes ensures excellent corrosion resistance. 

Bearing bars and cross rods are pultruded and fabricated into grating for many industries such as 

electroplating, water and waste, marine, offshore and others. 

Another example of the use of pultruded products for corrosion resistance is mist eliminators. 

Louver blades separate vapors and solid particles from stack emissions such as in coal burning 

utilities. Pultruded blades are replacing wood, stainless steel and thermoplastics giving an 

increased usable life. 

In the construction industry pultruded products are viable materials because of their strength, light 

weight, corrosion resistance, molded-in color and thermal and electrical insulation. For example, 

pultruded components make nonmetallic window frame and sash lineals the ultimate in 

performance. These components are quickly replacing aluminum and other competitive materials 

with a new generation of thermally efficient, dimensionally stable window frames. 

Another example for the construction industry is roof supports. Roofing systems with o four-to-one 

safety factor for wind and snow loads and the added benefit of corrosion resistance have been 

installed for pole enclosures. 

Pultrusions have long been accepted in the transportation market. Pultruded panels run the entire 

length of the Intercity Transit Bus and provide insulation and dent resistance as well as long-term 

improved appearance. Automotive Class A surface is attainable with pultruded parts. Part 

consolidation and a lock together design of two pultruded parts cut production line time by 

replacing 22 roll-formed aluminum parts. 

The pultrusion process, because of its many benefits, lends itself to a variety of other applications, 

the most popular being standard structural shapes. From 1 /8" rod to 48" wide flat sheet, pultruded 

components are stocked by manufacturers, distributors and fabricators in all major cities in the 

United States and throughout the world for corrosion, electrical and construction applications. 

In conclusion, although the pultrusion process is almost 40 years old. it is still basically in its Infancy. 

New products and processing techniques are being developed every day. Carbon and 

thermoplastic fibers and cloths provide an even wider range of properties to the pultruded 

product line for custom applications. 

New thermosetting resins and pultrudable phenolic and the work currently being done in 

thermoplastic resins offer a potential for an unlimited combination of fibers and resin matrices. The 

pultrusion industry has been growing steadily and new ideas and process development are 

making pultruded products the system of choice for many current and potential applications. 

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