kanerva's occupational dermatology || plastic composites

56 Plastic Composites1 2 1 3

T. Rusteme

DOI 10.100

Kyllikki Tarvainen . Tuula Estlander . Pirkko Pfaffli . Katri Suuronen1Helsinki, Finland2Terveystalo Healthcare Oyj, Helsinki, Finland3Occupational medicine, Finnish Institute of Occupational Health, Helsinki, Finland

Core Messages

● Plastic composites are combinations of a polymer

matrix and a solid reinforcement material.

● Thermosetting and thermoplastic resins are used as

matrices of plastic composites.

● Epoxy resins are the most common thermosetting

resins in modern plastic composites.

● Dermatitis is a common occupational complaint in

this industrial area.

● Skin hazards include irritant and allergic contact der-

matoses and contact urticaria, as well as thermal or

chemical burns.

● Epoxy resin compounds are the most common

cause of allergic contact dermatitis from plastic

composites.

● Man-made mineral fibers (MMMF) used for rein-

forcement are the main cause of irritant contact der-

matitis in the manufacture of composite products.

● The development of occupational dermatitis depends

on the materials (resins, reinforcements, and auxiliary

substances), specific work tasks, working methods,

workplace environment, and personal protection.

1 Introduction

Composites are combinations of two or more materials

that are not dissolved or melted together. Plastic compos-

ites (PC) are manufactured by combining materials, at

least one of which is plastic. In practice, they are combi-

nations of a polymer matrix and a solid reinforcement

(either plastic or another) material. A PC product may

have a sandwich structure, having the matrix and the

reinforcement material in layers, or it may be a mixture

of un-oriented or oriented fibers or particles dispersed in

thematrix. The purpose of the reinforcement is to increase

the strength of the final product, while the matrix binds

the fibers and protects them from corrosion, oxidation

and from other degrading factors arising from the

environment.

yer, P. Elsner, S.M. John & H.I. Maibach (eds.), Kanerva’s Occupat

7/978-3-642-02035-3_56, # Springer-Verlag Berlin Heidelberg 20

The PCmatrices are either thermosetting resins, which

are cured from a liquid state, or thermoplastics, which are

processed through a melt-freeze cycle. Seventy percent of

modern reinforced plastics contain thermosetting resins

(> Table 56.1), while the use of thermoplastics, especially

polyethylene, polypropylene, and polyamides as the

matrix resin is increasing. Nonplastic reinforcement mate-

rials include glass fiber, other man-made mineral fibers

(MMMF), metal particles, stone, cement, and silica; nat-

ural fibers are increasingly used in the manufacture of

wood PCs (Ashori 2008). In dental composites, fine glass

particles or silica are usually embedded in an acrylic poly-

mer (Kanerva et al. 1989). The term composite also

includes semifinished products called prepregs, which are

reinforcing materials preimpregnated with resins.

The commercial PC industry began with glass-fiber-

reinforced boats in the 1940s. Since then, PC products have

increasingly been manufactured for the electrical, marine,

aircraft, and aerospace industries. Thanks to their versatil-

ity, PCs are useful in construction, in the manufacture of

corrosion-resistant equipment and in transport, as well as

in a wide range of consumer goods, such as caravan bodies,

pipes, bath tubes, roof panels, skis, racquets, and other

sports equipment. Composite materials, especially

advanced PCs, offer a number of advantages compared to

other materials, the main advantages being their excellent

strength and lightness. Reinforced PCs are also finding

a place in corrosion repair, particularly in the gas and oil

industry, thanks to their good corrosion resistance. Thus,

due to the above-mentioned properties and their versatil-

ity, PCs are nowadays used in nearly all industrial areas.

People working in the manufacture and processing of

PCs are exposed to matrix resins, resin precursors,

reinforcing materials, such as glass fiber dust, plastic addi-

tives, and auxiliary chemicals used for assembling or

finishing the products, as well as chemicals for cleaning

purposes. Many of these compounds are skin sensitizers or

have irritating potential (Midtgard and Knudsen 1994;

Tarvainen and Kanerva 1999). Dermatoses from the man-

ufacture of PCs have been reported since their production

ional Dermatology,

12

. Table 56.1

Polymers used in reinforced plastics composites

Thermosetting resins Thermoplastic resins

Polyester resins Polyphenylene sulfides (PPS)

Epoxy resins Polyetheretherketones (PEEK)

Vinyl ester resins Polyether sulfones (PES)

Phenol-formaldehyde

resins

Polyvinyl chloride (PVC)

Polyurethanes Polypropylene (PP), polyethylene (PE)

Polyimides Polyamide

622 56 Plastic Composites

was started (Bourne andMilner 1963;Malten and Zielhuis

1964; Wehle 1966).

2 Plastic Composite Industry

The PC product industry is diverse and employs a wide

variety of processing methods and materials. An enor-

mous number of combinations can be made, depending

on the design and cost of the final product. The manufac-

turer has the possibility to combine resin compounds,

reinforcements, and various additives when making PCs,

or to use preassembled material, such as prepregs, pro-

duced by specialist suppliers. The principal manufacturing

process includes the molding of reinforcements and the

matrix resin into the desired shape. Before the molding,

resins are formulated bymixing themwith solvents, curing

agents, accelerators, fillers, mold releasers, dyes, fire retar-

dants, and other additives needed for the desired proper-

ties. The cured composite pieces or ready products usually

require finishing by sawing, drilling, sanding, or cutting

with diamond-coated tools, lasers, or abrasive water jets

(Rolston 1980; Bruze and Almgren 1989). During

finishing operations, workers may be exposed to paints,

coatings, glues, and various solvents, such as trichloroeth-

ylene, turpentine, methylene chloride, acetone, and tolu-

ene, as well as to woods, wood preservatives, and dust

from the machining of the hardened product (Brigham

and Landrigan 1985; Tarvainen and Kanerva 2000).

3 Fabrication of Plastic Composites

Contact molding, also called hand lay-up lamination, is

the most commonly used open process method. Reinforce-

ments and resins are laid down manually, using a roller, or

sprayed over the mold in successive layers. In addition to

wet hand lay-up methods, dry hand lay-up (prepregs) can

also be used. Boats, caravan bodies, andmany small articles

are usually manufactured using the hand lay-upmethod. In

the filament winding method, the reinforcements, wetted

with the resin, are wound around a rotating mandrel or

awork piece attached to a rotatingmandrel by amachine, by

robots ormanually. The filament winding process originates

from the aerospace industry, but is nowadays also used to

manufacture pipes, tanks, and various poles. In the injection

method, the products are made by feeding the matrix resin

or resin-reinforced mix into a closed mold using

a vacuum. In pressure molding, the resin is cast by means

of pressure between heated matched male/female molds;

these are the most widely used processes for large-scale

production of composites, including domestic articles, cab-

inets, containers, and cab panels. The pultrusion method is

a continuous process in which resin-impregnated fibers

are drawn through a heated die, where the resin cures. The

process is used in the production of structural elements,

such as pipes and spade handles. Other molding methods

include resin transfer molding,which is used to make small

composite parts, such as boxes, seats, and benches, and

reaction molding, which utilizes fast-reacting components.

Themethods of manufacturing PCs have been reviewed by

Ehrenstein and Kabelka (2007).

While manual processes increase the risk of skin contact

with harmful materials, pultrusion, centrifugal casting, resin

transfer, compression molding, vacuum-bag molding, and

prepregs are partly or totally automated working methods,

where skin exposure is more easily avoided (Kelly 1994;

Tarvainen and Kanerva 1999). However, even then the

introduction of the resin into the mold may be done man-

ually. Even in highly automated industries, workers may

performmanual operations during assemblyor repair work.

4 Matrices

4.1 Thermosetting Resins

The most widely used polymers in composite matrices are

the thermosetting resins: unsaturated polyesters, epoxies,

epoxy vinyl esters, phenolic resins, and polyurethane

resins (Ilschner et al. 2007). More information on these

resins can be found in other chapters of this book.

Unsaturated polyester resin (UPR, >Chap. 54, ‘‘Poly-

ester Resins’’) has been used extensively in the glass-fiber-

reinforced plastics industry manufacturing products for

transportation, construction, and marine applications.

UPR is also used for coatings, finishes, lacquers, putties

(Tarvainen et al. 1993b), and glues (Boenig 1964). Nowa-

days, in addition to boat building, there is a dynamic

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market for unsaturated polyester resins in wind turbine

industries, where UPRs are used to produce rotor blades,

engine housings, and gel coats in combination with epoxy

resins and epoxy vinyl resins.

Polyesters are available in two different forms: satu-

rated and unsaturated. UPRs are produced through ester-

ification of organic acids or their anhydrides, e.g., maleic

anhydride, phthalic anhydride (PA), or fumaric acid, with

diols, e.g., diethylene glycol or 1,2-propylene glycol. The

term ‘‘unsaturated’’ means that there are reactive double

bonds within the resin that are able to form cross-links

between the polymer chains. When a UP resin is

manufactured, 10–50% styrene is added; the styrene serves

both as a viscosity-reducing solvent and as a reactive

monomer in cross-linking the linear polyester chains. In

addition to styrene, vinyl toluene, methyl methacrylate, or

diallyl phthalate can be used. Accelerators, such as cobalt

naphthenate, cobalt octoate or tertiary amines such as

dimethyl aniline, are necessary for the curing of plastic at

room temperature. Hydroquinone is added to prevent

premature cross-linking. Other additives include pig-

ments, fillers, inhibitors, and light stabilizers. Halogenated

monomers have been used as flame retardants in UPRs,

and a new ‘‘flame-retardant polyester resin’’ with

a copolymerized high concentration of phosphorus and

fillers has also been developed. Polymerization of the UPR

occurs after adding a polymer initiator, such as benzoyl

peroxide or methyl ethyl ketone (MEK) peroxide.

Epoxy resin systems (>Chap. 51, ‘‘Epoxy Resins’’) are

used especially in the manufacture of composites for

sporting goods, boats, automobile, and transport indus-

tries, as well as for military, aerospace, and power produc-

tion applications; for example, wind turbine systems and

the aircraft industry commonly utilize epoxy composites

(Ponten et al. 2004; Rasmussen et al. 2005). Epoxy resins

are also used in the electrical industry, in the manufacture

of circuit boards and covers for components (Isaksson and

Bruze 2000; Kanerva et al. 1996). The epoxy resins used in

the composites are commonly based on diglycidylether of

bisphenol-A (DGEBA) epoxy resin or diglycidylether of

bisphenol-F (DGEBF) epoxy resin, while other glycidyl

derivatives, such as tetraglycidyl-4-40-methylendianiline

(TGMDA) and triglycidyl-p-aminophenol (TGPAP),

have been used in special PCs. The most important hard-

eners of epoxy resins are the aromatic amines, including

xylylene diamine and 4,40-methylene dianiline, and ali-

phatic amines such as triethylenetetramine (TETA) and

diethylenetriamine (DETA). Carboxylic acid anhydrides,

e.g., hexahydrophthalic anhydride (HHPA) and methylte-

trahydrophthalic anhydride (MTHPA) are used as latent

hardeners in some epoxy resin PCs; in such products, the

latent hardener activates only at elevated temperatures,

and therefore heat is needed to cure them. The resins in

prepreg PCs are most often epoxy compounds. The epoxy

prepregs may contain DGEBA or DGEBF epoxy resin and

diglycidyl ether of tetrabromo-bisphenol A (brominated

DGEBA-epoxy resin); however, due to difficulties with

their adherence to carbon or graphite fibers, the non-

DGEBA epoxy resins 4-glycidyloxy-N,N-diglycidylaniline,

TGMDA, TGPAP, and o-diglycidyl phthalate are often

used (Kanerva et al. 2000). The most common fiber rein-

forcements are glass, graphite, and aramide (aromatic poly-

amide) fibers, whereas the particulatemicrocomposites and

novel nanocomposites are usually reinforced with small

silica or calcium carbonate particles.

Epoxy vinyl ester resins are used in products that are

highly resistant to chemicals and corrosion. The epoxy

vinyl ester resins (sometimes referred to as ‘‘vinyl esters

resins’’) are alsomore resistant to moisture than, for exam-

ple, standard UPRs. For this reason their use in boat build-

ing has increased. Epoxy vinyl esters are epoxy di(meth)

acrylates (b-hydroxyester (meth)acrylates), which are

obtained by reacting liquid DGEBA-epoxy resin or other

epoxy resins with (meth)acrylic acid and diluted with

styrene to 35–40% solvent by weight. Epoxy vinyl esters

can be polymerized by electron beams, ultraviolet light,

and by peroxides. The same cross-linker (styrene), hard-

eners (peroxides), and accelerators (cobalt) as for UPR, are

used (Rolston 1980; Kanerva et al. 1989). Dental composite

resins (>Chap. 143, ‘‘Occupational Contact Dermatitis in

Dental Personnel’’) based on DGEBA-epoxy resin mono-

mers and methacrylates or acrylates, e.g., BIS-GMA or

BIS-GA, have been used since 1962 (Bowen 1962). In

addition to the acrylic binders, dental composites contain

inorganic reinforcements (also referred to as fillers), such

as small glass particles or silica, and additives. The addi-

tives include (1) hardeners such as benzoyl peroxide,

(2) activators such as tertiary aromatic amines, and

(3) inhibitors such as hydroquinone.

Phenol-formaldehyde resins (PF resins, >Chap. 52,

‘‘Contact Allergy to Phenol-Formaldehyde Resins’’) are

polycondensation products of phenols and aldehydes, in

particular, phenol, and formaldehyde. Phenol-

formaldehyde resins are divided into resols that are self-

curing in elevated temperatures and novolacs that require

additional curing agents. PF resins have many industrial

applications. Glues based on PF are used in the plywood

industry, the building industry, and in boat building and also

in aircraft construction. PF resins are also used as matrices

for glass or mineral fibers in the production of various

insulatingmaterials and as binders of sand in foundry casting

molds. PF resins are modified by fillers, e.g., minerals,

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graphite, cellulose, or wood particles, when needed

(Zimerson 2006). PF resins are also used in prepregs with

glass or carbon fiber reinforcements and processed by

various automatic methods in the aircraft industry.

Polyurethane resins (PUR) are reaction products of di-

or polyisocyanates and polyols (>Chap. 53, ‘‘Polyure-

thane Resins’’). PURs are available in many forms. In

addition to coatings, adhesives, and rigid and flexible

foams, PURs are used also in advanced composite pro-

cesses, such as pultrusion and filament winding. Many

additives, such as fire retardants, fillers, coloring agents,

and blowing agents, are needed. Urethane acrylates are

used in dental composite and sealant applications and

have the same role as BIS-GMA.

4.2 Thermoplastic Resins

The complete lists of applicable thermoplastics is exten-

sive, and includes polypropylene (PP), polyethylene (PE),

polystyrenes, polysulfones and polyvinyl chloride (PVC),

acrylonitrile-butadiene-styrenes (ABS), acetals, acrylics,

fluoropolymers, polyacrylsulfone, polycarbonates, ther-

moplastic polyesters, polyether ketone, polyether sulfones,

and poly(phenylene sulfides).

Thermoplastics currently account for a relatively small

proportion of the PC industry. They are solids and usually

appear as pellets that are melted by applying heat and

subsequently cast by application of pressure into the fin-

ished part. PP and PE are the most common thermoplastic

resins in PCs. Chopped glass, carbon, aramid or metal

fibers are usually used as reinforcements. For example, PP

is used in the manufacture of packaging equipment and in

plastic parts or fibers in the automotive and electrical

industries. One of the most important applications is the

glass-mat-thermoplastic, which is a thermoplastic laminate

molded with a continuous glass-fiber-reinforced sheet and

used in advanced aerospace industry applications and for

the production of structural profiles and pipes (Bjorkner

2006). Polypropylene and polyethylene have been used for

the manufacture of plastic boats in small series since the

1970s. Rotation molding and thermo-molding are the

methods used in manufacturing thermoplastic boats.

5 Additives in Synthetic Polymers

Additives are used to modify the properties of plastics

materials. Nearly 2,500 individual chemicals or mixtures

are used as additives in polymer formulations, including

synthetic polymers, biopolymers, composites, and

biocomposites. Plastic additives are classified into three

main groups: (1) additives that stabilize plastics against

degradations involve antioxidants, light and heat stabilizers,

(2) additives that affect the process include lubricants, mold

release agents, and blowing agents, and (3) additives that

impart new desirable qualities to plastics; these include

flame retardants, fillers, dyes, pigments, antistatic agents,

optical brighteners, and plasticizers. The concentration of

additives varies greatly, from a few parts per million (ppm)

to more than 50%. Plastics generally contain many addi-

tives, which either form an inherent part of the composite

itself or are employed in a somewhat external manner.

Resins commonly already contain additives when purchased

from the manufacturers. Fillers and auxiliary substances are

mixed with the resins at the workplace to improve its work-

ability and the properties of the final product (IPCS 1997,

Stepeck and Daoust 1983). Depending on the resin, addi-

tives may have different ways of functioning: for example,

flame retardants can either bond covalently with the poly-

mer molecules or be mixed into polymers (> Table 56.2).

An additive may also have many functions: it can, for

example, act as an antioxidant and stabilizer in the

uncured resins, or as a flame retardant in the finished

product. reviewed by Wolf and Kaul (2007).

5.1 Plasticizers

A plasticizer is a substance incorporated into a material to

increase its flexibility or workability. Approximately 450

plasticizers are commercially available. The most com-

monly used are esters of carboxylic acids, phthalates,

phosphates, adipates, and trimellitates. Other plasticizers

are chlorinated paraffins, epoxidized vegetable oils, and

adipate polymers. The principal use of plasticizers is in

thermoplastic resins, and 80–85% of the world’s produc-

tion of plasticizers is used in PVC manufacturing. There

are about 100 phthalates, but 14–15 are most frequently

used (> Table 56.3). Adipates and other aliphatic diesters

are used in low-temperature applications, while

trimellitates are used for high-temperature applications.

Methyl-, ethyl-, and butyl phthalates are more often used

as solvents than as plasticizers in the plastics industry.

5.2 Fillers

When used in composite laminates, inorganic fillers may

account for 40–65% of the composition. Calcium carbon-

ate, kaolin (hydrous aluminum silicate), alumina

trihydrate, and calcium sulfate can be used to improve

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. Table 56.2

Examples of flame retardants used in plastics (halogen compounds and organophosphates with a synergetic compound)

Commercial names of plastics Flame retardant

Low-density polyethylene (LDPE) Chlorinated paraffin with antimony trioxide (Sb2O3) as a synergic compound

LDPE, cross-linked Brominated aromatic compounds

High-density polyethylene (HDEP) Brominated aromatic compound

Polyolefins Cycloparaffins, hexabromobenzene, tetrabromophthalic anhydride

Polypropylene Tetrabromobisphenol A, bis(2,3-dibromopropyl ether) with Sb2O3

Unsaturated polyester Chlorine- and bromine-containing organic compounds with Sb2O3 or Al(OH)3, chlorendic

anhydride, or chlorendic acid

Epoxy resin Tetrabromobisphenol A, tetrabromodienes alone or with organophosphates

Polyamides Brominated aromatic or cycloaliphatic compounds with Sb2O3, melamine

Polycarbonates Tetrabromobisphenol A, brominated organic oligomers, sulfonate salts

Expandable polystyrene Hexabromocyclododecane

High-impact polystyrene (HIPS) Decabromodiphenyl ether, tetrabromobisphenol A with Sb2O3

Acrylonitrile-butadiene-styrene Octabromodiphenyl ether, SB2O3, peroxides, brominated compounds

PVC Chlorinated paraffin, phosphate ester with Sb2O3 or Al(OH)3

Polyurethane foams Organophospates, brominated organic compounds with Al(OH)3

Polyurethanes Polyols with a halogen, organophosphates, organophosphates with a halogen

Vinyl ester resin Tetrabromobisphenol A, tetrabromodienes, organophosphates

Data from: (Stepeck and Daoust 1983), IPCS (1997) (International Programme on Chemical Safety) World Health Organization. Environmental

Health Criteria, Geneva 1997, 133p.

. Table 56.3

The most commonly used phthalate plasticizers

Diethylhexyl phthalate (DEHP) also called dioctyl phthalate

(DOP)

Butyl benzyl phthalate (BBP)

Diisononyl phthalate (DINP)

Diisodecyl phthalate (DIDP)

Methyl-, ethyl-, butyl phthalate

Dialkyl (C6 C11) phthalate

Diethylhexyl adipate


mechanical properties. Fillers are used mostly in the man-

ufacture of thermoplasts, such as PVC. Today,

nanoparticles of variousmaterials can also be used as fillers

(Saarela et al. 2007)

5.3 Flame Retardants

Polymer materials are often flammable and thus require

flame retardants, which may be inorganic compounds,

halogenated organic compounds, organophosphorus

compounds, or other organic substances. About 10% of

all plastics (chiefly PVC, ABS, polystyrene, unsaturated

polyesters, polypropylene, polyethylene, and polyure-

thanes) contain flame retardants (> Table 56.2). Chlorine-

and bromine-containing aliphatic, cycloaliphatic, and aro-

matic compounds are the most widely used. Others are

antimony trioxide, aluminum hydrate, and chloroparaffins.

A more fire-resistant epoxy resin can be produced by

bromating bisphenol A in epoxy resins to form tetrabromo-

bisphenol A.

5.4 Stabilizers

Special heat stabilizers are required for processing PVC.

There are several kinds of stabilizers on the market.

The most important of these contain lead, tin, calcium

and zinc, or barium and zinc. Metal-free stabilizers are

used in conjunction with metal-containing stabilizers.

The principal epoxy stabilizers are epoxidized plant

oils, chiefly soybean oil. Epoxidized oils and esters

are also used. Diphenyltiourea is used as a heat stabilizer

in PVC.


5.5 Antioxidants

Antioxidants prevent the autoxidation of polymers

and minimize associated damage, e.g., discoloration. Exam-

ples of antioxidants are alkylated phenols and polyphenols

(e.g., butylated hydroxytoluene (BHT) and 4-tertiary-bytyl-

cathechol) and epoxidized soybean oil. Bisphenol A is used

as an antioxidant in polyvinyl chloride plastics and corro-

sion-resistant unsaturated polyester resins.

5.6 UV-Light Absorbers

Radiation from the sun or fluorescent light degrades most

plastics. Light stabilizers are mainly employed in plastics

for outdoor services, e.g., garden furniture and automo-

tive parts. The most widely used UV light absorbers

belong to the following chemical classes: (1) benzophe-

nones, (2) benzotriazoles, (3) salicylates, (4) acrylates,

(5) organo-nickel derivates, (6) hindered amines, and

(7) metal complexes with dialkyldithiocarbamate. The

most common are 2-hydroxybenzophenones, 2-hydrocy-

phenyl-benzotriazoles, and 2-cyanodiphenylacrylate

(Bjorkner 2006).

5.7 Biocides

Biocides are usually added to plastic products used in

environments with high temperature and humidity, such

as saunas and boats, since micro-organisms can cause

discoloration and cracks in plastic materials. Especially

PVC, polyurethane, silicon products, and fiber products

based on polypropylene and polyamide are easily attacked

by microorganisms. The most commonly used biocides

are methyl- and octyl isothiazolinones and oxybisphe-

noxarsine (Bjorkner 2006).

5.8 Colorants (Dyes and Pigments)

Dyes and pigments are chosen from a wide range of

organic and inorganic compounds. Inorganic pigments

are insoluble in plastics, and due to the resulting stability,

they are usually preferred. The most common inorganic

pigments include titanium dioxide, zinc, iron oxide,

chromium oxide green, lead chromate, and cadmium

pigments. Organic pigments, although not as common,

may be used either as such or in combinations with

inorganic pigments. The chemical classes are numerous

and include azo, phtalocyanide, and metal complex

compounds.

5.9 Initiators

Polymer initiators must be used for starting the curing of

UPRs and acrylic polymers. The curing agents are

discussed under the heading Thermosetting resins and

elsewhere in this book.

6 Reinforcements

Glass fibers, carbon fibers, and aramid fibers account for

the majority of reinforcements found in PCs (Ehrenstein

and Kabelka 2007). In the large-scale production of cer-

tain consumer products, hybrid composites are used, in

which glass fibers are mixed with carbon or aramid fibers.

The concentration of reinforcements in the composites

ranges from less than 10% to over 80% by weight (Rolston

1980). Almost any inorganic fibers can be incorporated

into a composite. Natural fibers such as cotton, jute,

hemp, paper, and silk have been studied as reinforcements.

However, the major problem is their susceptibility to

fungal and insect attack and to degradation by moisture.

Synthetic fibers, cellulosics, polyamides, polyvinyls, poly-

acrylonitrile, polyethylene, and polyesters have also found

uses in composites.

Glass fibers belong to a group of inorganic man-made

mineral fibers (MMMF). The main component in glass is

silicon dioxide. The glass is usually in the form of contin-

uous or chopped fibers in PCs (Tarvainen et al. 1994).

The glass fibers are coated (sized) with chemicals to facil-

itate their binding to roving or to the matrix: they may be

coated, for example, with polyvinyl polyacetate, chro-

mium chloride, polyvinyl acetate, polyester silane, or

epoxy silanes. Organic chromium compounds are used

for coupling, and solid or liquid epoxies, polyesters, and

polyvinyl acetate are useful for film forming. The lubri-

cants and emulsifiers used in glass fibers are usually water-

soluble oils or other mixtures containing surface-active

agents (Rolston 1980).

Graphite and carbon fibers are generally prepared by

the thermal decomposition of three fibrous organic

precursors: polyacrylonitrile (PAN), rayon (cellulose),

or pitch. The primary advantages of graphite over glass

fibers are, among other things, its higher modulus

and lower density. Graphite fibers are available in var-

ious forms: continuous, chopped, woven fabric, or

mat. Hybrid fabrics with glass or aramid fibers are

available. The carbon fibers usually intended for rein-

forcement are spun into rows and prepared for pre-

pregs by impregnation with resins (Midtgard and

Knudsen 1994).


Aramid fiber is a common name for aromatic polyam-

ide fibers, which are fire-resistant and strong synthetic

fibers. The fibers are produced as continuous filaments,

and they are used primarily in high-temperature engineer-

ing thermoplastics, such as polyamides, polybutylene,

terephthalate, and polycarbonate. Application areas

include marine, aerospace, and military equipment.

Prepregs are materials that have been impregnated

with a partially cured polymer matrix. Glass, carbon,

graphite, and aramid fibers, in woven, roving, or in unidi-

rectional tape form, are combinedwith specially formulated

pre-catalyzed resin systems. Prepregs are provided as rolls,

tapes, or precut squares, rectangles, and as laminates, and

are used to produce composites that are faster and cleaner

to apply than wet lay-up systems. Covered by a flexible

backing paper, prepregs can easily be handled, molded, or

laminated into the desired shape. Hardening of prepreg

laminates is usually achieved by heating at elevated temper-

atures under pressure or by autoclave in accordance with

the manufacturer’s specification, resulting in activation of

the curing system (Stewart 2009). Thermosetting prepregs

are most often used in the aircraft industry, in the manu-

facture of boats, rotor blades, windmill parts, and various

sporting and leisure goods. Thermoplastic resins, such as

polypropylene and polyamides, are also used in prepregs.

The working methods are the same as those used for

thermosetting resin prepregs.

In addition to continuous fibers, other types of rein-

forcements are also used. These include particulate mate-

rials, such as graphite and glass in powder form, as well as

silica and clay. The use of nanomaterials in PCs will,

without doubt, increase in the future.

. Table 56.4

Prevalence of occupational dermatoses in the plastic composit

Product Methods Number of workers P

Aircraft Clinical 30

Hat rack Clinical 50


Ski poles Clinical 101

Printed circuit boards Clinical 79

Boats, pipes Clinical 89

Skis Clinical 22


Boats Questionnaire 151

Boats, tanks Questionnaire 148

Wind turbines Clinical 603

aCalculated from figures in the publications (Data from Tarvainen and Kan

7 Dermatoses from PlasticComposites

In the PC industry, skin hazards include the following

contact dermatoses: ACD, irritant contact dermatitis

(ICD), and contact urticaria. The skin symptoms of

occupational dermatitis usually appear on the hands,

but also on other open skin areas, such as the wrists,

flexures, face, legs, and ankles, which are exposed to

workplace dusts and fumes. A finished PC product only

occasionally causes contact allergy. Epidemiological stud-

ies have been conducted in the aircraft and boat building

industries, in a factory manufacturing various glass-fiber-

reinforced plastics, and in the manufacture of hat racks,

ski poles, skis, and printed circuit boards (> Table 56.4)

(Tarvainen and Kanerva 2000). Most of the reported

dermatoses in PC manufacture have been case reports;

these, together with the causes, are listed in >Tables 56.5

and > 56.6.

8 Allergic Contact Dermatitis

8.1 Epoxy Resins

Currently, epoxy resin compounds are the most common

cause of ACD from PCs. The clinical picture of allergic

epoxy dermatitis from composites may vary. Most cases

of ACD caused by epoxy resin have been reported

regarding DGEBA epoxy resins (see >Chap. 51, ‘‘Epoxy

Resins’’). Epoxy resin hardeners, such as diethylene-

triamine (DETA) and triethylenetetramine (TETA),

e industry

revalence of dermatoses (%)a References

6 Malten (1956)

25 Malten and Zielhuis (1964)

5 Bord and Castellain (1967)

15 Suhonen (1983)

22 Bruze and Almgren (1989)

26 Tarvainen et al. (1993b)

26 Jolanki et al. (1996)

16 Bruze et al. (1996)

25.6 Ruttenberg et al. (2001)

58,8 Minamoto et al. (2002)

62.4 Rasmussen et al. (2005)

erva 2000)

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http://dx.doi.org/10.1007/978-3-642-02035-3_51

. Table 56.5

Causes of occupational allergic contact dermatitis and con-

tact urticaria from plastic composite manufacture

Product Cause Dermatitis

Aircraft DGEBA ER ACD

ER amine hardener ACD

Non-DGEBA epoxy resin ACD

UP resin ACD

Chromium (VI) ACD

Cyclohexanol peroxide ACD

Boat UP resin ACD

Cobalt ACD

Phenol formaldehyde resin ACD

Natural rubber latex CU

Ski and ski poles DGEBA ER ACD, CU

ER amine hardener ACD, CU

MTHPA CU

Polyester resin CU

Cobalt ACD

Tennis rackets ER IPDA hardener ACD

TV cabinets UP dust ACD

Rubber gloves ACD

MEK peroxide ACD

Various DGEBA ACD

UP resin ACD

Dental

composites

Methacrylates ACD

Wind turbines DGEBF ACD

Data from: Tarvainen and Kanerva (1999)

ACD allergic contact dermatitis, CU contact urticaria, DGEBA

diglycidylether of bisphenol-A, DGEBF diglycidylether of bisphenol-F,

UP unsaturated polyester, IPDA isophoronediamine, ER epoxy resin,

MEK methylethyl ketone

. Table 56.6

Causes of irritant occupational contact dermatoses from

plastic composite manufacture

Product Cause

Aircraft Glass fiber

Mold releasers

Prepregs

Boats UP resin

Glass fiber

Styrene

Prepregs Methylene dianiline

Glass fiber

Skis and skipoles Glass fiber dust

DGEBA ER

Data from: Tarvainen and Kanerva (1999)

DGEBA diglycidylether of bisphenol-A, UP unsaturated polyester, ER

epoxy resin


ethylenediamine, isophoronediamine (IPDA) (Lachapelle

et al. 1978), or hexavalent chromate in an epoxy resin

hardener, have also been reported to cause ACD. In the

manufacture of carbon-fiber-reinforced composites,

workers have been sensitized to non-DGEBA epoxy resins,

including tetraglycidyl-4-40-methylendianiline (TGMDA),

triglycidyl-p-aminophenol (TGPAP), and 4-glycidyloxy-

N,N-diglycidylaniline (Burrows et al. 1984; Mathias

1987; Lembo et al. 1989; Tarvainen et al. 1995; Jolanki

et al. 1996). Not only workers manufacturing PC products

but also cleaners have had delayed allergic reactions to

a DGEBA epoxy resin used in ski poles (Suhonen 1983).

Six workers exposed to epoxy resin in a ski factory

showed allergic reactions to the standard DGEBA epoxy

resin as well as to a DGEBA epoxy resin used in the ski

factory (Jolanki et al. 1996). Three of the workers reacted

to reactive diluents (diethylene glycol diglycidyl ether

DEGDGE) (> Fig. 56.1), phenyl glycidyl ether (PGE),

and 1,4-butanediol diglycidyl ether (BDDGE). In

a cross-sectional study of four facilities producing wind

turbine systems in Denmark, clinically diagnosed derma-

titis was found in 35.8% of 724 production workers; 61%

were allergic to epoxy compounds and 37.9% to hardeners

(Rasmussen et al. 2005). Epoxy resin compounds in pre-

pregs are reported to cause ACD in workers in aircraft

factories. In addition to ACD affecting the hands, patients

also had airborne symptoms on the face when working in

roomwhere epoxy chemicals were handled (Kanerva et al.

2000).

Epoxy resins have been reported to cause skin sensiti-

zation more frequently than unsaturated polyester resins

during simultaneous exposure to both resins. They are

also suspected to be a concomitant factor in unsaturated

polyester allergy (Wehle 1966).

8.2 Epoxy Vinyl Ester Resins

No cases of allergic or irritant contact dermatitis or con-

tact urticaria caused by epoxy vinyl ester resins in indus-

trial PCs have been reported. Sensitization from epoxy


(meth)acrylates (BIS-GMA) has been reported in dental

personnel (Aalto-Korte et al. 2003), and in connection

with the use of the ultraviolet (UV) curing inks and

anaerobic glues (Kanerva et al. 1989). Glycidyl methacry-

late has been reported to cause a severe chemical burn after

an accidental spill (Shimizu et al. 2008).

8.3 Unsaturated Polyester Resin

ACD caused by PCs were first reported in connection

with unsaturated polyester resins by Lieber (1955),

followed by Malten and Zielhuis (1964), who described

five patients with contact eczema and positive patch

tests to unsaturated polyester resins in a group of

30 workers in an airplane factory. ACD has been reported

in connection with a limb prosthesis made from unsatu-

rated polyester resin (Vincenzi et al. 1991). Cases of

ACD caused by unsaturated polyester resin in lamination

work, UV-light-cured inks, unsaturated polyester dust

from reinforced plastic products, and automobile-repair

putty have also been reported (Tarvainen et al. 1993a).

The small number of cases of ACD in the reinforced

plastics industry is probably due to the low sensitizing

capacity of unsaturated polyester resin (>Chap. 54,

‘‘Polyester Resins’’) (Bourne and Milner 1963; Tarvainen

et al. 1993a, b; Tarvainen et al. 1995). The allergens in

unsaturated polyester resins are often the auxiliary

chemicals in the resin, such as cobalt naphthenate or

cobalt octoate, phthalates, tricresyl phosphate, peroxide

hardeners, or cross-linking monomers. Para-tertiary-

butyl catechol used in the manufacture of styrene has

caused contact allergy followed by vitiligo in workers in

the PC industry (Bourne and Milner 1963; Malten and

Zielhuis 1964; Horio et al. 1977).

O

CH2 CH2 CH2CH O

. Fig. 56.1

Ethylene glycol diglycidyl ether (Quetol 651, n = 1) and diethy

CH2 CH2 CHHO O C

O

. Fig. 56.2

Diethyleneglycol maleate (DGM)

The starting materials or intermediate substances in

resin production, such as free or terminal maleic, fumaric,

or adipic acids and their anhydrides, have also caused

ACD (Minamoto et al. 2002). A macromolecule

containing maleic ester, polyester methacrylate, or

diethylene glycol maleate (DGM) (> Fig. 56.2) has also

been reported as a cause of sensitization (Tarvainen et al.

1993a; Liden et al. 1984).

8.4 Polyurethane Resins

Fully cured polyurethane products do not generally cause

dermatitis, but there are circumstances where skin prob-

lems can arise. Monomeric di-isocyanate may remain

inside the product as a result of the slow curing process.

Release of free isocyanate may then occur during heating,

cutting, and sanding. Exposure to di-isocyanates may

cause allergic or irritant dermatitis or urticaria. The

main occupational hazards from polyurethanes are the

di-isocyanates, which are well-known for their ability to

cause rhinitis, asthma, and conjunctivitis (Estlander et al.

1992).

8.5 Phenol-Formaldehyde Resins

PF resins can cause chemical burns, irritant and allergic

contact dermatoses, contact urticaria, and depigmentation.

Residual raw materials and the intermediates and oligo-

mers used in the formation of the resin have been reported

as causative agents (>Chap. 52, ‘‘Contact Allergy to Phe-

nol-Formaldehyde Resins’’). ACD is possible, especially

when handling fresh resins, for example, when cellulose

or other prepregs are impregnated with phenol-

O

CH2 CH2 CH2CHOn

leneglycol diglycidyl ether (DEGDGE, n = 2)

CH2 CH2 OHCH OC

O

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http://dx.doi.org/10.1007/978-3-642-02035-3_52

http://dx.doi.org/10.1007/978-3-642-02035-3_52

http://dx.doi.org/10.1007/978-3-642-02035-3_52


formaldehyde resin or melamine-formaldehyde resin.

Concomitant ACD caused both by phenol formaldehyde

resins and melamine formaldehyde resins has been

reported (Isaksson et al. 1999).

8.6 Polyethylene and Polypropylene

Cases of irritant and ACD caused by polyethylene and

polypropylene are rare. Contact dermatitis may be caused

by plastic additives such as catalysts and initiators. Heat,

sawing, and other forming may cause degradation of the

plastic and therefore release reactive chemicals into the air.

Thus, airborne dermatitis is also possible in such opera-

tions (Bjorkner 2006).

8.7 Additives

ACD is reported in connection with various plastic addi-

tives (Bjorkner 2006), mostly in UPR and epoxy resins.

Several allergic agents have been identified, althoughmany

of them are used only infrequently. Cases of ACD caused

by dibutyl phthalate in a plastic watch strap, diethyl

phthalate in spectacle frames, dimethyl phthalate in com-

puter mice, and o-diglycidyl phthalate in aircraft produc-

tion have been reported (Bjorkner 2006). ACD has also

been found to be caused by bisphenol A in PVC gloves

(Aalto-Korte et al. 2003).

8.8 Man-Made Mineral Fibers

ACD from glass fibers has been caused by sizing chemicals

in MMMF production, such as epoxy resin of amine-

functional methoxysilane (Sertoli et al. 2000) The risk of

sensitization by contact with glass fibers is mainly due to

professional exposure to the resins used for the finishing

of glass fibers. ACD is reported in those who are in contact

with uncured sizing resins, in particular epoxy and form-

aldehyde resins (Sertoli et al. 2000). Aramid fibers are not

sensitizing.

9 Irritant Contact Dermatitis

Fiber reinforcements are the main cause of irritant contact

dermatitis, both in the manufacture of PCs and in the

finished products (> Table 56.6). Workers exposed to

MMMF most frequently suffer itching without dermatitis,

or rapidly healing papules and vesicles. Secondary lesions

from scratching may lead to bacterial infections. Most

workers will develop tolerance to MMMF itch within a few

weeks of continuous exposure. However, not all workers

become tolerant, and they may need to be transferred to

another job. Of 28 patients who had been diagnosed with

occupational dermatitis and had to change jobs, 21 patients

were found to have irritant contact dermatitis caused by

MMMFs (Sertoli et al. 2000; Tarvainen and Kanerva

2000). In addition, glass fibers in a school desk have

caused irritant contact dermatitis (Eby and Jetton 1972).

The health hazards of carbon fiber handling are due to

mechanical irritation and abrasion similar to that caused

by glass fibers. Carbon fibers are easily broken by

stretching, and the fibers can easily produce a fine dust

during cutting. The particle size of the carbon fiber dust in

the machining of PCs is considered to be too large to

damage the respiratory system. Uncontrolled micro fibers

have a potential to adhere to human skin or mucous

membranes, causing irritation. Aramid fibers irritate the

skin only in special situations. Rubbing of the fiber causes

scaling into small, thin fibers which irritate the skin and

may be inhaled deep into the respiratory organism

(Saarela et al. 2007).

Although DGEBA epoxy resins are not strong irritants,

cases of irritant contact dermatitis caused by DGEBA

epoxy resins have been reported (Jolanki et al. 1996).

Latent epoxy resin hardeners, namely, the carboxylic acid

anhydrides may cause severe chemical burns when heated.

On the sweating skin, anhydrides are hydrolyzed to the

corresponding acids and may cause caustic dermatitis and

burns (Jolanki et al. 2000). The hardener MTHPA has

been reported to induce redness and hives on the skin

(Kalimo et al. 1990). The irritant properties of unsaturated

polyester resins and epoxy vinyl ester resins are most likely

due to cross-linking styrene, or previously to

diallyphthalate. Styrene is classified as a mild irritant, but

repeated skin contact with styrene causes drying of the

skin and may give rise to primary irritation, blisters, or

even chemical burns (Bruze and Fregert 1994). However,

skin resorption experiments with liquid styrene (Berode

et al. 1985) have not caused skin symptoms in human

volunteers. At levels of 50 ppm (215 mg/m), styrene

vapor may irritate the conjunctivae and nasal mucous

membranes. Some mold-releasing agents irritate the

skin. For example, a patient packing thin composite

bundles made of carbon fibers and DGEBA also used

a mold-releasing agent containing 3% (wt./vol.) alkyl

orthophosphate. The patient’s hand dermatitis was

located at the contact site of the bundles. Standard patch

tests and the patient’s own chemicals were negative, while


according to the material data sheet, alkyl orthophosphate

is a caustic chemical (Tarvainen et al. 1995).

Organic peroxides used as a 3–10% solution to initiate

the curing reaction of unsaturated polyester, epoxy vinyl

ester, and acrylic resins, have caused irritant dermatitis

and blisters in workers in the PC industry (Bourne and

Milner 1963). Reactive peroxide molecules in unhardened

resin dust may cause stinging of uncovered skin areas

during spray lamination. Acetone is used to clean equip-

ment in the unsaturated polyester- and vinyl-ester-resin

industries. On repeated contact, acetone defats the skin

and has been reported to be a contributing factor for

irritant dermatitis in the PC industry.

10 Contact Urticaria

Occupational allergic contact urticaria refers to the

IgE-mediated, type I immediate contact reactions caused

by exposure to substances in the work environment. Most

cases of contact urticaria in PC manufacture have been

caused by the natural rubber latex (NRL) proteins in

protective rubber gloves. There are only a few reports of

contact urticaria caused by the epoxy resin compounds

used for PCs, including DGEBA epoxy resin and

a polyamine hardener. On the other hand, IgE-mediated

allergy and contact urticaria to carboxylic acid anhydrides

(MTHPA,MHHPA and phthalic anhydride) in heat-cured

epoxy resins and the starting materials of unsaturated

polyester resin are reported more often, and they some-

times present in connection with generalized urticaria

and/or upper respiratory symptoms. The processes have

included lamination work, and the use of prepregs and

sealants (Helaskoski et al. 2009; Tarvainen et al. 1995).

Immediate allergy has been verified by an open skin test

with 100% MHHPA and by positive skin scratch tests and

radioallergosorbent tests (RASTs) using a human serum

albumin (HSA)-conjugated test substance as the allergen

(Helaskoski et al. 2009).

In a recent report, workers who experienced contact

urticaria from acid anhydrides were working near the area

for the curing of plastics, or mixing resin and hardener,

cleaning the curing oven, repairing the curing area, or

welding painted pipes. The principal route of exposure

to acid anhydride was direct contact, or in a few cases

airborne exposure. Airborne concentrations caused more

widespread urticaria than direct skin contact. While IgE-

mediated allergy to carboxylic acid anhydrides has been

shown in many patients, it seems that allergic respiratory

diseases, such as asthma and rhinitis, are more common

than urticaria (Helaskoski et al. 2009).

11 Other Skin and Health Hazards

The use of machining equipment is associated with a risk

of mechanical injuries, such as cuts or abrasions. Some

processes operate at high temperatures and involve

a danger of severe burns. A risk of fire and explosion is

inherent to the nature of the raw materials used in indus-

try. Styrene, acetone, and peroxides form flammable and

explosive concentrations at normal room temperature.

Certain chemical combinations are particularly hazard-

ous, such as the mixture of organic peroxides and cobalt

accelerators (Brigham and Landrigan 1985).

The health hazards in PC operations include respira-

tory hazards from exposure to toxic monomers, curing

agents, solvents, dust, and fumes from thermal degrada-

tion products. Vapors of monomers and solvents are

released into the ambient air during repair operations

and during the curing of the resins. Solvent exposure is

highest during degreasing and cleaning procedures and

when using styrene-containing polyester resins (Midtgard

and Knudsen 1994). Carboxylic acid anhydrides can cause

IgE-mediated rhinitis and asthma. DGEBA epoxy resin

has been considered to be responsible for IgE-mediated

asthma. During open lamination, workers are exposed to

styrene vapor (Eriksson and Wiklund 2004). The most

common health problem related to styrene exposure is its

neurotoxicity, resulting in symptoms of solvent encepha-

lopathy. Symptoms include depression, concentration and

memory problems, muscle weakness, fatigue, unsteadi-

ness, and nausea. Exposure to styrene may also irritate

the nose, throat, and eyes. Dermal absorption of styrene

fumes has been shown to be low in humans compared with

inhalation exposure (Riihimaki and Pfaffli 1978).

12 Diagnosis of Allergic ContactDermatitis Caused by PlasticComposites

The cause of ACD in the handling of PC should be verified

by patch tests. In the reported cases, standard patch-test

trays have been used together with special epoxy resin test

substances, other plastic chemicals, and chemicals from

workplaces (Burrows et al. 1984; Mathias 1987; Lembo

et al. 1989; Tarvainen et al. 1995; Jolanki et al. 1996). Safety

data sheets (SDS) or product declarations on the

chemicals are essential in choosing the correct patch test

substances and concentrations. Care should be taken to

prevent active sensitization through patch testing with test

concentrations that are too high. The risk of active sensi-

tization should be borne in mind, especially in testing


prepregs, which are solid material and cannot be diluted.

Prepregs may contain 10–25% by weight of uncured resin.

Patch tests with samples cut from epoxy prepreg should

only be performed on individuals already suspected on

a clinical basis to be allergic (Mathias 1987).

Immediate allergy can be examined by skin-prick tests,

scratch tests, or use tests, and determination of specific IgE

antibodies in the patient’s serum. Low-molecular-weight

chemicals can be conjugated with HSA (Howe et al. 1983)

before they are used in skin-prick tests or RASTexamina-

tions (Cesca and Lundgvist 1972).

Chemical analyses may be needed for the identifica-

tion of new allergens and in order to find the allergens

responsible for the patient’s reactions to PC materials.

These analyses may require liquid or gas chromatography

coupled with spectroscopic methods, and they are often

carried out in specialized laboratories. Thin-layer chroma-

tography (TLC) can also be used in the separation of resin

allergens, e.g., in unsaturated polyester resin and

phenolformaldehyde resins (Tarvainen et al. 1993b)

Up-to-date knowledge about commercial raw mate-

rials, devices (equipment), and accessories can be found

on the web sites of the companies and communities

concerned. This knowledge may help both in the investi-

gation of the causes of occupational disorders and in

planning workplaces and working methods.

13 Prevention of OccupationalDermatitis

Irritant dermatitis and skin trauma often predispose indi-

viduals to ACD. In the PC industry, skin-irritating sol-

vents, resins, and glass fibers predispose the skin to

sensitization to resins, especially to epoxy resins. Exposure

to epoxy chemicals may be low and of short duration

before the appearance of dermatitis. Uncured chemicals

on the surface of prepregs can easily cause sensitization

(Estlander et al. 1992). Workers feeling only a slight tack-

iness of resin may not protect themselves sufficiently com-

pared to the protection they would use during the

handling of epoxy resin in its liquid form (Mathias 1987;

Lembo et al. 1989; Tarvainen et al. 1995).

Even very small amounts of allergen can evoke derma-

titis in previously sensitized subjects; this is also encoun-

tered in PC workers (Tarvainen et al. 1995). Thus, careful

avoidance of any contacts with the allergens is needed in

order to prevent skin manifestations. A small amount of

the allergen in dust or in a finished product is sometimes

enough to maintain or restore dermatitis, and in such

cases, the sensitized person may have to change to another

job. Discontinuing work with epoxy chemicals immedi-

ately after the diagnosis of contact allergy may also be

beneficial in preventing respiratory problems. Dermatitis

due to epoxy resin compounds is more severe when the

exposure time to the causative agent has been long

(Jolanki et al. 1996).

The use of protective gloves is essential in avoiding

exposure to PC materials. Protective gloves are helpful in

preventing dermatitis due to chemicals and glass fibers as

well as mechanical, thermal, or chemical injuries or burns.

Furthermore, workers who use gloves wash their hands

less frequently, thus avoiding the drying effect of frequent

hand washing (Tarvainen et al. 1993b). Chemical protec-

tive gloves suitable also for solvent work are often needed;

general recommendations for the use of appropriate

gloves are available in textbooks and from the glove sup-

pliers. Rubber gloves do not necessarily offer enough pro-

tection against the solvents used in the PC industry and

may cause sensitization to NRL or to rubber chemicals

(>Chapter 65, ‘‘Rubber’’). However, cotton under-gloves

may prevent sensitization to NRL or to the rubber

chemicals in protective gloves.

Incomplete protection has frequently been the cause of

occupational PC dermatitis. Workers have been sensitized

through epoxy resin splashes, uncured resin compounds

in composite waste materials or through vapors, despite

the use of protective gloves (Jolanki et al. 1996).

Good working practices and workplace hygiene are

necessary, along with well-organized general and local

ventilation, and automatic or closed processes should be

used. These measures are important in the prevention of

occupational dermatoses as well as respiratory and cen-

tral nervous system symptoms. Workers should be aware

of the best working techniques and the risks associated

with the chemicals being handled. Workers need to be

educated regarding the potential hazards when handling

PCs and auxiliary chemicals, and they should be taught

to use ‘‘no-touch’’ techniques when working with these

materials, whether liquid or prepregs (Isaksson and

Bruze 2000). Good skin care with emollients and rapid

treatment of skin injuries also reduces the risk of allergic

dermatitis.

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