acids/alkalies. Theyh ave at emperature resistance of 225 8 F/108 8 Cd ry;
1508 F/668 Cw et.
These resins are quite expensive.
8.2.8P olyesters
In the coating industry,p olyesters are characterized by resins based on
components that introduce unsaturation (–Ca C–) directly into the polymer
backbone. The most common polyester resins are polymerizationp roducts
of maleic or isophthalic anhydride or their acids. In producing paint,
the polyester resin is dissolved in styrene monomer,togetherwith pigment
and small amounts of inhibitor. Af ree radical initiator,c ommonly a
peroxide, and additional styrene are packaged in another container.W hen
applied, the containers are mixed.S ometimes, because of the fast initiating
reaction (shortp ot life), they are mixed in an externally mixing or dualheaded spray gun. Afterbeingmixed and applied, arelatively fast reaction
takesplace, resulting in cross-linking and polymerizationofthe monomeric
styrene with the polyester resin.
Polyester coatings exhibith igh shrinkage after application. The effect
of high shrinkage can be reduced by proper pigmentation that reinforces
the coating and reduces the effect of the shrinkage.
1. Resistance: Excellent resistance to acids and aliphatic solvents;
good resistance to weathering.
2. Temperature resistance: 1808 F/828 Cdry and wet.
3. Limitations: Not suitablef or use with alkaliesa nd most aromatic
solventsb ecause they swell and softent hese coatings. Theya lso
have ashort pot life and must be applied with special equipment.
4. Applications: Coatings for tanks and chemical process equipment.
8.2.9V inyl Esters
The vinyl estersa re formulated in am anner similar to the polyesters.
Theyare derived from aresin based on areactive end vinyl group that can
open and polymerize. The vinyl estersh ave betterm oisture and chemical
resistance than the polyesters. They also have good resistance to weathering
and acids.
8.3A utooxidativeCross-Linking Paints
Paints of this type rely on the reaction of ad rying oil with oxygen to
introduce cross-linkingwithin the resin and attainment of final film properties. The final coating is formed when adrying oil reacts with aresin that is
Corrosion of Linings and Coatings
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CAT8247—CHAPTER 8—17/10/2006—14:20—SRIDHAR—XML MODEL B–pp. 487–507
1508 F/668 Cw et.
These resins are quite expensive.
8.2.8P olyesters
In the coating industry,p olyesters are characterized by resins based on
components that introduce unsaturation (–Ca C–) directly into the polymer
backbone. The most common polyester resins are polymerizationp roducts
of maleic or isophthalic anhydride or their acids. In producing paint,
the polyester resin is dissolved in styrene monomer,togetherwith pigment
and small amounts of inhibitor. Af ree radical initiator,c ommonly a
peroxide, and additional styrene are packaged in another container.W hen
applied, the containers are mixed.S ometimes, because of the fast initiating
reaction (shortp ot life), they are mixed in an externally mixing or dualheaded spray gun. Afterbeingmixed and applied, arelatively fast reaction
takesplace, resulting in cross-linking and polymerizationofthe monomeric
styrene with the polyester resin.
Polyester coatings exhibith igh shrinkage after application. The effect
of high shrinkage can be reduced by proper pigmentation that reinforces
the coating and reduces the effect of the shrinkage.
1. Resistance: Excellent resistance to acids and aliphatic solvents;
good resistance to weathering.
2. Temperature resistance: 1808 F/828 Cdry and wet.
3. Limitations: Not suitablef or use with alkaliesa nd most aromatic
solventsb ecause they swell and softent hese coatings. Theya lso
have ashort pot life and must be applied with special equipment.
4. Applications: Coatings for tanks and chemical process equipment.
8.2.9V inyl Esters
The vinyl estersa re formulated in am anner similar to the polyesters.
Theyare derived from aresin based on areactive end vinyl group that can
open and polymerize. The vinyl estersh ave betterm oisture and chemical
resistance than the polyesters. They also have good resistance to weathering
and acids.
8.3A utooxidativeCross-Linking Paints
Paints of this type rely on the reaction of ad rying oil with oxygen to
introduce cross-linkingwithin the resin and attainment of final film properties. The final coating is formed when adrying oil reacts with aresin that is
Corrosion of Linings and Coatings
492
CAT8247—CHAPTER 8—17/10/2006—14:20—SRIDHAR—XML MODEL B–pp. 487–507