is characterizedb ym ethylene linkagesr athert hanm ethylolg roups.
These products are not heat reactive and requirea dditional cross-linking
agents such as hexamethylenetetramine to become thermosetting.
Both polymerizationr eactions evolve water during curing. This condensation reaction serves to limit film thicknesses to approximately 3mil
because the volatiles willc ause blistering while curing takes place.
The outstanding phenolic systems are those that are baked at approximately 4508 F( 2308 C) to provide a3 –5 mil (75–130 m m) liningo fh igh
chemical resistance.
Phenolic coatings have awet temperature resistance to 2008 F(938 C). They
are odorless, tasteless, nontoxic, and suitablef or food use. They mustb e
baked at am etal temperature ranging from 350 to 4508 F( 175–2308 C). The
coating must be applied in athin layer (approximately 1mil (0.03 mm))and
partially baked between coats. Multiple thin coats are necessary to allow
removal of water from the condensation reaction. The cured coating is
difficult to patch due to extreme solvent resistance.
Abrown color results upon baking that can be used to indicate the degree
of cross-linking. It can be modified with epoxies and other resins to enhance
water,c hemical, and heat resistance.
Phenolic resins exhibit excellent resistance to most organic solvents,
especially aromatic and chlorinated solvents. Organic polar solventscapable
of bonding, suchasalcohols and ketones, can attackphenolics. Although the
phenolics have an aromatic character,t he phenolic hydroxyls provide sites
for hydrogen bonding and attackb yc austics.
Phenolics are not suitablefor use in strongalkaline environments. Strong
minerala cids also attackt he phenolics, and acids such as nitric, chromic,
and hydrochloric can cause severe degradation. Sulfuric and phosphoric
acids may be suitableunder someconditions. There is some loss of properties
when phenolics are in contact with organic acids such as acetic, formic,
or oxalic.
Although attacked by oxidants and even by dilute alkalies, the phenolics
provide both corrosion and contamination protection in aw idev ariety of
chemical and petroleum services. Refer to Table 4.4 for the compatibility of
phenolics with selected corrodents.
Modified air-dried phenolics arenearly equivalent to high-baked phenolics
with adry heat resistance of 1508 F(658 C). Theycan be formulated for excellent
resistance to alkalies, solvents, fresh water,s alt water,d eionizedw ater,
and mild acid resistance.
4.10.2E poxy
Epoxyr esins can be formulated with aw ide rangeo fp roperties. These
medium to high-priced resins aren oted for their adhesion. Epoxyl inings
provide excellent chemical and corrosion resistance. They exhibitg ood
resistance to alkalies, non-oxidizing acids, and manys olvents. Typically
Liquid-Applied Linings
85
CAT8247—CHAPTER 4—17/10/2006—14:33—SRIDHAR—XML MODEL B–pp. 69–174
These products are not heat reactive and requirea dditional cross-linking
agents such as hexamethylenetetramine to become thermosetting.
Both polymerizationr eactions evolve water during curing. This condensation reaction serves to limit film thicknesses to approximately 3mil
because the volatiles willc ause blistering while curing takes place.
The outstanding phenolic systems are those that are baked at approximately 4508 F( 2308 C) to provide a3 –5 mil (75–130 m m) liningo fh igh
chemical resistance.
Phenolic coatings have awet temperature resistance to 2008 F(938 C). They
are odorless, tasteless, nontoxic, and suitablef or food use. They mustb e
baked at am etal temperature ranging from 350 to 4508 F( 175–2308 C). The
coating must be applied in athin layer (approximately 1mil (0.03 mm))and
partially baked between coats. Multiple thin coats are necessary to allow
removal of water from the condensation reaction. The cured coating is
difficult to patch due to extreme solvent resistance.
Abrown color results upon baking that can be used to indicate the degree
of cross-linking. It can be modified with epoxies and other resins to enhance
water,c hemical, and heat resistance.
Phenolic resins exhibit excellent resistance to most organic solvents,
especially aromatic and chlorinated solvents. Organic polar solventscapable
of bonding, suchasalcohols and ketones, can attackphenolics. Although the
phenolics have an aromatic character,t he phenolic hydroxyls provide sites
for hydrogen bonding and attackb yc austics.
Phenolics are not suitablefor use in strongalkaline environments. Strong
minerala cids also attackt he phenolics, and acids such as nitric, chromic,
and hydrochloric can cause severe degradation. Sulfuric and phosphoric
acids may be suitableunder someconditions. There is some loss of properties
when phenolics are in contact with organic acids such as acetic, formic,
or oxalic.
Although attacked by oxidants and even by dilute alkalies, the phenolics
provide both corrosion and contamination protection in aw idev ariety of
chemical and petroleum services. Refer to Table 4.4 for the compatibility of
phenolics with selected corrodents.
Modified air-dried phenolics arenearly equivalent to high-baked phenolics
with adry heat resistance of 1508 F(658 C). Theycan be formulated for excellent
resistance to alkalies, solvents, fresh water,s alt water,d eionizedw ater,
and mild acid resistance.
4.10.2E poxy
Epoxyr esins can be formulated with aw ide rangeo fp roperties. These
medium to high-priced resins aren oted for their adhesion. Epoxyl inings
provide excellent chemical and corrosion resistance. They exhibitg ood
resistance to alkalies, non-oxidizing acids, and manys olvents. Typically
Liquid-Applied Linings
85
CAT8247—CHAPTER 4—17/10/2006—14:33—SRIDHAR—XML MODEL B–pp. 69–174