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Chemical Resistance of Thermoplastics - Fingertips Facts

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Chemical Resistance of Thermoplastics - Fingertips Facts

Post by ioncube on Mon Apr 02, 2012 11:37 pm

Again the rules of thumb to ease out the hell life of plant engineers...
Corrosion is estimated to account for a significant portion — 8–10% — of total annual-plant-capital expenditures for the chemical process industries. To avoid it, engineers can consider corrosion-resistant plastics for process piping and storage vessels. Thermoplastics are generally resistant to chemical attack and thus suitable for many process applications. However, plastics must be selected based on process specifics. When chemicals affect plastics, it usually happens as: chemical solvation or permeation, where physical properties may change, but the polymer molecular structure is not chemically altered; and direct chemical attack, where a a chemical reaction with the polymer occurs.

Chemical resistance of selected commercial thermoplastics and elastomers
Name Notes Recommended UsesUses to Avoid
ABS (acrylonitrile butadiene
styrene)
Smooth inner surface and resistance
to deposit formation
Resistant to a wide variety of
materials up to 65ºC (150°F)
•Commercial sanitary systems
•Weak acids
Oxidizing acids
PVC (polyvinyl chloride) Most frequently specified of all
thermoplastic materials
•Chilled water
•Deionized water, irrigation
•Salt solutions
•Acids
•Alkalis
Polar solvents, such as ketones
CPVC (chlorinated polyvinyl
chloride)
Better chemical resistance than
PVC
•Hot corrosive liquids
•Hot or cold water
Ultraviolet (UV) radiation
PE (polyethylene) Lowest-cost commercially available
plastic. Pipes generally
must be supported
•Ethanol, methanol
•Sodium, potassium, calcium
hydroxide (30%)
•Glycol
•Oils, natural gas, gasoline
•Diethylether
•Methylene chloride
•Ethylene chloride
PP (polypropylene) Lightweight polyolefin
Can be used at higher temperatures
than PE
•Organic solvents
•Resistance to sulfur-bearing
compounds
•Salt-water disposal lines
•Crude-oil piping
•Mixtures and acids, bases,
solvents
•Strong oxidizing agents
•Chlorinated hydrocarbons
•Aromatics
PVDF (polyvinylidene fluoride)Best combination of strength,
chemical resistance and working
temperatures
•Wet or dry chlorine, bromine,
other halogens
•Acids, bases, organic solvents
Fuming sulfuric acid
EPDM (ethylene propylene
diene monomer)
Good abrasion and tear
resistance
Variety of acids and bases,
alcohols, ketones
•Petroleum oils
•Strong acids
•Strong bases
Chlorosulfonated polyethylene
(Hypalon)
Good resistance to ozone,
flames
Salt solutions, nitric, sulfuric,
hydrofluoric acids
Fuming nitric and sulfuric acids
Neoprene Among the first synthetic
rubbers developed
•Food and beverage
applications
•Vegetable oils
•Strong oxidizing agents
•Chlorinated solvents
•Esters
•Ketones
Nitrile Copolymer of butadiene and
acrylonitrile
•Solvent
•Oil
•Water
•Hydraulic fluid
•Highly polar solvents
•Chlorinated hydrocarbons
Polyamide (Nylon) Hygroscopic material
Good abrasion resistance
•Gasoline
•Alkanes
•Acetone, methylethyl ketone
•Strong oxidizing agents
•Phenols
•Mineral acids
Fluorocarbon Inherently compatible with a
wide spectrum of chemicals
•Mineral acids
•Salt solutions
•Chlorinated hydrocarbons
•Petroleum oils
Steam
Polytetrafluoroethylene
(PTFE; Teflon)
Most chemically resistant plastic
commercially available
Outstanding resistance to most
chemicals and solvents
Molten metals
PEEK (polyether etherketone) Can be used at higher temperatures
than PTFE; physical
characteristics approaching
some metal
•Heat transfer fluids
•Steam
•Hydrocarbons
Concentrated nitric, hydrochloric,
hydrobromic, hydrofluoric
and sulfuric acids
Polyethylene teraphthalate
(PET)
Shows resistance to ultraviolet
radiation
•Hydrocarbon fuels
•Water
•Ethanol, ethyl ether
•Concentrated sulfuric acid
•Phenol
•Acetone


References
1. “Perry’s Chemical Engineers’ Handbook: 8th ed.” McGraw Hill, New York, 2008.
2. Nibco Chemical Resistance Guide. Nibco Inc. Elkhart, Ind. 2003.
3. Plastics Pipe Institute. Chemical Resistance of Thermoplastics. Techincal Report 19. 2007.
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