Kynar® Resin
Chemical & Fuel Resistance
CHEMICAL RESISTANCE OF KYNAR® PVDF FLUOROPOLYMERS
Kynar® PVDF resins are chemically resistant to a wide range of chemicals. Most acids and acid mixtures, weak bases, halogens, halogenated solvents, hydrocarbons, alcohols, salts and oxidants pose little problem for Kynar® PVDF. At ambient temperatures Kynar® PVDF homopolymers are generally resistant to chemicals with a pH up to 12 and Kynar Flex® copolymers are generally resistant to chemicals with a pH up to 13.5.
FACTORS AFFECTING CHEMICAL RESISTANCE
Many factors can affect a materials chemical resistance. These include, but are not limited to, exposure time, chemical concentration, extreme temperature and pressure, frequency of temperature and pressure cycling, attrition due to abrasive particles, and the type of mechanical stress imposed. The fact that certain combinations of chemical exposure and mechanical load can induce stress cracking in many otherwise chemically resistant materials, both metallic and nonmetallic, is of particular significance. In general, the broad molecular weight distribution of Kynar® resins results in greater resistance to stress cracking.
Factors such as permeability and adhesion affect the chemical resistance of Kynar® PVDF coatings. Consequently, coatings may not exhibit exactly the same properties as melt-processed Kynar® resin. Maximum use temperature for dispersion-applied or powder coatings should not exceed 100°C (212°F). However, assuming chemical resistance is still adequate, laminated systems can be used from 120°-135°C (248°-275°F).
OPERATING PARAMETERS
Operating parameters are dependent on the particular application of Kynar® resin and differ from those experienced in either laboratory testing or apparently similar field service. Because corrosive fluids or vapors are often mixtures of various individual chemicals, it is strongly recommended that trial installations be evaluated under actual service conditions. For example, immersion testing of Kynar® resins in individual chemicals at a specific operating temperature, will not necessarily predict the performance of Kynar® PVDF-fabricated components when they are exposed to an exothermic reaction between the individual chemicals.
Chemical Resistance of Kynar® Homopolymer Resin vs. Other Well-Known Plastics at 93°C (200°F)
The chemical resistance of Kynar® fluoropolymer is indicated in the figure on the left. In this chart, the behavior of Kynar® homopolymer resin at 93°C (200°F) in contact with nine general chemical species is compared with that of other well-known plastics. The rating system ranges from unacceptable severe attack in the outer segment of the circle to excellent (inert) in the bulls eye.
An alphabetic listing of chemicals and their maximum usage temperature with Kynar® resins is available upon request from the Fluoropolymers Business Unit. An additional chemical resistance guide for short term drain pipe applications is also available. Chemical applications can be complex and the information provided here should be considered a general guideline. For more information, contact a Technical Service Representative.
Kynar® resin ratings are based on long-term immersions assuming worst-case scenarios.
FUEL AND OFFSHORE APPLICATIONS
Kynar® and Kynar Flex® resins are used all along the petroleum supply chain, from oil and gas exploration and production to transportation and distribution. Examples include flexible pipes and umbilicals for offshore exploration, pipe for natural gas distribution, underground pipe for gas stations, and fuel lines in trucks and automobiles.
In addition to improved corrosion resistance over metals in fuel service, Kynar® and Kynar Flex® resins have the broadest range in fuel service among the commonly used plastics. Many traditional materials are unsuited for the new fuels and fuel blends. Kynar® and Kynar Flex® resins can be used to handle even aggressive blends like gasoline/MTBE blends, gasoline/ethanol blends, and diesel/bio- diesel blends.
PERMEABILITY AND TENSILE STRENGTH RETENTION
Kynar® and Kynar Flex® resins also exhibit low permeability to most fuels while demonstrating good dimensional stability and low weight gain. Kynar® resin retains its physical properties in fuel service and offers extended service life compared to other materials.
The table on the right shows that Kynar® and Kynar Flex® maintain their tensile strength after six months of exposure to a variety of fuels. Bondable grades of Kynar® are also available to create multilayer structures for fuel service wherein Kynar® resin is used as a barrier layer, tied to other materials like PE, PP, TPU, TPE, rubber, and metals.
PERCENT RETENTION IN THE TENSILE STRENGTH OF KYNAR® AFTER EXPOSURE TO FUEL AT 40°C FOR SIX MONTHS:
|
|
KYNAR® |
KYNAR FLEX® 2850 |
KYNAR FLEX® 2800 |
|---|---|---|---|
|
C |
110.7 |
107.8 |
104.4 |
|
CE10a |
97.8 |
94.6 |
91.0 |
|
CE85a |
99.4 |
98.2 |
99.2 |
|
B20 |
115.5 |
114.2 |
117.9 |
*Fuel C is a 50/50 mixture of Toluene and Iso-Octane
*Fuel CE10a Contains 10% Ethanol
*Fuel CE85a Contains 85% Ethanol
*B20 is 20% biodiesel fuel
"a” at the end of the name denotes an aggressive version of the fuel containing peroxide and copper ions.