Corrosion of Polymer (Plastic) Materials
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and (2) partially fluorinated polymers such as ETFE, PVDF, and ECTFE,
called fluoropolymers. The polymeric characteristics within each group are
similar but there are important differences between the groups.
5.5 Thermoset Polymers
Once formed, thermoset polymers, unlike the thermoplasts, cannot be heated
to change their shape. Consequently, they cannot be recycled. These resins are
initially liquid at room temperature and then by adding a catalyst or accelerator, they are changed into a rigid product that sets or cures into its final shape.
The thermoset resins are high-molecular-weight polymers that are reinforced
with glass or other suitable material to provide mechanical strength. The most
commonly used resins are the vinyl esters, epoxies, polyesters, and furans.
For reinforcing these polymers, fibrous glass in the F and C grades is
the most commonly used. Other reinforcing materials used include boron
nitride, carbon fiber, ceramic fibers, graphite jute, Kevlar, metallic wire or
sheet, monoacrylic fiber, polyester fiber, polypropylene fiber, quartz, sapphire whiskers, and S-grade glass.
The advantages of the thermosets are many; they
1. Are less expensive than the stainless steels
2. Have a wide range of corrosion resistance
3. Are light in weight
4. Do not require painting
5. May be formulated to be fire retardant
Unreinforced, unfilled thermoset polymers can corrode by several mechanisms. The type of corrosion can be divided into two main categories: physical and chemical.
Physical corrosion is the interaction of a thermoset polymer with its environment so that its properties are altered but no chemical reactions take
place. The diffusion of a liquid into the polymer is an example. In many
cases, physical corrosion is reversible; once the liquid is removed, the original properties are restored.
When a polymer absorbs a liquid or a gas resulting in plasticization or
swelling of the thermoset network, physical corrosion has taken place. For
a crosslinked thermoset, swelling caused by solvent absorption will be
at a maximum when the solvent and polymer solubility parameters are
exactly matched.
Chemical corrosion takes place when the bonds in the thermoset are broken by means of a chemical reaction with the polymer’s environment. There
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and (2) partially fluorinated polymers such as ETFE, PVDF, and ECTFE,
called fluoropolymers. The polymeric characteristics within each group are
similar but there are important differences between the groups.
5.5 Thermoset Polymers
Once formed, thermoset polymers, unlike the thermoplasts, cannot be heated
to change their shape. Consequently, they cannot be recycled. These resins are
initially liquid at room temperature and then by adding a catalyst or accelerator, they are changed into a rigid product that sets or cures into its final shape.
The thermoset resins are high-molecular-weight polymers that are reinforced
with glass or other suitable material to provide mechanical strength. The most
commonly used resins are the vinyl esters, epoxies, polyesters, and furans.
For reinforcing these polymers, fibrous glass in the F and C grades is
the most commonly used. Other reinforcing materials used include boron
nitride, carbon fiber, ceramic fibers, graphite jute, Kevlar, metallic wire or
sheet, monoacrylic fiber, polyester fiber, polypropylene fiber, quartz, sapphire whiskers, and S-grade glass.
The advantages of the thermosets are many; they
1. Are less expensive than the stainless steels
2. Have a wide range of corrosion resistance
3. Are light in weight
4. Do not require painting
5. May be formulated to be fire retardant
Unreinforced, unfilled thermoset polymers can corrode by several mechanisms. The type of corrosion can be divided into two main categories: physical and chemical.
Physical corrosion is the interaction of a thermoset polymer with its environment so that its properties are altered but no chemical reactions take
place. The diffusion of a liquid into the polymer is an example. In many
cases, physical corrosion is reversible; once the liquid is removed, the original properties are restored.
When a polymer absorbs a liquid or a gas resulting in plasticization or
swelling of the thermoset network, physical corrosion has taken place. For
a crosslinked thermoset, swelling caused by solvent absorption will be
at a maximum when the solvent and polymer solubility parameters are
exactly matched.
Chemical corrosion takes place when the bonds in the thermoset are broken by means of a chemical reaction with the polymer’s environment. There