Chemical Engineering August 2018 - 48

Feature Report
PVDF:
A Fluoropolymer for
Chemical Challenges
When it comes to selecting materials of construction, keep in mind the favorable properties of
fluoropolymers for corrosive service
Averie Palovcak
and Jason
Pomante,
Arkema, Inc.
IN BRIEF
PVDF AND THE
FLUOROPOLYMER FAMILY
COPOLYMERS CHANGE
FLEXURAL PROPERTIES
PVDF COMPONENTS
S
ince its commercialization in the
mid-1960s, polyvinylidene fluoride
(PVDF) has been used across a
variety of chemical process industries
(CPI) sectors due to its versatility and
broad attributes. With flagship applications
in architectural coatings and the CPI, the
breadth of industries where PVDF is utilized
today is expansive. PVDF components (Figures
1 and 2) are utilized and installed where
engineers are looking to maximize longevity
and reliability of process parts in many CPI
sectors, including semiconductor, pharmaceutical,
food and beverage, petrochemical,
wire and cable, and general chemicals.
PVDF and the fluoropolymer family
PVDF is a high-performance plastic that falls
into the family of materials called fluoropolymers.
Known for robust chemical resistance,
fluoropolymers are often utilized in areas
where high-temperature corrosion barriers
are crucial. In addition to being chemically
resistant and non-rusting, this family of polymers
is also considered to have high purity,
non-stick surfaces, good flame and smoke
resistance, excellent weathering and ultraviolet
(UV) stability.
Fluoropolymers have carbon and fluorine
as the main components of their chemical
backbone. Small changes in percent fluorination
or addition of other elements may
change the performance properties. Fluoropolymers
are divided into two main categories:
perfluorinated and partially fluorinated
[1]. The partially fluorinated polymers
contain hydrogen or other elements, while
the perfluorinated (fully fluorinated) polymers
are derivatives or copolymers of the
tetrafluoroethylene (C2F4) monomer. Com46
FIGURE
1. A variety of fluoropolymer components are shown
here
monly used commercial fluoropolymers
include polytetrafluoroethylene (PTFE),
perfluoroalkoxy polymer (PFA), fluorinated
ethylene propylene (FEP), polyvinylidene
fluoride (PVDF), ethylene tetrafluoroethylene
(ETFE), and ethylene chlorotrifluoroethylene
(ECTFE).
PVDF is a partially fluorinated polymer
consisting of repeated units of the vinylidene
fluoride (VF2) monomer [(C2H2F2)].
Standard PVDF homopolymer is 59.4% fluorinated
and PVDF copolymers (described
in later sections) can reach up to 65% fluorination.
Generally, the higher the fluorine
content, the higher the chemical resistance,
as the carbon-fluorine bond is one of the
strongest known in chemistry. PVDF homopolymers
can tolerate chemistries from a
pH of less than 1 up to 12 and PVDF copolymers
can extend that range from much
less than 1 up to 13.5.
While PTFE, with its high melting point of
325°C, is well known as a liner for high temperature
applications, PVDF homopolymer
has a melt point between 165 and 172°C and
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