Feature Stories Archive
PET & PETG Drive a
Despite a plethora of competing
thermoplastics in the market, PET and PETG have made solid
strides to become a popular choice for extruders and
fabricators in the plastics industry.
BY KEVIN BASTIAN
In the food industry, presentation is often just as
important as taste. To achieve an eye-catching appearance,
PET and PETG are called to duty. Food storage and
containers, among several other plastic products in such
markets as electronics packaging and point-of-purchase
displays, benefit from the thermoplastics' excellent
PET, or polyethylene terephthalate, resins are
thermoplastic polyester engineering resins. Numerous
companies manufacture this resin, which is an inherently
crystallizable polymer. However, by replacing some of the
basic acid or glycol with secondary acids or glycols, the
crystallization can be slowed down. With a sufficient amount
of CHDM (1, 4-cyclohexanedimethanol) added, Eastman Chemical
Co., for example, is able to produce PETG, an amorphous
copolyester that will not crystallize. Eastman is considered
to be the plastics industry's chief supplier of PETG resin.
"PET is a semi-crystalline product that will turn white
when heated," said Randy Beavers, business market manager
for Eastman in Kingsport, TN. "Polymer chains align
themselves and the sheet or film turns opaque. PETG is
amorphous and will not crystallize. You can heat bend it and
it stays clear. Parts of PET are less tough in the
crystallized areas and may break when force is applied."
PET and PETG have competed with acrylic and polycarbonate
for many years in markets such as point-of-purchase displays
and fixtures, food packaging, indoor/outdoor signage, and
electronic and medical packaging markets. The resins possess
some advantages over their competitors while lacking in
Seeking the expertise of company representatives,
Plastics Machining & Fabricating asked leading
manufacturers, distributors and fabricators about the
1. What advantages/disadvantages do PET/PETG have
compared to other leading thermoplastics?
2. What are some of the most common and unique uses for
3. What developments do you foresee in the next decade
PET/PETG Properties: Advantages/Disadvantages
On the topic of PET and PETG's properties as compared to
other thermoplastics, a large number of manufacturers agreed
as to their best characteristics. "Impact resistance is
PETG's number one property -- without a doubt," said Daniel
Rustin, marketing manager for Acrilex Inc. in Jersey City,
"When PETG is extruded in sheet, the sheet product is 15
to 20 times tougher than general-purpose acrylic and three
to 10 times tougher than impact-modified acrylic," added
Beavers. "It's 60 to 70 percent as tough as polycarbonate,
but polycarbonate is sometimes over-engineered for its
applications. They don't need the toughness."
Though tough, PETG still faces stiff competition in
impact resistance, according to Scott Smith, executive
manager for Repete Plastics in Geneva, IL. "The glycol used
in the formulation makes PETG much less brittle than PET.
Although it is not as strong as PVC in the same gauge
comparison, you can compare a PETG in a gauge 2 to 3 mil (1
mil = 1/1000 of an inch) higher than PVC and you will
realize the same strength," said Smith.
Clarity is also a property in which both PET and PETG
could benefit from increased enhancement. While acrylic's
clarity reigns supreme among thermoplastics, PET and PETG's
optics rank about the same as polycarbonate sheet, according
PET's clarity is not as good as that of PETG mainly
because of thermoforming, Beavers added. During this
process, the polyester crystallizes, causing it to haze and
become less clear than PETG, which is designed to avoid
crystallization during forming. Sheets of PETG can have no
color, resulting in a perfectly suited material for food
packaging. The clarity allows for bar code reading through
the package as well as accurate inspection of packaged
components by manufacturing or customs personnel.
Besides non-crystallization, PETG's thermoformability is
also an advantageous property because of the material's wide
thermoforming window, reproducibility of products and
ability to form at lower temperatures (300F to 320F) with
shorter cycle times than acrylic or polycarbonate. According
to Beavers, PET has a narrow forming window and will haze if
formed at too hot or cold temperature.
Bob Crohan, product manager of Lustro Plastics Co. in
Evanston, IL, adds, "PETG does not require pre-drying like
polycarbonate and thermoformers benefit from lower initial
cost and lower processing costs."
Fabricating sheet produced from PETG is also easy because
of its toughness. Sawing, routing, die-cutting, drilling,
bending and flame polishing are all made simple. "No
challenges exist in regard to fabricating and machining,"
said Crohan. "Sheet extruded from PETG is easily fabricated
and can be cold-bent without crease whitening at the bend."
In regards to the handful of fabricating possibilities
with sheet material, Rustin added, "Polycarbonate and
acrylic may have some of these capabilities, but not all.
PETG has a broader range of properties."
"Polyesters inherently have good chemical resistance,"
said Beavers. "In heavy traffic areas (such as in grocery
and department stores), fixtures need to be cleaned every
day. Using a sheet of PETG, the products won't haze or
Probably the most beneficial of PETG's properties in the
long run is its cost-to-performance ratio. It is 15 to 25
percent more expensive than general purpose acrylic sheet, 2
to 10 percent lower than impact-modified acrylic sheet and
20 to 40 percent lower than polycarbonate sheet, Beavers
said. Sheet and film manufactured from PET is somewhat
cheaper than from PETG.
PET also offers users some profitable characteristics.
According to Michael Oliveto, marketing manager of DSM
Engineering Plastic Products, in Reading, PA, compared to
nylon and acetal, PET has "better resistance to acidic
solutions and chlorinated aqueous solutions commonly used to
sanitize food processing equipment."
Oliveto also referred to its high wear and abrasion
resistance, saying, "In both low load/high speed and high
load/low speed conditions, PET provides three times greater
wear life than acetal, based on a K factor, and up to 15
percent greater wear life than unfilled nylon. The high PV
capabilities, low friction and wear rate of PET allow
products made of this material to run fast and more
efficiently and last longer." He also noted that PET stock
shapes have very low residual stress and are porosity-free.
Dennis Magyar, business manager of the melinar PET
container resin region, a business of DuPont Polyester in
Wilmington, DE, also gave PET high marks. "It's
self-limiting so that it can be produced by the injection
stretch blow molding process, and environmentally friendly
as far as low metals, high oxygen content and recyclability.
And, of course, its low CO2 permeability makes it suitable
for CSD packaging," Magyar said.
A.F. Leger, executive chairman of Vesco Plastics in
Virginia, South Africa, agreed on PET's advantages
concerning its wear, chemical resistance and loading
strength, but also noted its downsides. According to Leger,
PET has a much lower water absorption than nylon and a low
resistance to alkalis and hot water.
PET also has a lower impact resistance than other
thermoplastics and is more difficult to cut, according to
Joe Rusinek, director of sales and marketing for PurePlast
Inc. in Cambridge, Ontario. Problems with PETG's gluing and
bondability capabilities also exist, added Rustin, but the
"practice makes perfect" method can be put to use. "Once
you've mastered the technique, it doesn't require any
further efforts. It's once you know how -- that's the key,"
Beavers also noted that PET and PETG are not inherently
UV-stable, meaning they will yellow and embrittle when
exposed to the sun for long periods of time.
PET and PETG's broad range of advantages makes them
suitable for a number of products in a number of different
markets. PET's primary market is packaging for soft drinks,
bottled water, fruit-based beverages and iced teas. PETG is
chiefly utilized in food, medical and electronic packaging.
It has also seen use in the display fixture industry.
"This represents a new standard in design freedom for
displays," said Beavers. "Excellent clarity, impact strength
-- even at thinner gauges and cold temperatures -- deep draw
characteristics and ease of fabrication, have all
contributed to the growth of this sheet in display and store
Smith sees PETG filling a more important role in a
separate industry. "The most common applications for PETG in
virgin form are medical and food packaging," he said.
"Blisters, clamshells and trays are the most common medical
packages for instruments and disposable trays. PETG is a
good choice for this mainly because of its ability to stand
up to gamma irradiation used to sterilize medical
instruments within the package." Smith cites blue tint PETG
as the most common medical packaging material used because
it aids greatly in the inspection and assurance of the seal
around the instrument packaged within. In food packaging, he
finds clear lids as the most common use of PETG because of
its favorable gas permeation properties for food and the
great clarity it provides, making for an attractive food
Smith's company, Repete Plastics, produces only recycled
PETG material, which cannot be used for either medical or
food packaging. "There are a variety of non-durable consumer
goods that are packaged in our material," he said. "PETG
provides excellent clarity and toughness. Bottom line -- it
makes for an attractive package."
Other applications using PET and PETG range from
electronic packaging and signage to architectural glazing,
game boards, graphic arts, and tub and shower surrounds.
With more and more applications requiring materials that
are stronger, clearer and more directed to their specific
needs, manufacturers of thermoplastics are constantly
working on new and improved developments and properties for
their resins. Regarding the future of PET, PETG and
copolymers, representative responses varied greatly due to
the diverse focuses of their respective companies.
"We foresee improvement in impact strength, service life
and resistance to hot water, as well as a broadening of the
size range produced, leading to new applications," said
Leger regarding the market for PET.
Mark Ballard, director of manufacturing for Kama Corp. in
Hazleton, PA, said he also expects greater acceptance of PET
by markets dominated by other clear resins as well as the
utilization of secondary finishing techniques such as sonic
and radio frequency sealing. Randy Deeley, process
improvement coordinator for Vinyl Plastics Inc. in Sheboygan
Falls, WI, adds, "PET and PETG will need to be blended with
other clear resins for price and performance enhancements."
In addition to improvements in PETG's brightness and
bondability, Beavers sees more advancements in UV protection
being made in the material's future, especially with
refrigerated vending machines. A current problem with the
majority of materials now being used is from fading or
yellowing due to overexposure to the sun.
Architectural building and construction markets, bus
shelters, office partitions, glazing applications, taxi
shields, machine guards and transparent golf cart tops are
other areas in which Beavers sees more affiliation in the
future of copolymers. "We're looking at market research and
putting together strategies to go after those markets," he
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