Bridging The Polymer Gap

Polymer Technology

Textile World AsiaSpecial ReportBridging The Polymer GapEngineering polymers take technical
fabrics to new levels.Engineering polymers have opened the world of technical fabrics to enable
them to meet the performance demands of new markets that offer higher profit margins than
traditional markets.Thermoplastics such as polybutylene terephthalate (PBT) and linear
polyphenylene sulfide (PPS) work effectively in extreme environments, including temperatures near
200°C and in the presence of nearly any chemical.Manufacturers have traditionally turned to
polypropylene (PP) for durable and disposable fibers and nonwovens, although they also have applied
such polymers as polyethylene terephthalate (PET) and nylon 6 when the demands of an application
warrant their use. While these materials perform well in many situations, there are times when they
are pushed beyond their thermal, chemical and mechanical limits. Fluoro-based and aramid polymers
often can provide the higher performance needed, but the high price of these materials makes them
impractical in many instances.Engineering thermoplastics bridge the cost-performance gap between
resins having modest performance characteristics and fluoro-based and aramid polymers.Many families
of engineering thermoplastics contain grades configured for the extrusion of fibers used in a
variety of woven and nonwoven applications, including monofilaments, multifilaments, staple fibers,
needlepunched fabrics, meltblowns, netting, cast/blown films, spunbonds and wetlaid nonwovens.

Celanex® polybutylene terephthalate (PBT) can be used in paintbrush filaments for improved
stiffness, softness, flexibility and durability.Five Engineering ThermoplasticsThe relative
inertness and sturdiness of many engineering thermoplastics improve the efficiency and life of
liquid and gas filters in the chemical, automotive, health care and pollution control fields. These
polymers also find use in furniture seating, apparel, structural supports, brushes, conveying
systems, and acoustic and thermal insulation.This article looks at five engineering resins to offer
those who make and use technical fabrics an understanding of the capabilities of these polymers,
which include PBT; PPS; thermoplastic copolyester elastomer (TPE); acetal copolymer, also known as
polyoxymethylene (POM); and cyclic olefin copolymer (COC). It also takes a closer look at PBT and
the numerous technical fabric solutions that emerge with this engineering polymer.PBT resists
chemicals and high heat in products made from meltblown fibers, staple fibers, monofilament,
multifilament and other materials. It is used in filter media for blood, oil, fuel and other
fluids. As a spun yarn, it provides good stretch and comfort in apparel textiles and a hand much
like that of high-quality cotton. It offers better processing performance than PET.
Low-melting-point copolyesters are applicable as melt adhesives used to thermally bond many
nonwovens, such as automotive headliners.Linear PPS is stable, tough and chemically resistant at
high temperatures. It is inherently flame-retardant and resists hydrolysis, acids, bases, oxidizing
bleaches and all known solvents at temperatures below 200ºC. It often is used in tough environments
such as bag-house and flue-gas filters, paper machine dryer fabrics, food process screens, and
filters for dairy products and hazardous liquids.Linear PPS can be meltblown into lofty or stiff
fabrics, spunbonded, and made into staple fibers for needlepunched composites and other felt
substrates.TPEs combine elasticity and strength. Fibers made from them have low initial modulus,
high elongation at break and good stretch recovery. They withstand abrasion, have good chemical and
thermal resistance, and are stable in high-temperature water and steam, such as occurs during
dyeing. TPEs are available in a wide range of hardness (durometers from 25 to 77 Shore D), so
fabric manufacturers have many strength and stiffness options. They are used in a growing variety
of fiber and fabric applications including conventional and suspension seating fabrics;
incontinence sheets; non-skid fabrics; and medical applications such as transdermal patches,
protective apparel and breathable barriers against infectious diseases.POM combines strength,
stiffness and chemical resistance. It withstands exposure to hot water and prolonged contact with
fuel and oil, which has made it an excellent choice for auto fuel and oil filters. It processes
easily on machines used for polypropylene (PP) at a lower melt temperature of 190°C to 225ºC,
versus 230ºC to 260ºC for PP. Its fibers can be extruded in a variety of thicknesses and in
textures ranging from soft to stiff.COC has greater charge retention at elevated temperature and
humidity than other olefins when used in air filter fabrics. It resists polar solvents, alkalis and
hydrolysis and has excellent moisture-barrier properties. When COC is blended into traditional
polyolefins, it increases stiffness and reduces elongation in nonwoven fabrics. In PP, it reduces
fiber-to-fiber and fiberto- metal friction.

U.S.-based Matrex produces furniture seating using elastomeric fabric made with Teijin
monofilament containing Ticona’s Riteflex® thermoplastic copolyester alloy.PBT In NonwovensPBT,
which is more commonly used for injection-molded products, is seeing increasing application in
technical fibers. It is strong and tough and has low creep, even at elevated temperatures. It
absorbs little moisture and resists many chemicals, including oils, greases, solvents, dilute
acids, bases, salt solutions, organic chemicals and ozone. It also resists fungal growth, can be
immersed in water for extended periods, and can resist short-term exposure to steam and water at
temperatures as high as 150ºC. Given their wide range of viscosities, PBTs perform well in nearly
all fabric and nonwoven processes from spunbond and meltblown to monofilaments, staple fibers and
multifilaments.Grades available through Ticona — a business unit of U.S.-based Celanese Corp. —
have melt indices of about 5 grams to 350 grams per 10 minutes, and intrinsic viscosities of about
0.57 to 1.40 deciliters per gram. PBT typically melts at 225ºC and undergoes glass transition
between 50ºC to 60ºC. As a result, lower-melt-viscosity PBTs can be meltspun at temperatures
similar to those of polypropylene.

The excellent flexibility of Celanex® PBT combined with its high melt strength allows
extremely fine fiber sizes for meltblown nonwovens as needed for blood filtration media, according
to Ticona.PBT has many advantages over PET in processing as well as enduse. PBT is dried at a lower
temperature (121ºC versus 136ºC for PET), has a lower melt temperature (225°C versus 260°C), and
generally has a faster throughput than PET. It resists hydrolysis better than PET and tends to
shrink and distort less after processing because of its faster crystallinity. PBT also makes softer
and more flexible fabrics than PET and yields fine fibers more readily.PBT has a broad processing
window when it is spunbonded. At throughputs of 0.40 to 0.80 grams per hole per minute, extruder
temperatures can range from 210ºC to 282ºC and die melt temperatures from 250°C to 280ºC, depending
on the viscosity of the grade selected.New PBT grades that are excellent candidates for technical
fabrics continue to appear. Celanex® PBT 2000-K, for example, is designed to replace PET in
selected homogenous and bicomponent spunbond applications. It yields finer-denier fibers than PET,
and fabrics made from this grade shrink less during processing, and are softer and more flexible.
When blended with PET, it reduces the stiffness of PET fabrics and increases processing throughput.

This polyester automobile headliner contains Celanex® PBT binder material from Ticona.Another
new grade of Celanex PBT is a low-melt polyester copolymer binder — with a melt point of 147°C —
that is an excellent material for making polyester automotive headliners, hood liners and trunk
liners that meet European recyclability regulations.These liners weigh significantly less than
traditional liners made with cotton shoddy or glass fibers impregnated with phenolic resin.This PBT
grade also can be used in powdered form to fuse mats of PET staple fibers, which typically melt at
250°C to 257°C. Polyester liners involve a simple thermal operation as opposed to phenolicbased
liners, which involve curing and the possible release of formaldehyde. The new binder can be used
with other fibers in felts or fabrics and can be fabricated as staple fiber, sheet or film, and as
a bicomponent fiber.

This cartridge filter made with meltblown Fortron® polyphenylene sulfide fibers on a central
support is stable to acids, bases and organic solvents. It also resists high temperatures and has a
long service life, according to Ticona.Paving The Way For New Market OpportunitiesEngineering
thermoplastics such as PBT, PPS, TPE, POM and COC can open new doors for nonwovens and fiber
manufacturers. They provide a broad palette of material for use in higher-performance niches in
markets as diverse as chemical processing, health care, automotive and furniture. The ability to
work effectively under demanding thermal and chemical conditions allows technical fabrics made from
them to displace other materials, such as stainless steel, ceramics and glass.

High-Performance BenefitsEngineering polymers give technical fabrics manufacturers the
ability to produce products for challenging applications. High-performance capabilities for this
broad range of polymers include:• resistance to most acids, bases and solvents;• melt temperatures
of up to 285°C;• excellent elasticity, stretch recovery and durometer from 25 to 77;• high tensile
strength;• melt flow index rates from 10 to 350, which make them suitable for filaments, meltblown
fabrics and films;• a wide range of wetting properties;• a high charge retention at elevated
temperature and humidity;• compliance to many standards and regulations;• food contact approvals;•
health care approvals; and• UL, NSF and ISO ratings.

Editor’s Note: This article was written by Ticona’s Kari Karandikar, Jeff Sawka and Ramesh
Srinivasan. Karandikar and Sawka are marketing specialists, and Srinivasan is a business
development engineer.

July/August 2005