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Additive Solutions for Manmade Fibers and Nonwoven Materials BY DR VAMAN G KULKARNI DIRECTOR OF POLYMER ADDITIVES DEVELOPMENT AMERICHEM

A dditives play an important role in the manufacture and use of manmade fibers

including textiles nonwovens and geotshyextUes Different additives fulfill various needs ranging from process enhanceshyment to imparting specific end use properties The need for specialized functional additives such as antimicroshybials flame-retardants (ultraviolet) UV stabilizers antistatics tracers and others is on the rise owing to the use of manshymade fibers in a wide range of applicashytions This article discusses various functional additives as well as solution dyeing as a green coloring technology

Weathering performance is critical in many fiber and nonwoven applicashytions such as commercial carpets awningoutdoor fabrics synthetic turf and geotextiles The effects of weathshyering are a combination of chemical and physical effects that occur when textile materials are exposed to outshydoor conditions

Polymeric materials used to make synthetic fibers are susceptible to heat and sunlight and require stabilization during process ing and long-term use UV radiation has a profound effect on service Ii fc of texti Ie materials Further depending on the chemistry or the polymer moisture and oxygen playa role in weathering The degradashytion of fibers and textile materials is manifested by changes in mechanical and physical properties as well as yelshylowing of the polymer

Depending on the chemistry of the polymer hindered amine light stabilizshyers (HALS) or UV absorbers can be used to protec t the textiles from the damaging effects of UV radiation

UV absorbers as the name implies absorb the damaging UV radiation and diSSipate the energy at

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Figure 1 Efficacy of two UV stabilization packages on 4 dpf (-14 ~m) natural polyester as a

function of UV exposure

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p 100c Qj Qj 95 ~

gt 90u nI 85c ~ 80

2000 4000 6000 8000 10000

Hours ISO 4892-2

UV 1

Figure 2 Efficacy of two UV systems on synthetic turf green formulation as a function of

bull PET Neat

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250 500 750 1000

Hours - J 1960

UV exposure

lower wavelengths HALS on the other hand act as free radical scavshyengers and hydroperoxide decomshyposers to quench the damaging effects of UV radiation

Most fibers used in textiles and carshypets are very thin ranging in thickness from about 2 denier per filament (dpO to 20 dpf 00 11m to about 45 11m) and do not provide su rficienr absorption depth which puts an additional chalshylenge on selection of UV absorbers

Often combination systems are required for optimum performance

Pigments espeCially carbon black have been known to provide protecshytion against UV radiation and the proper choice of titanium dioxide is needed for effective stabilization OrganiC and inorganic pigments proshyvide varying degrees of protection against weathering Figure 1 shows the stabilizing effect of two UV systems on 4 dpf polyester fiber and Figure 2

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Figure 3 Vertical burn test results of polyester fiber containing 75 masterbatch compared with neat polyester and polyester fiber made using an inherently FR polyester chip

shows the effect of two UV packages in synthetic turf green formulation

Flame retardant (FR) textiles such as upholstery fabrics bedding and carpets find application in hotels apartments and transportation The use of haloshyge na ted compounds is synonymous with flame retardancy In combina tion with antimony trioxide they have been the mainstay of FR plas ti cs as inexpenshysive and effective flam e-re ta rdams However owing to regulatory and env ishyronm ental footprint considerations they arc currently out of favor

Mineral fl ame-retardants are typishycally not an option for textiles and nonwovens owing to th e large amount of additive need ed The synthetic fiber industry led by polyester has long adopted phosphorous as the preferred FR chemistry Phosphorous and nitroshygen chemistries are commonly used as FR additives for manmade fibers including nylon and polypropylene

Phosphorous containing coshymonom ers and oligo me rs are employed in the manufacture of FR polyester containing a defined amount of phosp horous The phosphorous

thus becomes an integral part of the polymer and offers durability coupled with excellent flame re tardancy Such a product is typically supplied as a res in and is spun as a neat polymer

With the d emand for tuned pershyfonn ance coupled with in creased demand for recyc led fiber the industry is looking for a mas terbatch approach to produce yarns with varying amounts of phosphorous

Over the past few years Americhem has been working to deve lop a mastershybatch solution to impart FR properties to polyester fiber Metal phosphinates and more recently polyphosphinates are employed to impart FR properties to polyester fibers and tex tiles

Americhem offers several s tandard and cus tomized products with tuned performance-based phosphorous chemistry that offer inherent durable and eco-friendl y flam e retardancy to

polyet hylene terephthalate (PET) and polytrimethylene terephthalate (PTT)

At a use rate of 5-8 depending on the fabric construction one can achieve Ml classification as per NF P 92-507 (2004) and pass several other

industry standards Shown in Figure 3 are verti cal burn tests on specimens containing 75 Americhem mas te rshyba tch compared with specimens made with neat PET and indus try standard PET FR chip

Technologies based on nitrogen and nitrogenphosphorous chemistries have been developed for imparting FR properties to polyamide (PA) 6 PA 6 6 a nd polypropylene (PP ) fibers However unlike polyester the te chshynology for PA and PP fibers is not that well advan ced Newer formulations are being developed to address the growing need in the market

Microbes are all around us Some are beneficial and others can cause probshylems The growth of microbes on textile materials leads to foul odors discolshyoration and in some cases loss o f textile properties The nutrients in sweat body warmth moisture and dark atmosphere are ideal conditions for bacterial growth

There has been an increasing demand for textiles and nonwovens vvi th antimicrobial properties in a wide range of applica tions In addition to

medical and healthcare applications

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Contact time (hour)

Staphylococcus aureus ATCC 6538 CFUsample

Eschenchia coli ATCC 8739 CFUsample

Control 26 x 10 27 X 10l

ohour (C) 25 x 105 24 x 105

ohour (8) 22 x 105 26 x 105

24 hour (A) lt100 lt100

Reduction (R) gt9996 gt9995

Table 1 Efficacy of Americhem antimicrobial masterbatch in PET at 3 use rate

there is a drive by todays consumer to embrace the fresh and well-being aspect in textiles as a result antimishycrobial tex tiles are routinely used in performance apparel undergarments hosiery and home textiles

Textiles containing antimicrobial additives must be effective against a broad range of microbes and be effective after multiples washes While a range of antimicrobial solutions are available silshyver-based antimicrobials are the most suited for use with manmade fibers

Leading textil e fibers such as polyshyester and PA are melt spun at temperashytures in the range of 270-295degC This requires that the antimicrobial additive be stable a t these temperatures during compounding and spinning stages

Silver-based antimicrobials can be successfully incorporated into synthetshyic fibers by addition during the spinshyning process owing to their high thershymal stability Further the additive becomes an integral pan of the textile

fiber enhancing durability Tab le 1 shows the efficacy of

Americhem antimicrobial masterbatch in PET CFUsample refers to colony fonning unit per sample

Antistatic fibers and nonwoven structures are wielely used in many applications such as carpets and texshytil es c1eanroom fabrics and medical textil es Antistatic agents reduce the electros tati c propensity of fib e rs Antistatic agents can be broadly classi shyfied as migrating and permanent antisshytats ( inherently dissipative polymers and those based on conductive fill ers)

Migrating antistats are typically used in nonwovens and s hort-term applications Such chemistries work by attracting water crea ting a conducshytive pathway that dissipates the charge buildup Typical surface resistivities attained are in the 1011 to 10 12 O sq

Antistatic fibers used in textiles and carpets on the other hand require lower resistivities and demand perma-

Surface Resistivity Static Decay NFPA 99)

ASTM D-257 Seconds

OhmsSq Seconds

50 RH20 RH 50 RH20 RH

Spunbond PP No Discharge Observed

Spunbond PP with antistat 1 036246

Spunbond PP with antistat 2 ND ND022

ND =Not determined

Table 2 Effect of antistatic additives on the static decay of spun bond polypropylene

nent antistatic properties These are typically based on co nductive particles such as carbon black or antimony-coatshyed titanium dioxid e The conductive compound is incorporated into the fiber using a bicomponent technology that delivers durable antistatic propershyties A typical example o f an antistatic nonwoven fabric is shown in Table 2

GREEN COLORING TECHNOLOGY PET commonly referred to as polyshy

ester is the most important manmade fiber and comprises the largest segshyment o f the synthetic fib er industry with more than 50 million tons of polyester filament and staple produced globally in 2012 It has also seen extensive use in carpets over the recent years

Sustainability is a t the center of the growth strategies in the synthetic fiber industry There are many ways that the industry is addreSSing sustainability including fibers from recycled polyshyes ter and bio-polyester as well as susshytainable developments in production and processing of fibers and ya rns

Since a large proportion of polyshyester textiles and carpets are colored eco-friendly coloring o f textiles is of paramount importance Solution dyeshying or dope dyeing offers an environshymenta lly fri endly way to color polyshyester and other manmade fibers and nonwovens

In this process color in th e form of a masterbatch is added to the poly111er melt during the ex trusion phase of the fiber manufacturing process Thus fiber spinning and coloring are achieved in one step without the use of

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water reducing the env ironmen tal footprint and eliminating effl uent treatment w hile offering cost benefi ts Further solution dyed yarns offer sevshyeral advantages over traditionally dyed yarns includ in g

bull Superior color fastness to ligh t bleach and durability

bull Softerlbetter hand than traditionally dyed fiber and comparable to natural un-dyed yarn

bull Customi zed products by combining color and additives

s such as antimicrobials UV enhancement etc

e e At the co re o f solution dyeing is the y mas terbatch It is more than jus t conshy

centrated co lor It defines co lor qualishy

ty lot-to-Iot consistency and offe rs yarn produ ce rs va lu e in terms of extended pack life fewer spin breaks and higher yield Americhem has been supplying masterbatches for so lu tion dyed manmade fibers (ca rpets and texshytiles) for more than 25 years

Solution dyed recycled fiber is a step ahead in green coloring PET is by far the most widely recycled polymer in the world Historically recycled polyester has been used to make black fibers However with recent advancements in recycling it is used in a wide ra nge of color and addit ive applications

Recycled polyester typically has a yelshylow tint and sometimes it is necessary to enhance the internal viscosity (IV) for better processing When used as a natushyral or white fiber it can have a dull look

Americhem can offer a renewal

additive that helps to mask the co lor and increase the value of the product Americhem is also working towards the development of an additive system for enhancing the IV of the resin

Many of the addit ive technologies such as antimicrobials and UV protecshytion can be adapted to recycled fibers The recently introduced masterbatch FR technology is particularly benefishycial for recycled polyester and offers performance similar to that of virgin polymerized FR resin

A number of other a ttribures are des ired in fibers and nonwoven appli shycatio ns such as soft hand dye enhancement (especially fo r polyshyesters) stain resistance for carpet and more Many of these properties require custom design and can be developed on a case-by-case basis lID

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