1

Development of Polyolefin Elastic Fibers

In early 1990, J. Stevens and coworkers (US patent 5278272) from Dow Chemical discovered metallocne catalyst for ethylene polymerization that can incorporate high amount of alpha olefin such as octene to make copolymer that has elastic properties of an elastomer. This discovery has revolutionized the polyolefin industries. The copolymer was commercialized under the commercial name of AFFINITY*TM. The elastomer has elastic properties for stretch apparel applications. However, its upper service temperature (about 60oC) is not high enough for the applications.

In 2000, T. Ho and coworkers (US patent 6803014) from Dow Chemical developed the process for crosslinking fibers from AFFINITY*TM to improve its upper service temperature. The crosslinked fiber has upper service temperature greater than 220 0C which is much better than the upper service temperature of Spandex (175oC). The commercial name of the crosslinked elastic fiber is XLA*TM.

2

R R

n m p

R R

n m p

R = C6H13 = crosslinking

R

R = C6H13

R

Polyethylene(rigid segment)

Ethylene-octene copolymer(soft segment)

n m p

Crosslinking Crosslinking

XLATM is a crosslinked ethylene-octene copolymer. Ethylene-octene copolymer is an elastomer that consists of a rigid segment of crystalline ethylene polymer and a soft segment of ethylene-octene copolymer that provides the elasticity. The crosslinking provides the high service temperature (greater than 220oC).

Chemical Structure and Morphology of XLA*TM

3

Crosslinking

XLA Fiber

Fabrication Process of Stretch Fabrics

Melt SpinningWrapped withnatural fiberFabric

TM

Co-knit with hard fiber

4

Properties of XLA*TM Fibers and Fabrics

• Soft stretch feature• Thermal resistance• Chlorine resistance• UV stability

5

Soft Stretch Feature of XLA Fiber

Elongation, %0 100 200 300 400 500 60

0

Load

, g

0

10

20

30

40

50DOW XLATM

Spandex

40 denier

For an equivalent of elongation, the load for spandex is greater than the load for the DOW XLA fiber. Therefore, it requires lower retract force for the DOW XLA containing stretch fabrics to relax. This translates to a softer and more comfortable stretch in garments containing DOW XLA.

6

Temperature, °C

25 50 75 100 125 150 175 200 225 250106

107

108

109

DOW XLA

Spandex

Temperature, °C

25 50

Temperature, °C

25 50 75 100 125 150 175 200 225 25075 100 125 150 175 200 225 250106

107

108

109

106

107

108

109

DOW XLA

Spandex

E’(dynes/cm2)

XLA*TM

Spandex

Fibers at 230oCDynamic Mechanical Thermal Analysis

Thermal Resistance

The left figure shows that spandex melts at about 175oC while DOW XLA has thermal resistance to greater than 220oC. The right picture shows that at 230oC spandex fiber melts and breaks while the XLA fiber is intact. The thermal resistance of DOW XLA translates into a fiber which can be processed, by fabric producers or consumers, at higher temperatures than typically recommended for spandex. Fabric mills can incorporate stretch into fabrics that are dyed using the thermosol process at 210°C, and consumers now have an elastic fiber that can be ironed on a high setting (above 200°C or “3 dots”) without concern of degrading its stretch properties.

7

Chlorine Resistance of Fibers

0

20

40

60

80

100

120

0 10 20 30 40 50

HOURS in Cl2 bath @50 C

% T

enac

ity r

etai

ned

XLA 40D

XLA 70D

XLA 140D

Spandex CR

Good chlorine resistance is required for applications such as stone washed jeans and swimwear. Fibers were exposed to a solution of 100 ppm of chlorine at 50oC. DOW XLA elastic fiber has much better chlorine resistance than spandex. This is another improvement in properties that allows design freedom for fabric and garment producers

8

Effect of UV Radiation Time on Tenacity for DOW XLA* and Spandex

0

0.5

1

1.5

0 5 10 15 20 25 30 35 40

UV Irradiation Time (hr)

Tena

city

(g/d

enie

r)

DOW XLA*

Spandex

The UV stability of DOW XLA is much better than spandex fibers. The resistance to UV degradation is critical to applications such as swimwear, outdoor wear, and other sports apparel.

9

Ready-to-wear (no need to iron)

SwimwearDenim

Active Wear Tailored Clothing

Intimates

XLA*TM fiber with improved service temperature, combined with good chlorine resistance and UV stability enables new concepts in stretch garment care and offers textile mills broader processing windows. Examples of applications of XLA*TM are shown below.

10

Conclusions• New polyolefin elastic fibers for stretch apparel were developed.

• The new fibers have the following advantage– Soft stretch

• Fabrics are softer and have more comfortable stretch– Superior thermal resistance

• High temperature dye process• High temperature heat set process• Can be ironed at high setting temperature

– Superior chlorine resistance• Stone washed jeans• Swimwear

– Superior UV stability• Outdoor wear

• XLA fibers enable new concepts in stretch garment and offer textile mills broader processing windows

• XLA has been awarded the new generic classification of lastol by the Federal Trade Commission

11

12

Dr. Thoi Ho is a technical consultant in the area of polymer additives for plastics. He obtained a BS in Chemistry from Saigon University, a PhD in Polymer Chemistry from Tohoku University, Sendai, Japan, and completed post doctoral work at Columbia University, New York. He served as a technical leader in Polycarbonate and Polyolefin R&D departments for Dow Chemical Co. Dr. Ho has over 26 years of experience in process chemistry, new product development, and polymer additives (antioxidants, light stabilizers, flame retardants, processing aids, and slip agents) for polycarbonates and polyolefins with Dow Chemical. He is an inventor and a co-inventor of 90 U.S. and world patents. He is currently chairman elect of the Polymer Modifier and Additive Division (PMAD) of the Society of Plastics Engineers.

Biography of the Speaker

13

Acknowledgment

The author would like to thank his former colleagues Drs. Selim Bensason and Rajen Patel for their expertise in material science and fiber spinning, and Dr. Rona Reid for her expertise in textile technology.

14

Key References

• W. Hoenig, T. Ho, R. Reid, and P. Yap, Development of a New Polyolefin Elastic Fiber- Enhancing Service Temperature and Chemical Resistance to Enable New Concepts Stretch Apparel Application, International Polyolefin Conference , 2004.

• T. Ho. S, Bensason, R. Patel, K. Houchens, R. Reid, S. Chum, L. Walsh, “Method of making elastic articles having improved heat resistance”, US patent 6,803,014 B2, 2004

• T. Ho and J. Martin, “Structure, Properties and Applications of Polyolefin Elastomers Produced by Constrained Geometry Catalysts, Metallocene-based Polyolefins Edited by J. Scheirs and Kaminsky , 2000 John Wiley & Sons Ltd, vol.2, page 175

• S.Y. Lai, J.R. Wilson, G.W. Knight. And J.C. Stevens, “Elastic Substantially Linear Olefin Polymers”, US patent 5,278,272

• S. Chum, C. Kao, and G. Knight, “Structure, Properties and Preparation of Polyolefins Produced by Single-site Catalyst Technology, Metallocene-based Polyolefins Edited by J. Scheirs and Kaminsky , 2000 John Wiley & Sons Ltd, vol.1, page 261

• Spandex-Wikipedia