Battles between flexible polymers and their rivals both inside and outside of the plastics industry have not cooled off along with the global economy. If anything, the skirmishes have heated up, as each percentage of market share gains value in a lower-growth climate.
At Flexpo 2002, held Sept. 18-20 in Houston, several end markets were dissected to show what kind of progress flexible polymers are - or are not - making.
Flexible materials will have to improve somewhat to cash in on a footwear market that consumed more than 11 billion pounds of soling material in 2001, according to Mike Zhuang, a polymer development chemist with boot maker Timberland Co. of Stratham, N.H.
Among plastics, PVC has the highest share of a market that's still dominated by rubber. PVC has a 20 percent share of footwear, while several kinds of rubber total 54 percent. But PVC's ``shiny'' appearance has relegated it to inexpensive rain boots and agricultural boots, Zhuang said.
Styrenic block copolymers hold a 15 percent market share, with ethylene vinyl acetate at 8 percent and polyurethane at 7 percent. Thermoplastic polyurethanes hold only a 1 percent share, with their high price limiting them to high-end specialty applications in athletic shoes.
``Shoes now are more about comfort, so manufacturers need a performance material,'' Zhuang said. ``It's not just function anymore.''
For example, TPEs - including SBCs and TPUs - need to improve their soft feel while reducing the amount of compression set they need, particularly in midsoles. Plastic materials also need increased shock absorption, Zhuang said, considering that the impact of the average person's shoe hitting the floor with each step can be as much as four times their body weight.
PVC remains the dominant plastic in flooring and looks to remain that way, although some challengers have made minor inroads in recent years, according to Chandresh Kedhambadi, a research analyst with Houston-based Chemical Market Resources Inc.
``There's been little recognition of PVC alternatives by flooring producers,'' he said. ``PVC remains unchallenged in [ultraviolet light] resistance, mildew resistance, sterilization and color- ability.''
Major flooring producers, including Armstrong, Congoleum, Mannington Mills, Domco, Tarkett Sommer and National Floor & Tile, remain committed to PVC to the extent that they each do their own compounding of the material. PVC flooring accounted for about 4 billion pounds of material in North America and Europe in 2001.
Some challenges to PVC have come from alternate natural materials such as linoleum, bamboo and wood, but PVC's low cost - and low growth rate of 1-2 percent annually - may be deterring others from entering the market.
One that has entered is Amtico Co., a Coventry, England, firm that last year commercialized its Stratica-brand polyethylene flooring. Stratica is made through a combination of ethylene copolymers with Wilmington, Del.-based DuPont's Surlyn-brand ionomer.
Tarkett Sommer also introduced a nonchlorinated plastic flooring in Europe last year, but Kedhambadi described Tarkett's approach as ``not very enthusiastic.''
Other potential rivals to PVC flooring include Dow Chemical Co.'s Affinity-brand polyolefin plastomer and Atofina Petrochemicals Inc.'s syndiotactic polypropylene. Dow's ethylene styrene interpolymer had made some inroads in flooring before Dow announced it would stop producing the material because of insufficient growth.
PVC flooring's low installed cost of $1.50-$2.25 per square foot also works in its favor, since similar costs for competing materials range between $3 and $10 per foot.
Kedhambadi said the drive to replace PVC flooring is stronger in Europe than North America. Yet the European PVC flooring market remains slightly larger than its North American counterpart, suggesting such efforts have been less than successful.
A more positive flexible polymer growth story comes from Pliant Corp. of Schaumburg, Ill., where metallocene or single-site-based enhanced PE now accounts for about 20 percent of the firm's stretch film production, according to senior product development engineer Brooke Kitzmiller.
Single-site linear low density PE has improved the puncture resistance and load retention of Pliant's stretch film in numerous applications, but Kitzmiller pointed out that film processors still need to use the material ``discriminately'' because of its higher cost and shortcomings in tear strength.
Market performance backs up Pliant's acceptance of metallocene/single-site materials. Since 1995, metallocene/single-site PE sales have grown to represent 12 percent of total LLDPE volume in North America. Growth in butene-based LLDPE has been 50 percent since the metallocene/single-site materials began to assert themselves in the market.
Pliant uses its highest metallocene/single-site LLDPE content in stretch film, but also uses the materials in blends for packaging and masking films, Kitzmiller said.
PVC also retains a dominant market share of 33 percent in the North American wire and cable market, but most volume growth in the past 15 years has been captured by flexible polyolefins, according to CMR senior research analyst Faisal Syed.
PVC use in North American wire and cable totaled 500 million pounds in 2001, primarily in jacketing and insulation.
Cross-linked PE has continued to phase out oil- and paper-based cable based on performance and handling, while use of nonhalogenated flame-retardant systems also is on the rise, Syed said.
Other wire and cable trends identified by Syed include downgauging in automotive applications and further penetration of metallocene grades of PE and ethylene propylene diene monomer into medium voltage uses and other niche segments. Overall plastics use in wire and cable is growing almost 3 percent per year.
``Wire and cable is a maturing market, and that's forcing producers to drive down costs while enhancing performance,'' Syed said.
In commercial roofing, EPDM holds a market share of almost 30 percent, based on its durability, cost and weatherability, but thermoplastic olefins are charging fast, with annual growth rates of almost 9 percent, according to CMR research analyst Vipool Bhatt.
EPDM and styrenic block copolymers each are growing at rates of 4.5 percent, while atactic polypropylene is growing at less than 3 percent. PVC - at less than 2 percent - has the lowest growth rate of major commercial roofing plastics, accoring to Bhatt.
Single-ply commercial roofing - using EPDM and PVC - will continue to take market share away from older, asphalt-based, ``built-up'' commercial roofing, Bhatt added.
But PVC will lose market share within that sector because of increased use of modified bitumen roofing, which uses SBC and atactic PP.
TPOs became a viable material in commercial roofing when technological advancements allowed the material to be calendered like PVC, Bhatt said.