Polyurethane Fabric
Polyurethane (PU) is a composite material made of: (1) one or more layers of polymer resins joined by urethane links; and (2) a woven or non-woven textile backing such as polyester, cotton, nylon, or ground leather. The PU coating is applied to a single side of the base fabric and then treated to look more like animal hide. This makes the fabric water resistant, light weight and flexible. This fabric provides the most realistic imitation of leather when it comes to its soft supple hand. When stitched, gathered, or tufted it actually “breaks” or wrinkles like real leather.
PU resins are made of a soft polymer and unlike vinyl don’t need added plasticizers. Because no plasticizers are used in PU upholstery there is no cracking or peeling, and it remains soft and supple for the duration of time it remains on the furniture. PU fabrics are also easier to decorate. PU is considered greener than vinyl because it does not create dioxins. PU costs less than real leather, but it can be more expensive to produce than vinyl.
Polyurethane Resin Systems
All polyurethane coated fabrics are made from polymer resins. There are three basic types of resins used in making polyurethane coated fabrics.
1. Polycarbonate (PC) – The best resin available. It is very durable with high resistance to humidity, heat and light. PC resins are suitable for high traffic commercial upholstery applications.
2. Polyether (PET) - Good resistance to humidity, heat and light. PET resins are suitable for most commercial applications.
3. Polyester (PES) - Low resistance to humidity, heat and light. PES resins are only suitable for low activity commercial applications (e.g., headboards and pillows).
These resins can be used individually or in combination, such as:
• Polycarbonate
• Polyether – Polycarbonate
• Polyether- Polyester
The cost of the PU upholstery fabric is directly correlated to the quality of the resin that is used, as well as other performance additives that are required to consider a PU fabric suitable for commercial use. Colorfastness and stain resistance are achieved through the skin layer and/or top finish of the fabric. Chemical additives can improve the performance of abrasion resistance, hydrolysis resistance, flame retardation, lightfastness, and cleanability.
Polyurethane Coated Fabric Manufacturing Process
There are two processes available for manufacturing polyurethane coated fabrics, referred to as “Wet” and “Dry.”
Wet PU Process
The Wet PU manufacturing process consists of coating a coagulated base on a substrate backing. An adhesive layer is then applied to the base and another layer, or top coat is decorated with color and design. The wet process can use any of the resin system combinations described previously. The wet process is used in the vast majority of PU upholstery on the market today.
Dry PU Process
In the Dry PU manufacturing process, the coagulate base is totally eliminated. The PU is coated directly on the face of the backing. The chemical reaction in the dry process provides enhanced strength and performance. The resin system can be either: two-component reactive polyether-polycarbonate; or high solid polycarbonate. The high quality resins are processed in a cleaner and more environmentally sound manufacturing environment. Over 99% of solvents are recaptured and recycled. The dry manufacturing process uses about 25% less energy than the wet process.
Timeline of Polyurethane Applications
1937
Dr. Otto Bayer discovers the basic polyurethane chemistry at the I.G. Farben Laboratories, a subdivision of Bayer Corporation, in Leverkusen, Germany.
1940s
The practical application of polyurethane dates to the beginning of World War II where it is was first developed as a replacement for rubber. The versatility of this new organic polymer and its ability to substitute for scarce materials, spurred numerous applications. During World War II, polyurethane coatings were used for the impregnation of paper and the manufacture of mustard gas resistant garments, high-gloss airplane finishes, and chemical and corrosion resistant coatings to protect metal, wood and masonry.
The first commercially available polyurethane was introduced by DuPont Corporation in 1948. The material was rigid foam used in the insulation of beer barrels. Dow Chemical, BASF, and Mobay Corporation introduced polyurethane materials.
1950s
Shoe soles for sneakers introduced synthetic polyurethane leather. Flexible foam cushions for seating were introduced with the first commercial production in Europe and soon thereafter in the United States. In just a few years flexible polyurethane foam became the material of choice for furniture upholstery and car seats.
1960s
Polyurethane made its way into apparel with DuPont’s Spandex fiber renamed Lycra. The fiber soon ended up in men's and women's figure-flattering swimwear and then hit the ski slopes in 1968 in the Lycra garments of the French Olympic ski team. In the mid-60s polyurethane was being used in automobile upholstery.
The first all plastic automobile (made from polyurethanes..!) introduced in 1969 by Bayer AG Corporation in Dusseldorf, Germany.
1970s
In the 1970s, cyclists traded in their woolen shorts for "aerodynamic" spandex shorts, and the versatile fiber began to find its way into dancewear, tights, and stretch jeans.
Polyurethane used as a spray building insulation as rising energy costs drove down the use of PVC, one of the most common synthetic building materials in the world.
1980s
By the 1980s, spandex had a commanding presence in hosiery. As pop singer Madonna started a trend in the '80s to wear innerwear as outerwear and sports-looks translated into new street-wear fashions, Chanel couture skirts set fashion trends with the use of spandex in leggings.
Energy absorbing polyurethane foams began being used in automobiles for passenger safety.
1990s
Thin wall medical hoses (i.e. catheters) are made with polyurethane.
CFCs no longer added to polyurethane products and are replaced by alternative substances (hydrocarbons, HCFCs, CO2, etc.) that are environmentally-friendly.
2000s
Beginning in the early 2000s, industry efforts to become more environmentally friendly created polyurethanes made from vegetable oil polyols, most notably soy-based polyurethane used by Ford Motor Company in recent automobile interiors (dashboards, side-panels, etc.). A significant development in that evolution of luggage came in 2000, when Rimowa introduced the first suitcase made of polycarbonate. Lighter than aluminum and highly durable, polycarbonate set the stage for the hard-shell cases that are now made by many major players in the luggage industry.
2010s
In 2010, The Mitchell Group introduces Sta-Kleen®, the first dry erase ink and stain resistant polyurethane upholstery fabric.
In 2017, The Mitchell group introduces Sta-Kleen Polycarbonate™, a PU made from 100% polycarbonate resins.
Today an amazing number of products are made from polyurethane. They include bowling balls, surf boards, roller coaster wheels, soccer balls, housing insulation, bandages, denim jeans, running track and roofing tiles.
In 2016, polyurethane accounted for about 1.1 billion dollars in sales in the United States from all applications. The end use of polyurethane can be segmented as follows:
Shoes 32%
Furniture 26%
Automobile 13%
Clothes 05%
Other 24%