Commonly known as "poly-coating," PU coating is polyurethane applied to the surface of a fabric. Polyurethane is a type of polymer, a synthetic compound made from petroleum residue. PU coating on fabric is an excellent way to ensure the material doesn't get ruined. Applied to fabrics like polyester, nylon, cotton, and leather, it acts as a protective film, usually on one side of the material.
Fabrics with PU coating are more lightweight, water-resistant, and flexible. The protective PU coating can be single-coated (on one side) or multi-coated (on both sides). Polyurethane is often applied to polyester, typically through heat lamination. Industries such as pharmaceutical, diaper, activewear, and pet product companies all use polyurethane fabrics.
Properties of Polyurethane
Polyurethane fabrics are breathable and lightweight. Clothing with PU coating retains its properties even after 100+ washes and dries. Originally intended for hospitals, PU coating provides durable, waterproof materials for bedding and scrubs—essential in environments where strong, waterproof fabrics are a must.
PU coating on fabric can be manufactured in various thicknesses, making it versatile for different uses. Diapers use thinner coatings compared to camping gear, but the material remains durable and waterproof. Polyurethane fabric can also be fire-retardant, airtight, and resistant to abrasion and humidity, making it suitable for many applications. It's often applied to only one side of the material.
PU Fabric
Polyurethane fabric closely imitates leather, especially when gathered or stitched. Unlike vinyl, PU coating includes resins that don't need plasticizers, resulting in a softer polymer that resists cracking and splitting.
Polyurethane fabrics are preferred for furnishings due to their durability and ease of decoration. A significant advantage is that PU coating is a greener option than vinyl, as it doesn't create dioxins. While more expensive than vinyl, it's cheaper than real leather.
About Polyurethane Resin Systems
All fabrics coated with polyurethane contain polymer resins. The three main types of resins in PU coating include:
- Polycarbonate (PC): Durable with high heat and light resistance, suitable for commercial upholstery in buses, trains, and airplanes.
- Polyester (PES): Ideal for low-activity commercial applications like headboards and pillows, but has low resistance to heat, light, and humidity.
- Polyether (PET): Excellent resistance to humidity, light, and heat, making it suitable for many commercial applications.
These resins can be used individually or in combination. The cost varies depending on the resin quality. Performance additives are also required to ensure polyurethane fabric is safe and ready for commercial use. PU coating on fabric is known for its color-fastness and stain resistance. Adding new chemicals can enhance its resistance to abrasion and flames.
PU Coating On Fabric - The Manufacturing Process
There are two main processes for manufacturing polyurethane-coated fabrics: wet and dry.
Wet Polyurethane Process
The wet process involves coating a coagulated base on a substrate backing. It uses resin system combinations with adhesive layers applied to the bottom and top. Topcoats are colored and designed. This process is mainly used in upholstery today.
Dry Polyurethane Process
The dry method doesn't use a coagulate base. The polyurethane adheres directly to the face of the backing, offering a chemical reaction that provides better strength and performance. Two resin systems are used: solid polycarbonate and polyether-polycarbonate. Higher quality resins are processed in more environmentally friendly environments, with almost 100% of solvents recaptured and recycled. The drying process also uses 25% less energy than the wet process.
PU Coating On Fabric: Things To Consider
There are many benefits to using PU coating on fabric. Here are some key advantages:
Environmentally Friendly
The dry process for polyurethane is an environmentally friendly option. Polyurethane fabric doesn't use solvents and doesn't produce harmful toxins. Unlike materials like PVC, polyurethane is strong, durable, waterproof, and heat-resistant. PU ensures a reduction in waste and is ideal for products like life vests.
Easy To Clean
Polyurethane fabric is one of the most durable materials for furnishings. Its ability to block moisture makes it easy to clean. Stains can be removed with soap and water. Diluted bleach or other spirits can be used on solvent-resistant blends. Avoid harsh chemicals like acetone or vinegar, as they can damage the material. Always follow the care instructions on the label to avoid ruining the fabric blend.
The History of Polyurethane Application
Here's a timeline of the history of polyurethane fabric:
1937
Dr. Otto Bayer discovered the basic polyurethane chemistry at the IG Farben Laboratories.
The 1940s
Polyurethane started replacing rubber and was used for paper impregnation and mustard gas-resistant clothing. It was also used in high-gloss airplane finishes. In 1948, DuPont Corporation made polyurethane commercially available as a rigid foam for beer barrel insulation.
The 1950s
Synthetic polyurethane leather was first used in sneaker soles. Foam seat cushions began in Europe and then in the US, with flexible polyurethane foam becoming the material of choice for car seats and furniture upholstery.
The 1960s
DuPont used polyurethane in clothing, rebranding Spandex fibers into Lycra for swimwear. In 1969, Bayer AG Corporation introduced polyurethane to the all-plastic car in Germany.
The 1970s
Cyclists used PU coating on fabric for aerodynamics. Spandex shorts became popular as versatile exercise clothing. In the late 1970s, polyurethane was used as a spray for building insulation due to rising energy costs.
The 1980s
Spandex was popular in hosiery and regular wear, like leggings and Chanel skirts. Polyurethane foams were used in automobiles for passenger safety.
The 1990s
Polyurethane was used in thin-wall medical hoses, such as catheters, due to its environmental benefits.
The 2000s
Industries shifted towards more environmentally friendly practices. Polyurethanes were made from vegetable oil polyols, such as soy-based polyurethane used by Ford. Rimowa introduced the first polycarbonate suitcase, which was lighter than aluminum options.
The 2010s
The Mitchell Group introduced Sta-Kleen, the first dry-erase ink and stain-resistant PU upholstery fabric. In 2017, they introduced Sta-Kleen Polycarbonate, a polyurethane made from 100% PC resins. Polyurethane accounted for $1.1 billion in sales in the US in 2016 and is a primary material for pet-related products, beanbags, canopies, life vests, and boats. The diaper industry also uses polyurethane fabrics as a replacement for disposable options.