PVC and polyurethane are thermoplastic materials that can be formed into a variety of shapes, including tubing and reinforced hose. Both materials are useful in numerous applications. But depending on factors such as temperature, chemical compatibility and plasticizer use, one product may perform better than the other in a particular application. This article examines each material’s benefits, drawbacks, and common uses as they pertain to products that are generally available for variety of industries.
Although no plastic tubing product can universally handle all applications, PVC (polyvinyl chloride) products cover one of the widest ranges of applications serviced by any one type of plastic material. Flexible PVC tubing offers a broad range of chemical and corrosion resistance, excellent abrasion and wear resistance, rubber-like flexibility, visual contact with the flow (with clear styles), and outstanding flow characteristics. These features, along with various construction options like wire, spiral, or braid reinforcement or unreinforced tubing, and the different formulations available (industrial, fuel and oil grade, 3-A, FDA, NSF, USP Class VI), make PVC attractive for a wide variety of uses. (See Figure 1)
Examples include chemical processing, water transfer, waste product lines, viscous fluid handling, wet or dry food handling, beverage transfer, dairy processing, granular material conveyance, air and gas supply, vacuum lines, pump discharge, spray systems, small engine fuel lines, protective jacketing, potable water, and irrigation systems.
Some of PVC’s disadvantages are that it may harden and become less pliable when certain fluids—concentrated acids and alkalis, for example—are transferred through it. Standard PVC tubing does not react well with fuels and oils; the tubing will harden and crack. Special PVC formulations are available for fuel and oil applications, such as those involving small engines.
Industries that use PVC tubing include: medical; industrial; laboratory; chemical; food, beverage, and dairy; appliance; cleaning apparatus; pool and spa; and energy.
Polyurethane, often abbreviated as PU, PUR, or TPU, combines the best properties of plastic and rubber. It offers high elongation values (stretchability) like rubber and abrasion resistance that’s superior to PVC. Polyurethane is naturally flexible and does not use additives to retain its flexural properties.
Combining good chemical resistance with excellent weathering characteristics sets polyurethane apart from other thermoplastics. Polyurethane is generally more resistant to pressure and vacuum applications than corresponding sizes of PVC or rubber. It is also more cut resistant than most other thermoplastics. (See Figure 2)
The two basic formulations of urethane, ester and ether, have some important differences. Water attacks ester-based urethane, causing a significant reduction in physical properties. Ether urethanes exhibit far superior hydrolytic stability, especially in humid environments. Ether-based materials also resist fungus growth better than ester-based materials.
Generally, polyurethane is tackier than PVC. It may stick to itself, which— especially in the case of tubing—can result in tangles. Additives can be mixed with the polyurethane resin during manufacture to reduce tackiness. Material combinations such as PVC/polyurethane blends can also change the surface characteristics, but PVC by itself has a naturally slipperier surface than 100% polyurethane.
Typical polyurethane tubing applications include pneumatic control systems, cable jacketing, air lines, powder and granular material transfer, fluid lines, sleeving, low pressure hydraulics and robotics.