Plastic tubing is tubing constructed from plastic compounds for use in fluid flow or structural systems, or as insulation or sheathing for electrical or heating assemblies. Plastic tube is lightweight and versatile, used commonly as flow lines for fluids and gases in pneumatic, hydraulic, process, medical and many other applications. Tubing can be flexible or rigid depending on the material type and its intended purpose, though tubing listed in this product area is generally smaller and less rigid than materials classified as hose or pipe. For sourcing larger and more rigid plastic vessels, refer to the Plastic Pipe product area.

Plastic Materials

The most important consideration in plastic tubing selection is the type of plastic material. Most of the physical properties of the tubing will vary with different types of plastic.

EVA (Ethyl Vinyl Acetate) is a plastic that exhibits high impact strength, excellent low temperature properties, and good resistance to grease, oil, and weathering. EVA tubing is an excellent substitute for types of vinyl tubing used in surgical and pharmaceutical applications.

Fluoropolymers, such as PFA and FEP, are versatile plastics used in nearly every field of industry and technology. They have an excellent temperature resistance in a range from -200 to 500°F continuously, and are inert to almost all industrial chemicals and solvents. These properties make them particularly suited for corrosion protection and high or low temperature applications. Some notable fluoropolymers include PTFE and PVDF.

• Polytetrafluoroethylene (PTFE) is a fluoropolymer often marketed as Teflon^®, a registered trademark of DuPont Dow Elastomers. It has one of the lowest coefficients of friction against any solid, giving it the highest service temperature of all plastic tubing and making it ideal for handling viscous and sticky materials. PTFE also has excellent dielectric properties which are convenient for electrical sheathing and insulating applications.
• Polyvinylidene fluoride (PVDF) is a melt-processable fluoropolymer which has better strength and lower creep than other fluoropolymer types. PVDF has good wear resistance and excellent chemical resistance, but does not perform well at elevated temperatures. Its common trade name is Kynar^® (Elf AtoChem).

Nylon (polyamide) is a trademark plastic developed by Dupont in the 1930s. It has been recognized as an industry standard for assemblies (particularly pneumatic) which require higher pressure and good temperature and chemical resistance. Nylon has excellent elastic memory and can withstand repeated flexing over an extended period without wear or tube damage. It also exhibits high impact resistance down to subfreezing temperatures, and low moisture absorption which diminishes size/dimensional instability.

Polyethylene (PE) is a lightweight plastic used readily in food and beverage, laboratory, and chemical processing applications due to its high degree of inertness. It is notably inexpensive compared to most other plastics and can handle a wide variety of applications.

Polyketones (PEEK, PEK, PEKK) are high-performance thermoplastics with melting points in the range of 490°F. They are relatively inexpensive and exhibit good solvent resistance and mechanical properties.

Polypropylene (PP) is the lightest weight thermoplastic. It has excellent dimensional stability and electrical properties as well as good surface hardness and chemical resistance. It is inexpensive, and can be used as a low-cost alternative to fluoropolymer tubing. Polypropylene is also weldable, which can be ideal for structural (non-fluid flow) applications.

Polyurethane (PU) is a softer plastic that combines the best properties of plastic and rubber. It has excellent flexibility, good chemical and abrasion resistance, and excellent weathering characteristics. It can also withstand higher pressures than PVC. Polyurethane has notable resistance to gasoline, oils, and other petroleum-based chemicals, making it an excellent choice for fuel lines and similar applications. It is important to distinguish between the ester and ether formulations of polyurethane. The ether version has superior hydrolytic stability, while the ester type has slightly higher strength and temperature resistance but degrades when subjected to water or humid environments.

PVC (poly-vinyl chloride) is a plastic with a broad range of physical properties. These include good chemical and corrosion resistance, excellent abrasion and wear resistance, excellent flexibility, and outstanding flow characteristics. It can be manufactured to various levels of hardness including wire/braid reinforced and rigid pipe. PVC is available in a number of formulations certified for various industries and applications such as potable water lines, food and beverage, chemicals, protective coverings, and insulation sleeving.

Sizing

Correctly sizing plastic tubes is important for fitting them to the needs of the application. Nominal sizes for tubing are based on the outside diameter, which measures across the full cross section of the tube. Wall thickness and inner diameter can then be used to determine the thickness of the tube wall and the flow area (if applicable) for fluid flow inside the tube.

Performance Specifications

Tube performance is typically rated based on a few key specifications, most of which are dependent on the material(s) of construction.

Pressure rating defines the minimum or maximum pressures the tube is designed to withstand, measured in pounds per square inch (psi). This rating is defined for tubes in fluid flow applications.

Maximum vacuum defines the maximum vacuum pressure that can be created in the tube, most frequently given in inches or millimeters of mercury, referenced below one standard atmosphere.

Minimum bend radius is a rating based on the acceptable amount of deformation the tubing cross-section can undergo, typically given in inches or millimeters. This is particularly important for structural applications where the tubing is subject to loading.

Temperature range defines the full range of ambient temperatures that the tubing is designed to operate within. Operating outside the specified temperature range of the tubing affects its performance and could cause permanent damage or failure.

Finish

In some applications, it may be important to consider the finish or color of the rubber tubing.

• Clear tubing is completely see-through, which is important for liquid handling applications where the flow must be monitored.
• Solid tubing is opaque and is finished with one solid color. Some applications involving multiple tubes may require a number of different colors to distinguish between separate flow lines or cables.
• Translucent tubing allows partial light passage so liquid flow is partly visible and can be monitored.
• Multi-colored tubing is finished with more than one color, either for decorative or indicating purposes.

Features

Rubber tubes may incorporate a number of features based on the application they are designed for.

• Reinforced tubing material is reinforced with fibers, wires, or banding for added strength.
• Spark resistant tubing is constructed to maintain integrity in the presence of electrical discharge or sparking. This is a crucial feature for tubing used in electrical applications.
• Sterilizable tubing has the ability to be sterilized for sanitary applications. Methods for sterilization include the application of dry heat, gamma irradiation, or chemical disinfection, as well as autoclaving.

References

Plastic Tubing - Teel Plastic, Inc.

Plastic Tubing and Hose - New Age Industries

Image Credit: ICO RALLY | Automationdirect.com | Ark-Plas® Products, Inc.