Poly Tubing
Poly tubing is a very broad term encompassing the wide spectrum of rigid to flexible, heavy to thin wall, transparent to opaque, cut-to-length or spooled varieties of tubing made from poly materials. The varied characteristics of poly tubing include coiled or spiral, corrugated or convoluted, flat, anti-static, resistant to heat, spark and flame, explosion proof, multi-colored, multi-element or co-extruded and double walled or multi-layered. Materials for flexible poly tubing include polyurethane tubing (PU), flexible vinyl tubing (FPVC), low density and linear low density polyethylene tubes (LDPE and LLDPE). For applications requiring rigid tubing, the following materials are commonly used: polycarbonate tubing (PC), rigid vinyl tubing (RPVC) and high impact polystyrene tubes (HIPS). A polycarbonate tube can be semi-rigid as well as polypropylene tubing (PP) and high density polyethylene tubing (HDPE). Poly tubing can be sterilized to food and beverage grade, making it useful for food processing, medical, pharmaceutical and beverage industries. In addition, poly tubing is used to convey fluids or gases, such as oxygen, water or air, in waste water, commercial pool, industrial and chemical processing industries.
Made through the extrusion process, poly tubing is both durable and cost-effective. To begin the extrusion process, poly resin pellets, also called nurdles, are fed into the extruding machine's hopper, which is a funnel-shaped receptacle through which contents pass by gravity into a receptacle below. The receptacle contains a screw conveyor, which by rotating its screw, serves to continuously convey the pellets forward. In addition, the receptacle is heated and the pellets are being softened by both heat and friction as they are conveyed forward. By the time the pellets comes to the end of the screw conveyor, the pellets have become "plasticized", or made completely molten. On the end of the conveyor channel a die orifice is secured which forms the molten plastic into a specific profile as it is pushed, or "extruded" through by the screw conveyor. In order to form a poly tube, a pin or mandrel must be placed inside of the die and a positive pressure is applied to the internal cavities through the pin. This creates the hollow inside of the tube. The newly formed poly tubing is instantly cooled with cold water and becomes solidified. Lastly, the poly tubing is conveyed onwards to take-off rollers, which actually pull the softened poly material from the die, to a series of conveyors and is then cut to length.