Pulling all the right strings
Diversity and multiplicity
What are pultrusions?
Formed from the words pull and extrusion, pultrusions are reinforced composite structural profiles such as rods, tubes or channel sections made from fibreglass, aramid (an exceptionally strong and lightweight synthetic fibre), carbon or even jute, and a matrix formed from resins such as polyester, polyurethane or epoxy. The combination is extruded through a heated die to polymerize the resin and shape it to the desired profile.
Today Pultron Composites fabricates thousands of products for applications in defence, electrical engineering, civil construction, sewage and water supply infrastructure, mining and petroleum exploration, and recreation. Aside from electric fence posts, products range from tent poles and trampoline springs through to sail battens, rock bolts for mine and tunnel supports, reinforcing re-bars, marine mooring whips, walkways and walkway gratings, pier ladders, tool handles, cables, antennas, power pole cross arms and separator rods.
Such application and product diversity is only possible because pultrusions offer a unique combination of properties. When compared with aluminium, brass, steel and stainless steel, pultrusions offer greater durability and resistance to corrosive chemicals, have an excellent strength-to-weight ratio, and are three times stronger than mild steel under tension, with a much lower modulus making it more flexible. It also has a quarter the density of steel.
Pultron Composites specialises in the design of high-performance rods, springs and small cavity profiles.
Pultrusions can withstand up to five times as much stretch under the same load, making them ideal for spring applications in chairs or trampolines, or any other application that requires a specialized structural profile. The ultimate tensile strength of a unidirectional pultrusion can be over 1,200 megapascals with a modulus over 50 gigapascals, depending on the construction.
Pultrusions also offer excellent insulation properties, which is why they are ideal for use in electrical engineering applications. A pultrusion can act as 200-kilovolt insulator, for example, and at the same time withstand a heavy structural load. Similarly, the ladders used by lines crews around New Zealand to service electricity lines are made from Pultron's pultrusions because they offer better electrical safety should a crew member accidentally touch live wires. Pultron Composite's re-bars for concrete reinforcing are used for specialist applications. For example, a construction project in the Marshall Islands where the concrete was mixed using salt water rather than fresh water. In this situation, steel re-bars would last less that a year, whereas pultruded re-bars are immune to this corrosive environment.
