Plastic Strapping Characteristics
Nowadays everyone takes plastic strapping for granted but its not been around that long and prior to its discovery and development steel strapping and wire were the materials used to secure product onto pallets. The Dupont Company in USA discovered Nylon in 1934 and further developments resulted in it being developed to the point where it became universally used in the from about 1940 textile industries.
At the begininning of the 1960's Du Pont developed a process for "orienting" nylon strapping, a process that increases the linear strength 3 to 4 times and therefore strong enough and with sufficient impact resistance to tightly secure pallet loads of goods during shipment from factory to customers. Tools and machines were developed to apply the nylon strapping, primarily by Signode and in the UK, Gerrard Industries based in Rotherham. These two companies held between them approx 90% of the UK steel and wire strapping market and consequently the introduction of nylon strapping into the UK was rather slow, as neither company wanted to devalue their own current steel strapping customer base but companies were happy to convert each others steel user accounts.
In the event however the defensive attitude adopted by both Companies was largely responsible for the rapid and successful introduction of Polypropropylene strapping by P.P.Payne Company of Nottingham and it could be said that this company was largely responsible for the rapid decline in steel strapping usage in the UK. Isotactic polypropylene was discovered in 1954 by the Italian chemist Guilio Natta and his assistant Paulo Chini, working in conjunction with the Italian company Montecatini. Catalysts of the type invented by Karl Ziegler, the German chemist, for the production of polyethylene at ambient pressure were used.
Commercial production of polypropylene began in 1957 with Hercules Incorporated, Montecatini and Farbwerke Hoechst AG. ICI produced polypropylene resin as Propathene in 1954. Natta and Ziegler were awarded the Nobel Prize for Chemistry in 1963 in recognition of their work on "Ziegler-Natta" catalysts.
Polypropylene is an important plastic and is used in many different forms and applications through a range of manufacturing processes. A large proportion of polypropylene is used in fibres as constituents of fabrics, upholstery and carpets. Many industrial uses involve ropes, woven and non-woven fabrics and reinforcements. Blow moulded containers, such as bottles for foods, shampoos and other liquids, form part of everyday experience. A wide range of injection moulded items exists in appliance housings, resistant containers, car components, toys and furniture. The remarkable fatigue resistance properties of polypropylene has seen valuable applications in long life hinge designs in packaging containers and elsewhere. Since the 1980s the production, consumption and applications of this important polymer have increased through the application of even more efficient catalysts and property enhancements.
Today, there are five strapping products available in the UK market place to secure pallet loads. In addition to nylon and steel, polypropylene and polyester, with polypropylene strapping being the most popular, followed by the rapidly growing use of extruded polyester strapping, largely replacing steel strapping in most industries,then corded polyester and steel strapping. Nylon Strappingf is seldom used.
A comparison of the features of the three plastic straps available is shown on the following page. A summary of each strap's performance capability is as follows:
- Polypropylene — Least initial tightness after joint is made and highest relaxation over time. Lowest tensile strength and abrasion resistance of the 3 strap types. However, good enough for many applications and lowest cost.
- Polyester — Much stronger than polypropylene (comparable to nylon). Initial tightness on the load is retained over time provided initial elongation is put into strap at time of application. . Excellent resistance to shock loading. If pallet is dropped, more likely for steel strap to break than polyester strapping as required energy to break. polyester is much greater. Intermediate in price between polypropylene and steel other two straps.
- Nylon — Regarded by many as the premium nonmetallic strap. When applied to pallet load, is elongated approx. 7% and retains this extra tension over time. If load shrinks or shifts during transit, strap recovers and shrinks back to maintain tight grip on load. If load is dropped, momentary additional elongation will occur and prevent strap breakage. Best impact strength and abrasion resistance of any other strap product. Priced such that many users regard the incremental additional price as an insurance premium against loose and/or broken straps, especially with shipments of higher value goods. One of the most cost effective of all strapping materials. Nylon strap can be heat sealed, friction welded, or joined with scored metal or grit seals.
Features of Plastic Strapping