PLASTIC STRAPPING – AN OVERVIEW

Over the last 30 years, plastic strapping has grown in popularity as a method of securing goods for transit. This article sets out to examine the different types of plastic strapping available, as well as their properties and characteristics.  

The two main types of plastic strapping are PP (polypropylene) and PET (polyester), both of which are recyclable. However, before plastic strap became available from the 1960’s onwards, Woven Strap or Steel strap were the main materials used to strap packs or pallets.   

Woven Strap is generally made from polyester or rayon yarns woven together and bonded in a hot melt process, and is sometimes referred to as corded strapping. Woven strap is usually applied by hand using buckles to tension it to the pack, and is mainly used where lighter tension is required. 

For high tension applications such as bricks, concrete blocks, timber and tiles etc., steel strap used to be the material of choice, however since the 1990’s Steel has been largely superseded by PET. The advantages of PET compared to Steel are as follows:

-         PET strap slips around the edges of the pack better with less friction and therefore provides better tension and holding force during transit. 

-         PET strap does not kink on the edges, meaning little edge damage to the strapped product. This reduces the need to use edge protection, thereby reducing cost.

-         There are more metres of PET than Steel strap per coil meaning less coil changes.

-         A coil of PET weighs around 24kg whereas a coil of steel weighs around 45kg.

-         Steel strap will rust and can stain the product or packaging that has been strapped.

-         PET less expensive than steel (by at least 30%).

PP Strap is generally extruded from virgin polymer (although some manufacturers add regrind which can lead to issues with splitting) and is available in a variety of colours. Commonly available widths are 5mm, 6.5mm, 9mm, 12mm, and the strap usually has an embossed texture. High Elongation PP (typically 25-50%), which renders the strap less stiff, is useful for smaller packs especially with sharp corners). 

PET used to be made from virgin polymer, but over the last 20 years the trend has been towards using recycled PET bottles to make PET strap hence it is often referred to as RPET. The world’s most advanced PET strap producers have strict quality control procedures not only on the final product but just as importantly on the raw material input because impurities in the recycled raw material could compromise the efficacy of the strap itself. Commonly available widths are 9mm, 12mm, 15.5mm, 16mm and 19mm, and the strap is available either in smooth or embossed variants. Smooth strap would usually be used where the customer requires the lowest possible elongation and the highest possible breaking strength. PET strap is generally green in colour although other colours are available subject to minimum order quantities.   

As well as being available in different widths and gauges, plastic strap is available with different breaking strengths, typically from 55kg up to 730kg according to whether a lighter or a heavier tension is required. When selecting the right strap, it is important to know the dimensions and weight of the pack and how it will be stored and transported. 

Some companies use pre-printed strap either to enhance company branding or to comply with traceability regulations. Alternatively, it is possible to print in-line directly onto the strap meaning that dates and batch codes can easily and quickly be entered into the printer.