TPU is one of the strongest elastomeric polymers available and is ideally suited for making fully reusable products. It can be produced in a variety of different grades ranging from extremely soft & flexible, to fully hard & rigid. Our standard range of Classic and i-Tie rapstraps are made using a relatively soft TPU (90A shore hardness) currently supplied by Coim S.p.A. in Milan. At least 30% of the material we use is recycled.

The rapstrap Classic uses this 90A material to offer maximum elasticity, whereas our second-generation rapstrap i-Tie can be moulded from stiffer grades for extra strength (up to 60D hardness).

A fire-retardant i-Tie is available using a soft TPU that meets UL-94 V2 at 0.8mm.

Fully recycled PVC (taken from old cable sleeving) offers a 100% recycled alternative to our standard TPU rapstraps. This material can be used to produce heavy duty versions of the rapstrap Classic, and we have also successfully produced rapstrap i-Ties using it.

By itself, this reclaimed PVC material is not sufficiently elastomeric to produce a convincing rapstrap, so we blend it with around 25% reclaimed TPU to compensate.

This is unusual, as most polymers cannot be simply mixed together like this. But surprisingly, the resulting polymer alloy is almost as strong as pure TPU. Furthermore, it's more weather-resistant than standard TPU, and the high PVC content offers better chemical resistance in acidic environments.

Developed in France in the 1940s, PA11 ("nylon 11") is a renewable resource bio-plastic made from castor oil*. It is softer and more flexible than other types of nylon, but somewhat stronger and stiffer than even the hardest grades of TPU. It is widely used for pipes, hoses and other tubing applications.

Although expensive to produce and not as strong as nylon 66, PA11 does exhibit superior weather-resistance. It offers low moisture absorption and is quite tolerant to UV-exposure. (Only the very expensive fluoropolymers are better in this respect.)

To exploit this useful property, rapstrap have developed a custom PA11 variant of the i-Tie that's intended for long duration outdoor use, particularly for cable management applications on solar farms.

(* Note that although PA11 is a bio-plastic, it is not biodegradable.)

PVOH is a water-soluble and fully biodegradable polymer that's normally used as a glue or binding agent. (It's also the component of PVA adhesive that cross-links with borax to produce "slime".)

Although not common practice, certain grades of this polymer can be successfully injection moulded, and this has allowed us to create a novel waste-free and rapidly disposable version of our i-Tie. These PVOH rapstraps are very flexible and semi-elasticated, but are (understandably) not quite as strong as our standard TPU versions.

In dry conditions they have proven to be quite stable over long periods, but once in contact with water, our PVOH i-Ties rapidly start to swell and will dissolve completely in a few hours.

Even undiluted, the resulting gloop is readily consumed by microbes over a period of a few weeks. As seen here, dissolved rapstraps "go mouldy" as microbial colonies form in the gel. The black residue is the resulting bio-mass left by the digestion process.

PCL is one of the most instrinsically biodegradable plastics currently available. It was first reported by Frank van Natta, Julian Hill, and Wallace Carothers in the mid 1930s, and is known to biodegrade under both aerobic and anaerobic conditions, including in freshwater, marine and soil environments.

Unfortunately, the material is very expensive and difficult to work with. It's also too soft & weak to produce a standard rapstrap - we tried!

So to make use of this material, over 30 prototypes were needed to evolve a new cable tie design that did work.

The resulting PCL cable ties have been shown to start biodegrading in as little as a few weeks when buried in common garden soil at temperatures of 10-20C, although this is highly dependant on the exact conditions. Generally they can last for several years and are more suitable for long duration applications where eventual biodegradation is required.

Although the exact proprietary composition is not disclosed, this material is made from potato starch blended with a biodegradable polyester, most likely an adipate or sebacate such as PBAT or PBST.

Adipates and other synthetic polyesters were shown to be fully biodegradable in the 1960s, and these materials can offer physial properties similar to LDPE. Whilst not providing the same elasticity of our standard TPU range, this bioplastic material has nevertheless proven to be quite suitable for making biodegradable rapstraps.

These biodegradable materials only became commercially available in the late 1990s, but have been extensively studied since their introduction. Although they have been shown to be intrinsically biodegradable in the environment, the process can be quite slow in marine and freshwater conditions. In the case of PBAT, over 30% mass loss in about 6 months has been reported for topsoil burial, but less than 5% weight loss per year has been reported for marine biodegradation.