Recycling & Sustainability

cable tie litter

The world uses about 1 billion cable ties every day, but the waste is rarely collected for recycling. There is therefore no adequate supply of reprocessed material to make new ties from.

Rapstrap's Solutions

Ideally, all plastic products should be made from recycled materials; They should be reusable in service; And they should be recycled again at the end of their useful life. This is easier said than done.

Rapstrap have invested much time & effort in developing products that reduce & reuse the amount plastic needed for tying applications. Our core products are accordingly multi-use items that are designed to be used & reused many times. But the recycling part of the equation is still problematic.

Very few plastics are currently used in a fully closed-loop manner, and estimates claim that up to 90% of plastic is instead lost through littering, landfilling or incinerating. Recycled materials are therefore limited in both diversity and supply.

We have so far established two solutions to this supply problem: One was to identify a reliable source of usable scrap plastic and design our products around it; The other was to turn to Nature.

scrap cable sleeving

When old cables are sent for reprocessing, the operators are only interested in the high-value copper. The stripped sleeving piles up in spoil heaps and has few applications.

The Recycling Route

All thermoplastics can be recycled, but it is only economical if the material is uncontaminated and available in sufficient quantity. In the case of mixed post-consumer waste, only the most common plastics are worth recovering (typically PE, PP and PET), and these generally come from (and are largely returned to) the packaging sector. Although readily available, PET is not well-suited to injection moulding, and PE & PP are both waxy materials with insufficient strength for many engineering applications.more

Industrial recycling can offer a broader choice of materials, but ongoing supply is not guaranteed: Recyclers can only acquire so-much waste from primary processors, and if faced with greater demand, they cannot simply increase their output like a chemical plant would.

Old cable sleeving before reprocessing

Raw fragments of reclaimed cable sleeving. It's a mix of PVC, TPU, PE, copper strands, paint, dirt and who-knows-what.

There are, however, some industries that generate more waste than reprocessors can deal with, and here there are opportunities. We found one such source in cable recycling, which generates mountains of scrap sleeving as a byproduct. It is mostly black PVC, and requires some cleaning-up (to remove residual wire strands and yard grit), but the result is a fairly consistent material that has useful physical properties. It is also easy to work with, and if it isn't reclaimed, much of it may end up in landfill.

To improve its performance, we combine it with a little polyurethane elastomer, and this also comes from recycled sources wherever possible. The resulting rapstraps are typically over 70% recycled and yet functionally comparable to our premium polyurethane versions, being just slightly less elasticated. Although available only in black, the high PVC content gives them superior UV-resistance, and these recycled straps are therefore more suitable for outdoor use.

Reprocessed TPU-PVC granules

Once cleaned and homogenised, granules of polyurethane and PVC are sutable for melt-processing into new rapstraps.

Closing The Loop

After use, these PVC/TPU rapstraps can in principle be recycled along with other PVC products (resin code 3), although be aware that not all curbside programmes will have facilities to successfully extract PVC from a mixed waste-stream. (Check locally before disposal.more)

Alternatively, used straps can be returned directly to ourselves for reprocessing, or where possible, they can be recycled along with old wire & cables. By this route, they will end up back at a cable recycling plant, and from there, (hopefully) be reprocessed again.

Currently, there is much room for improvement in the plastics recycling industry, but closed-loop recycling is possible. As our recycled rapstraps demonstrate, by identifying promising waste-streams and designing products around them, everyday plastic items can be manufactured in a more sustainable way.

Natural green recycling

Fragments of a biodegradable rapstrap made using potato starch. According to the manufacturers, this material contains 23% biocarbon.

The Natural Options

Recycling is not always possible, and many useful thermoplastics cannot be easily recovered from post-consumer waste. This breaks the cycle for any products that rely on these polymers, and fresh material is continually needed.

Renewable-resource materials can reduce this need, but their production still requires energy & water resources, and they may also divert agricultural production away from other applications.

Despite these concerns, starch has become a very popular plastic alternative, especially for single-use disposable items. Although starch can be used neat, it is normally blended with an underlying polymer to maintain adequate strength. Most starch-based polymers contain less than 30%, and this is also the case with our biodegradable i-Ties.

Another option we considered were the naturally occurring polyesters extracted from bacteria. Known as PHAs, these have been commercially available for over 40 years now (since ICI's Biopol programme). However, they have not found widespread use, tending to be weak and difficult to process. Despite several attempts, no viable rapstrap has yet been produced from these polymers.

More recently, lactic acid and succinic acid have been industrially fermented (often from crop waste), and their polymers (PLA and PBS) have become very popular. Rapstraps have been successfully produced from both of these materials, but there are other issues to consider.

Renewable ≠ Biodegradable

Cable tie urban little

Cable ties are frequently seen littering urban areas. They also pollute the wider environment, including the oceans.

Renewable-resource bioplastics are not a complete solution due to the ongoing issue with plastic products being lost (or discarded) into the environment. Cable ties are quite notorious for this, and because they may never be recovered, we needed to find a material that would also biodegrade:

  • PLA is largely unsuitable because it is quite durable at ambient temperatures; It requires hot composting conditions to rapidly decompose.
  • PBS can biodegrade in soil, but it is only semi-renewable at present.more
  • PBAT is a similar polymer that's also soil biodegradable. Based on adipic acid, it is somewhat more degradable than PBS, but it is currently not made from any renewable resources.more

Ultimately, when selecting materials suitable for cable ties, we have to make a trade-off between renewable or biodegradable. The only way to have both is to compromise on strength, which clearly has its limits.

State of the Art

Mould growth on starch-polyester compound

We currently use this starch compound for making our biodegradable i-Ties - mould seems to like it.

The producers do not disclose their material recipe, but the binding polymer is likely PBAT or PBS. (They have confirmed it is not based on PLA.)

At the moment, the most useful biodegradable plastics we can use are PBS and PBAT with about 30-40% renewable content. (PLA rapstraps can be also be made, but they would only be suitable for disposal via industrial composting. If they ended up anywhere else, they would simply add to the durable plastic waste already polluting the environment.more)

Apart from PBS and PBAT, no significant biodegradable plastics have been developed since the 1990s, and most of the others have been around for a century or so.

One of these old-timers, polycaprolactone (PCL), is potentially suitable for making rapstraps, although it's still a work-in-progress. It is just a little too weak for our current products, but biodegradable PCL cable ties have been successfully manufactured from it. These can biodegrade in pretty much any natural environment, including the oceans, so it is good stuff. (We're working on it.)

Another 1920s polymer is PVOH (poly vinyl alcohol, aka PVA), which is normally used as a glue. If correctly prepared, this polymer will dissolve in cold water and is generally regarded as being biodegradable once dispersed. It is, of course, not much use for outdoor applications - especially in the UK! But it can be easily disposed of, and PVOH rapstraps are available. The material is more commonly used for soluble detergent pouches, and also as a sizing agent for paper. (Our PVOH ties can therefore be used for packaging applications, and are potentially recyclable along with paper and card.)

Regardless of their origins, all of these biodegradable materials are weaker and more expensive than commodity durable plastics, some considerably so. But their ability to break down in the environment makes them an attractive solution for some applications. They still have to be used wisely, but compared to nylon ties, they do offer a less-worse alternative.

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