By Kevin Ross, Impact Solutions

Introduction
We use plastic every day of our lives, at work and at home, and much of it has a very short life cycle. The question of what we do with end of life plastic is of growing importance due to environmental concerns and in some parts the developed world, the escalating costs of disposal (often the result of deliberate government policy).  So, given these commercial and other pressures why is all plastic not recycled?

The Challenge
The two most significant stumbling blocks are material variability and the costs associated with identifying and separating waste plastics into recognisable grade ranges. The more knowledge you have about the material you intend to recycle the easier it is to put into valuable second use applications.  Plastics are highly engineered products manufactured in sophisticated and highly controlled manufacturing operations to meet clear specifications which correlate to a well defined set of physical properties. These properties are chosen to fit specific end-use applications and set the manufacturing specifications.

For example, polyethylene is produced using numerous different technologies in a wide range of densities and molecular weights. The resulting materials are designed to suit thousands of specific applications, ranging from assorted films, blown/rotationally/injection moulded bottles, sealing caps, oil tanks, specialised gas & potable water pipe grades through to Ultra High Molecular Weight Polyethylene (UHMWPE) often used in biomedical applications. This already diverse supply chain is further complicated via blending, the use of additives (colour, UV protection etc.) and fillers. Furthermore, end users can also add their own functional additives and may use two or more very different plastics in a product. (e.g. composite films)

As a result, single plastics with known properties and additives are the easiest to reuse, assuming they can be collected and reprocessed cost effectively.  However, in many cases it is not cost effective to collect waste plastics due to low volumes and material diversity. Technically it is possible to separate most mixed plastics into recognisable streams, but commercially this is currently only economically feasible for higher value plastics. (e.g. PET or the HDPE used in bottles) Effective recycling therefore is dependent upon knowing the property range of the materials you separate, having an efficient collection infrastructure that can consistently gather the desired products and a method of reprocessing the waste plastic that produces a product suitable for re-use.

There are two extremes on the recycling continuum; at one end of the scale is the factory which reprocesses its own off-spec products, and at the other end of the scale is material such as the plastic blend found in domestic black bag waste which can contain large numbers of different polymers which are often contaminated.  Variability and the investment cost of separation equipment are key reasons why only 25% of domestic plastic waste and 40% of bottles are recycled.

The Impact Solution
Impact Solutions has been working on developing applications for diverse and varying blends of plastics, and is also evaluating novel low cost plastic separation technologies based upon density separation. Impact Solutions believes if this technology can be commercialised it could significantly increase the volume of available recycled plastic. Most currently available recovered plastic streams will almost certainly be a mixture of different polymers, different grades, and different colours. This is especially true of plastics in domestic waste streams.

Currently the market for lower value mixed plastic is limited with much being exported to  low labour cost economies where manual separation of higher value fractions is feasible, and where residues can be used in other applications such as fuels.  There are however applications being developed to utilise lower grade mixed plastics some examples being:

Powder Impression Moulding (PIM): A process where low value and even highly diverse plastic blends can potentially be used to create a range of moulded items.  This process is now being successfully used in the production of hoarding panels by the UK’s 2K Manufacturing. Encapsulation: Using the recycled plastic as a “former” which is then encapsulated by a thin layer of higher value plastic. This enables the product to have the appearance and much of the performance of the higher value encapsulated plastic. Fibre Plastic Composites (FPC):  Have experienced significant growth since the early 1990’s in the US and have been successfully developed for niche applications in Europe.  Composites can contain a wide range of both plastics fibres from high value PET with carbon nano-tubes to low value wood and other waste cellulosic fibres combined with mixed polyolefins. 

Impact are actively developing FPC formulations and applications for low value plastic blends and using these in combination with low value, difficult to recycle waste fibres. Our goal is to produce low cost FPC, initially for low tech outdoor applications including decking and fencing. We are also targeting development of formulations suitable for wood replacement in internal applications such as skirting and other non-structural uses. Historically the key barrier to the successful introduction of FPC’s in Europe has been their high costs due to the use of either virgin polymer or single grade highest value recyclates.  Impact Solution’s recent work in this area has focussed upon the low value plastic obtained via a mass treatment of un-segregated domestic black bag waste. We have successfully combined various fractions of this waste stream with a range of low value fibres including MDF, wet strengthened paper waste and even waste carpet trimmings.

The work has seen Impact produce FPC’s which have the required physical properties for our chosen applications.  If our scale-up efforts are successful these will be produced at significantly lower cost than current FPC’s. This work is being supported by the Scottish Government and current effort is focused on better defining a clear processing window and producing pilot scale quantities of selected formulations. The use of low cost waste steams as plastic additives and fillers is another area of active investigation for Impact.  The addition of filler usually results in a reduction in polymer cost due to substitution. In particular, Impact has examined the performance of a low value and readily available powder waste that behaves similarly to higher value talc fillers.  This material has proven to be easily incorporated and processed, and commercial scale trials will commence in the near future.

The Future
Many technologies exist which facilitate the separation of mixed waste plastic into fractions of various purities and values,  but the economic argument for using these on the majority of low value mixed plastics is still very far from proven.  However, it is Impact’s view that current developments in large scale, more efficient processes for handling un-segregated waste will change both these economics and step-change the availability of consistent plastic waste. Surely the key challenge for us all is to view ALL plastic waste as a valuable resource and to develop techniques and processes that convert these materials into ever higher value products.

Impact is at the forefront of this activity, and is proud to be involved in efforts to maximise the reuse of this valuable resource.

Contact:
CHRIS BEAUMOUNT
Tel: +44 (0) 1324 489182
Fax: +44 (0) 1324 489633
Mob: +44 (0) 7545 539629
Email: chris.beaumont@impact-solutions.co.uk
Web: www.impact-solutions.co.uk