BOSS case study – Melt flow rate

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How BOSS improves your Melt Flow Rate

We are often asked how BOSS can add value to your mixed rigids, especially when compared to other technologies and melt flow rate is a key parameter for plastic recycling.  Our first commercial plant has now been operating for a number of months and producing some fantastically high grade PE and PP material.

If you are not currently familiar with the BOSS technology, you can learn more about it here.  BOSS can fit into a number of different operations, or be deployed as a standalone processing plant for a new operation.

Our first commercial plant has been operating at the end of an optical line.  A £1.5m facility was set up to process mixed rigid plastics, originating from MRF facilities around London.  These mixed rigid bales were broken down, shredded and run through a Redwave optical sorting machine, picking for PP (Polypropylene) and PE (Polyethylene).  While the optical line could produce material of a high quality, when it was run at the speed required to make a commercial return on investment their PP and PE outputs were not at the required quality.  Purities were dropping as low as 80 – 85% PP or PE, mixed with other materials such as Polystyrene, ABS, Polyurethanes and even PVC – these impurities badly affect the melt flow rate.

The pictures below show the purity of the input material to BOSS and the result after BOSS.  The material is placed in a density controlled solution at 0.925 g/m3 density, meaning the PP will float and any PE/others will sink.

Before BOSS

density sink float measurement

After BOSS

boss purity by density

BOSS was introduced to the end of this process, taking the granulated streams from the optical plant and turning them into 98%+ pure streams.  This immediately offered the recyclers a £150 uplift on the value of their plastics, but also enabled them to sell material quicker and easier due to the high demand for a product which is purer than others on the market.

One of the key indicators of the material quality is the Melt Flow rate.  The optical PP produced material is shown below.  The melt flow is calculated by passing a sample of the regrind through a Melt flow rate machine, which uses a weight to force molten material through a die head.  The weight of material extruded in a set space of time is measured, and used to calculate how fast a material flows.  You can find out more about Melt Flow rate testing here.

Generally PP is desired with as fast a melt flow as possible.  The reason for this is PP is commonly used in injection moulding applications, which depends on the speed of production to keep costs down and therefore the melt flow rate is critical.

PP being produced off the optical was showing between MFR 4g/10min at 2.16kg weight to 9g/10min.  This is a typical range for optically sorted PP from a mixed rigid source.  This material generally needs to be ‘blended’ away with higher melt flow rate PP to create a compound which is more desirable.  This results in lower demand and hence prices.

Melt flow rate before BOSS

melt flow of optical material

Melt Flow rate after BOSS

melt flow after BOSS

However, after this material has been through BOSS, the Melt flow rates were massively improved.  The Melt flow rate results below show how much this has improved, with an MFR of 27 – 30 g/10min at the same 2.16kg weight.  This is at injection mould quality and thus can be sold at higher prices and at higher volumes.

Impact have produced a range of business plans for how BOSS can be used to improve the quality of your mixed polyolefin rich recycled feedstocks.  We can work with you from baled product, right through to high quality regrind, or introduce you to a business model to take the extensive range of mixed polyolefin regrind in the market and turn it into high quality feedstocks.  Contact the recycling team now on 01324 489 182 or email for more information.

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