Many plastics processors are still reluctant to use raw materials with post-industry or post-consumer qualities, although there are several reasons in favour of this and legislation is increasingly obliging them to do so. Polytives’ technology can help in the decision to take this step. Their polymer additives optimise the processability of materials for the plastics processing market. If recycled materials can be made the first choice, the circular economy concept will be significantly strengthened.

Plastics based purely on petrochemicals are increasingly being scrutinised. This is reflected in the historical development of the many polymers used and the incipient rethinking in the search for renewable and more sustainable alternatives. It doesn’t matter whether we are looking at high-performance plastics such as PEEK or commodities such as PVC. What they have in common is that their technical performance, their economic necessity and their social acceptance are also based on their additive content. As a rule, plastic additives are essential for adapting the addressed materials for their intended use. Among other things, they act as plasticisers, antioxidants, impact modifiers and flame retardants. They can also create an antibacterial effect or individualise plastics using pigments. The range of additives available on the market illustrates how necessary their use is. This inevitably poses a major problem for recycling and the circular economy.

Returning to intrinsic grade purity

During mechanical recycling, plastic waste is generally collected, sorted, shredded, washed and converted into regrind. In an ideal sorting process, each plastic would be separated by type to be reused as high-quality post-consumer material. However, it is often a composite material, including the additives it contains. Process optimisation would mean reducing the differences between polymer and additive – but since it is precisely the differences between the materials that serve to modify the properties, it is difficult to make any progress in this direction.

Polytives GmbH from Rudolstadt (Thuringia) has nevertheless succeeded in meeting this challenge with a smart additive polymer design. The company produces polymer additives that differ from conventional plastics in their molecular architecture. If, for example, the melt viscosity of a polymer is to be reduced by a processing aid, the structure of the compatible additive ideally complements the existing design. It can be used in all common plastics. In addition to the pure solution, blends can also be processed.

Addressing sustainability in terms of energy, materials and supply chains

The use of polymer additives as processing aids gives rise to three core statements that are valid for petrochemical plastic products, for renewable alternatives and for post-consumer qualities:

  1. The use of a smart additive reduces the required energy input.

This is due to the fact that the introduction of the additive significantly reduces the pressure ratios in the handling process, which means that the processing temperatures can be significantly lowered. A lower melting temperature enables gentler processing, places considerably less strain on the system and contributes to CO2 savings by reducing the energy required.

The smoother process control also has a positive effect in terms of the circular economy: The number of possible cycles in which a recyclate can fulfil the specified requirements is significantly increased. Sustainability is therefore literally a given, as the material can circulate more often than before.

  1. Manufacturing processes benefit from reduced melt viscosity.

Taking the injection moulding process as an example, the viscosity of an injection moulding compound can be massively reduced by using polymer additives. In the process, this leads to easier filling of the injection mould, which means that intricate components are sometimes possible in the first place and can be produced with fewer rejects. An enormous reduction in cycle times of up to 40% is also within the realms of possibility.

By regulating the amount of additive, the viscosity can be optimised in such a way that the original extrusion quality can be raised to the level of injection moulding quality. Figure 1 shows the influence of additives with polymer additives on the melt volume flow rate (MVR) and the length of the flow path of flow spirals.

Use of polymer additive with recycled material. Influence on melt volume flow rate (MVR) (left) and flow path length (right). Graphic:Polytives

This enables recyclers/compounders/processors to intervene flexibly in the machine configuration and to harmonise different flow profiles, or to get the big picture, to harmonise the entire range and make it efficiently processable. In some cases, these effects are already achieved with dosages of 1 – 3 wt.% and are suitable also for regrind.

  1. Polymer additives contribute to raw material diversity and supply chain resilience.

In conjunction with the lowering of melt pressures and the associated temperature reduction, this indicates what is possibly the greatest potential: Some raw materials face challenges due to the low thermal decomposition temperature of the material itself or the increased use of thermally sensitive reinforcing and functional materials. Smart additives, on the other hand, can significantly expand this scope and thus make virgin or recycled materials that were previously not processable available for usage. This gives the value chain more opportunities to expand the raw material portfolio and minimise risks from supply shortages on the market.

A more diverse feedstock portfolio or increased access to bio-based and/or biodegradable and post-consumer grades will strengthen the implementation of circular economies and reduce the impact of supply chain disruptions. In terms of sustainability, it is important to examine the extent to which a product can be realised based on different raw materials, both ecologically and economically.

Development results have shown that polymer additives improve the performance of recycled bottle PET material, for example, to such an extent that it can be easily processed in injection moulds originally designed for ABS grades and high-quality technical components. With this exemplary outlook into the possibilities offered by polymer additives, the use of recycled goods can become a new ‘business normal’.

Recognising recyclate as an opportunity

The bad image that plastics unfortunately now have can be summarised in a few key words: Environmental and marine pollution, the risk of toxic substances, energy requirements and the waste of materials for crude oil and natural gas or chemical base materials for synthesis. However, since plastic has unalterably characterised our social life and technologically permeated it as a reliable and valuable material, it is illusory to turn away from it. Instead, it is now important to use the existing material wisely and process it as efficiently as possible.

The Polytives GmbH team. Photo: Polytives

Smart polymer additives can be used to increase the efficiency of collection and sorting systems by making the process purer. Additives are added according to the design-for-recycling principle. By harmonising different flow profiles, a material quality can be created with simultaneous economic efficiency of the regrind. The interplay of these points and a focus on circular economy and sustainability can also increase the social acceptance of plastics.

As a contribution to this vision, Polytives is developing polymer additives such as the flow improver bFI A 3745. The latest research project, implemented with strong partners in the region, is investigating the interaction between smart additives, bio-based and biodegradable materials. The knowledge gained in recent years from applications with petrochemically produced plastics can now also be transferred to bio-based polymers and recycled goods.

Meet Polytives soon at the Plastics Recycling Show Europe (PRSE) in Amsterdam (Hall 10, Stand Y4). There, the team will be presenting application examples and answering further questions about their products.

Photo Top: Flow spiral of a material processed with a polymer additive. The reduction in viscosity leads to an extension of the flow path (highlighted in colour). Picture: Polytives


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