Blends with benefits

By looking into the matter of reaching circularity in an economic and social sense, a pushing factor in this direction are overall costs that companies have to calculate to take this path. Technical innovations and cutting-edge developments on a material level usually help to reduce those costs, accelerating the transition into circular processes. One of those approaches in the field of additives seems very promising. Polytives, a young company from Thuringia, Germany, developed the bFI product family, a bunch of polymeric additives which works as universal processing aids.

bFI: Not your standard processing aid

What is special about the bFI product family? Uncommonly, these additives are polymers themselves. Plastic processors, recyclers, masterbatchers, compounders etc. will mix these polymeric additives to their virgin, post-industry, or post-consumer recycled polymers.

But first and foremost, these additives are specially designed: Unlike many plastics consisting of a linear polymer backbone, bFI additives have a polymeric structure. This change on a molecular level yield to a set of well-defined material properties, that are brought into the targeted material.

The highest impacts observed by adding a branched polymeric additive to a standard plastic material is a noticeable change in melt viscosity and a low impact on the glass transition temperature of the whole blend. Blending is possible with almost every polymer (i.e. thermoplastics, epoxide resins, acrylic systems, rubber, and bioplastics etc.) and testing was already performed with recycled materials, as shown in Table 1.

With a better viscosity performance in general, different processing parameters can be adjusted. Taking a deeper look at the injection moulding cycle, the following benefits are identified: There is either a massive reduction in processing temperatures or a relevant lowering of various pressures, resulting in a shorter overall cycle and therefore increasing the output and reducing costs. A lowered temperature also decreases costs for maintaining the thermal energy levels and reduces the cooling duration of the mould (i.e. with lower maximum temperature the cooling time is shortened above 40%). With decreasing melt viscosity, more fine grain detailing of the mould is possible, and its cavity can be emptied with less effort.

Moreover, in addition to these primary effects there can be a couple of other advantages when using branched polymeric flow improvers. Aside from saving raw materials and abandoning previous additive components, the lowered glass transition temperature affirms two opportunities: If the needed processing temperature level sinks significant in comparison to the state-of-the-art level, a drop in the needed energy to heat the materials will be noticeable. The energy difference will contribute to fewer costs and a smaller carbon footprint. Finally, a smooth handling of plastic processing at lower temperatures could lead to the combination of different materials together, which laid in the field of imagination until now.

Enabling more efficient recycling processes

The examples above define branched polymeric additives as universal processing aids which approach the reduction of total costs for plastic processors and recyclers. For the evaluation of their impact on the circular economy, a more in-depth sight follows: As mentioned above the additives are polymers. The materials are based on common plastics known and handled by the industry for many years. In contrast to completely new chemicals, these polymeric additives share the familiar behaviour of their base polymer, in other words a branched additive based on polymethylmethacrylate (PMMA) will chemically and toxicologically act like PMMA in general. This characteristic will also rate materials higher regarding their recycling capabilities. Furthermore, a softer version of a recycling process, as illustrated in the section before, increases the times a material can be recycled.

One big advantage of most plastics is their non-toxic, sometimes even food-prove performance. The branched polymeric additives have inherited this attribute. Because of their polymeric nature outgassing from the material will not happen. The non-toxicity is a further pro argument to use these processing aids in approaches, where bio-based and bio-degradable plastics may suffer some processing drawbacks. Regarding the actual debate on per- and polyfluoroalkyl substances (PFAS), the flow improvement could be one piece of the puzzle to find sustainable alternatives.

Usually when it comes to processing post-industry and post-consumer materials, plastics differ in their viscosity profile. Here, a universal flow improver is the key to harmonise the different LOTs and bulks, enabling the recycler to process without further separation and the selection of material streams without significantly changing material properties other than viscosity, as shown in Figure 1. For example, it may be possible to process all mouldings on one big injection unit at once or even switch to a smaller one with a smaller machine-hour rate. With more flexibility in processing and recycling processes a more efficient handling of plastics and plastic waste is possible. A simplification of material management and machine capacity will be another logistic advantage.

In conclusion branched polymeric additives have high potential to change the perspective on previous standard plastics as well as recycled or bio-based ones. They show an innovative way to convert standard materials into high performing ones, which are needed to face the challenges arisen by the goal of a circular economy.

Polytives GmbH will be present at PRSE 2024, Hall 10 booth Y4