Plastics Polymeric additives as key components

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Wuxi InfiMotion Technology Co., Ltd.

Processors of plastics and compounds are aware of the limits of the application range of their materials and procedures and rely on established processes and years of experience. Polymeric additives can now shift these limitations.

Given the myriad of additives and processing aids used for various applications in plastic processing, it's easy to lose track. One commonality among stabilizers, plasticizers, fillers, flame retardants, pigments, etc., is that they often significantly differ from the plastic to which they are added, in terms of molecular and physical properties, and often in their state of matter as well. It's usually only through these technological compromises that the final product can be endowed with the desired properties through the use of additives.

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What if, in the future, processing aids could be similar or "chemically identical" to the target polymer and still induce the desired property changes? Polytives GmbH from Rudolstadt in Thuringia has pondered this question. Since 2020, they have developed and distributed polymeric additives. This multi-award-winning young company plays a pioneering role in making polymeric additives usable for every type of plastic and user with its bFI (Flow Improver) product family. The Thuringian team describes itself as polymer architects who provide solutions with their additive toolbox for plastic raw material producers, plastic recyclers, masterbatch producers, plastic processors and recyclers, and compounders. These solutions can also be tailored to individual needs.

Compatible with petrochemical or biologically based plastics

The auxiliary substances used in polymeric additives are polymers themselves, bringing the chemical, physical, and macroscopic behavior closer to that of the target polymer. These additives differ only in the structure of their internal architecture, known as molecular architecture, from the target plastic. Moreover, the use of such additives greatly expands their application possibilities, making them compatible with most known plastics based on petrochemicals or biobased materials, whether virgin material or quality from post-industrial or post-consumer cycles.

Altered molecular architecture provides additive effects

The polymeric additives can be added to most types of plastics and polymer systems as a single variety as well as in blends, easily and in a manner typical for the industry. The additives are universally applicable: they show high compatibility in resin and thermoset applications.

In summary, a plastic is additivated with a plastic. The additive has a modified structure, which ensures that it behaves chemically, physically, and macroscopically similar to the target plastic but can specifically influence desired process and/or product properties to a significant extent. The simple secret of the additive effects is the aforementioned altered molecular architecture.

Polymeric additives enhance performance

Various studies have shown that the addition of polymeric additives leads to significantly lower melt viscosities. This improvement in flow behavior results in the Melt Flow Index (MFI or MVR) in some cases more than doubling. Therefore, polymeric additives can be used for bulk materials with different viscosity profiles. These can be subject to rheological homogenization without affecting other material properties. An extrusion product can be upgraded to injection molding grade. This qualitatively activates recyclates for the injection molding market, which has largely been closed to them, without their typically lower rheological quality leading to a loss of attractiveness.

Better realization of delicate injection-molded components

The reduced viscosity also offers advantages elsewhere in the processing process: Delicate injection-molded components can be better realized since the shaping is facilitated by improved mold filling. The additive integrates evenly within the molding compound into the polymer matrix. This effect comes from the very close chemical resemblance and the associated relationship between the additive and the material. Thus, the base polymer retains the additive's effect throughout its entire lifespan.

By adding polymeric additives, the original property of the material is preserved, with only the plastic-specific processing and product properties changing. The type of modification depends on the type of base polymer and also on the type and amount of the added additive. A performance comparison, for instance, between PMMA 7N and a corresponding blend of PMMA 7N with 10 wt% of a polymeric additive, illustrates that while the MVR is significantly increased, the pure additive modification of acrylic glass presented here does not lead to any loss in transparency.

Process aids for more sustainable production

When the polymeric additive is mixed with the plastic, processing temperatures can be significantly reduced. This effect is enabled by the described reduction in melt viscosity. As a result, plastics can be processed at lower plastification temperatures. Components and fillers that thermally decompose at elevated temperatures can be used in this now more gentle process environment, allowing for new products to be added to the portfolio of plastic processors.

The energy required to maintain temperature zones can also be reduced. Polytives has demonstrated this using polycarbonate as an example: here, the temperatures could be reduced from over 280°C to 230°C, thereby reducing them by about 20%. As a result, components can be more easily demolded at the end of the processing line: cooling times and cycle times can be reduced.

In addition to energy savings through reduced temperatures, injection molding pressures can be reduced. The pressure reduction also results from the rheological influence on the polymer melt. During the processing of PMMA on an injection molding machine, a pressure reduction of up to over 30% was observed.

The fleet of injection molding machines can thus be used much more broadly and flexibly for a part of the product assortments where previously clamping forces were limiting factors. With lower injection pressures, fewer inherent stresses remain in the component – improving component quality. Processors can therefore save energy and thus CO₂ at different or even multiple points in their workflow and come closer to their optimization goals.