Systems Integration: Functionality of Materials, Processes and Design

The prefix “bio” in the case of so-called biobased plastics stands for raw materials derived directly from nature. They are obtained from variety of carbohydrates such as sugars, starches, proteins, cellulose, lignins, biological greases and oils. Along with PLA, PHA and both cellulose and starch derivatives, biobased plastics also include biopolyethylene. In Brazil, this is obtained from bioethanol which, in turn, is a product of sugar cane. What sometimes leads to confusion is the fact that these bioplastics need not necessarily be biodegradable. For instance, biopolyethylene is a 100% derivative of renewable raw materials and has the same properties as conventional polyethylene, but is in no way biologically degradable. Consequently, the social advantages of the increased usage of renewable raw materials of this sort are, primarily, to be found in a reduction in the use of fossil hydrocarbons and the level of CO2 released into the environment.

Biologically degradable plastics are created almost exclusively from biodegradable polymers and additives. They are metabolisable for special bacteria and fungi after macromolecules have first achieved a particularly small degree of fragmentation through other degradation mechanisms. “Metabolising” in this context means complete conversion into biomass, CO2 or methane, water and minerals. This clearly indicates that the term “bio” in “biologically degradable” relates to the reversion of the plastic to a natural state. Biologically degradable plastics can offer a solution in applications that frequently remain in the natural environment, including abrasive particles in peelings that get into waste water, lawn trimmer particles that remain on lawns and sapling guards that are left in forests. In countries with underdeveloped waste management systems, they can help to reduce the level of plastic waste polluting the environment. PLA, PHA, cellulose derivatives and starches are examples of biologically degradable polymers, but they also include petroleum-based PBAT and PBS. Fears that biological degradation could also occur during normal use are unfounded.

The plastics industry will doubtlessly have to confront growing market pressure and the diminishing acceptance of plastic packaging at K2019, a reaction which has already spread to other applications involving plastic. The fact that bioplastics can contribute to a solution will be demonstrated in an impressive manner at K2019 on the stands of bioplastic manufacturers and those of research institutes on the Science Campus.

Professor Dr. C. Bonten (Univ.-Prof. Dr.-Ing.), Institute for Plastics Engineering (IKT) at the University of Stuttgart

„The plastics industry will doubtlessly have to confront growing market pressure and the diminishing acceptance of plastic packaging at K2019, a reaction which has already spread to other applications involving plastic. The fact that bioplastics can contribute to a solution will be demonstrated in an impressive manner at K2019 on the stands of bioplastic manufacturers and those of research institutes on the Science Campus.“

Plastics offer unique possibilities when there is a need to integrate several different functions in a single component. By means of design and processing, locally distinct morphologies and, consequently, different properties can be created in a single manufacturing step with semicrystalline thermoplastics. For example, a simple shampoo bottle conveniently integrates both sealing and hinge functions in its cap. Functionally reliable, it is a single-material solution ideally suited for recycling and, additionally, extremely cost-effective in manufacturing terms.

However, the mechanical performance potential of plastics is frequently inadequate for the production of highly stressed components (i.e. for structural applications). The remedy here is to combine the polymer with a second heavy-duty component, with fibre-reinforced plastics being a prime example of these composite materials. A coherent plastic matrix is responsible for fixation and protection of the load-bearing fibers dispersed in it.

This means that extensive freedom of design can be combined with low weight and excellent mechanical properties. Sports equipment such as tennis racquets and golf clubs, bicycle frames and, indeed, aircraft structures and lightweight car bodies are just some examples.

In addition to fibre-reinforcement, the incorporation of a variety of ceramic materials with different geometries on extreme length scales in the plastic matrix is becoming increasingly important. While a few years ago enormous sums were still being spent in researching and developing nanocomposites, the potential is currently perceived to be in the combination of reinforcing materials on different length scales (i.e. in the case of so-called hybrid materials). Using these materials, components with a delicate design and locally diverse levels of filling and orientation (i.e. ultimately locally targeted property generation) can be created through intelligent manufacturing processes.

Manufacturing costs are governed heavily by the geometric arrangement of the disperse components in the plastic matrix. Thermoplastic materials filled with spherical substances and with discontinuous fibre reinforcement can be transferred with exceptional ease to the component shape in familiar plastic manufacturing processes. Conversely, the processing of continuous long fibre-reinforced materials does present a challenge in terms of costs. Combinations of highly efficient plastics manufacturing processes with screw plasticising at their core offer promising solutions here. In joint projects involving industry, universities and research institutes (and significant support through research funding provided by the German Federal Ministry of Education and Research (BMBF)), the sector is currently developing intelligent process chains with the aim of achieving a significant reduction in cycle times and costs. Development of Industry 4.0 is also helpful in this context. In addition, new momentum is provided through dynamic development in 3D printing. Initial systems permit the targeted deposition of fibre/matrix filament in the direction of loads acting within the component. This enables the manufacture of macroscopic anisotropic components and exploitation of reinforcement structure potential at the highest level. However, the cycle time in contemporary engineering solutions depends heavily on the transfer of heat. For example, in fused deposition modeling, where the filament is first melted through contact heating, throughput is 100 times lower than in a modern industrial plastics processing system. Screw plasticising can also be benificial.

While material development has for many years focused heavily on the property profile demanded by the user, the manufacturing process is also becoming an issue of equal and increasing interest in development. This perspective has ensured the success story of plastic in recent decades. Excellent solutions for the engineering of plastics can only be created through a collaboration of material, process and design. K2019 will also demonstrate this in an impressive manner for hybrid plastic-based materials in lightweight construction applications.

Professor Alois K. Schlarb (Uni.-Prof. Dr.-Ing.), Chair of Composite Engineering (CCe), University of Kaiserslautern (TUK)

„While material development has for many years focused heavily on the property profile demanded by the user, the manufacturing process is also becoming an issue of equal and increasing interest in development. This perspective has ensured the success story of plastic in recent decades. Excellent solutions for the engineering of plastics can only be created through a collaboration of material, process and design. K2019 will also demonstrate this in an impressive manner for hybrid plastic-based materials in lightweight construction applications.“

For almost 100 years, the world has been benefitting from a steadily expanding plastics industry offering a wide range of materials with highly versatile property profiles. Today, high-performance polymers with minimum weight and impressive mechanical strength can make cars and aircraft lighter, a significant contribution to the reduction of these product’s energy footprint. Not only that, some high-performance polymers are also weather-resistant, resistant to chemicals and even UV-resistant, which makes them ideal for medical engineering, construction and even aerospace applications.

With a global production volume of 348 m tonnes in 2018, the plastics sector is among the most successful economic segments in the world, and a major factor in many countries’ trade balance. While fifteen years ago, Europe and the US were the main players in terms of plastics production and consumption, it is now Asia in general, and China in particular, that have become the new heavyweight in the conventional plastics segment (Fig. 1).

All industrial plastics are made from crude oil, which is still the dominant, fossil raw material for this global industry. Because of their chemical stability, they do not degrade very well, which leads to the regrettable side effect that a major part of these vast production volumes accumulates in the environment, a situation that is often aggravated by not yet fully functional recycling systems. If the indisputable success of modern plastics is to continue to enhance our lives and further improve the global quality of living, the major focus of the plastics industry at the beginning of the 21st century must lie on the development of sustainable polymer materials (and efficient recycling methods).

A selection of polymer materials may allow the crucial modification of exchanging oil-based carbon for carbon dioxide (CO2). Already, hydrating CO2 to methanol, and converting methanol (CH3OH, MTP process) to propylene, the production of acrylonitrile and PAN, and the acrylic acid production via propylene oxidation have become established as standard procedure in chemical production (Fig. 2).
Synthetic, biologically degradable polymers definitely play a special role here (cp. “Synthetic Biodegradable Polymers”, Rieger, Künkel, Coates, Reichardt, Dinjus, Zevaco (Eds.), Springer, Advances in Polymer Science 2012), with polypropylene carbonate (PPC) and polyhydroxy butyrate (PHB) as key players. Not only is it possible to produce these materials entirely from CO2, synthetic PHB is also considered a “hidden champion”, which means that its properties closely resemble those of typical packaging materials such as polyethylene (PE) and polypropylene (PP) – but it is completely and quickly biodegradable.

Professor Rieger was appointed to the WACKER-Chair of Macromolecular Chemistry at the Technical University of Munich (TUM) and became Director of the Institute of Silicon Chemistry, where he is currently also acting as Chairman of the TUM Senate. After completing his studies of chemistry at the Ludwig Maximilian University of Munich (LMU), Professor Rieger spent a year as a postdoctoral researcher at the University of Massachusetts, Amherst, USA, before joining BASF SE in Ludwigshafen, where he worked in a plastics laboratory. He completed his postdoctoral teaching qualification in inorganic chemistry at the University of Tübingen and, in 1997, moved on to the University of Ulm, where he became head of the department for “Materials and Catalysis”. He is a member of the Finnish Academy of Sciences & Letters, the European Academy of Sciences in Brussels, and acatech, the German Academy of Science and Engineering.

In 2006, he was awarded with the “Philip Morris Forschungspreis”, and in 2013 he won the “Wöhler-Preis für Nachhaltige Chemie”. He was awarded an honorary Ph.D. by the University of Helsinki and the author of more than 350 original publications and holds more than 140 patents. In 2013 he became member of the Science Council of the K trade show.

A range of key issues from the area of polymer material engineering can be pooled under the header of “system integration: functionality through material, process and design”. Modern technologies used in mobility, aeronautical and medical engineering pose new challenges for the applied materials. This also and particularly applies to polymer materials, elastomers and related additives. These materials offer unique optimization options which can accommodate individual application requirements and specific property profiles. Used in combination with modern production techniques such as additive production (3D print), these materials provide a variety of functionalities and allow almost infinitely random part construction and design opportunities. Functionality at the highest level is demonstrated by highly conductive elastomers in flexible electrodes used in medical applications such as implants, or magneto-rheologic elastomers with adjustable stiffness levels as used in “Softrobotic” or automotive applications (chassis suspension, optimized drive assembly suspension) or in special sensors, where micro-electronics and polymer matrixes act in tandem.

New developments such as e-mobility require new functional profiles and materials properties. Polymer high-performance materials for batteries and fuel cells are now in rising demand. The use of highly efficient reinforcing fillers, particularly those with a low density, opens up new and far-reaching development opportunities for elastomers in terms of lightweight engineering, durability and stress resistance. A mid-range car, for example, contains a high proportion of plastic products, but also between 65 – 70 kg of elastomers (including tyres). Even with tyres excluded, we still see an impressive amount – about 15 kg – of highly developed technical elastomer product used in every car. In the wake of rising e-mobility, many elastomer components in drive and cooling systems will become redundant or will at least undergo substantial changes. The use of renewable resources in polymers and elastomers, even when used as additives, and a positive CO2 footprint of elastomer and plastic products are very important, as are materials of high durability, even under heavy-duty conditions, lightweight engineering through smart compounding and intelligent materials with integrated and adjustable properties. In order to ensure their economic survival, companies must not only take these requirements into account, but must also consider the corresponding structural changes within their corporations. Consumers, raw material producers, the processing industry and suppliers will be impacted in equal measure.

This is why the key issue of functionality through material, process and design will play a major role in this year’s K trade show.

Prof. Dr. Ulrich Giese is Managing Director at the German Institute of Rubber Engineering (DIK) in Hannover.