Plastic and Recycling

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Quo vadis, plastic?

No other material involves such controversial debate and environmental concerns as plastics. However, no other material is as versatile and indispensable. That’s why environmental issues are a top priority for plastics production and finishing.

Trends in this industry reflect major global issues in microcosm. According to the 2019 World Economic Forum, the world’s top three risks are environmental – extreme weather, lack of climate policy progress and natural disasters. 1,000 economic, political and civil society experts agree on this point. The top three are followed in fourth and fifth place respectively by data theft and cyber attacks. When applied to the plastics industry, the priorities are very similar – recycling, closed-loop materials management and environmental issues are right at the top of the agenda, followed by energy efficiency and Industry 4.0. Furthermore, the industry has recognized that it has an image problem. Littering of the seas, microplastics in food and other negative headlines have discredited a material that, if used and disposed of properly, provides a large number of benefits and is often irreplaceable.

What can and should be done? Industry only has limited scope of action as far as the disposal of packaging is concerned. In contrast, it can have a direct impact on plastics production and processing. In this respect, suitable measures include:

  • Substitution of fossil through renewable resources
  • Reduction in plastics quantities through efficient production processes
  • Return of reject and waste materials into the production process
  • Use of recycled materials
  • Proactive design of recycling processes
  • Provision of information to the public through studies and association activities

Problem recognized, action taken?
Renewable raw materials and biotechnology processes are gaining importance in the industry. In fact, the bioplastics family is huge – it is split into those that are made of renewable raw materials and those that are biodegradable, and includes the group of materials that provide both benefits. Some bioplastics are capable of replacing conventional ones, while others feature new properties and threfore increase choice.

Bioplastics – an overview:

  • Bio-based (partly), non-biodegradable plastics: polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), high-performance technical polymers, such as polyamide (PA), polytrimethylene terephthalate (PTT) or (partly) bio-based polyurethane (PUR)
  • Bio-based, biodegradable plastics: polylactic acid (PLA), polyhydroxyalkanoates (PHA), polybutylene succinate (PBS) and starch blends
  • Fossil-based, biodegradable plastics: polybutylene adipate terephthalate (PBAT)

For the most part, bioplastics are not dependent on fossil resources and are capable of reducing the carbon footprint considerably particularly in combination with recycling and closed-loop materials management, says industry association, European Bioplastics. Many bio-based polymers are equivalent substitutes for conventional plastics. For example, these include polylactide (PLA), which is derived from fermented starches and sugar, as well as bio-based polyethylene terephthalate (Bio-PET) and polyethylene (Bio-PE). The raw materials for these polymers include sugar cane and bioethanol (source: Wuppertal Institute). Initial innovations, like compostable PLA, PHA and PBS, are even exhibiting new, enhanced properties. Brand new materials such as polyethylene furanoate (PEF) exhibit better barrier properties than established polymers and, more importantly, can be easily recycled. A detailed table is available at the end of this article.

As far as production is concerned, new materials entail the development of new processes. The flow properties of these alternative bioplastics exhibit different characteristics from conventional pellets. Feeder manufacturers like Brabender Technologie can assist producers here. Newly developed products can be tested at its in-house Technical Center where the appropriate feeder can be selected then configured accordingly. In some cases these new materials also require design innovation – Brabender Technologie is always geared up to undertake technical enhancements.

Recycling within a production environment
Even bioplastics do not eliminate the need for recycling. They too must be included in a reusable material cycle as they are not necessarily biodegradable. The logistical challenge of recycling both conventional and alternative plastics is significantly less to an industrial business than it is when consumer waste is involved. Manufacturing experts usually know exactly what production waste consists of, and it is to some extent even homogenous or mono-material. Reject components, from injection molding for example, can be returned easily into the production process. First of all, they are shredded then milled. The ground material is then homogenized in an extruder and processed into strand-shaped pellets. The resultant recycled pellets can however exhibit differing properties to the source material.

Another example is processing film edge trimmings. When films are manufactured, their edges are straigtened at the end of the process, meaning some waste is unavoidable. This material is difficult to handle and must often be processed into pellets before it can be added back into the production process. In collaboration with its partners, Brabender Technologie has developed technologies like the FiberXpert feeder, which feeds these film edge trimmings directly after shredding and conducts them to the extruder.

Keeping an eye on energy-saving potential
In the energy transformation age cost-saving measures are on the agenda of practically every company in an industry where 30 to 40 percent of process costs are accounted for by energy inputs, depending on production priorities. Here the focus is on those processes – the improvement of generating energy-saving potential. An example of this is when waste material is refed directly back into the production process without involving an intermediary treatment process.

Another example are carbon fibers, which can be obtained from carbon fiber-reinforced plastics by means of pyrolysis and reused. These fibers tend to clump together, are contiguous and also have a very low bulk density. The FiberXpert, which feeds these challenging materials perfectly, was developed specifically for these kinds of materials. The idea behind this product innovation is to save the additional process and energy costs involved in the treatment process as well as transport and management costs.

However, the priority in control systems is being able to synchronize processes better in order to avoid scrap materials. One example of this is filling a weigh feeder to a level where as little unwanted material as possible remains at the end of a batch or maintenance intervals are identified as early as possible (predictive maintenance). Such integrated processes are challenging and can make major demands of control systems. Brabender Technologie is in the process of meeting these requirements and is set to unveil an OPC-UA interface at K 2019, the purpose of which is to analyze process and feed data at the customer’s facilities. “Industries will be able to keep much better track of their equipment in the future and coordinate processes and maintenance accurately, especially given the new 5G cellular network standard,” states Bernhard Hüppmeier, Business Development executive at Brabender Technologie

 

(published in FLUX 1/2019)