Bioplastic compound box for storing cereal
Application

Compounding systems for bioplastics

Ecological awareness promotes new developments in the field of bioplastics

Bioplastics have already existed for a very long time. The first industrially produced plastics were cellulose-based and produced industrially as of 1869 and casein, which was produced in large quantities at the beginning of the 20th century as so-called synthetic horn. The discovery of plastic manufacturing based on crude oil in the early 20th century replaced the bioplastics fast and for several decades because it enabled considerably cheaper plastics production.

It was not until the 1980s that increasing crude oil prices and a gradually changing ecological conscience brought new, interesting developments in the field of bioplastics, and with it new compounding systems for production.

Typical areas of application

Bioplastic box for storing fresh salad, consisting of compounded biopolymers
Granulate from bioplastics manufactured on a compounding system, decoratively presented on fresh leaves
Blue bioplastic granulate after compounding
Bioplastic as the basic material for lunch boxes. Biopolymers are compounded with BUSS compounding systems
Light-blue granulate from a compounding system
Bioplastic water bottles as an example for compounding technology for biodegradable plastics

Its main applications are packaging, consumer goods and technical components from the transport and construction industry.

The term bioplastics or biopolymers is still not used in a uniform manner. It generally summarizes a large number of plastics which meet at least one of two criteria:

  • bioplastics consist at least one part from renewable (plant-based) raw materials. Virtually all bioplastics are bio-based.
  • Bioplastics are biodegradable, i.e. they can be broken down into water and CO2 by naturally occurring microorganisms, producing a small amount of biomass. Bioplastics from fossil raw materials can also be biodegradable.

Both these properties which either occur in isolation or jointly are used to define bioplastics: bioplastics are bio-based, biologically degradable or both together. Traditional plastics meet neither of these criteria. The biogenic raw materials or biological macromolecules which exist in nature such as proteins as well as materials filled with or reinforced with natural fibres are not meant by this.

Further insights into our options for the plastics and food industry

Benefits

BUSS compounding systems offer the following specific benefits

Uniform shear rates allow controlled mixing in the compounding machine at lower temperatures while imparting only the required shear energy for the task at hand. The narrow shear rate distribution compared to alternative systems ensures uniform shear histories for every individual particle. This results in high-quality processing with reduced energy input.

Volatile substances are usually degraded by vacuum degassing at the end of the process section or additionally in the discharge unit. The high number of mixing cycles, shearing and rearrangements of the BUSS Co-Kneader technology within the compounding system ensures a continuous renewal of the compound surface. In this way, air inclusion or volatile components can be minimized highly efficiently.

The BUSS Co-Kneader allows precise temperature control due to controlled energy input and uniform, moderate shear rates as well as their temperature monitoring by thermocouples, which are mounted in drilled kneading pins surrounded by polymer at relevant positions along the process section.

The BUSS compounding machine technology allows high filler loadings by splitting to 2-3 feed positions, use of feed-in processes such as side feeders, gravimetric dosing units, back venting and excellent conveying efficiency. The moderate shear rates of the Co-Kneader allow effortless handling of the high viscosities arising with high filler loadings.

The separate execution of compounding in the BUSS Co-Kneader and pressure build-up in the discharge unit enables processing at low pressures and temperatures. Thus, the configuration of application-specific screw geometries in each process zone can guarantee an optimized temperature profile in each process zone.

Compounding requirements

for bioplastics

Excellent dispersive and distributive mixing processes at moderate shear rates and low product temperatures are the key prerequisites for compounding bioplastics in order to ensure the lowest possible molecular weight degradation and thus the desired properties.

The gentle integration of fibres, fillers and additives often requires multiple splitting of the dosage flows and, if applicable, also the injection of liquid additives at defined positions in the compounding machine.

The BUSS Co-Kneader can demonstrate its specific abilities especially well in these applications: the enormously high number of mixing cycles at moderate, adjustable shear rates due to the operating principle allows top mixing efficiency on short process sections with narrow dwell time spectra. With the BUSS Co-Kneader's two-stage system, compounding and the pressure build-up step are strictly decoupled.

This enables optimization of the process steps independent of each other. The hinged BUSS Co-Kneader housing secures quick access to and high system availability.

The modular and therefore adjustable structure of the entire line and the widely supported BUSS process expertise make the BUSS Co-Kneader an excellent choice for compounding technical bioplastics.

Typical plant layout

Typical plant layout for a bioplastic compounding system

COMPEO compounder for bioplastics compounding

Take a look at our typical plant layout for the production of bioplastic compounds in our COMPEO showroom.

Get to know our COMPEO compounder series

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COMPEO series

We present: COMPEO, the state-of-the-art compounder that offers more versatility in its application, higher flexibility in process engineering, and increased added value in compound manufacturing.

Natural fiber-reinforced plastics

For many centuries, people used natural materials as primary materials. Wood was used for building houses and ships, flax and hemp fibre were processed as ropes and technical textiles such as sails and grain sacks.

Plant and System Solutions

Custom compounding systems from BUSS: tailor-made concepts, integration of all components, precise assembly, and smooth commissioning. Comprehensive expertise results in sustainable compounding solutions for a wide range of material applications.