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Biopolymer aids bionics

Interplay of Design + Material

Specialising in innovative, application-orientated plastic compounds for over 25 years, AKRO-PLASTIC GmbH has partnered with ZIEHL-ABEGG SE to develop a polyamide-6.10-based AKROMID® S compound for the “bionic bio-fan.”

AKROMID® S, the PA 6.10 compound from AKRO-PLASTIC, satisfies the common definition of a bioplastic with a biogenic C-portion of up to 70 %. Castor oil from the seeds of the castor oil plant (Ricinus communis) forms the basis of sebacic acid which in turn serves as the basis for the polymer’s renewable raw material portion. PA 6.10 is not biodegradable. In engineering plastics applications, this property is completely undesirable, as these applications require a long service life of the end product and an equally high material resistance which cannot be fulfilled by a degradable plastic.

Through the use of plant-based raw materials, which have already removed CO2 from the environment during their growth phase, the carbon footprint of this material is more favourable than that of polymers based on fossil raw materials. ZIEHL-ABEGG recognised the advantages of bionics early on in the area of ventilation technology and has consistently applied the acquired knowledge in the design of their new generation of fans whose blade geometry is based on an owl-wing pattern, resulting in a reduction in fan noise.

Bionic design of ZIEHL-ABEGG fan blade with optimised geometry for reducing drive power and noise (photo credit ZIEHL-ABEGG).

Bionics, which utilises design solutions based on examples found in nature, ensures continual improvement in the development of solutions for technical design work. Alongside lightweight construction due to material reductions, high mechanical strengths through the use of struts in the necessary places and a reduction in notching effects due to special notching geometries, amongst others, various solutions have been developed based on the knowledge gleaned. The latest-generation axial fan from ZIEHL-ABEGG, made from AKRO-PLASTIC polyamide 6.10, was developed in this way.

Whereas knowledge of mechanical strengths ensures a design’s longevity, further knowledge of fluid mechanics is necessary for fan blades. Compared to standard polyamides, such as PA 6 and PA 6.6, PA 6.10 has advantages in terms of less water absorption, better chemical resistance and lower density. The use of this material in ZIEHL-ABEGG fans provides the following advantages:

• up to 6 % lower component weight

• less effect of moisture on the mechanical properties

• greater dimensional consistency

• CO2 savings of up to 60 % with respect to the percentage of polyamide

The mechanical properties of AKROMID® S, reinforced with 30 % glass fibre, ensure safe operation of the fan even at higher speeds. Excellent surface quality is also achieved with this glass fibre content. Not least, this is the result of the process technology used in the manufacturing method. The twin-screw extruder from Sinzig-based sister company FEDDEM GmbH & Co. KG, which has no kneading block, ensures careful dispersion. The incorporated glass fibres are not reduced as drastically in length with this gentle compounding method, allowing greater values to be achieved in tensile strength and impact strength.

These bionic fans will soon be used in refrigeration technology (refrigeration chain to the supermarket), heaters and heat pumps and for electronics cooling (computing centres and switchgear cabinet and inverter cooling). In these areas, the fans ensure that noise emissions are greatly reduced, in addition to making efficient use of resources in terms of materials. The environmentally-friendly bionic concept from ZIEHL-ABEGG has received honours and awards in a number of competitions.

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