Industry News
Spiders create plastics with biotech silk
6 years, 2 months ago Posted in: Industry News 0

Date: 05/05/11 By: European Plastics News staff

Source: European Plastics News.com

The potential for producing biopolymer plastics from silk woven by spiders for their webs was presented in a paper by Prof. Thomas Scheibel from the faculty of applied sciences at Bayreuth university at the VDI plastics in automotive engineering conference in Mannheim, Germany in April.

The scientific basis behind the development lies in the proteins which give the webs and fibres their unique stability and stretching ability. Scheibel pointed out that proteins usually consist of 20 types of amino acids that are bound to each other via peptides and that the variable arrangement of the amino acids enables a protein of chain length 100 to result in more than 10130 different amino acid chains.

Silk spun by insects and spiders consist mainly of structural proteins, derived not from naturally occurring amino acids, but from glycine, alanine, proline and glutamine, built up from repetitions of 20-100 amino acid modules. These are held together by van der Waals forces to form a flexible 3D structure with excellent mechanical properties.

Scheibel put this in context by saying that spider silk filaments can absorb three times more energy than Kevlar, one of the most tear-resistant synthetic fibres.

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Industrial processing of the silk fibres involves casting or spray processes, giving rise to homogenous and relatively resistant, crystal-clear silk films with thickness in the order of nanometres to micrometres.

Scheibel said such films possess lower air and much higher water moisture permeability compared with films made from PVC or PE. Unlike these conventional films, silk-based films can be modified by metals (for conductivity), enzymes or chemical coupling (for diverse functions), he said.

Scheibel showed a process in which a silk solution is evaporated to form a soluble film that can be transformed into an insoluble film. A chart was shown comparing such a film’s mechanical properties and permeability with conventional thermoplastic films.

Here, the spider silk film had “strength” of 20MPa, compared with 24MPa, 33Mpa and 74MPa for respectively PE, PP and PET films. Oxygen permeability ranged from 18,500 cm3.1µm/m2/d at 23°C for silk film, through values of respectively 55,000, 70,000 and 1,400 for the other films. Water moisture permeability values were given of 17,500 g.1µm/m2/d at 23°C and 85% humidity for silk film, compared with values of 30, 55 and 200 for the respective PE, PP and PET films.

BASF senior VP engineering plastics Europe Dr Willy Hoven Nievelstein told European Plastics News at the VDI conference that he had been impressed with the spider silk development, although he suspected the limiting characteristic of the material may be relatively low heat resistance.

Industrial processing of silk fibres into technical applications is being pursued by AmSilk in Planegg/Martinsried, a spin-off company from Munich technical university that was awarded an “Industriepreis 2011” award for production of spider silk as “an accolade for cutting edge industrial solutions”. AmSilk is financed by MIG Funds and AT Newtec, both of Munich, Germany.

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