Composites from Flax and Bio-resins

More from the EDANA NIA 2013 Conference in Roubaix...

Prof. Philippe Vroman of ENSAIT (France) was working on making nonwovens and composites using flax, jute and bio-based materials to replace glass reinforced plastics with green composites.  He explained the terminology:

•        Biocomposites referred to oil based polymers reinforced with natural fibres, or bio-sourced polymers reinforced with oil-based fibres.
•          Bio-sourced polymers were those made from starch, castor oil or sugar-cane via ethanol such as PLA, PA11 and PE. 
•          Green composites were bio-sourced polymers reinforced with natural fibres.
•          Natural fibres suitable for reinforcement were flax, jute, hemp, sisal, bamboo and kenaf

Commercial examples were from the boating industry:

•          The “Gwalaz” trimaran based on cork, flax and balsawood reinforced with flax.
•          The “Araldite 6.5” yacht 50% of which was made from flax-reinforced composites.
•          The “Plasmor” kayak made from flax/starch-based composite.

Flax was also being used in conjunction with glass and carbon in a variety of sporting goods and automotive panels.

Green composite manufacture involved blending the natural fibres with bio-sourced thermoplastic fibres and compression moulding them to the desired shape.  Physical properties of the composites had been measured in comparison with glass/PP structures.  All the green composites had tensile strength and flexural moduli better than the glass/PP control, with Flax/PA11 proving to be twice as strong.  50/50 Glass/PP had the best impact resistance with the 70/30 flax/PP composite coming a close second.  70/30 Flax/PLA had the best sound absorbency.  However the density of the green composites was generally much higher than the control and the effects of humidity, temperature and UV on the ageing of the green composites had yet to be determined.  In response to questions the other issues in need of further research included “fogging” when used in car interiors, costs of the green composites c.f. current products, appearance of the composites in home furnishing applications, and optimisation of the interface between fibre and resin in each case.