Converting flax processing waste into value added biocomposites

Flax fibers have excellent strength and other properties preferable for textile, composites and other applications. In addition to being an important industrial crop, many studies have been reported on the use of flax fibers, flax fabrics and other flax based products as reinforcement for composites. Processing flax fibers into yarns generates considerable (up to 25%) amounts of fibrous and non-fibrous waste which is generally discarded or used for low value applications. Pure flax fiber have current selling price between 6.5 and 7 Euro/kg compared to 0.16–0.19 Euro/kg for the flax waste used in this study which could make the composites highly affordable. To realize the unique properties of flax fibers such as its relatively high strength and add value to the waste, flax processing waste were used as reinforcement for polypropylene (PP) composites. Flax waste was separated into fibrous and non-fibrous (powder) components and combined in various ratios with poly(propylene) as the matrix. A compatibilizer (maleated polypropylene) (MAPP) was used to improve the surface interaction and adhesion between reinforcement and matrix and enhance the properties. Substantial increase in strength and modulus were observed due to the addition of the compatibilizer. A compatibilizer content of 3% was found to be optimum when the tensile strength was highest at 27 MPa and tensile modulus was 1212 MPa. The thermal conductivity and noise insulation properties also showed an improvement from 0.050 to 0.039 W/mK and 0.05–0.35 respectively after the addition of the compatibilizer. Flax-PP composites have properties surpassing that of commercially available medium density particle boards and that of neat PP.