Effects of Interfacial Enhancing by Aldehyde-Based Surface Modification of Flax Fibers on their Polymer Composites

Abstract

Flax fibers were chemically modified on their surface with aldehyde-based glutaraldehyde, glyoxal, or butryaldehyde to enhance their adhesive interconnections with polypropylene (PP) matrix. Mechanical (tensile and elastic) properties were most improved with glutaraldehyde modification compared with glyoxal or butryaldehyde. Using glutaraldehyde modified flax fibers, the optimal modification parameters that produce the most improvement to the mechanical properties and tensile strength were then evaluated by Fourier Transform Infrared Spectroscope (FTIR) and scanning electron microscopy (SEM). Optimal modification of flax resulted from an acetalation reaction involving glutaraldehyde and anhydro-D-glucopyranose (AGU) flax at a concentration of 3 mol/AGU, performed at 60oC for 5 h (pH = 2.0). Composites were then created by mixing the modified flax fibers with PP matrix at a 20:80 wt% ratio at 180oC for 40 min using a co-rotational twin screw inner melt mixing kneader. FTIR and SEM analysis demonstrated that reinforced PP composites had a 31.63% increase in tensile strength and a 19.61% increase in the elastic modulus when compared with the original flax fibers. Compared with other reported surface modification methods, this method exhibited better performance in enhancing the mechanical properties of flax/PP composites.