Properties of binary and ternary composites of polypropylene containing soybean oil-g-chitosan and hydrophobic phosphonated silica

Abstract

PP/soybean oil-g-chitosan binary composite, PP/hydrophobic phosphonated silica binary composite, and PP/chitosan/hydrophobic phosphonated silica ternary composite were prepared.  Firstly, the preparation of soybean oil-g-chitosan was carried out by surface hydrophobicity modification of chitosan powder with soybean oil maleate and hydrophobically phosphonated silica was prepared by silanization of phosphonated silica with hexadecyltrimethoxysilane (an organosilane).  Binary and ternary composites were prepared using a twin screw extruder.  It was found that soybean oil-g-chitosan not only caused a decrease in tensile strength but also enhanced flexibility of PP due to its plasticization effect.  In the opposite direction, the addition of hydrophobic phosphonated silica resulted in an increase in tensile modulus and a decrease in percent elongation at break due to reinforcement characteristic of silica particle.  Effects of soybean oil-g-chitosan and phosphonated silica on antimicrobial activity and flame retardancy property, respectively, were evaluated.  Results showed that binary PP composites containing soybean oil-g-chitosan exhibited antimicrobial performance when compared to neat PP.  For binary composite containing phosphonated silica, flame resistance was improved which was indicated by relative char content.  An addition of soybean oil-g-chitosan led to phosphorus-nitrogen synergism effect (70 % of remaining residue weight at T 450 ^oC) as found in case of ternary composite containing 1 wt% soybean oil-g-chitosan and 1 wt% phosphonated silica.