Bio-based high-grafting-rate compatibilizer: Dynamic reactive extrusion synthesis of itaconic anhydride-based copolymers with polypropylene grafts and the application in plant fiber composites

A bio-based high-grafting-rate compatibilizer, itaconic anhydride grafted polypropylene (ITA-g-PP), was successfully prepared using 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (L101) as the initiator and assisting by the radical trapping agent α-methyl styrene (AMS). Itaconic anhydride (ITA) was synthetically grafted onto polypropylene (PP) through a dynamic reactive extrusion. The influences of variant contents of ITA and L101 on the grafting reaction were systematically investigated using infrared spectroscopy (IR), acid-base titration, melt flow index, contact angle, differential scanning calorimetry (DSC), mechanical properties and rheological testing methods. The mechanical performances and microstructure of the wheat fiber (WF) enhanced PP composites were investigated. In addition, a series of comparisons were made between ITA-g-PP and self-made maleic anhydride grafted polypropylene (MAH-g-PP) under the same conditions. The results show that the highest grafting rate of ITA-g-PP reached 1.45 %, greatly improving the hydrophilicity of PP. Under the same conditions, ITA-g-PP grafting rate can reach 1.2 %, and self-made MAH-g-PP grafted rate was only 0.75 %. The prepared ITA-g-PP can significantly enhance the adhesion of interfacial between WF and PP compared with traditional MAH grafted PP, thereby improving impact and tensile properties. Among them, adding ITA-g-PP to WF/PP composites can increase the impact strength by up to 29 %, while adding MAH-g-PP can only increase it by 17 % in WF/PP composites. • A biobased high-grafting-rate compatibilizer (PP-g-ITA) was prepared by dynamic reactive extrusion. • The effects of different contents of ITA and L101 on the grafting reaction were investigated. • The presence of α-methyl styrene effectively reduced the degradation of PP chain. • Adding PP-g-ITA enhanced the interfacial adhesion of PP and wheat fibre. • PP-g-ITA can improve tensile strength, tensile modulus and impact strength of the composite.