Investigation on the microscopic mechanism of potassium permanganate modification and the properties of ramie fiber/polypropylene composites

The microscopic mechanism of potassium permanganate (KMnO4) modification and the properties of ramie fiber/polypropylene (RF/PP) composites were investigated with experiments and molecular dynamics (MD) simulations at the molecular and atomic levels. The MD simulations suggested that the microscopic modification mechanism for the improved properties of the KMnO4 modified RF/PP composites were contributed to the decrease of the free volume of cellulose molecular and increase of the weak Van der Waals force at the interface of the modified fiber and PP matrix. The decrease of the free volume of cellulose molecular can reduce the water absorption of natural fiber. Conversely, the increase in the weak Van der Waals force at interface can improve the interface adhesion strength of the composites and further result in the improvement of the compatibility of RF/PP composites. Additionally, the experimental work showed that KMnO4 treatment led to a higher surface roughness of the modified fiber besides the oxidization effect of oxidizing hydroxyl groups within cellulose molecular to be aldehyde and carboxyl groups. This can achieve a better bond strength at interface of fiber and polymer matrix, and finally resulted in the good mechanical properties of the KMnO4 modified RF/PP composites. POLYM. COMPOS., 39:3353-3362, 2018. (c) 2017 Society of Plastics Engineers