Effect of Maleic Anhydride Modification of PP and Alkali Treatment on the Interfacial Shear Strength between Pineapple Leaf Fiber and PP

Abstract

Pineapple leaf fiber (PaLF) shows promise as a reinforcement material for polymer matrix composites due to its high tensile strength and Young's modulus, comparable to those of flax fibers. However, due to the non-polar nature of polypropylene (PP), forming a composite with cellulose-rich PaLF is challenging without surface modification. This study investigates the interfacial shear strength between PaLF and PP, focusing on the effects of maleic anhydride modification of PP and fiber treatment with a NaOH solution. Additionally, a method was developed to precisely estimate the circumference of PaLF cross-sections prior to micro-drop tests for measuring interfacial strength. Inaccurate circumference estimation is identified as a potential source of data variability. PaLFs were extracted using a water-jet process, and the circumferences at the micro-drop test site were estimated by measuring fiber width from multiple directions. The correlation between estimated circumferences and measured circumferences showed reasonable accuracy, with errors below 10%. The highest interfacial strength between PaLF and PP was achieved with the addition of 4% maleic anhydride to PP, increasing the interfacial strength by approximately 80% compared to the unmodified case. Immersing PaLF in a NaOH solution significantly improved interfacial strength, even without PP modification.