Dynamic and thermo-mechanical properties of polypropylene reinforced with date palm nano filler

Abstract

Lignocellulosic based nano-sized filler are effective substituent for switching from manmade nanofillers (i.e. carbon, glass etc.) to reinforce polymer composites owing to their lightweight, plentifulness, and fully compostable characteristics. The present study adapted a dry mechanical ball mill assisted downsizing process to produce nanoscale filler from waste date palm agro residue. Then, the melt mixing technique was used to fabricate biocomposites of polypropylene (PP) with 1–5 wt% loading of this nanofillers. To investigate the variations in dimensional stability of the composites, thermo-mechanical analysis (TMA) was used. The thermomechanical analysis indicated that these composites exhibits low coefficient of thermal expansion (CTE). The CTE values for the highest nanofiller loaded sample (i.e.5 wt%) was found to be 95 and 138 at 40 °C and 80 °C, respectively, when compared to neat PP (which is 80.4 and 125) at the same temperatures. Moreover, the viscoelastic parameters of the biocomposites, such as storage modulus (E’), loss modulus (E′′), and damping factor (tan δ) were examined by using dynamic mechanical analysis (DMA) in both solid and molten state. It is observed that the both E′ and E′′ decreases with temperature in all composites compared to the neat PP in the solid state. The storage modulus (E’) difference between the biocomposites and PP at −50 °C was found to be only 9 %. On the other hand, E′ and E′′ were found to increase with the entire angular frequency range in the molten state. The E’ at 0.1 rad/s of the neat PP is 732 Pa, while the sample with 1 wt% of nanofiller loading shows storage modulus 850 Pa. Overall, these composites demonstrated good dimensional stability in a given temperature range and frequency in the solid state, as well as typical viscoelastic behavior of entangled polymeric liquid in the molten state. Consequently, these analyses provided useful information for the development of natural fiber-based composites for long-term stability in outdoor applications.