Processing, Characterization and Flammability Behavior of Coir Fiber/Sirisha Bark Filler Reinforced Hybrid Polymer Composite

Abstract

Recently, natural fibers are replaced synthetic fibers to a great extent as reinforcement to the polymer composites. Among the natural fibers, coir fiber has the potential to be used in various applications because of its abundant availability, non-toxicity, low cost, and resilient properties. Coir fiber has high lignin content (46 %) as compared to jute (23 %), hemp (10 %), and kenaf (16 %) fibers making it a preferable reinforcement in the development of polymer composites to enhance the flame-resistant properties. Generally, polymeric materials are susceptible to flame. That is why it is essential to measure the performance of polymer composites before their applications in construction, automotive parts, etc. The neat polypropylene (PP) is extremely sensitive to flame and therefore it is a challenging task for the researchers to reduce the flammability properties of PP-based composites. Though the artificial flame retardant fillers reduce the flame propagation, these are hazardous, costly, not environment friendly and they reduce the mechanical strength of the polymer composites upon higher loading. To overcome these limitations, in this work the novel natural Sirisha bark filler is reinforced as flame retardant filler to the coir fiber reinforced PP composites. The objective of the present investigation is to produce a compatibilized blend of a natural fiber with a thermoplastic to produce coir fiber/Sirisha bark filler-based PP hybrid composites with improved fire performance for applications in the auto industry for indoor application where the load is not a critical issue and to study the mechanical and flammability properties. The dynamic mechanical behavior, thermal stability, and wettability properties of composites are also studied. The PP hybrid composites may also be used in decking and cladding. The hybrid composites provide satisfactory fire performance along with the mechanical properties at lower filler loading without any compatibilizer. The 10 wt. % bark filler reinforced composites attain a V-0 rating with zero flame propagation speed. The time to ignite (TTI) of the hybrid composites increases due to the filler addition in comparison to neat PP. The impact strength also increases with the filler loading. The thermal stability of the hybrid composites increases due to the bark filler loading than the neat PP and the coir fiber/PP composites. The SEM micrographs show the well-defined grain boundaries of the composites that reveal the strong bond of the bark filler with the PP matrix. The char morphology conforms to the formation of carbonaceous char coating over the hybrid composites surface that act as a hindrance to flame.