Vol. 28, No. 2, 29-39 (2015) DOI: http://dx.doi.org/10.7234/composres.2015.28.2.029 ISSN 2288-2103(Print), ISSN 2288-2111(Online) Review Paper A Review on the Flammability and Flame Retardant Properties of Natural Fibers and Polymer Matrix Based Composites M.N. Prabhakar * , Atta Ur Rehaman Shah * , Jung-Il Song * † ABSTRACT: Natural fibers reinforced polymer composites are being used in several low strength applications. More research is going on to improve their mechanical and interface properties for structural applications. However, these composites have serious issues regarding flammability, which are not being focused broadly. A limited amount of literature has been published on the flame retardant techniques and flammability factor of natural fibers based polymer matrix composites. Therefore, it is needed to address the flammability properties of natural fibers based polymer composites to expand their application area. This paper summarizes some of the recent literature published on the subject of flammability and flame retardant methods applied to natural fibers reinforced polymer matrix composites. Different factors affecting the flammability, flame retardant solutions, mechanisms and characterization techniques have been discussed in detail. Key Words: Flammability, Natural fibers, Polymer composites, Flame retardants, Nano-fillers 1. INTRODUCTION Light weight, low cost and ecofriendly characteristics of nat- ural fibers based polymer matrix composites have become a need of the hour due to the rising prices of petroleum prod- ucts and their environmental risks [1]. Due to the uncertainty of aluminum supply during the Second World War, Mr. Gor- don (an undergraduate) at Trinity College presented an idea to utilize flax fiber. The Aero Research Limited Company adopted this idea and the first natural fiber reinforced composite (flax/ phenol formaldehyde) was developed and used in the spar of a bomber aircraft [2]. Natural fibers reinforced composites (NFRC) are also being used extensively in the interior parts of automobiles and construction industry [3,4]. Aside numerous potentials, The NFRC has inferior flame resistant character- istic [5-7]. Several in-flight flame incidents have been recorded in the transport airplanes history [8]. According to a report of society of automotive engineers, in USA, in-flight smoke inci- dents happen frequently [9]. This smoke may sometime erupt flame, which causes major accidents. Flames in automobiles can be extinguished if detected in the beginning. According to Boeing Company, most of the flame incidents are caused by the fume or smoke created through electrical sources [10]. Due to their undesirable flammability characteristics, more research is needed on the flame retardant approach and mech- anism of NFRC [11-13]. Researchers are trying to invent new mechanisms which can make NFRC able to resist to the flame propagation [14]. Still not much literature is available on the flammability and flame retardancy of NFRC. Fig. 1 shows an estimated comparison of the number of articles published in the last five years in Elsevier publishing journals on the topics of natural fiber composites and flame retardant natural fiber composites. The comparison clearly shows how little research is being carried out on the flammability of natural fiber com- posites. However the encouraging factor is that the trend is going on increasing with time. It is expected to increase more in future. The different phenomenon has been introduced to achieve flame retardancy. One way is to modify the chemistry of the polymer matrices. Sauca et al. obtained phosphorous-con- taining polymers by chemically modifying poly(vinyl alcohol) [15]. Flame retardant coatings of polymers and composites are also a well-known method against flammability. Zeytuncu et al. deposited UV-curable boron containing hybrid coatings on Received 27 December 2014, received in revised form 25 April 2015, accepted 28 April 2015 * * Department of Mechanical Engineering, Changwon National University Department of Mechanical Engineering, Changwon National University, Corresponding author (E-mail: jisong@changwon.ac.kr)