Effect of Interfacial Bonding Characteristics on Fire Performance of Flax Fiber Reinforced Composites

Flax fibers are mainly oriented to their use in handicrafts, furniture, decorations, carpets. However, in recent years, these fibers have been directed towards other industrialized sectors such as automotive, construction, military, and transportation due to their high rigidity and resistance. Flax fiber is often used as a reinforcing phase in thermoplastic composites and, to a lesser extent, as a natural reinforcement in thermosetting resins. In this way, composite materials reinforced with flax fiber are in the spotlight for developing new products and boosting other markets, complying with environmental regulations, and reusing abundant waste at a low cost. However, natural fibers have specific weaknesses, such as their hygroscopic nature and low resistance to fire, and flax fiber is no exception. Additionally, the intrinsic nature of the constituents of the composites (linen fiber and polymer resins) are generally incompatible, so the interfacial bonding is fundamental to looking for optimal mechanical performance and its behavior against fire, essential for its use and commercial application. Optimizing the interface between the natural reinforcement and the polymeric matrix is perhaps the most critical aspect in developing polymeric composites reinforced with flax fibers. Natural fibers are flammable and therefore add to the flammability of composites in which the organic matrix is also volatile. This book chapter presents an overview of the effect of interfacial bond compatibility between components of natural fiber-reinforced composites, including surface treatments intended to improve compatibility and strategies to increase the fire resistance of flax fibers.