10 - Biodegradability studies of lignocellulosic fiber reinforced composites

Abstract

Synthetic polymers often present increased life span, taking decades or even centuries to fully degrade in the environment. Due to the increasing demand for polymeric materials in the last decades, an overwhelming amount of waste materials are generated, creating a major pollution problem. The polymer composite industry consists of synthetic materials for matrices and reinforcements. Most of these are petroleum derivatives leading to major environmental issues. In this context, the use of renewable and biodegradable agro-based materials, such as lignocellulosic fibers, has recently increased. The lignocellulosic fiber reinforced polymer composites (LFRPC) are produced by the combination of the fibers with thermoset, thermoplastic or natural polymer matrices. Synthetic polymers are generally resistant to fungal and bacterial attack, however, vegetal fibers in the composite remains susceptible to biological degradation. Biodegradation is defined as the conversion of a material to CO2 or CH4 (under anaerobic conditions), H2O, trace inorganic products and biomass by microorganisms (bacteria, fungi, algae…). To ensure LFRPC structural stability over its service life, biodegradation mechanisms have to be properly accessed and understood. The present chapter brings an overview of the studies focusing on the biodegradability of LFRPC and the current standards/methods utilized to evaluate this property. Biodegradation can be translated as changes in the material physical properties (mass, mechanical, visual, etc.), the evolution of CO2/CH4 generated by microorganisms and the incorporation of carbon-14 labeled polymers into their biomass. Since environmental factors influence the microbial population and the activity of the different microorganisms, the symbiotic effect of abiotic degradation (weathering) combined with biotic degradation is also addressed.