Extrusion strategies for bio-based and biodegradable poly(butylene succinate-co-adipate)/thermoplastic starch blends

Over the past decades, economic growth led to an increase in the use of plastics. Reliance on plastics continued to grow because they offer advantages such as durability, versatility, lightweight, and cheapness. This led to a rapid accumulation of solid waste, which harms the environment due to their resistance to biodegradation. Nonrenewable feedstocks are environmentally harmful and are becoming more expensive, leading to questioning about their sustainability and thus motivating study and development of renewable alternatives. In this setting, biodegradable and bio-based polymers have received increased attention. Starch, a fully biodegradable polysaccharide, is the most widely applied renewable resource in the world. In the presence of heat, shear and a limited amount of water or other plasticizers, starch undergoes spontaneous de-structuration, forming a homogeneous melt known as thermoplastic starch (TPS). However, thermoplastic starch cannot be employed directly in several applications because of its poor mechanical properties and high water sensitivity. Poly(butylene succinate adipate) (PBSA) is an emerging biodegradable polyester with water and chemical resistance, good processability, and flexibility, but relatively more expensive. Blending these two polymers represents a potential strategy to overcome their intrinsic drawbacks. This thesis aims to develop PBSA/TPS blends with improved performance maximizing the starch content. More specifically, the purpose is to obtain a polymer blend with good processability suitable for film-blowing, and design different processing approaches to make the production more efficient, i.e. minimizing energy consumption. Two-steps, a one-step and a reactive one-step extrusions were explored, and the performances of the resulting blends were thermally, mechanically and morphologically characterized. Melt film blowing has been performed on selected blends to validate their enhanced processability.