SYNTHESIS AND CHARACTERIZATION OF BIOBASED BIODEGRADABLE POLYESTERS TO REPLACE LDPE/LLDPE IN FLEXIBLE FILM PACKAGING

Abstract

This dissertation investigates the recent advancements in the development of biobased and biodegradable polyesters have shown significant promise for replacing conventional petrochemical-based plastics, particularly in flexible film packaging applications. Poly (pentylene adipate-co-terephthalate) (PPeAT) and poly (dodecamethylene furandicarboxylate) (PDDF) were synthesized using direct esterification and polycondensation methods, incorporating various branching agents and nucleating agents to the former to enhance their thermal, mechanical, and rheological properties. Chapter 1 serves as the introduction to this dissertation, providing an overview of the project's motivation, rationale, and the current possible alternative polymers in the field. This chapter outlines the driving forces behind the research, detailing the pressing need for advancements in the area and the potential impact of the project. Chapter 1 dives into the reasons for undertaking the study, highlighting the gaps in existing knowledge and the anticipated contributions to the field. Chapter 2 reviews the latest technologies and methodologies that form the foundation of the research, setting the stage for the detailed exploration and innovative solutions presented in the subsequent chapters. The preliminary results for the pentanediol – furandicarboxylic acid-based polyesters are reported in Chapter 3. None of these polymers were suitable for flexible-film applications because the glass transition temperature was too high, or the melting temperature was too low. Chapter 4 explores the synthesis and characterization of PPeAT, a polymer synthesized with a 40/60 adipic acid/terephthalic acid mole ratio; a mole ratio chosen to best match the glass and melting temperatures of commercial flexible-film packaging resins. PPeAT exhibits high thermal stability and molecular weight, making it a promising candidate for film-blowing applications, despite its inherently slow crystallization rate. Chapter 5 examines the impact of incorporating nucleating agents, such as Li, Mg and Na-neutralized ethylene-methacrylic acid copolymer-based ionomers and un-neutralized ethylene-methacrylic acid copolymer. These nucleating agents significantly decreased the crystallization half-time, thereby enhancing PPeAT's potential as a biodegradable alternative to linear low-density polyethylene (LLDPE). Chapter 6 investigates the compression molded and film blowing of PPeAT. The blown polyester films were compared with film blown with commercially available polymers such as LLDPE and PBAT. PPeAT showed lower oxygen and carbon dioxide permeability compared with PBAT and LLDPE and lower water vapor transmission rate than PBAT. Film blown PPeAT showed promising results and eventually could be used as a drop-in replacement for LLDE in flexible film packaging Chapter 7 discuss the synthesis and characterization of another possible polymer useful for flexible-film: PDDF, a polymer derived from furandicarboxylic acid and a 12-carbon diol. This polymer demonstrates exceptional gas barrier properties, surpassing those of linear low-density polyethylene (LLDPE) and poly (butylene adipate-co-terephthalate) (PBAT). PDDF's reduced oxygen and carbon dioxide permeability, combined with its robust mechanical properties, makes it an excellent candidate for packaging applications. These developments underline the potential of biobased polyesters to address environmental concerns associated with plastic waste while meeting the demands of global packaging needs.