ABSTRACT
This chapter offers a comprehensive overview of current commercial and experimental grades of poly(lactic acid) or polylactide (PLA) formulated for additive manufacturing (AM), and includes extensive data from technical publications and suppliers’ data sheets. PLA is the sustainable polymer mostly used for AM. Properties, benefits, limitations, price, production processes, suppliers, current and future market, and applications of PLA for AM are discussed. Commercial PLA grades converted into AM feedstocks, and commercial PLA filaments for AM from major suppliers, and a wide range of properties (physical, mechanical, thermal, and electrical) of those feedstocks and filaments are reported, including data relative to compression, shear, fatigue, and creep that are rarely disclosed. Experimental PLA powder for laser sintering is also illustrated. PLA is compared to popular fossil-based polymers similar in price and performance to it, and biodegradable polymers. The effect of variables such as anisotropy and infill on the mechanical properties of filaments, and the limitations and interpretation of suppliers’ data sheets are included. Commercial and experimental composite PLA filaments are described, along with the processes to develop the latter ones, and with physical and mechanical properties for both types. The number of commercial and experimental versions of unfilled and filled PLA is large and keeps growing. PLA is combined with non-sustainable (carbon, glass, etc.) and sustainable fillers (bamboo, cellulose, etc.), and nanosized fillers, resulting in composites that are elucidatesin other chapters of this book focusing on each natural filler. Mechanical properties of PLA composites are below their maximum potential that can be approached f.e. by increasing filler-matrix interfacial adhesion and reducing porosity. Commercial recycled PLA grades for AM are also reported. In summary, PLA typically is strong and stiff but it also features brittleness and low maximum service temperature, with the latter ones being addressed by R&D, and can enable advanced applications (biomedical) and processes (4D printing), but its cost must be reduced in order to spread its use. The chapter closes by summarizing the most recent technical literature on a broad range of physical and mechanical properties of PLA filaments, the factors affecting and improving these properties, and how these factors influence processability and printing quality. Many property values lacking in suppliers’ data sheets, such as fatigue and properties above room temperature, are selected from the technical literature and included. Actual and potential applications are mentioned whenever possible to serve as a benchmark, indication, guide, and suggestion for product development. About 250 recent references on neat and composite PLA comprising technical papers and patents permit the readers to delve in all the topics discussed. When technical information on PLA for AM was not available, non-AM PLA grades were described in the place of it.
