Thermal degradation of poly(lactic acid)–zeolite composites produced by melt-blending

• Published in: Polymer bulletin (Berlin, Germany) Germany), 2020-04, Vol.77 (4), p.2111-2137
• Main Authors: Pires, Marçal, Murariu, Marius, Cardoso, Ariela M., Bonnaud, Leila, Dubois, Philippe
• Format: Article
• Language: English
• Subjects: Acids; Alkalinity; Aluminum; Biopolymers; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Complex Fluids and Microfluidics; Composite materials; Decomposition; Fillers; Fly ash; Mechanical properties; Melt blending; Molecular sieves; Organic Chemistry; Original Paper; Physical Chemistry; Polylactic acid; Polymer Sciences; Polymers; Pore size; Pyrolysis; Rheological properties; Soft and Granular Matter; Solvents; Temperature; Thermal degradation; Zeolites
• ISSN: 0170-0839; 1436-2449
• DOI: 10.1007/s00289-019-02846-4

Various zeolites (4A, Y, 13X) and related fillers (molecular sieves and coal fly ash) were used to prepare PLA composites and to assess their degrading effect on the polyester matrix under different processing conditions, at various zeolite/filler loadings. In this objective, untreated fillers, as well as washed and thermally activated zeolites, were used. PLA–zeolite composites were produced by melt-blending step followed by the evaluation of rheological information and molecular and thermal characteristics. The degradation of PLA during the preparation and processing of PLA–zeolite composites, or due to the presence of fillers, was evidenced by specific analyses (SEC, DSC, TGA, TG-FTIR). PLA degradation was mainly dependent on the nature of zeolite, filler loading, and thermal and processing history. The results of the study suggest that a stronger degradation effect is obtained by the addition of zeolite 4A into PLA (at loading of 5–10%) with respect to other zeolites (e.g., 13X and Y). It was also revealed the key roles of the temperature and residence time (as parameters in melt-mixing process), free alkalinity level, and water uptake in determining the ultimate characteristics of composites. The washing and thermal activation pretreatments of fillers have diminished in some cases the degradation of PLA matrix. Finally, the study also highlights the zeolite grades capable of being used to produce new PLA composites with competitive properties and those that could be of interest to improve PLA recycling by pyrolysis.