title: Kinetics and mechanism of the biodegradation of PLA/clay nanocomposites during thermophilic phase of composting process.
abstract: The degradation mechanism and kinetics of polylactic acid (PLA) nanocomposite films, containing various commercially available native or organo-modified montmorillonites (MMT) prepared by melt blending, were studied under composting conditions in thermophilic phase of process and during abiotic hydrolysis and compared to the pure polymer. Described first order kinetic models were applied on the data from individual experiments by using non-linear regression procedures to calculate parameters characterizing aerobic composting and abiotic hydrolysis, such as carbon mineralization, hydrolysis rate constants and the length of lag phase. The study showed that the addition of nanoclay enhanced the biodegradation of PLA nanocomposites under composting conditions, when compared with pure PLA, particularly by shortening the lag phase at the beginning of the process. Whereas the lag phase of pure PLA was observed within 27days, the onset of CO2 evolution for PLA with native MMT was detected after just 20days, and from 13 to 16days for PLA with organo-modified MMT. Similarly, the hydrolysis rate constants determined tended to be higher for PLA with organo-modified MMT, particularly for the sample PLA-10A with fastest degradation, in comparison with pure PLA. The acceleration of chain scission in PLA with nanoclays was confirmed by determining the resultant rate constants for the hydrolytical chain scission. The critical molecular weight for the hydrolysis of PLA was observed to be higher than the critical molecular weight for onset of PLA mineralization, suggesting that PLA chains must be further shortened so as to be assimilated by microorganisms. In conclusion, MMT fillers do not represent an obstacle to acceptance of the investigated materials in composting facilities.
authors.affiliation: Centre of Polymer Systems, Tomas Bata University in Zlín, nám. TGM Sqr. 5555, 760 01 Zlín, Czech Republic; Department of Environmental Protection Engineering, Faculty of Technology, Tomas Bata University in Zlín, nám. TGM 5555, 760 01 Zlin, Czech Republic. Electronic address: StloukalP@seznam.cz.
authors.forename: Petr
authors.initials: P
authors.lastname: Stloukal
authors.affiliation: Department of Environmental Protection Engineering, Faculty of Technology, Tomas Bata University in Zlín, nám. TGM 5555, 760 01 Zlin, Czech Republic.
authors.forename: Silvie
authors.initials: S
authors.lastname: Pekařová
authors.affiliation: Polymer Engineering, Faculty of Technology, Tomas Bata University in Zlín, nám. TGM 5555, 760 01 Zlin, Czech Republic.
authors.forename: Alena
authors.initials: A
authors.lastname: Kalendova
authors.affiliation: Department of Polymer Engineering, Chair of Polymer Processing, Montanuniversitaet Leoben, 8700 Leoben, Austria.
authors.forename: Hannelore
authors.initials: H
authors.lastname: Mattausch
authors.affiliation: Department of Polymer Engineering, Chair of Polymer Processing, Montanuniversitaet Leoben, 8700 Leoben, Austria.
authors.forename: Stephan
authors.initials: S
authors.lastname: Laske
authors.affiliation: Department of Polymer Engineering, Chair of Polymer Processing, Montanuniversitaet Leoben, 8700 Leoben, Austria.
authors.forename: Clemens
authors.initials: C
authors.lastname: Holzer
authors.affiliation: Materials Center Leoben GmbH, 8700 Leoben, Austria.
authors.forename: Livia
authors.initials: L
authors.lastname: Chitu
authors.affiliation: Materials Center Leoben GmbH, 8700 Leoben, Austria.
authors.forename: Sabine
authors.initials: S
authors.lastname: Bodner
authors.affiliation: Materials Center Leoben GmbH, 8700 Leoben, Austria.
authors.forename: Guenther
authors.initials: G
authors.lastname: Maier
authors.affiliation: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, 162 06 Praha 6-Břevnov, Czech Republic.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Slouf
authors.affiliation: Centre of Polymer Systems, Tomas Bata University in Zlín, nám. TGM Sqr. 5555, 760 01 Zlín, Czech Republic; Department of Environmental Protection Engineering, Faculty of Technology, Tomas Bata University in Zlín, nám. TGM 5555, 760 01 Zlin, Czech Republic.
authors.forename: Marek
authors.initials: M
authors.lastname: Koutny
mesh_terms: D001546:Bentonite / Q000378:metabolism*; D001673:Biodegradation, Environmental; D006358:Hot Temperature; D006868:Hydrolysis; D007700:Kinetics; D019344:Lactic Acid / Q000378:metabolism*; D053761:Nanocomposites / Q000737:chemistry*; D011091:Polyesters; D011108:Polymers / Q000378:metabolism*; D018505:Waste Management
chemical_list: D011091:Polyesters; D011108:Polymers; D001546:Bentonite; D019344:Lactic Acid; C033616:poly(lactide)
keywords: Abiotic hydrolysis; Biodegradability; Biodegradation kinetics; Composting; Layered silicates; Polylactic acid