Abstract
The paper is part of a series in which the influence of the manufacturing defects on the functional behavior in biodegradation medium of some items obtained, both by 3D printing and by classical procedure (pressing), from an originaly renwable matrials based on polylatic acid will be presented. The first results regarding the correlation of the defects appeared at manufacturing into plates with the biodegradation behavior in an Aspergillus Niger(A.niger) medium, studied by SEM microscopy, are presented. These results demonstrated that the development of the A. Niger microorganism is related manly to the defects appeared at the melt processing of renewable polymeric material into finished product. A notable role in controlling the appearance of the manufacturing defects belongs both to the melt rheological properties which are responsible for the continuous or discontinuous flow and to the technical performance of the used equipement, 3D printer or classic hydraulic press. If the polymeric material melt has too high viscosity than the continuous flow is not possible and so the overlapped melt fronts are created which generate the voids formation, sometimes joined by small nano and/or micrometric channels. The rheological properties of the melts depend both on the material formulation and the seleted melt processing conditions.
Highlights
Due to its functional properties, polylactic acid (PLA) is a renewable polyester successfully used instead of conventional polymers such as PP, PET which an be transformed into finished product considering both classical melt processing technologies and the revolutionary 3D printing methods
The plate’s defects generated by the obtaining procedure (3D printing or pressing) were identified by SEM microscopy and the plates whose surface or mass defects were identified were immersed in the biodegradable medium
The voids number is relatively higher on the 3D printed plate surface which was in contact with the printer surface
Summary
Due to its functional properties, polylactic acid (PLA) is a renewable polyester successfully used instead of conventional polymers such as PP, PET which an be transformed into finished product considering both classical melt processing technologies and the revolutionary 3D printing methods. Biodegradation of polyesters is a complex process that takes place in the following stages: biodeterioration (modification of the physical and chemical properties of the polymer [11,12]), depolymerization (transformation of the polymer into monomers and dimers by enzymatic cleavage [13]), bioassimilation (absorption of molecules by microorganisms [13]), mineralization (formation of oxidative metabolites after degradation [14]). First report on microbial degradation of PLA highlighted the role of serine proteinase K released by a strain of the mould Tritirachium album [18]
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