Analysis of the Degradation During Melt Processing of PLA/Biosilicate® Composites

Abstract

Poly (lactic acid) (PLA)/bioactive composites are emerging as new biomaterials since it is possible to combine stiffness, mechanical resistance, and bioactive character of the bioglasses with conformability and bioabsorption of the PLA. In this study, PLA/Biosilicate® composites were prepared using a melt-processing route. The processability and properties were evaluated aiming to produce composites with bioactive properties. Two different PLA (PLA 2003D and PLA 4043D) were tested with the addition of 1 wt. % of Biosilicate®. Both materials presented a huge reduction in melt viscosity after internal mixer processing. The degradation effects of the addition of Biosilicate® in the PLAs matrices were evaluated using zeta potential tests that showed a very high liberation of ions, which catalyzes PLA thermo-oxidative reactions. To understand the extension of degradation effects during the processing, the composites were characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and rheological tests. GPC results showed that PLA with the lowest residual acid content (RAC), PLA 2003D, presented higher thermal stability, higher molecular weight, and viscosity baseline compared to PLA 4043D. The composites showed a significant decrease in molecular weight for both PLA with the addition of Biosilicate®. TGA results showed that Biosilicate® might have reduced the activation energy to initiate thermodegradation reactions in PLAs and it occasioned a reduction in the Tonset by almost 40 °C. The DSC results showed that severe matrix degradation and the presence of bioglass did not significantly affect glass transition temperature (Tg), melting temperature (Tm) and crystallinity of PLAs, but it influenced cold crystallization peak (Tcc). In this way, the type of PLA used influences the processability of this material, which can make the production of filaments of this material for 3D printing unfeasible.

Fabrication of Biocompatible Composites of Poly(lactic acid)/Hydroxyapatite Envisioning Medical Applications

“…Blaker et al [14] have noted premature degradation of the PLA/45S5 during melt-compounding, and they attributed this to the liberation of counterions of 45S5 that hasten thermal degradation reactions in PLA matrix [14]. More recently, Backes et al [29] observed the same behavior for PLA/Biosiolicate ® composites during similar processing conditions. The results of zeta potential for HA show a considerable liberation of ions that might contribute to catalyzing the polymer degradation during thermal processing.…”

Influence of the Chitosan and Rosemary Extract on Fungal Biodegradation of Some Plasticized PLA-Based Materials

“…The effect of the fungi on the structure was evidenced by the disappearance of the shoulder and the determined thermal events are shifted indicating presence of smaller molecules which crystalize leading to higher crystallinity. Backes et al [63] observed a similar phenomenon during the study of PLA/Biosilicate composites and concluded that the crystallization of PLA occurs easier in degraded systems with greater mobility. This outcome can support the hypothesis that after biodegradation in the presence of the two fungi, the chains of PLA/PEG/R became shorter in accordance with GPC results.…”

Development and characterization of printable PLA/β‐TCP bioactive composites for bone tissue applications

“…2,32 Despite its ongoing evolution process, PLA alone lacks bioactivity and exhibits limited interaction and integration with the tissue host. 33,34 Therefore, the development and evaluation of mechanical, thermal, rheological, and biological properties of PLA bioactive composites is an important step to consolidate the PLA along with AM.…”

“…Surface properties play a significant role in cell attachment and proliferation; therefore, suitable wettability is beneficial for cell interaction with materials. 15,34 The results of relative cell viability using PLA and PLA/TCP extracts are exhibited in Figure 5(b), and they were corrected using the cell with α-MEM as blank. They show that the PLA and PLA5TCP extracts presented behaviors similar to that of the control for both timepoints analyzed, exemplifying that the samples do not release harmful debris, which might reduce cell viability.…”