Effect of biodegradation on thermo-mechanical properties and biocompatibility of poly(lactic acid)/graphene nanoplatelets composites

• Published in: European polymer journal 2016-12, Vol.85, p.431-444
• Main Authors: Pinto, Artur M., Gonçalves, Carolina, Gonçalves, Inês C., Magalhães, Fernão D.
• Format: Article
• Language: English
• Subjects: Biocompatibility; Biodegradation; Biodegradation assays; Creep (materials); Creep-recovery; Degradation; Differential scanning calorimetry; Fibroblasts; Fillers; Fourier transforms; Gel permeation chromatography and size exclusion chromatography (GPC-SEC); Graphene; Heat measurement; Infrared spectroscopy; Mechanical properties; Melt blending; Molecular weight; Nanostructure; Polylactic acid; Scanning electron microscopy; Size exclusion chromatography; Spectrum analysis; Tensile tests; Thermal analysis; Thermal degradation; Thermogravimetric analysis; Thermomechanical properties; Toughness; X-ray diffraction
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2016.10.046

[Display omitted] •PLA/graphene nanoplatelets 0.25wt.% composites were produced by melt-blending.•PLA showed a 10-fold decrease in toughness (AUC) after 6months degradation.•Incorporation of 0.25wt.% GNP-M and C decreased toughness loss to 3.3 and 1.7-fold.•PLA ruptured after 4 cycles in cyclic creep-relaxation testing; composites did not.•HFF-1 cells grown normally at composites’ and degradation products were not toxic. Two types of graphene nanoplatelets (GNP-M and GNP-C) were incorporated in PLA by melt-blending at 0.25wt.% loading, and the resulting composites subject to hydrolytic degradation for 6months in phosphate-buffered saline (PBS) at 37°C. The materials were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), size exclusion chromatography (GPC-SEC), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile testing, creep-recovery testing, and biocompatibility assays. After two months degradation, all materials presented a low decrease in molecular weight (about 10%), while after six months the decrease was higher than 85%. For this degradation time, temperatures of onset of intense thermal degradation decreased by about 10 °C for all samples. Both fillers were able to improve the mechanical properties of PLA, and to reduce the decay of its mechanical performance after 6months biodegradation. Unfilled PLA showed a 10-fold decrease in toughness (AUC) after 6months degradation, while toughness was only reduced by 3.3 and 1.7-fold, respectively, for the GNP-M and GNP-C composites. In addition, the composites had stable behaviour under cyclic creep-relaxation testing, while PLA exhibited significant cumulative permanent stain and ruptured after only 4 cycles. Comparing with PLA, the GNP-based composites presented similar human foreskin fibroblasts (HFF-1) adhesion and growth at the surface until 72h, and did not release toxic products after the degradation period.