Improvements in thermal and mechanical properties of composites based on thermoplastic starch and Kraft Lignin.

Thermoplastic starch (TPS) is a widely studied biopolymer as an alternative to the use of conventional polymers. In this sense, the incorporation of fillers or reinforcements coming preferably from other substances of natural origin, can be an alternative to try to improve some mechanical and thermal properties of starch polymers. Thus, Kraft Lignin (KL), can be an excellent filler to be incorporated, since it presents mechanical and thermal properties and reduces the cost and weight of the final compounds. TPS films were prepared by casting using dimethyl sulfoxide (DMSO) as solvent and additives with 2, 4 and 8% KL. Characterization of TPS films and compositions with KL were carried out by Fourier-Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM), Thermogravimetric Analysis (TGA), Dynamic Thermomechanical Analysis (DMTA), tensile testing and contact angle. Samples were also analyzed for biodegradation and for the ability to remove contaminants in water, Metil Orange (MO), by Ultraviolet-Visible Spectroscopy (UV-Vis). The FT-IR spectra of the films showed bands typical of functional groups derived from starch and lignin, with the intensity of these bands varying among the samples studied. Micrographs revealed slightly different morphologies among the films, but all showed irregular shapes with structures that appeared as plots. Increasing the percentage of KL led to an increase in contact angle values, showing a more hydrophobic behavior. In the TGA analysis, it was possible to observe a change in the main degradation event of the films for lower temperatures, especially of TPS - 4 and 8% KL compared to the TPS film. Films with KL had the peak of maximum degradation shifted to temperatures below the starch film, where the decrease in intensity of the main peak in the TPS - 4% KL and TPS - 8% KL samples demonstrates that there was less mass loss in the event. There was also in the percentage of residue as the addition of KL was increased The DMTA analyses allowed for the conclusion that presence of KL in TPS film allowed for an increase in its energy storage property, and that the loss modulus followed a decreasing order of storage modulus values to TPS - 8% KL from TPS. For the tensile strength property only TPS - 4% KL has significant improvement, and the elongation at break showed an increase for TPS - 4 and 8% KL compared to TPS. Samples showed a continuous and progressive biodegradation process, being completely biodegraded within 10 days. The monitoring of the ability to remove contaminants from water by UV-Vis, also showed promising results of compounds for this application. The best results were obtained, in most tests, for the TPS- 4% KL films.

Thermomechanical and in vitro biological characterization of injection-molded PLGA craniofacial plates.

PURPOSE:: To evaluate the thermomechanical and in vitro biological response of poly(lactic-co-glycolic acid) (PLGA) plates for craniofacial reconstructive surgery. METHODS:: PLGA 85/15 craniofacial plates were produced by injection molding by testing two different temperatures (i.e., 240°C, PLGA_lowT, and 280°C, PLGA_highT). The mechanical properties of the produced plates were characterized by three-point bending tests, dynamic mechanical analysis, and residual stress. Crystallinity and thermal transitions were investigated by differential scanning calorimetry. Finally, in vitro cell interaction was evaluated by using SAOS-2 as cell model. Indirect cytotoxicity tests (ISO 10-993) were performed to prove the absence of cytotoxic release. Cells were then directly seeded on the plates and their viability, morphology, and functionality (ALP) checked up to 21 days of culture. RESULTS:: A similar performance of PLGA_lowT and PLGA_highT plates was verified in the three-point bending test and dynamic mechanical analyses. Also, the two processing temperatures did not influence the in vitro cell interaction. Cytotoxicity and ALP activity were similar for the PLGA plates and control. Cell results demonstrated that the PLGA plates supported cell attachment and proliferation. Furthermore, energy-dispersive X-ray spectroscopy revealed the presence of sub-micron particles, which were identified as inorganic mineral deposits resulting from osteoblast activity. CONCLUSION:: The present work demonstrated that the selected processing temperatures did not affect the material performance. PLGA plates showed good mechanical properties for application in craniofacial reconstructive surgery and adequate biological properties.

Chitosan-based nanocomposite matrices: Development and characterization.

Chitosan-based nanocomposites have a significant industrial impact related to the possibility to design and create new materials and structures. Cellulose nanocrystals (CNC) can be extracted from microcrystalline cellulose (MCC) by controlled acid hydrolysis with H2SO4. This work was focused on: to study the microstructure of CNC isolated from MCC after different hydrolysis times; to develop nanocomposites chitosan-based films; to characterize their structural and thermo-mechanical properties; to analyze the spectral differences among samples by means of ATR-FTIR in combination with principal component analysis (PCA) and square partial minimums model (PLS). It is worth noting that the selected condition for isolate the CNC from MCC was the acid treatment for 2 h, evidenced by size measurements. This fact was supported by transmission electron microscope (TEM) and dynamic light scattering (DLS). In this regard, SEM studies of films showed an assembly process between the nanocelluloses and the CH matrix. The incorporation of CNC into the films resulted in strong interactions between the filler and the matrix demonstrating the affinity between the phases and modifying the mechanical profiles. In summary, CNC was found to be a satisfactory reinforcing agent in biodegradable nanocomposite chitosan-based packaging and are promising as a means to develop tailor-made materials.