RESUMO
Thermoplastic polyurethane (TPU) is a versatile polymer with unique characteristics such as flexibility, rigidity, elasticity, and adjustable properties by controlling its soft and hard segments. To properly design and understand the TPU foaming process through supercritical CO2, a design of experiments approach, the Box-Behnken design (BBD) was adopted using commercial TPU 85A as the model compound. The effect of saturation pressure, saturation temperature, and immersion time on the mean pore size and expansion ratio were investigated. The design space for the production of TPU foam was shown, and the significance of process parameters was confirmed using the analysis of variance (ANOVA). In addition, extrapolation foaming experiments were designed and validated the feasibility of the response surface model developed via BBD. It was found that the pore size of TPU 85A foam could be controlled within 13 to 60 µm, and a stable expansion ratio could be designed up to six.
RESUMO
The physical and mechanical properties of novel bio-based polymer blends of polylactic acid (PLA), poly(butylene succinate) (PBS), and poly (butylene adipate-co-terephthalate) (PBAT) with various added amounts of nanohydroxyapatite (nHA) were investigated in this study. The formulations of PLA/PBS/PBAT/nHA blends were divided into two series, A and B, containing 70 or 80 wt% PLA, respectively. Samples of four specimens per series were prepared using a twin-screw extruder, and different amounts of nHA were added to meet the regeneration needs of bone graft materials. FTIR and XRD analyses were employed to identify the presence of each polymer and nHA in the various blends. The crystallization behavior of these blends was examined using DSC. Tensile and impact strength tests were performed on all samples to screen feasible formulations of polymer blends for bone graft material applications. Surface morphology analyses were conducted using SEM, and the dispersion of nHA particles in the blends was further tested using TEM. The added nHA also served as a nucleating agent aimed at improving the crystallinity and mechanical properties of the blends. Through the above analyses, the physical and mechanical properties of the polymer blends are reported and the most promising bone graft material formulations are suggested. All blends were tested for thermal degradation analysis using TGA and thermal stability was confirmed. The water absorption experiments carried out in this study showed that the addition of nHA could improve the hydrophilicity of the blends.
RESUMO
In this study, the rapid expansion of the supercritical solutions (RESS) process was used to produce microparticles of a commonly used anti-inflammatory drug, ethenzamide. The effects of process parameters in RESS including the extraction temperature, pre-expansion temperature, and post-expansion temperature were investigated using the Box-Behnken design. According to the results of the analysis of variance (ANOVA), the effect of pre-expansion temperature is the most significant parameter on the mean size of RESS-produced ethenzamide. A higher pre-expansion temperature benefits the production of smaller crystals. In addition, a quadratic effect of the post-expansion temperature was also identified. Through RESS, ethenzamide microparticles with a mean size of 1.6 µm were successfully produced. The solid-state properties including the crystal habit, crystal form, thermal behavior, and spectrometric property were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectrometer (FTIR), differential scanning calorimeter (DSC), and powder X-ray diffraction (PXRD). These analytical results show that the rod-like crystals were generated through RESS, and the crystal form, thermal behavior, and spectrometric property of RESS-produced crystals are consistent with the unprocessed ethenzamide.
