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This study attempts to optimise poly(lactic acid) processing parameters using central composite design approach which is well known statistical tool in design of experiments. Three factors and five levels were chosen for carrying out the analysis. The parameters include mixing temperature (180–210°C), screw speed (50–100 rev min-1) and mixing time (5–10 min), which were varied independently. The results were evaluated based on maximum stress, tensile modulus, and impact strength under different conditions and the significant factors were determined using variance analysis (ANOVA). An optimum balance between the mechanical properties was obtained when the samples were blend at 180°C at 100 rev min-1rotor speed for 10 min. Moreover, validation of the predicted results confirmed the optimised parameters, which were further complemented by morphological and thermal studies.

ABSTRACTThis study attempts to optimise poly(lactic acid) processing parameters using central composite design approach which is well known statistical tool in design of experiments. Three factors and five levels were chosen for carrying out the analysis. The parameters include mixing temperature (180–210°C), screw speed (50–100 rev min−1) and mixing time (5–10 min), which were varied independently. The results were evaluated based on maximum stress, tensile modulus, and impact strength under different conditions and the significant factors were determined using variance analysis (ANOVA). An optimum balance between the mechanical properties was obtained when the samples were blend at 180°C at 100 rev min−1rotor speed for 10 min. Moreover, validation of the predicted results confirmed the optimised parameters, which were further complemented by morphological and thermal studies.

In this work, the effect of using zirconium(IV) hydroxide (Zr(OH)4) nanoparticles in the enhancement of the thermal stability and viscoelastic properties of organically cross-linked polyacrylamide (PAM) hydrogels using hydroquinone (HQ) and hexamethylenetetramine (HMT) was studied. The thermal stability and viscoelastic properties of the PAM gels were studied by DSC and DMA, respectively. From the DSC analysis, the bound and free water contents were analyzed along with the degradation enthalpy to give a preliminary clue about the direct vs indirect interactions taking place in the gel. With the addition of 0.2–0.8 wt % Zr(OH)4, the thermal stability of the PAM hydrogel improved by 3–5 °C (reaching 187 °C) compared to PAM alone. Moreover, the elasticity of the PAM hydrogel increased with the addition of Zr(OH)4which was also supported by the strong interaction bond formed as demonstrated from the higher degradation enthalpy and free water recorded. These interactions were further explained using FTIR and optical microscope images. The TGA results also revealed the functionalization of PAM gel and showed that the gel was thermally stable even at 400 °C. In addition, the effects of calcination, organic cross-linker, salinity, and pH on the gel properties were investigated. From DSC and DMA analysis, it was found that the optimal conditions for the polymer gel were as follows: PAM at 4 wt %, Zr(OH)4at 0.2–0.8 wt %, organic cross-linkers (OrgCL) at 0.3 wt %, and KCl or MgCl2at 2 wt %.

In this study, poly-lactic acid (PLA), nanohydroxyapatite (NHA), and graphene nanoplatelets (GNP) were blended to develop a nanocomposite material suitable for load-bearing bone implants with the potential for strain-sensing applications. The tensile properties and impact strength of the PLA-NHA nanocomposite were analyzed, as these are crucial biomechanical properties for load-bearing and strain-sensing applications. It was found that the impact strength decreased by 7.9% (0.05 wt% GNP) and 25.7% (0.1 wt% GNP) with increasing GNP loading compared to 0.01 wt% GNP. Besides, the biocompatibility of nanocomposites (PLA-NHA, PLA-mNHA, and PLA-mNHA-GNP) was evaluated through in-vitro analysis by attaching MG63 cells to the nanocomposites and observing their proliferation and differentiation over 7 and 21 days of incubation. The biocompatibility of the prepared nanocomposites was determined based on their ability to attach with MG63 cells, thus allowing the cells to proliferate and enhance their ability to differentiate. Results showed that the PLA-5wt%NHA nanocomposite provided better cell spreading compared to pure PLA, while the PLA-5wt%mNHA nanocomposite had the highest rate of cell proliferation. The biocompatibility of the nanocomposites was further confirmed by field emission scanning electron microscope (FESEM) imaging, MTT assays, and alkaline phosphatase (ALP) assays.