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In this study, injection molding of three poly lactic acid (PLA) based bone screws was simulated and optimized through minimizing the shrinkage and warpage of the bone screws. The optimization was carried out by investigating the process factors such as coolant temperature, mold temperature, melt temperature, packing time, injection time, and packing pressure. A response surface methodology (RSM), based on the central composite design (CCD), was used to determine the effects of the process factors on the PLA based bone screws. Upon applying the method of maximizing the desirability function, optimization of the factors gave the lowest warpage and shrinkage for nanocomposite PLA bone screw (PLA9). Moreover, PLA9 has the greatest desirability among the selected materials for bone screw injection molding. Meanwhile, a finite element analysis (FE analysis) was also performed to determine the force values and concentration points which cause yielding of the screws under certain conditions. The Von-Mises stress distribution showed that PLA9 screw is more resistant against the highest loads as compared to the other ones. Finally, according to the results of injection molding simulations, the design of experiments (DOE) and structural analysis, PLA9 screw is recommended as the best candidate for the production of biomedical materials among all the three types of screws. [ABSTRACT FROM AUTHOR]

In this study, the poly( l -lactide)/thermoplastic poly(ester urethane) (PLA/TPU) blend was employed as the matrix for preparation of nanocomposites with several halloysite nanotube (HNT) concentrations. This design was hypothesized based on a morphological conversion according to the assessment of thermodynamic equilibrium calculated by the contact angle measurements. HNTs as nanoparticles were applied to create PLA/TPU nanocomposites with more polymer interfaces for greater interactions, more compatibility, and a higher toughness. The addition of adequate HNTs, which have a thermodynamic inclination of settling in the low viscosity PLA phase, penetrates in the PLA phase and saturates the surface of this phase, as a result, the sea-islands transforms to quasi-cocontinuous morphology. If the added HNT is more, the nanoparticles not only disperse in the PLA phase and the interface but also penetrate into the TPU and agglomerate in some areas. The predicted morphology and microstructure were observed by the SEM and elemental analyses. The chemical structure changes and thermal properties of composites were investigated by the FTIR, DSC and TGA, respectively. The thermal stability of nanocomposites was investigated and shown that this property was improved by the presence of HNT in the nanocomposites. Also, the mechanical properties of the prepared composites, including elongation at break, tensile strength, elastic modulus, toughness, impact strength and hardness were reinforced. The melt flow properties of the designed composites were also investigated by the dynamic rheological analysis. Due to the reinforced thermal stability, fortified mechanical properties, high toughness and high melt elasticity, the designed composites are capable of being used in several applications such as packaging, thermal sealing, thermoforming, and melt spinning of plastics. [ABSTRACT FROM AUTHOR]

In this study, an optimized interface-modified ternary blend with antibacterial activity based on polylactic acid/starch/poly ε - caprolactone (PLASCL20), mixed with nano hydroxyapatite (nHA) via melt blending. This method results in a homogeneous nanocomposite blend in which the addition of 3% nHA improves the overall properties such as hydrolytic degradation, hydrophilicity, antibacterial activity and the drug release comparing to PLASCL20. Moreover, the simultaneous use of nHA and encapsulated triclosan (LATC30) compensated the negative effect of triclosan through increasing the possible cell attachment. According to the contact angle results, nHA was thermodynamically driven into the interface of PLA and PCL/Starch phases. The addition of 3% nHA showed a good adjustment between the hydrolytic degradation and the release profile, therefore, their electrospun microfibers demonstrated an improved fibroblast (L929) cell attachment. The aforementioned nanocomposite blend is a suitable antibacterial candidate for many medical applications with minimum side effects due to the controlled release of triclosan. [ABSTRACT FROM AUTHOR]