Dispersion fraction enhances cellular growth of carbon nanotube and aluminum oxide reinforced ultrahigh molecular weight polyethylene biocomposites

Contact stress and sliding wear damage tolerance of hydroxyapatite and carbon nanotube reinforced polyethylene cup liner against zirconia femoral head

A finite element modeling (FEM) approach is carried out to estimate the contact stresses such as von-Mises and shear stress on the acetabular cup liner, made up of ultra-high molecular weight polyethylene (UHMWPE)-hydroxyapatite (HAp)-carbon nanotubes (CNT) based composites. The highlights of this work include the effects of liners' material (UHMWPE-HAp-CNT composites), radial clearance (0.05 to 1 mm), and liners' wall thickness (3 to 8 mm) on contact stresses. The thick liner (thickness: 8 mm) with conformal geometry (radial clearance 0.05 mm) produced the lowest contact stresses (von-Mises: 13.8-17.5 MPa and shear stress: 2.3-3.3 MPa). In contrast, the thin liner (thickness: 3 mm) with higher radial clearance (1 mm) showed the highest von-Mises stress (78.6-131.0 MPa) and shear stress (17.0-23.3 MPa). According to ISO 7206-1, nearly 6-7 times reduced contact stresses were observed because of the wider articulating contact area provided by thick cup liner and its conformity with respect to the femoral head. The UHMWPE-2 wt % CNT composite (UC) showed low von-Mises stress (16.1 MPa) and lowest shear stress (2.3 MPa); thus, it is the most damage tolerant material (wear rate: 2.6 × 10-7 mm3/Nm). The excellent mechanical properties such as hardness (165 MPa), elastic modulus (2.28 GPa), and tensile strength (36.7 MPa) are reasoned to elicit an increased sliding-wear resistance of UC. Thus, CNT-based UHMWPE composite can be the potential acetabular cup liner with a thickness of 8 mm and clearance of 0.05 mm without plastic deformation.

Assessing the Influence of the Sourcing Voltage on Polyaniline Composites for Stress Sensing Applications

Polyaniline (PANI) has recently gained great attention due to its outstanding electrical properties and ease of processability; these characteristics make it ideal for the manufacturing of polymer blends. In this study, the processing and piezoresistive characterization of polymer composites resulting from the blend of PANI with ultra-high molecular weight polyethylene (UHMWPE) in different weight percentages (wt %) is reported. The PANI/UHMWPE composites were uniformly homogenized by mechanical mixing and the pellets were manufactured by compression molding. A total of four pellets were manufactured, with PANI percentages of 20, 25, 30 and 35 wt %. Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to confirm the effective distribution of PANI and UHMWPE particles in the pellets. A piezoresistive characterization was performed on the basis of compressive forces at different voltages; it was found that the error metrics of hysteresis and drift were influenced by the operating voltage. In general, larger voltages lowered the error metrics, but a reduction in sensor sensitivity came along with voltage increments. In an attempt to explain such a phenomenon, the authors developed a microscopic model for the piezoresistive response of PANI composites, aiming towards a broader usage of PANI composites in strain/stress sensing applications as an alternative to carbonaceous materials.

Evaluation of Mechanical Properties and Cell Viability of Poly (3-Hydroxybutyrate)-Chitosan/Al2O3 Nanocomposite Scaffold for Cartilage Tissue Engineering

BACKGROUND

The aim of this study was to evaluate the effects of alumina nanowires as reinforcement phases in polyhydroxybutyrate-chitosan (PHB-CTS) scaffolds to apply in cartilage tissue engineering.

METHODS

A certain proportion of polymers and alumina was chosen. After optimization of electrospun parameters, PHB, PHB-CTS, and PHB-CTS/3% Al2O3 nanocomposite scaffolds were randomly electrospun. Scanning electron microscopy, Fourier transform infrared spectroscopy, water contact angle measurement, tensile strength, and chondrocyte cell culture studies were used to evaluate the physical, mechanical, and biological properties of the scaffolds.

RESULTS

The average fiber diameter of scaffolds was 300-550 nm and the porosity percentages for the first layer of all types of scaffolds were more than 81%. Scaffolds' hydrophilicity was increased by adding alumina and CTS. The tensile strength of scaffolds decreased by adding CTS and increased up to more than 10 folds after adding alumina. Chondrocyte viability and proliferation on scaffolds were better after adding CTS and alumina to PHB.

CONCLUSION

With regard to the results, electrospun PHB-CTS/3% Al2O3 scaffold has the appropriate potential to apply in cartilage tissue engineering.