Adrian L. Kelly

In this study, we produced UH‐PO sols using twin screw extrusion and characterized their thermal and rheological properties to evaluate changes induced by composition variation and extrusion process parameters. Extruder screw configuration, temperature profile, and UHMWPE mass fraction were varied, and the influence of N₂ inert gas purge during processing was also assessed. Rheological measurements using parallel plate rheology served as a diagnostic tool to study the sol‐state viscoelastic behavior and to identify thermal‐mechanical and oxidative degradation, evident through changes in UHMWPE molar mass. Thermogravimetric analysis was employed to examine the extrudates' composition and solvent evaporation dynamics. The trials demonstrated the feasibility of increasing polymer concentration while maintaining proper sol and gel formation. Additionally, N₂ gas tests highlighted that degradation of UH‐PO sols is predominantly oxygen‐driven, with inert gas purge showing significant protective effects, particularly at elevated temperatures. These findings underscore the potential of tuning process parameters to improve UHMWPE material properties while promoting cost efficiency and sustainability.

The sustained and controlled delivery of antimicrobial drugs has been largely studied using nanomaterials, like metal organic frameworks (MOFs), and various polymers. However, not much attention has been given to combining MOFs and biodegradable polymers towards the potentially more sustained release of active pharmaceutical ingredients. Herein, we report a comparative study of two widely used antimicrobial drugs, cephalexin and metronidazole, from zinc-based MOF-5 incorporated into biodegradable polycaprolactone (PCL) and poly-lactic glycolic acid (PLGA) composites. Cephalexin and metronidazole were separately loaded into MOF-5 post-synthetically, followed by their integration into biodegradable PLGA and PCL composites. The pristine MOF-5 and the loaded MOFs were thoroughly characterised using Fourier-transformed infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD). Ultraviolet-visible (UV-Vis) spectroscopy studies were carried out to assess the release of the drugs in PBS for up to 72 h, showing a cumulative release of 24.95 wt% and 27.84 wt% for cephalexin and metronidazole, respectively. The antibacterial properties of the pristine MOF, pure drugs, drug-loaded MOFs and the loaded composites were assessed against Gram-positive and Gram-negative bacterial strains, Staphylococcus aureus or Staphylococcus epidermidis and Escherichia coli or Acinetobacter baumanii, respectively. A cephalexin-loaded MOF-5 composite of PCL (PCL-ceph@MOF-5) showed the best efficiency for the controlled release of drugs to inhibit the growth of the bacteria compared to the other composites. This study demonstrates that the combination of MOFs with biodegradable polymers can provide an efficient platform for the sustained release of antimicrobial drugs and can be a promising tool to manage antimicrobial resistance (AMR).

: In the present study polypropylene containing 0, 2 and 4wt% of carbon nanotubes were prepared by melt compounding using twin screw extruder. The blends were t

Extrusion reprocessing can significantly influence the structure and properties of polymer nanocomposites. In this study, two batches of polypropylene (pp) containing 4wt% of multi-walled carbon nanotube (MCNT) loading with 4wt% of two different types of compatibilizers were prepared (one in the presence of compatibilizer at low graft level and another one with compatibilizer at high graft level). The nanocomposites were passed into the extruder for three cycles and the resultant dispersion of carbon nanotubes, mechanical, rheological, and electrical properties of the nanocomposite after each cycle were examined. For both nanocomposites, repetition of extrusion cycle improved tensile modulus, tensile strength, and flexural modulus of the nanocomposites. Rheological and electrical characterization indicated that the repetition of the extrusion cycle enhanced the dispersion of nanotubes and helped the formation of the percolation network. The electrical resistivity of the nanocomposites extruded three times was found to be up to nine orders lower than that of the first extrusion. From the morphological analyses performed by scanning electron microscopy, it was observed that the multiple extrusions assisted the homogeneous dispersion of carbon nanotubes within the polymer.

Die drawing has been used to produce polymeric products with superior mechanical properties by orientation of polymer chains. Although this process has been studied for a variety of thermoplastics and composites, there are no current publications exploring its efficacy to enhance thermoplastic vulcanizates (TPVs). TPVs combine the elasticity and high elongation at break of thermosets while maintaining the processability of a thermoplastic. For the first time, TPVs are die drawn and the effect upon their mechanical and thermal properties is investigated. TPVs based upon ethylene propylene diene monomer (EPDM) and polypropylene (PP) as well as ground tyre rubber (GTR) and PP are prepared by dynamic vulcanization using a twin‐screw extruder. In all cases, die drawing leads to an increase in tensile strength and modulus of the material along the drawing direction, often at the cost of elongation at break. At a draw ratio of 2, EPDM/PP TPVs exceed the strength and modulus of neat polypropylene whilst maintaining an elongation at break in excess of 200%. For EPDM/PP, tensile strength increases from ≈21 MPa to over 90 MPa using a draw ratio of 4, whilst for GTR/PP this increases from ≈15 to ≈57 MPa.

Healthcare applications are known to have a considerable environmental impact and the use of bio-based polymers has emerged as a powerful approach to reduce the carbon footprint in the sector. This research aims to explore the suitability of using a new sustainable polyester blend (Floreon™) as a scaffold directed to aid in musculoskeletal applications. Musculoskeletal problems arise from a wide range of diseases and injuries related to bones and joints. Specifically, bone injuries may result from trauma, cancer, or long-term infections and they are currently considered a major global problem in both developed and developing countries. In this work we have manufactured a series of 3D-printed constructs from a novel biopolymer blend using fused deposition modelling (FDM), and we have modified these materials using a bioceramic (wollastonite, 15% w/w). We have evaluated their performance in vitro using human dermal fibroblasts and rat mesenchymal stromal cells. The new sustainable blend is biocompatible, showing no differences in cell metabolic activity when compared to PLA controls for periods 1–18 days. Floreon^TM blend has proven to be a promising material to be used in bone tissue regeneration as it shows an impact strength in the same range of that shown by native bone (just under 10 kJ/m²) and supports an improvement in osteogenic activity when modified with wollastonite.

An experimental study has been performed to examine the crystallisation rate of poly(L)lactic acid (PLLA) blended with poly(D) lactic acid (PDLA) in order to reduce injection moulding cycle time. Optically pure PLLA was melt blended with up to 15wt% of its enantiomer PDLA in a twin screw extruder. Flow properties, melt strength and thermal properties of the blends were assessed. PLLA/PDLA blends were then injection moulded and allowed to crystallise using two different methods, either non-isothermally in a high temperature injection mould tool or isothermally by annealing moulded samples in a hot oven after conventional injection moulding. Mechanical and thermomechanical properties of the moulded samples were investigated and optical measurement of crystal formation using polarised light microscopy was performed at conditions representative of both crystallisation methods. Addition of PDLA was found to accelerate crystallisation rate by up to 80% and the resulting morphology demonstrated increased heat resistance, melt strength and stiffness, with a corresponding reduction in strain at break.