Enhancing the Bond Strength Between Glass Fibre Reinforced Polyamide 6 and Aluminium through µPlasma Surface Modification.

Thermoplastic polymers generally exhibit relatively low surface energies and this often results in limited adhesion when bonded to other materials. Plasma surface modification offers the potential to functionalise the polymer surfaces, and thereby enhance the bond strength between dissimilar materials. In this study, glass fibre reinforced polyamide 6 (GFPA6) was modified using a novel μPlasma surface treatment technique and the effectiveness of the adhesive bond with aluminium was evaluated. The treated GFPA6 surfaces were characterised using atomic force microscopy (AFM), Raman spectroscopy, contact angle measurements, surface free energy calculations and wetting envelope analysis. The results show that there was a near exponential growth in root mean square roughness with increasing treatment scans. A significant increase in carbonyl and amide functionality on the polymer surface was observed using Raman spectroscopy. The total surface energy was found to increase from 42.2 mN/m to 67.6 mN/m following a single treatment scan. Significant increases in the tensile shear strength were observed up to 10 treatment scans, going from 1 kN to 2.3 kN, but no further increase was observed with additional treatment scans. These observations, coupled with the atmospheric nature of the technique, points to great potential as a rapid, on-line, and effective, polymer surface treatment technique

Plasma defect-engineering of bulk oxygen-deficient zirconia

Oxygen-deficient zirconia (ZrO2-x) has recently emerged as a promising material for light absorption and photocatalytic applications. However, the economic and environmentally friendly manufacture of bulk ZrO2-x remains challenging and has limited widespread adoption. In this study, we present a novel low-pressure (300 Pa) plasma treatment (H2 gas at 500 °C for 5 h) capable of producing fully-dense bulk ZrO2-x without significant structural modifications. EPR (electron paramagnetic resonance) and XPS (X-ray photoelectron spectroscopy) characterisation of the plasma treated zirconia indicate the formation of Zr3+ ions and F2+ (V0) centres. The increase of oxygen vacancies is also supported by the greater exothermic heat flow and relative mass gain observed through TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry) analyses. Diffuse reflectance spectroscopy (DRS) reveals a substantial enhancement in light absorption, with an average increase of 66.2 % and >65 % absolute absorption across the entire spectrum (200–3000 nm). XPS and DRS measurements suggest significant reduction in both direct (from 4.84 to 2.61 eV) and indirect (from 3.19 to 1.45 eV) bandgap transition. By effectively enhancing the light absorption capability, reducing bandgap transitions, and maintaining the structural integrity of zirconia, low-pressure plasma treatments offer a promising and scalable approach for the environmentally friendly production of next-generation ZrO2-x materials

The Ageing of μPlasma Modified Polymers:the Role of Hydrophilicity

Thermoplastic polymers exhibit relatively limited surface energies and this results in poor adhesion when bonded to other materials. Plasma surface modification offers the potential to overcome this challenge through the functionalisation of the polymer surfaces. In this study, three polymers of differing hydrophobicity (HDPE, PA12, and PA6) were subjected to a novel, atmospheric, μPlasma surface treatment technique, and its effectiveness at increasing the surface energies was evaluated via measurement of the contact angle. To characterise the physical and chemical changes following μPlasma surface modification, the surface morphology was observed using atomic force microscopy (AFM), and the functionalisation of the surface was evaluated using infrared spectroscopy. Immediately after treatment, the contact angle decreased by 47.3° (HDPE), 42.6° (PA12), and 50.1° (PA6), but the effect was not permanent in that there was a pronounced relaxation or ageing phenomenon in operation. The ageing process over five hours was modelled using a modified stretched exponential function Kohlrausch–Williams–Watts (KWW) model, and it was found that the ageing rate was dependent on the hydrophilicity of polymers, with polyamides ageing more rapidly than polyethylene