TiO2 coatings deposited using reactive magnetron sputtering and spray coating methods, as well as Ag- and Mo-doped TiO2 coatings were investigated as self-cleaning surfaces for beverage processing. ...The mechanical resistance and retention of the photocatalytic properties of the coatings were investigated over a three-month period in three separate breweries. TiO2 coatings deposited using reactive magnetron sputtering showed better mechanical durability than the spray coated surfaces, whilst the spray-deposited coating showed enhanced retention of photocatalytic properties. The presence of Ag and Mo dopants improved the photocatalytic properties of TiO2 as well as the retention of these properties. The spray-coated TiO2 was the only coating which showed light-induced hydrophilicity, which was retained in the coatings surviving the process conditions.
Plasma-assisted chemical vapour deposition (PACVD) siloxane coatings from a mixture of hexamethyldisiloxane (HMDSO) and O
2, and hybrid coatings deposited by simultaneous sputtering of silicon and ...plasma polymerisation of HMDSO
+
O
2 were prepared on glass and steel substrates. The effect of the addition of sputtered silicon was investigated for coatings with different HMDSO/O
2 ratios. The microstructure and composition of coatings were affected by the coating parameters used. Silicon content was roughly the same for all coatings; carbon content decreased while oxygen content and surface energy increased with decreasing HMDSO/O
2 ratio in hybrid coatings. Hardness and modulus were higher for hybrid coatings and increased with decreasing HMDSO/O
2 ratio. Hybrid coatings showed much better scratch and wear resistance than PACVD coatings. All coatings showed good fouling-release performance with the freshwater bacterium
Pseudomonas fluorescens.
A range of SiO
x
-like coatings was deposited on glass slides from a hexamethylsiloxane precursor by plasma-assisted CVD. The effect of varying deposition parameters, specifically ion cleaning time ...and HMDSO/O
2 ratios, on the coating properties and antifouling performance was investigated. At low HMDSO/O
2 ratios, the resulting coatings were close to SiO
2. Carbon content in the bulk of the coatings increased with increasing HMDSO/O
2 ratio. Coatings deposited at high HMDSO/O
2 ratios and with the longest cleaning time (30
min), elevated the relative carbon content to 25 atomic %. Surface energies (22–43
mJ/m) were correlated with the degree of surface oxidation and hydrocarbon content. With the exception of the most polar coatings the apolar component of the surface energy (
γ
LW) was the dominant component. In the most hydrophilic coatings, the Lewis base component of the surface energy (
γ
−) was dominant. Significantly improved antifouling performance was detected with the most reduced coatings deposited using the extended ion cleaning times. For both, the removal of sporelings of the marine green alga,
Ulva
linza and the initial adhesion of the freshwater bacterium,
Pseudomonas fluorescens, there was a strong, positive correlation between strength of attachment and ion cleaning time. Increased ion cleaning time will elevate the deposition temperature, increasing decomposition rates and thus the crosslinking of the polymer. Increased cross-linking may render these coatings less permeable to penetration and mechanical interlocking by the adhesive polymers used by these organisms, thus reducing their adhesion. Films with improved biological performance have potential for use as coatings in the control of biofouling in applications such as heat exchangers, where thin films are important for effective thermal transfer, or optical windows where transparency is important.
Polymer-encapsulated carbon blacks were prepared using a surfactant-free emulsion polymerisation method. Emulsion polymerisation of acrylic and methacrylic monomer(s) were carried out in the presence ...of carbon black aggregates. When ammonium persulfate was used as initiator, successful emulsion polymerisation was carried out in the presence of a low surface-area carbon black, and polymer- encapsulated carbon blacks as well as independent polymer particles were produced. Emulsion polymerisation did not proceed in the presence of a high-surface area carbon black. Attempts to reduce the quinonic groups of the carbon black surface using sodium dithionite did not improve the conversion. Use of a non-oxidising initiator, the sodium salt of 4,4’-azobis(4-cyanopentanoic acid), led to successful polymerisation in the presence of the high surface-area carbon black.Polymer-encapsulated carbon blacks were prepared for compounding with acrylonitrile-butadiene styrene copolymer (ABS) in order to study the effect of encapsulation on the mechanical properties of carbon black-filled ABS. Butyl acrylate (BA) and methyl methacrylate (MMA) were chosen as the monomers for the encapsulations. The polymer was crosslinked using 2 mol% allyl methacrylate (ALMA) in order to permanently encapsulate the carbon black. One-stage poly(butyl acrylate) (PBA) and poly(methyl methacrylate) (PMMA) encapsulations and two- stage encapsulations with a PBA first stage and a PMMA second stage were carried out, and the products were compounded in ABS at carbon black concentrations in the range 0.75 - 5.00 wt%. The mechanical properties of the compounds investigated using tensile and impact tests revealed that polymer encapsulation of carbon black did not cause a significant change in the mechanical properties of carbon black-filled ABS. Compounds containing PMMA-encapsulated carbon blacks showed higher fracture stress and toughness than other products. Study of the fracture surfaces using scanning electron microscopy showed the same features for each of the compounds, suggesting that the fracture mechanisms were not affected by the type of encapsulation.The preparation of water-dispersible polymer-encapsulated carbon blacks for use as pigments in ink-jet inks was investigated. Encapsulation polymerisations using butyl methacrylate (BMA), MMA, BA, and mixtures of BA and MMA were carried out. Stabilising comonomers (acrylic acid, methacrylic acid, sodium styrene sulfonate, polyethylene glycol) macromonomers with different chain lengths, and 2-sulfoethyl methacrylate) were used to impart water dispersibility to the encapsulated carbon blacks. 2-sulfoethyl methacrylate was found to result in the best encapsulation properties, such as particle size and dispersion stability, and so was chosen as the stabilising comonomer for the encapsulations. Aqueous dispersions of polymer- encapsulated carbon blacks were analysed for ink properties such as viscosity and surface tension. Inks prepared from these carbon blacks were used in ink-jet printers. For thermal printing, there was an optimum Tg (~ 55 °C) of the encapsulating polymer; encapsulated carbon blacks containing polymers with Tg ≤ 42 °C were not printable and those with Tg ≥ 70 °C did not improve the print properties compared with inks based on non-encapsulated carbon black. The effect of incorporation of hydroxyl group-containing repeat units in the encapsulating polymer was investigated and was shown to improve the adhesion of the ink to paper.
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