In this research, the influence of titanium dioxide (TiO2) nanoparticles and their modifications on the weathering resistance of untreated and heat-treated wood was studied. The wood samples were ...coated with polyacrylate waterborne emulsion coatings that contain nano-TiO2 in the amount of 0.75 wt.%. Two types of modifiers were used to modify the nano-TiO2 surface: 2,2′-azobis(2-methylpropionamide) dihydrochloride (AIBA) and 3-aminopropyltrimethoxy silane (AMPTS). Coated and uncoated wood samples were exposed to accelerated weathering by application of sunlight, water and moisture for 360 h. During the research, the dry film thickness, color, gloss and hardness of the surface of the samples were measured. The obtained results showed that the effect of the addition and surface modification of nano-TiO2 on the color and gloss stability was different on untreated and heat-treated ash wood, and that accelerated weathering causes an increase in surface hardness and a decrease in thickness of the dry coating.
•Nano ZnO reduced flow time of waterborne polyacrylate coating and increased pH.•Nano ZnO decreased elongation of waterborne polyacrylate coating.•Nano TiO2 and ZnO caused chemical changes in coating ...after accelerated exposure.•Nano TiO2 and ZnO increased colour stability of waterborne polyacrylate coating.
The rapid development of nanotechnology allowed implementation of metal oxide nanoparticles in coatings and protection of coatings without significant influence on transparency. To avoid negative impact on coating properties it is important that nanoparticles are uniformly dispersed and that the emulsion of nanoparticles is compatible with the components in coating. In this article the effect of TiO2 and ZnO nanoparticles on properties of polyacrylate waterborne coating and on stability of coating films exposed to outdoor conditions are studied. The results of this research show that ZnO nanoparticles reduce flow time of waterborne polyacrylate coating and increase pH. Furthermore, TiO2 and ZnO nanoparticles increase colour stability of waterborne polyacrylate coating. Moreover TiO2 nanoparticles have a great impact on increase of Tg, and ZnO nanoparticles on decrease of elongation and thereby on increase of brittleness of waterborne polyacrylate coating.
The aim of this work is to prepare polyacrylate emulsions (PA) with the addition of modified titanium dioxide (TiO2) nanoparticles. The modifiers used in this work are the nonionic emulsifier TX-100, ...the cationic initiator AIBA, the silane AMPTS, and the trisilanol POSS. The results show that particles with a larger hydrodynamic diameter are formed by the addition of modified fillers and that the viscosity of the PA emulsion increases significantly due to the modification of the TiO2 surface. The morphology indicates poorer dispersibility and distribution of the modified fillers in the polymer compared to coating with unmodified fillers. The thermal stability of PA is significantly increased by the addition of modified TiO2 nanoparticles. The results have also shown that the modification of TiO2 with AMPTS increases the UV absorbing ability of TiO2, while the modification with other modifiers enhances the photocatalytic effect of TiO2.
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•Development of eco-friendly coatings with UV protective properties.•Thermal stability of PA is significantly increased by the addition of modified nanoparticles.•Modification of TiO2 surface can have both a positive and a negative effect on the UV absorbing power of TiO2.•Modification of TiO2 with silane AMPTS increases the UV absorbing ability of TiO2
This work aims to prepare a coating with good UV protection properties while maintaining optimal transparency. In this work, the addition of 0–2 wt.% TiO2 on the properties of polyacrylate (PA), the ...method of preparation, and the effect of UV exposure on coatings were investigated. Rutile TiO2/PA coatings were prepared by ex situ and in situ emulsion polymerization. The results showed that the addition of nanoparticles and the preparation method significantly affect the particle size distributions of PA, such that ex situ emulsions show the presence of agglomerates, while they are not visible in in situ emulsions. Viscosity also depends on the preparation method, so ex situ emulsions show no change with the addition of nanoparticles, while in situ emulsions show an increase in viscosity. In situ coatings also have better morphology and transparency compared to ex situ. The addition of nanoparticles increases the thermal stability of PA in the later stages of thermal degradation and causes a decrease in tensile strength with an increase in elongation at break of PA. In situ coatings also provide better UV protection properties compared to ex situ coating films.
Purpose
The purpose of this paper is to prepare stabile emulsions with 0–15% of colloidal silica and high monomer/water ratio and to investigate the influence of silica addition and surface ...modification on the polyacrylate properties.
Design/methodology/approach
Improving the properties of the composite can be achieved by optimizing the compatibility between the phases of the composite system with improving the interactions at the matrix/filler interface. Therefore, the silica surface was modified with nonionic emulsifier octylphenol ethoxylate, cationic initiator 2,2'-azobis-(amidinopropane dihydrochloride) and 3-methacryloxypropyltrimethoxysilane and polyacrylate/silica nanocomposites were prepared via in situ emulsion polymerization. Particle size distribution, rheological properties of the emulsions and morphology, thermal properties and mechanical properties of the film prepared from the emulsions were investigated.
Findings
Polyacrylate/silica systems with unmodified silica, silica modified with nonionic emulsifier and cationic initiator have micrometer, while pure PA matrix and systems with silica modified with silane have nanometer particle sizes. Addition and surface modification of the filler increased emulsion viscosity. Agglomeration of silica particles in composites was reduced with silica surface modification. Silica filler improves thermal stability and tensile strength of polyacrylate.
Originality/value
This paper provides broad spectrum of information depending on filler surface modification and latex preparation via in situ emulsion polymerization and properties with high amount of filler and monomer/water ratio with the aim that prepared latex is suitable for film formation and final application.
The development of coatings that maintain the attractive natural appearance of wood while providing ultraviolet (UV) protection is extremely important for the widespread use of wood products. In this ...study, the influence of different types (powder form and aqueous dispersions) of TiO2 in an amount of 1.0 wt% by monomer weight on the properties of environmentally friendly polyacrylate (PA)/TiO2 emulsions prepared by ex situ and in situ polymerization, as well as on the UV-protective properties of the coating films, was investigated. The results showed that the addition of TiO2 significantly affected the particle size distribution of PA and the viscosity of PA varied according to the preparation method. Compared with the ex situ preparation method, in situ polymerization provides better dispersibility of TiO2 nanoparticles in PA coating film, as well as a better UV protection effect and greater transparency of the coating films. Better morphology and transparency of nanocoating films were achieved by adding TiO2 nanofillers in aqueous dispersion as compared to the addition of TiO2 in powder form. An increase in the glass transition temperature during UV exposure associated with cross-linking in the polymer was less pronounced in the in situ-prepared coating films, confirming better UV protection, while the photocatalytic effect of TiO2 was more pronounced in the ex situ-prepared coating films. The results indicate that the method of preparation has a significant influence on the properties of the coating films.
Bacterial contamination of the membranes used during guided bone regeneration directly influences the outcome of this procedure. In this study, we analyzed the early stages of bacterial adhesion on ...two commercial dense polytetrafluoroethylene (d-PTFE) membranes in order to identify microstructural features that led to different adhesion strengths. The microstructure was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR). The surface properties were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), and surface free energy (SFE) measurements. Bacterial properties were determined using the microbial adhesion to solvents (MATS) assay, and bacterial surface free energy (SFE) was measured spectrophotometrically. The adhesion of four species of oral bacteria (
,
,
, and
) was studied on surfaces with or without the artificial saliva coating. The results indicated that the degree of crystallinity (78.6% vs. 34.2%, with average crystallite size 50.54 nm vs. 32.86 nm) is the principal feature promoting the adhesion strength, through lower nanoscale roughness and possibly higher surface stiffness. The spherical crystallites ("warts"), observed on the surface of the highly crystalline sample, were also identified as a contributor. All bacterial species adhered better to a highly crystalline membrane (around 1 log
CFU/mL difference), both with and without artificial saliva coating. Our results show that the changes in polymer microstructure result in different antimicrobial properties even for chemically identical PTFE membranes.
U ovom radu istraživan je učinak dodatka višestjenih ugljikovih nanocjevčica (MWCNT) te MWCNT-a modificiranog skupinama COOH (MWCNT-COOH) u rasponu masenih udjela od 0 do 4 % na svojstva ...termoplastičnog poliuretana (PU). Uzorci nanokompozita pripravljani su postupkom polaganog sušenja iz smjese poliuretana i nanopunila u acetonu pri sobnoj temperaturi. Učinak dodatka nanopunila na sferolitnu morfologiju poliuretana te raspodijeljenost nanopunila u matrici PU analizirana je optičkom polarizacijskom mikroskopijom. Toplinska svojstva u neizotermnim i izotermnim uvjetima istraživana su diferencijalnom pretražnom kalorimetrijom (DSC).
Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna .
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