Effect of Sodium Laureth Sulfate on Contact Angles of High-Impact Polystyrene and Acrylonitrile–Butadiene–Styrene from Recycled Refrigeration Equipment

This paper investigates the effects of sodium laureth sulfate (SLES) on the wettability of the surface of the two most common recycled plastics in refrigeration equipment: HIPS (high-impact polystyrene) and ABS (acrylonitrile–butadiene–styrene). These plastics, in the form of flakes, were identified on the basis of their FTIR spectra, and then, they were subjected to a study of contact angles using the sessile droplet method. The solutions for the angle analysis included tap water with the addition of SLES. The results of this study showed that at SLES concentrations of 0.1 g/L and 0.2 g/L, the differences in the contact angles for HIPS and ABS were 10.76° and 10.10°, respectively. This research confirmed the potential of using SLES as a support for the flotation separation of plastics with similar densities and surface characteristics, such as HIPS and ABS

A New Route for Preparation of Hydrophobic Silica Nanoparticles Using a Mixture of Poly(dimethylsiloxane) and Diethyl Carbonate

Organosilicon layers chemically anchored on silica surfaces show high carbon content, good thermal and chemical stability and find numerous applications as fillers in polymer systems, thickeners in dispersing media, and as the stationary phases and carriers in chromatography. Methyl-terminated poly(dimethylsiloxanes) (PDMSs) are typically considered to be inert and not suitable for surface modification because of the absence of readily hydrolyzable groups. Therefore, in this paper, we report a new approach for surface modification of silica (SiO2) nanoparticles with poly(dimethylsiloxanes) with different lengths of polymer chains (PDMS-20, PDMS-50, PDMS-100) in the presence of diethyl carbonate (DEC) as initiator of siloxane bond splitting. Infrared spectroscopy (IR), elemental analysis (CHN), transmission electron microscopy (TEM), atomic force microscopy (AFM), rotational viscosity and contact angle of wetting were employed for the characterization of the raw fumed silica and modified silica nanoparticles. Elemental analysis data revealed that the carbon content in the grafted layer is higher than 8 wt % for all modified silicas, but it decreases significantly after sample treatment in polar media for silicas which were modified using neat PDMS. The IR spectroscopy data indicated full involvement of free silanol groups in the chemisorption process at a relatively low temperature (220 °C) for all resulting samples. The contact angle studies confirmed hydrophobic surface properties of the obtained materials. The rheology results illustrated that fumed silica modified with mixtures of PDMS-x/DEC exhibited thixotropic behavior in industrial oil (I-40A), and exhibited a fully reversible nanostructure and shorter structure recovery time than nanosilicas modified with neat PDMS. The obtained results from AFM and TEM analysis revealed that the modification of fumed silica with mixtures of PDMS-20/DEC allows obtaining narrow particle size distribution with uniform dispersity and an average particle size of 15–17 nm. The fumed silica nanoparticles chemically modified with mixtures of PDMS-x/DEC have potential applications such as nanofillers of various polymeric systems, thickeners in dispersing media, and additives in coatings

Effect of the Synthesis Methods on Hydrophobic Properties of Modified Silicas

Composites based on fumed silica with surface hydrophobic groups were synthesized by chemical substitution of silanol groups' proton for trimethylsilyl (TMS) groups, adsorption of poly(dimethylsiloxane) (PDMS) and combined chemical-adsorption methods. Microcalorimetry measurements and values of the wetting contact angle with water (Θ) were obtained to investigate the hydrophobic properties of prepared materials. The hydrophilicity indexes (K h ) were determined from the relationship of heat of immersion in water Q w to non-polar decane Q d . The Θ and Q w demonstrated changes with increase of modification degree (d m ) for composites containing a monolayer of PDMS. All samples with excess of PDMS had high Θ (>110°) and relatively low Q w and K h . Composites modified with TMS groups demonstrated hydrophobic properties in accordance with K h at d m 0.7, whereas Θ > 90° is observed only for those samples with d m = 1.0. The different methods of synthesis may be applied based on the morphological characteristics and hydrophobicity of the samples

Hydrophobization of Cold Plasma Activated Glass Surfaces by Hexamethyldisilazane Treatment

The objective of this study was to investigate the modification of glass surfaces by the synergistic combination of cold plasma and chemical surface modification techniques. Glass surface hydrophobicity was obtained as a result of various plasma and deposition operational conditions. The mechanisms governing the hydrophobization process were also studied. Glass plates were activated with plasma using different gases (oxygen and argon) at different treatment times, ranging from 30 to 1800 s. Then, the plasma-treated surfaces were exposed to hexamethyldisilazane vapors at different temperatures, i.e., 25, 60, and 100 °C. Complete characterization, including contact angle measurements, surface free energy calculations, 3D profilometry, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy, was accomplished. It was found that the extent of the hydrophobicity effect depends on both the plasma pre-treatment and the specific conditions of the hexamethyldisilazane deposition process. Plasma activation led to the formation of active sites on the glass surface, which promoted the adsorption and reaction of hexamethyldisilazane species, thereby inducing surface chemical modification. Longer plasma pre-treatment resulted in stronger modification on the glass surface, resulting in changes in the surface roughness. The largest water contact angle of ≈100° was obtained for the surface activated by argon plasma for 1800 s and exposed to hexamethyldisilazane vapors at 25 °C. The changes in the surface properties were caused by the introduction of the hydrophobic trimethylsilyl groups onto the glass surface as well as roughness development

Measurement of the branching fractions for Cabibbo-suppressed decays D+→K+K−π+π0D^{+}\to K^{+} K^{-}\pi^{+}\pi^{0} and D(s)+→K+π−π+π0D_{(s)}^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0} at Belle

International audienceWe present measurements of the branching fractions for the singly Cabibbo-suppressed decays $D^+\to K^{+}K^{-}\pi^{+}\pi^{0}$ and $D_s^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0}$, and the doubly Cabibbo-suppressed decay $D^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0}$, based on 980 ${\rm fb}^{-1}$ of data recorded by the Belle experiment at the KEKB $e^{+}e^{-}$ collider. We measure these modes relative to the Cabibbo-favored modes $D^{+}\to K^{-}\pi^{+}\pi^{+}\pi^{0}$ and $D_s^{+}\to K^{+}K^{-}\pi^{+}\pi^{0}$. Our results for the ratios of branching fractions are $B(D^{+}\to K^{+}K^{-}\pi^{+}\pi^{0})/B(D^{+}\to K^{-}\pi^{+}\pi^{+}\pi^{0}) = (11.32 \pm 0.13 \pm 0.26)\%$, $B(D^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0})/B(D^{+}\to K^{-}\pi^{+}\pi^{+}\pi^{0}) = (1.68 \pm 0.11\pm 0.03)\%$, and $B(D_s^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0})/B(D_s^{+}\to K^{+}K^{-}\pi^{+}\pi^{0}) = (17.13 \pm 0.62 \pm 0.51)\%$, where the uncertainties are statistical and systematic, respectively. The second value corresponds to $(5.83\pm 0.42)\times\tan^4\theta_C$, where $\theta_C$ is the Cabibbo angle; this value is larger than other measured ratios of branching fractions for a doubly Cabibbo-suppressed charm decay to a Cabibbo-favored decay. Multiplying these results by world average values for $B(D^{+}\to K^{-}\pi^{+}\pi^{+}\pi^{0})$ and $B(D_s^{+}\to K^{+}K^{-}\pi^{+}\pi^{0})$ yields $B(D^{+}\to K^{+}K^{-}\pi^{+}\pi^{0})= (7.08\pm 0.08\pm 0.16\pm 0.20)\times10^{-3}$, $B(D^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0})= (1.05\pm 0.07\pm 0.02\pm 0.03)\times10^{-3}$, and $B(D_s^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0}) = (9.44\pm 0.34\pm 0.28\pm 0.32)\times10^{-3}$, where the third uncertainty is due to the branching fraction of the normalization mode. The first two results are consistent with, but more precise than, the current world averages. The last result is the first measurement of this branching fraction

Measurement of the B+/B0B^+/B^0 production ratio in e+e−e^+e^- collisions at the Υ(4S)\Upsilon(4S) resonance using B→J/ψ(ℓℓ)KB \rightarrow J/\psi(\ell\ell) K decays at Belle

We measure the ratio of branching fractions for the $\Upsilon (4S)$ decays to $B^+B^-$ and $B^0\bar{B}{}^0$ using $B^+ \rightarrow J/\psi(\ell\ell) K^+$ and $B^0 \rightarrow J/\psi(\ell\ell) K^0$ samples, where $J/\psi(\ell\ell)$ stands for $J/\psi \to \ell^+\ell^-$ ($\ell = e$ or $\mu$), with $711$ fb$^{-1}$ of data collected at the $\Upsilon(4S)$ resonance with the Belle detector. We find the decay rate ratio of $\Upsilon(4S) \rightarrow B^+B^-$ over $\Upsilon(4S) \rightarrow B^0\bar{B}{}^0$ to be $1.065\pm0.012\pm 0.019 \pm 0.047$, which is the most precise measurement to date. The first and second uncertainties are statistical and systematic, respectively, and the third uncertainty is systematic due to the assumption of isospin symmetry in $B \to J/\psi(\ell\ell) K$

Measurement of branching fractions of Λc+→pKS0KS0\Lambda_c^+\to{}pK_S^0K_S^0 and Λc+→pKS0η\Lambda_c^+\to{}pK_S^0\eta at Belle

We present a study of a singly Cabibbo-suppressed decay $\Lambda_c^+\to{}pK_S^0K_S^0$ and a Cabibbo-favored decay $\Lambda_c^+\to{}pK_S^0\eta$ based on 980 $\rm fb^{-1}$ of data collected by the Belle detector, operating at the KEKB energy-asymmetric $e^+e^-$ collider. We measure their branching fractions relative to $\Lambda_c^+\to{}pK_S^0$: $\mathcal{B}(\Lambda_c^+\to{}pK_S^0K_S^0)/\mathcal{B}(\Lambda_c^+\to{}pK_S^0)={(1.48 \pm 0.08 \pm 0.04)\times 10^{-2}}$ and $\mathcal{B}(\Lambda_c^+\to{}pK_S^0\eta)/\mathcal{B}(\Lambda_c^+\to{}pK_S^0)={(2.73\pm 0.06\pm 0.13)\times 10^{-1}}$. Combining with the world average $\mathcal{B}(\Lambda_c^+\to{}pK_S^0)$, we have the absolute branching fractions: $\mathcal{B}(\Lambda_c^+\to{}pK_S^0K_S^0) = {(2.35\pm 0.12\pm 0.07 \pm 0.12 )\times 10^{-4}}$ and $\mathcal{B}(\Lambda_c^+\to{}pK_S^0\eta) = {(4.35\pm 0.10\pm 0.20 \pm 0.22 )\times 10^{-3}}$. The first and second uncertainties are statistical and systematic, respectively, while the third ones arise from the uncertainty on $\mathcal{B}(\Lambda_c^+\to{}pK_S^0)$. The mode $\Lambda_c^+\to{}pK_S^0K_S^0$ is observed for the first time and has a statistical significance of $>\!10\sigma$. The branching fraction of $\Lambda_c^+\to{}pK_S^0\eta$ has been measured with a threefold improvement in precision over previous results and is found to be consistent with the world average

Test of light-lepton universality in τ\tau decays with the Belle II experiment

We present a measurement of the ratio $R_\mu = \mathcal{B}(\tau^-\to \mu^-\bar\nu_\mu\nu_\tau) / \mathcal{B}(\tau^-\to e^-\bar\nu_e\nu_\tau)$ of branching fractions $\mathcal{B}$ of the $\tau$ lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB $e^+e^-$ collider. The sample has an integrated luminosity of 362 fb$^{-1}$ at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood fit is performed using the momentum spectra of the electron and muon candidates. The result, $R_\mu = 0.9675 \pm 0.0007 \pm 0.0036$, where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the $W$ boson in $\tau$ decays of $0.9974 \pm 0.0019$, in agreement with the standard model expectation of unity

Test of light-lepton universality in τ\tau decays with the Belle II experiment

International audienceWe present a measurement of the ratio $R_\mu = \mathcal{B}(\tau^-\to \mu^-\bar\nu_\mu\nu_\tau) / \mathcal{B}(\tau^-\to e^-\bar\nu_e\nu_\tau)$ of branching fractions $\mathcal{B}$ of the $\tau$ lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB $e^+e^-$ collider. The sample has an integrated luminosity of 362 fb$^{-1}$ at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood fit is performed using the momentum spectra of the electron and muon candidates. The result, $R_\mu = 0.9675 \pm 0.0007 \pm 0.0036$, where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the $W$ boson in $\tau$ decays of $0.9974 \pm 0.0019$, in agreement with the standard model expectation of unity