Surface Activity and Emulsifying Effect of Non-Toxic Starch Nanocrystal

The purpose of this study is to investigate the surface activity of starch nanocrystals (SNC), material derived from starch, and confirm their usefulness as a surfactant. In order to evaluate the surface activity, the surface tension change of suspended SNC solution via the Wilhelmy plate method was measured and the values were compared with various synthetic surfactants. The effect of SNC as emulsifier was evaluated on emulsion formation and physical stability. The surface tension of the SNC-dispersed solution was decreased while its concentration was increased. When the 5.0% (w/v) of SNC was added, the surface tension was decreased from 70.3 to 49.5 mN/m. It was confirmed that the physical stability of the emulsion prepared by adding the SNC was improved compared to that of surface inactivity material (PEG 400). The phase separation was observed within 1 hour after preparation of the emulsion containing PEG 400, but the emulsion containing SNC was stable for 5 hours or more. To summarize this study, SNC, a natural-derived and non-toxic material, exhibits sufficient surface activity, thereby confirming the possibility of being applied to the food and pharmaceutical industry.

Non-fluorine surface modification of acetylated birch for improved water repellence

In this work, a non-fluorinated surface treatment, i.e., hydrophobized silicone nanofilaments, was applied on both birch and acetylated birch wood samples via a gas-phase based reaction. A superhydrophobic behavior was observed on both the surface-modified samples as revealed by the static water contact angles (CAs) greater than 160°, also valid for samples prepared with the shortest reaction time of 1 h. The dynamic wettability behavior of the samples was studied by a multicycle Wilhelmy plate method. The surface-modified acetylated birch exhibited a pronounced enhanced water resistance, resulting in very low water uptake of 3 ± 1 wt% after 100 cycles, which was not only about 29 and 5 times lower than that of the non-surface-modified birch and acetylated birch, respectively, but also three times lower than that of the surface-modified birch. Moreover, the aesthetic appearance of the acetylated wood was maintained as the surface modification only resulted in a small color change. This work shows the potential of preparing super water-repellent wood by non-fluorinated surface modification.

Wettability of welded wood-joints investigated by the Wilhelmy method: part 2. Effect of wollastonite additive

The effect of wollastonite on the wetting properties of welded Scots pine-joints was studied using the multicycle Wilhelmy plate method and by observation of the chemical composition of the welded joints. Welding pine with wollastonite for 5 s resulted in a decrease in the water uptake and the swelling, and an increase in the contact angle of the welded joint compared to welded wood without wollastonite. High-performance liquid chromatography and gas chromatography/mass spectrometry showed the presence of dehydration products such as furfural, 5-hydroxymethylfurfural, and levoglucosan in methanol extracts from welded joints of specimens welded with and without wollastonite. Phenols were also found by analysis using the Folin-Ciocalteu method and High-performance liquid chromatography. The importance of such compounds in relation to the wetting properties of the welded joint is discussed.

Wettability of welded wood-joints investigated by the Wilhelmy method: part 1. Determination of apparent contact angles, swelling, and water sorption

This study presents a novel application of the Wilhelmy plate method on welded joints of Scots pine sapwood and beech. Welding resulted in an increase in the contact angle (increased hydrophobicity) as well as a decrease in the water uptake and swelling of the welded pine-joint compared to non-welded pine. When the welding time was extended from 4 to 5 s, these properties were further pronounced. Welding of beech, on the other hand, led to an increase in the contact angle and a decrease in the water uptake, but an increase in the swelling.Fourier Transform Infrared spectroscopy showed that welding increased the aliphatic C–H and unsaturated C=C stretching absorption bands in pine and beech. Scanning electron microscopy showed a dense structure at the welded joints of the both species, giving evidence of a lower porosity that leads to a lower permeability as a result of the welding.

Sorptivity and water imbibition into air-dry surfactant-containing soil

<p>Surfactants have been widely used in agriculture mainly as adjuvants to aid foliar pesticides to stay on target areas and as wetting agents to counteract the deleterious impacts of soil hydrophobicity. The latter has gained increasing attention among scientists over decades. Many natural and urban hydrophobic soil surfaces (i.e post-fire forest land and golf greens with dry patches respectively) after surfactant application has observed to have improved hydrological behaviors such as enhanced infiltration rate, more evenly-distributed water content, thus resulting in higher water use efficiency, better performances of amenity surfaces and higher crop yield. In general, a surfactant can be classified as cationic, anionic or nonionic according to the charge of its polar group. Commonly, with anionic and nonionic surfactants are employed by either directly mixing with the soil or incorporated into the irrigating. Regardless of the application mode, the occurrence of surfactant adsorption onto soil particles after wetting/drying cycles is highly expected, which, in fact, has already shown in some studies to change the hydraulic properties of the soil, oppositely to initial expectation. Capillary rise, for example, was found to decrease in sand treated with laundry derived detergent. In addition, sub-critical hydrophobicity was observed in sands pre-saturated with greywater derived surfactants after some cycles of wetting and drying. Insights from these studies implied that surfactant application to hydrophilic soils may eventually induce temporal hydrophobic nature. In this regard, the main objective of this study was to quantify the sorptivity and imbibition rate of air-dry soil subjected to wetting and drying with surfactants. Specifically, we employed three types of surfactants: (i) anionic (SDS), (ii) cationic (CTAB) and (iii) nonionic (TX-100). Quartz sand was sieved through 0.5mm sieve and wet-packed into columns (I.D.=3.5cm and L=6cm) with surfactant concentrations above and below the CMC (Critical Micelle Concentration) and then oven-dried at 65<sup>o</sup>C for 24h. We have repeated this procedure to obtain soil samples undergoing 1 to 5 wetting/drying cycles. The soil samples were subjected to imbibition using the capillary rise method with water and ethanol, from which the initial sorptivity, imbibition rate and contact angle (CA) were calculated. The Wilhelmy plate method (WPM) and sessile drop method (SDM) was also used to measure the CA. The results showed that following one application of the three surfactants, the sorptivity was reduced relative to the control. Further reduction observed only for TX-100 and CTAB soil samples. The CA values obtained from the WPM and SDM implied that sub-critical hydrophobicity was induced only for the CTAB-treated, implying that water imbibition in the SDS and TX-100 treated soil in manly governed by the reduced surface tension rather than in the induced hydrophobicity (i.e. CA). Further discussion on the governing mechanism of wetting in surfactant-containing soils will be presented next to the results.           </p><p> </p><p> </p>

Study of Surface Tension and Natural Evaporation of Aqueous Surfactant Solutions

Surface tension and solution evaporation of aqueous solutions of sodium lauryl sulfate (SLS), ECOSURF™ EH-14, and ECOSURF™ SA-9 under natural convection is examined through experimental methods. SLS is an anionic surfactant while EH-14 and SA-9 are environmentally-friendly nonionic surfactants. Surfactants are known to affect evaporation performance of solutions and are studied in relation to water loss prevention and heat dissipation. Surfactants could be useful under drought conditions which present challenges to water management on a yearly basis in arid areas of the world. Recent water scarcity in the greater Los Angeles area, south eastern Africa nations, eastern Australia and eastern Mediterranean countries has high cost of water loss by evaporation. Surfactants are studied as a potential method of suppressing evaporation in water reservoirs. Surfactants are also studied as performance enhancers for the working fluid of heat dissipation devices, such as pulsating heat pipes used for electronics cooling. Some surfactants have been shown to lower thermal resistances and friction pressure in such devices and thereby increase their efficiency. The static surface tensions of the aqueous-surfactant solutions are measured with surface tensiometer using Wilhelmy plate method. The surfactants are shown to lower surface tension significantly from pure water. The surface tension values found at the Critical Micelle Concentration are 33.8 mN/m for SLS, 30.3 mN/m for EH-14, and 30.0 mN/m for SA-9. All three surfactants reduced natural convection water loss over 5 days with SLS showing the greatest effect on evaporation rates. The maximum evaporation reduction by each surfactant from distilled water with no surfactants after 5 days is 26.1% for SLS, 20.8% for EH-14, and 18.4% for SA-9.