Synergistic Action of Temperature and pH Factors in the Cleaning of Fatty Acids Soils; Analyzed by Probability Density Functional Method.

In this study, the interaction between the temperature and the pH of soil containing fatty acids with sodium dodecyl sulfate (SDS) aqueous solution was investigated to elucidate their synergistic effect in cleaning. A tergotometer was used for the cleaning test, and the cleaning results were analyzed by the probability density functional method, using the calculated parameter, µ rl , as an index of the cleaning power. The increase in µ rl by one of the factors was defined as ΔX or ΔY and the increase in µ rl by the both factors was defined as Δ(X + Y). It is assumed that there is a synergistic effect when Δ(X + Y) > ΔX + ΔY. The cleaning of fatty acid stains followed the addition rule pertaining to mechanical force and the pH effect. However, synergy was observed between the temperature and the pH effect. This was also supported by the plot of µ rl vs 1/T and observations using a phase-contrast microscope.

Kinetic analysis of hemoglobin detergency by probability density functional method.

In this study, washing tests were performed using samples prepared by contaminating fabrics with hemoglobin, and a kinetic analysis was conducted based the probability density functional method, which expresses the cleaning power using two parameters σrl (related to the cleaning mechanism) and µrl (related to the level of cleaning power). This method allows for the processing of uncertainties specific to protein washing under the assumption that the soil adhesion and detergency are in accordance with a normal distribution. A certain amount of hemoglobin solution was soaked in a cloth, dried, and steam-treated, and then used as a sample for a cleaning test. Two parameters σrl and µrl were calculated based on the detergency (%) after 5 min, 10 min, 15 min, and 20 min of washing with respect to different pH and temperature levels, and different sodium dodecyl sulfate (SDS) concentration and temperature levels. Based on the results, the value of σrl indicated that the hemoglobin was removed by the dissolving action. In addition, µrl increased in accordance with an increase in the pH, SDS concentration, and temperature. With respect to µrl, the relationship of ΔX + ΔY = Δ(X+Y) was observed in several cases, where ΔX represents the effect of the pH or SDS concentration, ΔY is the temperature effect, and Δ(X+Y) is the combined effect. Therefore, there may be an additive relationship between the pH and temperature effects, and the SDS concentration and temperature effects.

Influence of Surfactants and Fluoride against Enamel Erosion.

This study investigated the effect of surfactants associated with sodium fluoride (NaF) on enamel erosion prevention, using an erosion-remineralization in vitro model. Sodium lauryl sulfate (SLS), polysorbate 20 (P20), and cocoamidopropyl betaine (CAPB) were tested, at concentrations of 1.0 and 1.5%, and associated or not with NaF (275 ppm). The control groups were distilled water and the NaF solution. Bovine enamel samples (n = 12) were prepared and submitted to a 5-day cycling model: acid challenge (0.3% citric acid, pH 2.6, 4×/day), human saliva (2 h, 4×/day), and the treatment solutions (2 min, 2×/day). The protective potential of the agents against initial erosion was assessed by microhardness and the surface loss by profilometry. Enamel surface wettability was determined by goniometry, protein adsorption was measured by spectroscopy (FTIR), and the KOH-soluble fluoride was quantified. Goniometry showed that SLS and CAPB increased enamel wettability. No differences were found among the surfactants regarding protein adsorption. Microhardness showed that SLS reduced NaF protection. P20 (1 and 1.5%) and CAPB 1.5% presented a protective effect, but lower than the NaF solution. Profilometry showed that CAPB protected enamel, but no agent associated with NaF promoted a higher protection than the NaF solution alone. KOH-soluble fluoride analysis showed that all surfactants reduced the fluoride adsorption on the enamel surface. Therefore, the surfactants tested (except for P20) changed the enamel surface energy. The SLS decreased the protective potential of NaF on initial erosion, but no tested agent interfered with the protective effect of NaF on enamel erosive wear.