Tagawa Yumiko

<p>The detergency of polyethylene terephthalate (PET) films in an aqueous solution was investigated using a commercial ultrasonic cleaning apparatus operating at 38 or 130 kHz. Carbon black (CB) or colored oleic acid (OA) were deposited onto the PET film. The PET film was ultrasonically cleaned in an aqueous sodium chloride (NaCl) solution with or without sodium hydroxide (NaOH) or sodium dodecyl sulfate (SDS). The detergency was calculated using the microscopic image analysis system. It was found that CB detergency at 38 kHz was higher than that at 130 kHz for the same electric power. Ultrasonic washing was also carried out using PET fabrics and the detergency was evaluated by the surface reflectance method. The detergency was found to enhance in the presence of NaOH and SDS. The effect of the exposure direction of the ultrasonic wave on the fabric detergency and uneven washing was investigated using a self-developed ultrasonic cleaning apparatus operating at 38 kHz.</p>

The effect of ultraviolet light irradiation on the characteristics of the polyethylene (PE) surface was investigated by the quartz crystal microbalance (QCM) technique. The PE film was prepared on the gold electrodes of the QCM by spin-coating from the solution and then was treated by the excimer UV lamp in ambient air. The changes in the hydrophilic properties, moisture adsorption, and water retention of the PE film due to the UV irradiation were determined from the frequency change of the QCM. To evaluate the detergency of the PE film, stearic acid as model oily soil was deposited onto the PE film formed on the QCM by the Langmuir-Blodgett (LB) technique, and was ultrasonically cleaned in aqueous detergent solutions containing ethanol or surfactant. The removal efficiency obtained from the frequency change of the QCM was found to increase considerably after the UV irradiation. From independently determined contact angles and the surface free energy components of the PE film, the free energy change resulting from the penetration of the detergent solution between stearic acid and PE in the zone of contact was calculated. Good relation was found between the removal efficiency and the free energy change, indicating that the increase in the detergency of the PE surface by UV irradiation was explained by surface energetics.<br>

The detergency of particulate soil in aqueous solutions was examined by the quartz crystal microbalance (QCM) technique and was discussed on the basis of the surface free energies. The gold electrode and spin-coated film of polyethylene, nylon 6 and cellulose triacetate on the gold electrode of the QCM were used as substrates. As model particulate soils, polyethylene and nylon 12 particles were used. The QCM was perpendicularly immersed in aqueous dispersions of spherical particles to deposit the particles onto the substrate. After pulling the substrates out of the dispersion and drying in air, the substrates were cleaned in aqueous solutions with and without ethanol. The removal efficiency was calculated from the frequency changes of the QCM due to soil deposition and cleaning. The efficiency was dependent on the particles and substrates, and increased by the addition of ethanol in all system. The Lifshitz-van der Waals and acid-base components of the surface freed energy of the soil and substrate were estimated from the contact angles of three probe liquids. The detergency phenomenon in the present system was explained in terms of the free energy change due to soil removal, which was calculated from the surface free energy components.

Soil deposition on fibers was investigated from the standpoint of the waste water treatment. Polyethylene, poly (vinylidene chloride), poly (vinylidene fluoride), polyethylene terephthalate and nylon 6 fibers were used as soil collectors. Following immersion of the fibers in water from Sarusawa pond, water turbidity was measured. Turbidity decreased due to the deposition of soil onto the fiber surfaces. Poly (vinylidene chloride) fibers were more effective as a soil collector than any other fibers.<BR>Particle deposition from an aqueous solution was investigated using a model system consisting of spherical polyethylene or nylon particles and a polymeric plate. The plate was perpendicularly immersed in an aqueous suspension. The number of particles deposited on the plate appeared related to the polar components of surface free energies of the particle and plate. The results of particle deposition in the model system were in good agreement with those in systems using water from a pond.

Adhesion and removal phenomena in aqueous solutions were investigated using spherical polyethylene particles and a quartz plate. The experimental results are discussed and explained on the basis of the heterocoagulation theory, using ζ-potentials of the particles and the quartz plate as determined by micro-electrophoresis. The magnitude of the energy barrier preventing particle adhesion was found to be about 4000 κT for particles of 4-5μm in diameter. The Hamaker constant (A₁₁) of a polyethylene particle was estimated by the adhesion and removal phenomena and was determined as 6.06.8×10^-13ergs from curves of interaction energy plotted against separation.